Android 使用Picasso加载网络图片等比例缩放

转自：http://blog.csdn.net/picasso_l/article/details/50679177

最近做项目，要下载图片到本地（不是指缓存），之前用过HttpURLConnection和HttpCLient，但是感觉太繁琐，而且6.0之后到Apache包也不支持了，后来我想到了Picasso的缓存，Picasso缓存图片，那肯定是下载到本地实现了，我们只要更改下本地路径，就能轻松实现了。

废话不多说，直接上代码了。

private void download() {        //获得图片的地址        String url = mList.get(mPosition);        //Target        Target target = new Target(){            @Override            public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {                String imageName = System.currentTimeMillis() + ".png";                File dcimFile = FileUtil                        .getDCIMFile(FileUtil.PATH_PHOTOGRAPH,imageName);                LogCat.i("bitmap="+bitmap);                FileOutputStream ostream = null;                try {                    ostream = new FileOutputStream(dcimFile);                    bitmap.compress(Bitmap.CompressFormat.PNG, 100, ostream);                    ostream.close();                } catch (Exception e) {                    e.printStackTrace();                }                Toast.makeText(PicActivity.this,"图片下载至:"+dcimFile,Toast.LENGTH_SHORT).show();            }            @Override            public void onBitmapFailed(Drawable errorDrawable) {            }            @Override            public void onPrepareLoad(Drawable placeHolderDrawable) {            }        };        //Picasso下载        Picasso.with(this).load(url).into(target);    }

应网友要求，贴出FileUtil代码：


public class FileUtil {    /**     * 拍照路径     */    private static String FILE_NAME = "userIcon.jpg";    public static String PATH_PHOTOGRAPH = "/LXT/";    private static boolean isExternalStorageWritable() {        String state = Environment.getExternalStorageState();        return Environment.MEDIA_MOUNTED.equals(state);    }    public static File getAvailableCacheDir() {        if (isExternalStorageWritable()) {            return App.app.getExternalCacheDir();        } else {            return App.app.getCacheDir();        }    }    public static String getAvatarCropPath() {        return new File(getAvailableCacheDir(), FILE_NAME).getAbsolutePath();    }    public static String getPublishPath(String fileName) {        return new File(getAvailableCacheDir(), fileName).getAbsolutePath();    }    /**     * 保存图片     *     * @param bitmap     * @param filePath     */    public static void saveBitmap(Bitmap bitmap, String filePath) {        FileOutputStream bos = null;        File file = new File(filePath);        if (!file.getParentFile().exists()) {            file.getParentFile().mkdirs();        }        try {            bos = new FileOutputStream(file);            bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);        } catch (FileNotFoundException e) {            e.printStackTrace();        } finally {            try {                bos.flush();                bos.close();            } catch (IOException e) {                e.printStackTrace();            }        }    }    public static void deleteDir(File directory) {        if (directory != null){            if (directory.isFile()) {                directory.delete();                return;            }            if (directory.isDirectory()) {                File[] childFiles = directory.listFiles();                if (childFiles == null || childFiles.length == 0) {                    directory.delete();                    return;                }                for (int i = 0; i < childFiles.length; i++) {                    deleteDir(childFiles[i]);                }                directory.delete();            }        }    }    public static File getDCIMFile(String filePath, String imageName) {        if (Environment.getExternalStorageState().equals(                Environment.MEDIA_MOUNTED)) { // 文件可用            File dirs = new File(Environment.getExternalStorageDirectory(),                    "DCIM"+filePath);            if (!dirs.exists())                dirs.mkdirs();            File file = new File(Environment.getExternalStorageDirectory(),                    "DCIM"+filePath+imageName);            if (!file.exists()) {                try {                    //在指定的文件夹中创建文件                    file.createNewFile();                } catch (Exception e) {                }            }            return file;        } else {            return null;        }    }    public static File saveBitmap2(Bitmap bitmap, String fileName, File baseFile) {        FileOutputStream bos = null;        File imgFile = new File(baseFile, "/" + fileName);        try {            bos = new FileOutputStream(imgFile);            bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);        } catch (FileNotFoundException e) {            e.printStackTrace();        } finally {            try {                bos.flush();                bos.close();            } catch (IOException e) {                e.printStackTrace();            }        }        return imgFile;    }    public static File getBaseFile(String filePath) {        if (Environment.getExternalStorageState().equals(                Environment.MEDIA_MOUNTED)) { // 文件可用            File f = new File(Environment.getExternalStorageDirectory(),                    filePath);            if (!f.exists())                f.mkdirs();            return f;        } else {            return null;        }    }    public static String getFileName() {        String fileName = FILE_NAME ;        return fileName;    }    /**     * 由指定的路径和文件名创建文件     */    public static File createFile(String path, String name) throws IOException {        File folder = new File(path);        if (!folder.exists()) {            folder.mkdirs();        }        File file = new File(path + name);        if (!file.exists()) {            file.createNewFile();        }        return file;    }}

这样就轻松实现了，值得注意的是，我们经常用的是into（ImageView target），其实into还能传入很多不同的对象。今天有点晚了，先写到这，关于Picasso，还是有很多技巧可以探索的。之前还写过一篇Android 使用Picasso加载网络图片等比例缩放的文章，也欢迎大家有空去指点一下。

参考文献：
http://stackoverflow.com/questions/27729976/download-and-save-images-using-picasso