程序博客网 > 专业淘宝拍摄

Android中关于内部存储的一些重要函数

来源：互联网 发布：专业淘宝拍摄 编辑：程序博客网 时间：2024/05/01 13:53
From: http://blog.csdn.net/hudashi/article/details/8037076
一、简介
Android中，你也可以通过绝对路径以JAVA传统方式访问内部存储空间。但是以这种方式创建的文件是对私有，创建它的应用程序对该文件是可读可写，但是别的应用程序并不能直接访问它。不是所有的内部存储空间应用程序都可以访问，默认情况下只能访问“/data/data/你的应用程序的包名”这个路径下的文件。
Android中，你还可以使用Context对象的openFileOutput()和openFileInput()来进行数据持久化存储的这种方式，你的数据文件将存储在内部存储空间的/data/data/你的应用程序的包名/files/目录下，无法指定更深一级的目录，而且默认是Context.MODE_PRIVATE模式，即别的应用程序不能访问它。你可以使用openFileOutput()的int mode参数来让别的应用程序也能访问你的文件。
注意：保存在/data/data/你的应用程序的包名目录中文件，会在卸载你的应用程序时被删除掉。
 二、Context中关于内部存储的重要函数 

public abstract File getCacheDir ()

Since: API Level 1

Returns the absolute path to the application specific cache directory on the filesystem. These files will be ones that get deleted first when the device runs low on storage. There is no guarantee when these files will be deleted. Note: you should not rely on the system deleting these files for you; you should always have a reasonable maximum, such as 1 MB, for the amount of space you consume with cache files, and prune those files when exceeding that space.

该目录主要用于存放缓存文件，当系统的内存存储空间紧张时，该目录下的文件会被删除掉。关于这些文件究竟会在存储空间剩余多少的情况，没有严格的标准保障。
注意：你不应该依赖系统来清理这些缓存文件，你应该对这些缓存文件占用的最大存储空间设定个最大值，比如是1M，当实际占用空间超过这个值时，你应该对这些缓存文件做相应的清理工作（prune）。
Returns
  • Returns the path of the directory holding application cache files.
See Also
  • openFileOutput(String, int)
  • getFileStreamPath(String)
  • getDir(String, int)
  • 示例1

  • <li style="margin:0px 0px 4px"><span style=""><span class="kwd" style="color:#0088;">import</span><span class="pln"> android</span><span class="pun" style="color:#66660;">.</span><span class="pln">app</span><span class="pun" style="color:#66660;">.</span><span class="typ" style="color:#66066;">Activity</span><span class="pun" style="color:#66660;">;</span></span></li><li style="margin:0px 0px 4px"><span class="kwd" style="color:#0088;">import</span><span class="pln"> android</span><span class="pun" style="color:#66660;">.</span><span class="pln">content</span><span class="pun" style="color:#66660;">.</span><span class="typ" style="color:#66066;">Context</span><span class="pun" style="color:#66660;">;</span></li><li style="margin:0px 0px 4px"><span class="kwd" style="color:#0088;">import</span><span class="pln"> android</span><span class="pun" style="color:#66660;">.</span><span class="pln">os</span><span class="pun" style="color:#66660;">.</span><span class="typ" style="color:#66066;">Bundle</span><span class="pun" style="color:#66660;">;</span></li><li style="margin:0px 0px 4px"><span class="kwd" style="color:#0088;">import</span><span class="pln"> android</span><span class="pun" style="color:#66660;">.</span><span class="pln">util</span><span class="pun" style="color:#66660;">.</span><span class="typ" style="color:#66066;">Log</span><span class="pun" style="color:#66660;">;</span></li><li style="margin:0px 0px 4px"></li><li style="margin:0px 0px 4px"><span class="kwd" style="color:#0088;">public</span><span class="pln"> </span><span class="kwd" style="color:#0088;">class</span><span class="pln"> </span><span class="typ" style="color:#66066;">MainActivity</span><span class="pln"> </span><span class="kwd" style="color:#0088;">extends</span><span class="pln"> </span><span class="typ" style="color:#66066;">Activity</span><span class="pln"> </span><span class="pun" style="color:#66660;">{</span></li><li style="margin:0px 0px 4px"><span class="pln"> </span><span class="kwd" style="color:#0088;">final</span><span class="pln"> </span><span class="kwd" style="color:#0088;">static</span><span class="pln"> </span><span class="typ" style="color:#66066;">String</span><span class="pln"> TAG</span><span class="pun" style="color:#66660;">=</span><span class="str" style="color:#0880;">"robin"</span><span class="pun" style="color:#66660;">;</span></li><li style="margin:0px 0px 4px"><span class="pln">    </span><span class="com" style="color:#8800;">/** Called when the activity is first created. */</span></li><li style="margin:0px 0px 4px"><span class="pln">    </span><span class="lit" style="color:#06666;">@Override</span></li><li style="margin:0px 0px 4px"><span class="pln">    </span><span class="kwd" style="color:#0088;">public</span><span class="pln"> </span><span class="kwd" style="color:#0088;">void</span><span class="pln"> onCreate</span><span class="pun" style="color:#66660;">(</span><span class="typ" style="color:#66066;">Bundle</span><span class="pln"> savedInstanceState</span><span class="pun" style="color:#66660;">)</span><span class="pln"> </span><span class="pun" style="color:#66660;">{</span></li><li style="margin:0px 0px 4px"><span class="pln">        </span><span class="kwd" style="color:#0088;">super</span><span class="pun" style="color:#66660;">.</span><span class="pln">onCreate</span><span class="pun" style="color:#66660;">(</span><span class="pln">savedInstanceState</span><span class="pun" style="color:#66660;">);</span></li><li style="margin:0px 0px 4px"><span class="pln">        setContentView</span><span class="pun" style="color:#66660;">(</span><span class="pln">R</span><span class="pun" style="color:#66660;">.</span><span class="pln">layout</span><span class="pun" style="color:#66660;">.</span><span class="pln">main</span><span class="pun" style="color:#66660;">);</span></li><li style="margin:0px 0px 4px"><span class="pln">        </span><span class="typ" style="color:#66066;">Context</span><span class="pln"> context</span><span class="pun" style="color:#66660;">=</span><span class="kwd" style="color:#0088;">this</span><span class="pun" style="color:#66660;">;</span></li><li style="margin:0px 0px 4px"><span class="pln">        </span><span class="typ" style="color:#66066;">String</span><span class="pln"> path</span><span class="pun" style="color:#66660;">=</span><span class="pln">context</span><span class="pun" style="color:#66660;">.</span><span class="pln">getCacheDir</span><span class="pun" style="color:#66660;">().</span><span class="pln">getAbsolutePath</span><span class="pun" style="color:#66660;">();</span></li><li style="margin:0px 0px 4px"><span class="pln">        </span><span class="typ" style="color:#66066;">Log</span><span class="pun" style="color:#66660;">.</span><span class="pln">i</span><span class="pun" style="color:#66660;">(</span><span class="pln">TAG</span><span class="pun" style="color:#66660;">,</span><span class="str" style="color:#0880;">"path:"</span><span class="pun" style="color:#66660;">+</span><span class="pln">path</span><span class="pun" style="color:#66660;">);</span></li><li style="margin:0px 0px 4px"><span class="pln">    </span><span class="pun" style="color:#66660;">}</span></li><li style="margin:0px 0px 4px"><span class="pun" style="color:#66660;">}</span></li>
  • 运行结果

  • 10-01 14:57:52.296: I/robin(7835): path:/data/data/com.lenovo/cache

public abstract File getDir (String name, int mode)

Since: API Level 1

Retrieve, creating if needed, a new directory in which the application can place its own custom data files. You can use the returned File object to create and access files in this directory. Note that files created through a File object will only be accessible by your own application; you can only set the mode of the entire directory, not of individual files.

该函数主要用于得到一个文件夹的句柄，并通过该句柄创建和访问外文件夹。
注意：参数int mode是指文件夹的访问权限而并不包括其子文件夹和文件的访问权限
Parameters
nameName of the directory to retrieve. This is a directory that is created as part of your application data.modeOperating mode. Use 0 or MODE_PRIVATE for the default operation, MODE_WORLD_READABLE and MODE_WORLD_WRITEABLE to control permissions.
Returns
  • Returns a File object for the requested directory. The directory will have been created if it does not already exist.
See Also
  • openFileOutput(String, int)
  • 示例2

  • <li style="margin:0px 0px 4px"><span class="pln">        </span><span class="typ" style="color:#66066;">File</span><span class="pln"> file</span><span class="pun" style="color:#66660;">=</span><span class="pln">context</span><span class="pun" style="color:#66660;">.</span><span class="pln">getDir</span><span class="pun" style="color:#66660;">(</span><span class="str" style="color:#0880;">"download"</span><span class="pun" style="color:#66660;">,</span><span class="pln"> </span><span class="typ" style="color:#66066;">Context</span><span class="pun" style="color:#66660;">.</span><span class="pln">MODE_PRIVATE</span><span class="pun" style="color:#66660;">);</span></li><li style="margin:0px 0px 4px"><span class="pln">        </span><span class="typ" style="color:#66066;">String</span><span class="pln"> path</span><span class="pun" style="color:#66660;">=</span><span class="pln">file</span><span class="pun" style="color:#66660;">.</span><span class="pln">getAbsolutePath</span><span class="pun" style="color:#66660;">();</span></li><li style="margin:0px 0px 4px"><span class="pln">        </span><span class="typ" style="color:#66066;">Log</span><span class="pun" style="color:#66660;">.</span><span class="pln">i</span><span class="pun" style="color:#66660;">(</span><span class="pln">TAG</span><span class="pun" style="color:#66660;">,</span><span class="str" style="color:#0880;">"path:"</span><span class="pun" style="color:#66660;">+</span><span class="pln">path</span><span class="pun" style="color:#66660;">);</span></li>
  • 运行结果

  • 10-02 08:56:49.278: I/robin(12055): path:/data/data/com.lenovo/app_download

public abstract File getFileStreamPath (String name)

Since: API Level 1

Returns the absolute path on the filesystem where a file created with openFileOutput(String, int) is stored.

Parameters
nameThe name of the file for which you would like to get its path.
Returns
  • Returns an absolute path to the given file.
See Also
  • openFileOutput(String, int)
  • getFilesDir()
  • getDir(String, int)
  • 示例3

  • <li style="margin:0px 0px 4px"><span class="pln">        </span><span class="typ" style="color:#66066;">File</span><span class="pln"> file</span><span class="pun" style="color:#66660;">=</span><span class="pln">context</span><span class="pun" style="color:#66660;">.</span><span class="pln">getFileStreamPath</span><span class="pun" style="color:#66660;">(</span><span class="str" style="color:#0880;">"download"</span><span class="pun" style="color:#66660;">);</span></li><li style="margin:0px 0px 4px"><span class="pln">        </span><span class="typ" style="color:#66066;">String</span><span class="pln"> path</span><span class="pun" style="color:#66660;">=</span><span class="pln">file</span><span class="pun" style="color:#66660;">.</span><span class="pln">getAbsolutePath</span><span class="pun" style="color:#66660;">();</span></li><li style="margin:0px 0px 4px"><span class="pln">        </span><span class="typ" style="color:#66066;">Log</span><span class="pun" style="color:#66660;">.</span><span class="pln">i</span><span class="pun" style="color:#66660;">(</span><span class="pln">TAG</span><span class="pun" style="color:#66660;">,</span><span class="str" style="color:#0880;">"path:"</span><span class="pun" style="color:#66660;">+</span><span class="pln">path</span><span class="pun" style="color:#66660;">);</span></li>
  • 运行结果
  • 10-02 09:17:55.913: I/robin(12507): path:/data/data/com.lenovo/files/download

public abstract File getFilesDir ()

Since: API Level 1

Returns the absolute path to the directory on the filesystem where files created with openFileOutput(String, int) are stored.

Returns
  • Returns the path of the directory holding application files.
See Also
  • openFileOutput(String, int)
  • getFileStreamPath(String)
  • getDir(String, int)
示例4
<div><span class="pln">        </span><span class="typ" style="color:#66066;">File</span><span class="pln"> file</span><span class="pun" style="color:#66660;">=</span><span class="pln">context</span><span class="pun" style="color:#66660;">.</span><span class="pln">getFilesDir</span><span class="pun" style="color:#66660;">();</span></div><div><span class="pln">        </span><span class="typ" style="color:#66066;">String</span><span class="pln"> path</span><span class="pun" style="color:#66660;">=</span><span class="pln">file</span><span class="pun" style="color:#66660;">.</span><span class="pln">getAbsolutePath</span><span class="pun" style="color:#66660;">();</span></div><div><span class="pln">        </span><span class="typ" style="color:#66066;">Log</span><span class="pun" style="color:#66660;">.</span><span class="pln">i</span><span class="pun" style="color:#66660;">(</span><span class="pln">TAG</span><span class="pun" style="color:#66660;">,</span><span class="str" style="color:#0880;">"path:"</span><span class="pun" style="color:#66660;">+</span><span class="pln">path</span><span class="pun" style="color:#66660;">);</span></div>
运行结果
10-02 09:15:11.102: I/robin(12359): path:/data/data/com.lenovo/files

public abstract FileInputStream openFileInput (String name)

Since: API Level 1

Open a private file associated with this Context's application package for reading.

Parameters
nameThe name of the file to open; can not contain path separators.
Returns
  • FileInputStream Resulting input stream.
Throws
FileNotFoundException 
See Also
  • openFileOutput(String, int)
  • fileList()
  • deleteFile(String)
  • FileInputStream(String)

public abstract FileOutputStream openFileOutput (String name, int mode)

Since: API Level 1

Open a private file associated with this Context's application package for writing. Creates the file if it doesn't already exist.

Parameters
nameThe name of the file to open; can not contain path separators.modeOperating mode. Use 0 or MODE_PRIVATE for the default operation, MODE_APPEND to append to an existing file, MODE_WORLD_READABLE and MODE_WORLD_WRITEABLE to control permissions.
Returns
  • FileOutputStream Resulting output stream.
Throws
FileNotFoundException 
See Also
  • MODE_APPEND 表示写文件时是追加模式，即从文件末开始写数据
  • MODE_PRIVATE
  • MODE_WORLD_READABLE
  • MODE_WORLD_WRITEABLE
  • openFileInput(String)
  • fileList()
  • deleteFile(String)
  • FileOutputStream(String)
示例5
<div><span class="typ" style="color:#66066;">String</span><span class="pln"> FILENAME </span><span class="pun" style="color:#66660;">=</span><span class="pln"> </span><span class="str" style="color:#0880;">"hello_file"</span><span class="pun" style="color:#66660;">;</span></div><div><span class="typ" style="color:#66066;">String</span><span class="pln"> </span><span class="kwd" style="color:#0088;">string</span><span class="pln"> </span><span class="pun" style="color:#66660;">=</span><span class="pln"> </span><span class="str" style="color:#0880;">"hello world!"</span><span class="pun" style="color:#66660;">;</span></div><div><span class="typ" style="color:#66066;">FileOutputStream</span><span class="pln"> fos </span><span class="pun" style="color:#66660;">=</span><span class="pln"> openFileOutput</span><span class="pun" style="color:#66660;">(</span><span class="pln">FILENAME</span><span class="pun" style="color:#66660;">,</span><span class="pln"> </span><span class="typ" style="color:#66066;">Context</span><span class="pun" style="color:#66660;">.</span><span class="pln">MODE_WORLD_READABLE</span><span class="pun" style="color:#66660;">);</span></div><div><span class="pln">fos</span><span class="pun" style="color:#66660;">.</span><span class="pln">write</span><span class="pun" style="color:#66660;">(</span><span class="kwd" style="color:#0088;">string</span><span class="pun" style="color:#66660;">.</span><span class="pln">getBytes</span><span class="pun" style="color:#66660;">());</span></div><div><span class="pln">fos</span><span class="pun" style="color:#66660;">.</span><span class="pln">close</span><span class="pun" style="color:#66660;">();</span></div>
示例6
<div><span class="typ" style="color:#66066;">String</span><span class="pln"> FILENAME </span><span class="pun" style="color:#66660;">=</span><span class="pln"> </span><span class="str" style="color:#0880;">"hello_file"</span><span class="pun" style="color:#66660;">;</span></div><div><span class="typ" style="color:#66066;">String</span><span class="pln"> </span><span class="kwd" style="color:#0088;">string</span><span class="pln"> </span><span class="pun" style="color:#66660;">=</span><span class="pln"> </span><span class="str" style="color:#0880;">"hello world!"</span><span class="pun" style="color:#66660;">;</span></div><div><span class="typ" style="color:#66066;">FileOutputStream</span><span class="pln"> fos </span><span class="pun" style="color:#66660;">=</span><span class="pln"> openFileOutput</span><span class="pun" style="color:#66660;">(</span><span class="pln">FILENAME</span><span class="pun" style="color:#66660;">,</span><span class="pln"> </span><span class="typ" style="color:#66066;">Context</span><span class="pun" style="color:#66660;">.</span><span class="pln">MODE_WORLD_READABLE</span><span class="pun" style="color:#66660;">);</span></div><div><span class="pln">fos</span><span class="pun" style="color:#66660;">.</span><span class="pln">write</span><span class="pun" style="color:#66660;">(</span><span class="kwd" style="color:#0088;">string</span><span class="pun" style="color:#66660;">.</span><span class="pln">getBytes</span><span class="pun" style="color:#66660;">());</span></div><div><span class="pln">fos</span><span class="pun" style="color:#66660;">.</span><span class="pln">close</span><span class="pun" style="color:#66660;">();</span></div>
示例7
<div><span class="typ" style="color:#66066;">String</span><span class="pln"> FILENAME </span><span class="pun" style="color:#66660;">=</span><span class="pln"> </span><span class="str" style="color:#0880;">"hello_file"</span><span class="pun" style="color:#66660;">;</span></div><div><span class="typ" style="color:#66066;">String</span><span class="pln"> </span><span class="kwd" style="color:#0088;">string</span><span class="pln"> </span><span class="pun" style="color:#66660;">=</span><span class="pln"> </span><span class="str" style="color:#0880;">"hello world!"</span><span class="pun" style="color:#66660;">;</span></div><div><span class="typ" style="color:#66066;">FileOutputStream</span><span class="pln"> fos </span><span class="pun" style="color:#66660;">=</span><span class="pln"> openFileOutput</span><span class="pun" style="color:#66660;">(</span><span class="pln">FILENAME</span><span class="pun" style="color:#66660;">,</span><span class="pln"> </span><span class="typ" style="color:#66066;">Context</span><span class="pun" style="color:#66660;">.</span><span class="pln">MODE_APPEND</span><span class="pun" style="color:#66660;">|</span><span class="typ" style="color:#66066;">Context</span><span class="pun" style="color:#66660;">.</span><span class="pln">MODE_WORLD_READABLE</span><span class="pun" style="color:#66660;">;</span></div><div><span class="pln">fos</span><span class="pun" style="color:#66660;">.</span><span class="pln">write</span><span class="pun" style="color:#66660;">(</span><span class="kwd" style="color:#0088;">string</span><span class="pun" style="color:#66660;">.</span><span class="pln">getBytes</span><span class="pun" style="color:#66660;">());</span></div><div><span class="pln">fos</span><span class="pun" style="color:#66660;">.</span><span class="pln">close</span><span class="pun" style="color:#66660;">();</span></div>

public abstract boolean deleteFile (String name)

Since: API Level 1

Delete the given private file associated with this Context's application package.

Parameters
nameThe name of the file to delete; can not contain path separators.
Returns
  • True if the file was successfully deleted; else false.
See Also
  • openFileInput(String)
  • openFileOutput(String, int)
  • fileList()
  • delete()

public abstract String[] fileList ()

Since: API Level 1

Returns an array of strings naming the private files associated with this Context's application package.

Returns
  • Array of strings naming the private files.
See Also
  • openFileInput(String)
  • openFileOutput(String, int)
  • deleteFile(String)
三、Environment中关于内存部存储的重要函数

public static File getDataDirectory ()

Since: API Level 1

Gets the Android data directory.

用File返回数据文件的根目录，返回的文件的路径为“/data”。该目录下的文件是只读。应用程序无法对该目录下的文件进行写操作。

public static File getDownloadCacheDirectory ()

Since: API Level 1

Gets the Android Download/Cache content directory.

用File返回缓存文件的根目录，返回的文件的路径为“/cache”。对于第三方应用程序。该目录下的文件是只读。第三方应用程序无法对该目录下的文件进行写操作。

public static File getRootDirectory ()

Since: API Level 1

Gets the Android root directory.

用File返回Android系统文件的根目录，返回的文件的路径为“/system”。该目录下的文件是只读。应用程序无法对该目录下的文件进行写操作。

结束


0 0
专业淘宝拍摄 专业淘宝拍摄
原创粉丝点击
热门IT博客
15寸是多少厘米 mac15寸是多少厘米 mac
displaycal macdisplaycal mac
淘宝四件套什么牌子好
艾德思奇软件
淘宝买ipad知乎
郑州淘宝运营培训
下载软件creo2.0
驾校模拟开车软件
小米3怎么设置3g网络
菜鸟网络到底做什么
豆瓣阅读知乎
超过usb3.0端口数限制
ubuntu 中文字体
雅坊美工14 在线生成
mac迅雷会员无法加速
js input上传文件
淘宝号怎么解绑手机号
岑春煊 知乎
网络部招新面试问题
阿里云虚拟主机修改php
热门问题 老师的惩罚 人脸识别 我在镇武司摸鱼那些年 重生之率土为王 我在大康的咸鱼生活 盘龙之生命进化 天生仙种 凡人之先天五行 春回大明朝 姑娘不必设防，我是瞎子 迟阳 迟阳 如是非迎 迟顿的意思 岁月迢迢 迢迢 月升迢迢 修仙路迢迢 路远迢迢 山水迢迢 银汉迢迢 山也迢迢水也迢迢 迢迢新秋夕 千里迢迢的意思 千里迢迢意思 青山隐隐水迢迢 银汉迢迢暗度 双鲤迢迢一纸书 星河迢迢只为你 千里迢迢拼音 致岁月迢迢全文阅读 星河迢迢只见你免费阅读 致岁月迢迢txt 千里迢迢的拼音 宠妻路迢迢 蛋糕女王 千里迢迢的意思是什么 致岁月迢迢 绿亦歌 山水迢迢歌词 我的大唐公主殿下 幕云迢迢 无良闺秀之田园神医 浮绿迢迢 迢递 迤逦 迤逦怎么读 迤逦读音 迤逦意思 迤逦的意思 迤逦的拼音 迤逦是什么意思 迥 迥立 迥怎么读 迥组词

程序博客网，程序员的互联网技术博客家园。csdn论坛精品 msdn技术资料都在这里