Android中关于内部存储的一些重要函数

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。
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 ()

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.

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)
  • import android.app.Activity;
  • import android.content.Context;
  • import android.os.Bundle;
  • import android.util.Log;
  • public class MainActivity extends Activity {
  • final static String TAG="robin";
  • /** Called when the activity is first created. */
  • @Override
  • public void onCreate(Bundle savedInstanceState) {
  • super.onCreate(savedInstanceState);
  • setContentView(R.layout.main);
  • Context context=this;
  • String path=context.getCacheDir().getAbsolutePath();
  • Log.i(TAG,"path:"+path);
  • }
  • }
  • path:/data/data/com.lenovo/cache

public abstract File getDir (String name,
int mode)

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.

:参数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

name

Name of the directory to retrieve. This is a directory that is created as part of your application data.
mode Operating 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
String FILENAME = "hello_file";
String string = "hello world!";
FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_WORLD_READABLE);
fos.write(string.getBytes());
fos.close();
示例6
String FILENAME = "hello_file";
String string = "hello world!";
FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_WORLD_READABLE);
fos.write(string.getBytes());
fos.close();
示例7
String FILENAME = "hello_file";
String string = "hello world!";
FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_APPEND|Context.MODE_WORLD_READABLE;
fos.write(string.getBytes());
fos.close();

public abstract boolean deleteFile (String name)

API Level 1

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

Parameters

name

The name of the file to delete; can not contain path separators.
Returns
  • True if the file was successfully deleted; else false.

public abstract String[] fileList ()

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.
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 ()

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。

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