Fresco图片加载框架

来源：互联网发布：部队网络安全教育体会编辑：程序博客网时间：2024/04/20 13:40

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目录(?)[+]

Fresco图片加载框架的介绍,相关开源库以及工具类的封装

Fresco图片加载框架的介绍相关开源库以及工具类的封装
- 工具类FrescoUtils地址
- 简介
  - 优点一内存管理
  - 优点二更便捷的使用
- 相关文档及开源库
- 使用心得及一些方法的封装
  - 加载超级大图还是会卡
  - 初始化
  - 利用SimpleDraweeView加载图片的一般姿势
  - 显示图片时把人的头部给截掉了
    - 可用的缩放类型
  - 获取缓存的图片文件
  - 如果我想用fresco来下载图片不需要显示要怎么实现
  - 由于某种原因无法使用SimpleDraweeView来显示图片比如说弹幕上显示头像而需要直接操作bitmap那么要怎么拿到url返回的bitmap
  - Fresco中在listview之类的快速滑动时停止加载滑动停止后恢复加载时调用的API是什么
  - gif图片无法显示成圆形怎么办当然有的情况下jpg也无法显示圆形加一层和图片的parentview 背景色一样的圆形遮罩即可
  - 很多app都有清除磁盘缓存的功能那么fresco怎么清除缓存呢
  - 已经设置了downsampling和resize但是加载很大的gif图还是很卡怎么办
  - 高斯模糊

工具类FrescoUtils地址

简介

Fresco 是Facebook开源的安卓上的图片加载框架,也可以说是至今为止安卓上最强大的图片加载框架.

相对于其他几个图片加载框架,Fresco主要的优点在于更好的内存管理和更强大的功能,更便捷的使用,缺点则是体积比较大,引入后会导致应用apk增加1.5M到2M的大小,但是相对于其便捷性来讲,我觉得这都不是事儿.

优点一:内存管理

对于5.0以下系统,fresco使用”ashmem”（匿名共享内存）区域存储Bitmap缓存，这样Bitmap对象的创建、释放将不会触发GC,不会占用javaheap. 这个特点是其他图片加载框架所没有做到的.

5.0以上系统，由于安卓系统本身内存管理的优化，所以对于5.0以上的系统Fresco将Bitmap缓存直接放到了javaheap内存中.

并且,fresco实现了真正的三级缓存:两级的内存缓存+一个磁盘缓存.两个内存缓存为:bitmap缓存和未解码的图片缓存,这样既可以加快图片的加载速度,又能节省内存的占用.这个两级的内存缓存也是其他图片加载框架所没有做到的.

另外提一点,在app切换到后台时,fresco会自动清理两级的内存缓存,无需手动.

通过以上几点,使用fresco加载图片时内存占用要比其他图片加载框架小一大半,基本很少发生oom的事情.

几个图片加载框架的内存占用测试结果对比请戳这里:Android Image Loader 第三方库对比测试

优点二:更便捷的使用:

初期入门,轻度的图片加载,甚至可以直接用:

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">Fresco.initiliaze(context);<com.facebook.drawee.view.SimpleDraweeView    android:id=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@+id/my_image_view"</span>    android:layout_width=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"20dp"</span>    android:layout_height=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"20dp"</span>    fresco:placeholderImage=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@drawable/news_default"</span>      .../>simpleDraweeView.setImageURI(uri);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

其他都不用管,fresco自动帮我们做缓存,图片缩略.

显示圆角或圆圈图片也只是xml中配置一下而已:

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">圆圈 - 设置roundAsCircle为<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>圆角 - 设置roundedCornerRadius</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

另外再说一句,fresco还支持webp,所以,splash和引导界面的大图我一般都是用智图压成webp放在drawable中,用fresco加载就行了.

使用心得及一些方法的封装

加载超级大图还是会卡

首先,终极的解决方法肯定是,客户端在图片请求中带上需要的宽和高,服务器将图片缩略到该规格后返回该小图.这个做得比较好的是七牛.

注意:不管服务器能不能返回缩略图,所存储的原图都不应该太大,有时图片太大,甚至都无法下载下来(报504之类的错误).

那么,如果服务器只能拿到原图或大图,fresco怎么缩略显示?

fresco中提供了三个功能来生成缩略图:

Scaling :画布操作,通常是由硬件加速的。图片实际大小保持不变，它只不过在绘制时被放大或缩小.使用时需要配置缩放类型fresco:actualImageScaleType,具体类型名与Imageview的ScaleType几乎一样.
Resizing 是一种软件执行的管道操作。它返回一张新的，尺寸不同的图片,也就是说直接改变bitmap的大小,可惜是单独使用时,只支持jpg,当然,结合Downsampling使用时,可以支持除gif以为的所有常见图片,包括webp.
Downsampling 同样是软件实现的管道操作。它不是创建一张新的图片，而是在解码时改变图片的大小。同样是软件实现的管道操作。它不是创建一张新的图片，而是在解码时改变图片的大小。类似于android中的BitmapFactory在decodefile时的inSampleSize,都是指定一个采样率,默认是关闭的,如果开启,那么需要结合Resizing来使用.

综上,要缩小内存占用,以及减少cpu计算量,减少卡顿,应该是Downsampling结合Resizing来使用.其中Downsampling是在Fresco初始化时开启,而Resizing则是通过构建ImageRequest时通过制定宽高来实现,所以可以定制每一张或每一类图片的宽高. 示例代码如下

初始化:

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 初始化操作，建议在子线程中进行     * 添加的依赖：     *  compile 'com.facebook.fresco:fresco:0.10.0+'        compile 'com.facebook.fresco:animated-webp:0.10.0'//加载webp必须添加        compile 'com.facebook.fresco:animated-gif:0.10.0' //加载gif必须添加     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> context     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> cacheSizeInM  磁盘缓存的大小，以M为单位     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">init</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> Context context,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> cacheSizeInM){        DiskCacheConfig diskCacheConfig = DiskCacheConfig.newBuilder(context)                .setMaxCacheSize(cacheSizeInM*<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1024</span>*<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1024</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//最大缓存</span>                .setBaseDirectoryName(PHOTO_FRESCO)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//子目录</span>                .setBaseDirectoryPathSupplier(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Supplier<File>() {                    <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>                    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> File <span class="hljs-title" style="box-sizing: border-box;">get</span>() {                        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> context.getCacheDir();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//还是推荐缓存到应用本身的缓存文件夹,这样卸载时能自动清除,其他清理软件也能扫描出来</span>                    }                })                .build();        MyImageCacheStatsTracker imageCacheStatsTracker = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyImageCacheStatsTracker();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//缓存的监听接口,其方法空实现即可</span>        ImagePipelineConfig config = ImagePipelineConfig.newBuilder(context)                .setMainDiskCacheConfig(diskCacheConfig)                .setImageCacheStatsTracker(imageCacheStatsTracker)                .setDownsampleEnabled(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>)          <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//Downsampling，要不要向下采样,它处理图片的速度比常规的裁剪scaling更快，</span>          <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 并且同时支持PNG，JPG以及WEP格式的图片，非常强大,与ResizeOptions配合使用</span>                .setBitmapsConfig(Bitmap.Config.RGB_565)          <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//如果不是重量级图片应用,就用这个省点内存吧.默认是RGB_888</span>                .build();        Fresco.initialize(context, config);    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li></ul>

利用SimpleDraweeView加载图片的一般姿势:

注意,我这里没有去设置DraweeHierarchy,因为依照fresco的设计思维,DraweeHierarchy属于view层次的东西,应该在xml中配置.当然如果非要设置,请看这里.

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">load</span>(Uri uri,SimpleDraweeView draweeView,BasePostprocessor processor,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> width,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> height,                                BaseControllerListener listener){        ImageRequest request =                ImageRequestBuilder.newBuilderWithSource(uri)                        .setPostprocessor(processor)                        .setResizeOptions(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ResizeOptions(width,height))                        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//缩放,在解码前修改内存中的图片大小, 配合Downsampling可以处理所有图片,否则只能处理jpg,</span>                        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 开启Downsampling:在初始化时设置.setDownsampleEnabled(true)</span>                        .setProgressiveRenderingEnabled(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//支持图片渐进式加载</span>                        .setAutoRotateEnabled(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>) <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//如果图片是侧着,可以自动旋转</span>                        .build();        PipelineDraweeController controller =                (PipelineDraweeController) Fresco.newDraweeControllerBuilder()                        .setImageRequest(request)                        .setControllerListener(listener)                        .setOldController(draweeView.getController())                        .setAutoPlayAnimations(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>) <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//自动播放gif动画</span>                        .build();        draweeView.setController(controller);    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul>

显示图片时把人的头部给截掉了

这个就要用到Scaling了.图片的缩放拉伸以及裁剪模式.具体看文档

可用的缩放类型

类型描述center居中，无缩放。centerCrop保持宽高比缩小或放大，使得两边都大于或等于显示边界，且宽或高契合显示边界。居中显示。focusCrop同centerCrop, 但居中点不是中点，而是指定的某个点。centerInside缩放图片使两边都在显示边界内，居中显示。和 fitCenter 不同，不会对图片进行放大。如果图尺寸大于显示边界，则保持长宽比缩小图片。fitCenter保持宽高比，缩小或者放大，使得图片完全显示在显示边界内，且宽或高契合显示边界。居中显示。fitStart同上。但不居中，和显示边界左上对齐。fitEnd同fitCenter，但不居中，和显示边界右下对齐。fitXY不保存宽高比，填充满显示边界。none如要使用tile mode显示, 需要设置为none

这些缩放类型和Android ImageView 支持的缩放类型几乎一样.

图片默认是centerCrop,那么在用一个横向的SimpleDraweeView来显示一张竖着拍的人像时,就很可能把人的头部给截掉了,但对于在listview中展示的SimpleDraweeView来说,我们又无法用focusCrop直接指定其居中点在图片上半部分某个地方,因为其他图片可能是横着拍的或很正方形的自拍,这个时候怎么办?就需要根据人脸的检测来设置focusCrop的那个点了,而android从sdk 1.0开始就已经提供了一个人脸识别的类FaceDetector,原理是通过找眼睛来识别人脸,可以拿到眼睛的中心点坐标,那么根据该坐标,结合图片本身的宽高,计算出针对每张图片的focusCrop 需要设置的点,就能够解决这个问题了.

//todo 这个还没有去写方法,但有一个开源项目facecropper可以参考,他们的做法是将一个大的bitmap截图成小的bitmap. 同样的代码还有中文注释版的,汗…

获取缓存的图片文件

对于内存的缓存,fresco根据图片Uri,以及图片的resising参数和processor参数综合生成缓存key来缓存bitmap,而磁盘文件缓存则是只根据Uri生成key,那么,如果要获取文件缓存,只需要知道uri和通过key取file的api就行了,原先的调用链较长,故封装成单个方法:

需要注意的是文件名后缀不是普通的图片后缀(.jpg之类的),而是.cnt,但都是二进制文件,可以将文件直接拷贝到指定路径重命名成正常图片后缀即可.当然如果只是读取到内存做其他用途,可以直接读取,无需拷贝更改后缀,不影响使用.

以下是读取缓存文件的方法.而拷贝到其他文件目录的方法也已封装好于FrescoUtils中.

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> File <span class="hljs-title" style="box-sizing: border-box;">getFileFromDiskCache</span>(String url){        File localFile = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>;        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!TextUtils.isEmpty(url)) {            CacheKey cacheKey = DefaultCacheKeyFactory.getInstance().getEncodedCacheKey(ImageRequest.fromUri(url));            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (ImagePipelineFactory.getInstance().getMainFileCache().hasKey(cacheKey)) {                BinaryResource resource = ImagePipelineFactory.getInstance().getMainFileCache().getResource(cacheKey);                localFile = ((FileBinaryResource) resource).getFile();            } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (ImagePipelineFactory.getInstance().getSmallImageFileCache().hasKey(cacheKey)) {                BinaryResource resource = ImagePipelineFactory.getInstance().getSmallImageFileCache().getResource(cacheKey);                localFile = ((FileBinaryResource) resource).getFile();            }        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> localFile;    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>

如果我想用fresco来下载图片,不需要显示,要怎么实现?

首先,如果是单纯的下载,建议使用专门的文件下载框架FileDownloader

如果非要用fresco,那么需要绕一点弯:

通过imagePipeline.prefetchToDiskCache将图片缓存到disk,然后拷贝出来.缓存完成的监听采用fresco提供的BaseDataSubscriber,在文件缓存完成后回调,然后拷贝文件到指定目录.

注意:该方式不是很好用,偶尔会有失败的情况出现.

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 文件下载到文件夹中：将图片缓存到本地后，将缓存的图片文件copy到另一个文件夹中     *     * 容易发生如下异常，progress在100处停留时间长     * dalvikvm: Could not find method android.graphics.Bitmap.getAllocationByteCount,     * referenced from method com.facebook.imageutils.BitmapUtil.getSizeInBytes     06-21 16:15:39.547 3043-3244/com.hss01248.tools W/dalvikvm: VFY:     unable to resolve virtual method 569: Landroid/graphics/Bitmap;.getAllocationByteCount ()I     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> url     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> context     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> dir 保存图片的文件夹     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> listener 自己定义的回调     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">download</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> String url, Context context, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> File dir, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> DownloadListener listener){        ImageRequest imageRequest = ImageRequestBuilder.newBuilderWithSource(Uri.parse(url))                .build();        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ImagePipeline imagePipeline = Fresco.getImagePipeline();        DataSource<Void> dataSource = imagePipeline.prefetchToDiskCache(imageRequest, context, Priority.HIGH);        dataSource.subscribe(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BaseDataSubscriber<Void>() {            <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onNewResultImpl</span>(DataSource<Void> dataSource) {              File  file  =   copyCacheFileToDir(url,dir);                clearCacheByUrl(url);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//清除缓存</span>                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (file == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> || !file.exists()){                    listener.onFail();                }<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {                    listener.onSuccess(file);                }            }            <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onProgressUpdate</span>(DataSource<Void> dataSource) {                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onProgressUpdate(dataSource);                listener.onProgress(dataSource.getProgress());            }            <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onFailureImpl</span>(DataSource<Void> dataSource) {                listener.onFail();            }        }, CallerThreadExecutor.getInstance());    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li></ul>

由于某种原因无法使用SimpleDraweeView来显示图片(比如说弹幕上显示头像),而需要直接操作bitmap,那么要怎么拿到url返回的bitmap?

自己构建图片请求,然后类似上面的文件下载,还是采用DataSubscriber来监听回调,只不过返回的不是void,而是CloseableImage的bitmap,

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 拿到指定宽高，并经过Processor处理的bitmap     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> url     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> context     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> width     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> height     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> processor 后处理器,可为null     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> listener     *     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">getBitmapWithProcessor</span>(String url, Context context, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> width, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> height,                                              BasePostprocessor processor,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> BitmapListener listener){        ResizeOptions resizeOptions = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>;        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (width !=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> && height != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> ){            resizeOptions = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ResizeOptions(width, height);        }        ImageRequest imageRequest = ImageRequestBuilder.newBuilderWithSource(Uri.parse(url))                .setProgressiveRenderingEnabled(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>)           <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//我们是拿bitmap对象,不是显示,所以这里不需要渐进渲染</span>                .setPostprocessor(processor)                .setResizeOptions(resizeOptions)                .build();        ImagePipeline imagePipeline = Fresco.getImagePipeline();        DataSource<CloseableReference<CloseableImage>> dataSource = imagePipeline.fetchDecodedImage(imageRequest, context);        dataSource.subscribe(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BaseBitmapDataSubscriber() {            <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onNewResultImpl</span>(Bitmap bitmap) {                listener.onSuccess(bitmap);            }            <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onFailureImpl</span>(DataSource<CloseableReference<CloseableImage>> dataSource) {                listener.onFail();            }        }, CallerThreadExecutor.getInstance());    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li></ul>

注意,此bitmap对象的缓存由Fresco管理,所以不要去调用bitmap.recycle()之类的方法.

对此bitmap的一些处理,如果处理后的bitmap对象还是指向该bitmap引用,会影响到其他同样url,width height,并且同样Postprocessor的图片组件的显示,比如,将该bitmap高斯模糊了,就会影响到其他的这四个参数相同的SimpleDraweeView的显示.

那么,如果要不影响,怎么办?很简单,让四个参数任一一个不同就行.

Fresco中在listview之类的快速滑动时停止加载,滑动停止后恢复加载时调用的API是什么?

话不多说,直接看代码.

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 暂停网络请求     * 在listview快速滑动时使用     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">pause</span>(){        Fresco.getImagePipeline().pause();    }    <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 恢复网络请求     * 当滑动停止时使用     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">resume</span>(){        Fresco.getImagePipeline().resume();    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>

gif图片无法显示成圆形,怎么办?(当然有的情况下,jpg也无法显示圆形) –加一层和图片的parentview 背景色一样的圆形遮罩即可:

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setCircle</span>( SimpleDraweeView draweeView,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> bgColor){        RoundingParams roundingParams = RoundingParams.asCircle();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//这个方法在某些情况下无法成圆,比如gif</span>        roundingParams.setOverlayColor(bgColor);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//加一层遮罩,这个是关键方法</span>        draweeView.getHierarchy().setRoundingParams(roundingParams);    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

当然,无法圆角化,也是同样加一层遮罩:

很多app都有清除磁盘缓存的功能,那么fresco怎么清除缓存呢?

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 清除磁盘缓存     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">clearDiskCache</span>(){        Fresco.getImagePipeline().clearDiskCaches();    }    <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 清除单张图片的磁盘缓存     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> url     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">clearCacheByUrl</span>(String url){        ImagePipeline imagePipeline = Fresco.getImagePipeline();        Uri uri = Uri.parse(url);       <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// imagePipeline.evictFromMemoryCache(uri);</span>        imagePipeline.evictFromDiskCache(uri);        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//imagePipeline.evictFromCache(uri);//这个包含了从内存移除和从硬盘移除</span>    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul>

已经设置了downsampling和resize,但是加载很大的gif图还是很卡,怎么办

gif是一帧一帧的图组成,编码的方式跟jpg和png等图片有很大区别,downsampling和resize对gif是无效的.gif图太大了?

分辨率一大的话,那文件不得十几M几十M?下载都要等很久吧?

还是在服务器端放小一点的图吧…

高斯模糊

高斯模糊是app里设置一些背景效果常用到的手段.

在fresco中,可以通过postprocessor来实现,也可以自己拿到bitmap后将bitmap模糊化后设置到ImageView或SimpleDraweeView(这个不建议,会消除掉SimpleDraweeView的层级结构,变成单纯的ImageView)上.

推荐前一种: 用到别人封装好的BlurPostprocessor :

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">    <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 高斯模糊后显示     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> url     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> draweeView     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> width draweeView的宽     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> height draweeView的高     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> context     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> radius  高斯模糊的半径, 每一个像素都取周边(多少个)像素的平均值     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> sampling 采样率 原本是设置到BlurPostprocessor上的,因为高斯模糊本身对图片清晰度要求就不高,     *                 所以此处直接设置到ResizeOptions上,直接让解码生成的bitmap就缩小,而BlurPostprocessor     *                 内部sampling设置为1,无需再缩     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">loadUrlInBlur</span>(String url,SimpleDraweeView draweeView,                                     <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> width,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> height,Context context,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> radius,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> sampling){        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (sampling<<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>){            sampling = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>;        }        loadUrl(url,draweeView,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BlurPostprocessor(context,radius,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>),width/sampling,height/sampling,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>);    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li></ul>

当然,拿到bitmap自己去模糊也有开源框架:NativeStackBlur

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Bitmap <span class="hljs-title" style="box-sizing: border-box;">fastBlur</span>(Bitmap bkg, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> radius,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> downSampling) {        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (downSampling < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>){            downSampling = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>;        }        Bitmap smallBitmap =   Bitmap.createScaledBitmap(bkg,bkg.getWidth()/downSampling,bkg.getHeight()/downSampling,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>);        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>   NativeStackBlur.process(smallBitmap, radius);    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

也可以通过这个方法来封装自己的BlurPostprocessor,具体可参考上面封装好的BlurPostprocessor.

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