讲述 Environment 类

Public Methods

static File

getDataDirectory()

获得android data的目录。

static File

getDownloadCacheDirectory()

获得下载缓存目录。

static File

getExternalStorageDirectory()

或者外部存储媒体目录。

static File

getExternalStoragePublicDirectory(String type)

Get a top-level public external storage directory for placing files of a particular type.

static String

getExternalStorageState()

获得当前外部储存媒体的状态。

static File

getRootDirectory()

获得android的跟目录。

 

public static File getExternalStoragePublicDirectory (String type)

Since: API Level 8

Get a top-level public external storage directory for placing files of a particular type. This is where the user will typically place and manage their own files, so you should be careful about what you put here to ensure you don't erase their files or get in the way of their own organization.

Here is an example of typical code to manipulate a picture on the public external storage:

<span class="kwd">void</span><span class="pln"> createExternalStoragePublicPicture</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">    </span><span class="com">// Create a path where we will place our picture in the user's</span><span class="pln">    </span><span class="com">// public pictures directory.  Note that you should be careful about</span><span class="pln">    </span><span class="com">// what you place here, since the user often manages these files.  For</span><span class="pln">    </span><span class="com">// pictures and other media owned by the application, consider</span><span class="pln">    </span><span class="com">// Context.getExternalMediaDir().</span><span class="pln">    </span><span class="typ">File</span><span class="pln"> path </span><span class="pun">=</span><span class="pln"> </span><span class="typ">Environment</span><span class="pun">.</span><span class="pln">getExternalStoragePublicDirectory</span><span class="pun">(</span><span class="pln">            </span><span class="typ">Environment</span><span class="pun">.</span><span class="pln">DIRECTORY_PICTURES</span><span class="pun">);</span><span class="pln">    </span><span class="typ">File</span><span class="pln"> file </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">File</span><span class="pun">(</span><span class="pln">path</span><span class="pun">,</span><span class="pln"> </span><span class="str">"DemoPicture.jpg"</span><span class="pun">);</span><span class="pln">    </span><span class="kwd">try</span><span class="pln"> </span><span class="pun">{</span><span class="pln">        </span><span class="com">// Make sure the Pictures directory exists.</span><span class="pln">        path</span><span class="pun">.</span><span class="pln">mkdirs</span><span class="pun">();</span><span class="pln">        </span><span class="com">// Very simple code to copy a picture from the application's</span><span class="pln">        </span><span class="com">// resource into the external file.  Note that this code does</span><span class="pln">        </span><span class="com">// no error checking, and assumes the picture is small (does not</span><span class="pln">        </span><span class="com">// try to copy it in chunks).  Note that if external storage is</span><span class="pln">        </span><span class="com">// not currently mounted this will silently fail.</span><span class="pln">        </span><span class="typ">InputStream</span><span class="pln"> </span><span class="kwd">is</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> getResources</span><span class="pun">().</span><span class="pln">openRawResource</span><span class="pun">(</span><span class="pln">R</span><span class="pun">.</span><span class="pln">drawable</span><span class="pun">.</span><span class="pln">balloons</span><span class="pun">);</span><span class="pln">        </span><span class="typ">OutputStream</span><span class="pln"> os </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">FileOutputStream</span><span class="pun">(</span><span class="pln">file</span><span class="pun">);</span><span class="pln">        </span><span class="kwd">byte</span><span class="pun">[]</span><span class="pln"> data </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="kwd">byte</span><span class="pun">[</span><span class="kwd">is</span><span class="pun">.</span><span class="pln">available</span><span class="pun">()];</span><span class="pln">        </span><span class="kwd">is</span><span class="pun">.</span><span class="pln">read</span><span class="pun">(</span><span class="pln">data</span><span class="pun">);</span><span class="pln">        os</span><span class="pun">.</span><span class="pln">write</span><span class="pun">(</span><span class="pln">data</span><span class="pun">);</span><span class="pln">        </span><span class="kwd">is</span><span class="pun">.</span><span class="pln">close</span><span class="pun">();</span><span class="pln">        os</span><span class="pun">.</span><span class="pln">close</span><span class="pun">();</span><span class="pln">        </span><span class="com">// Tell the media scanner about the new file so that it is // 这一步非常重要！！</span><span class="pln">        </span><span class="com">// immediately available to the user.</span><span class="pln">        </span><span class="typ">MediaScannerConnection</span><span class="pun">.</span><span class="pln">scanFile</span><span class="pun">(</span><span class="kwd">this</span><span class="pun">,</span><span class="pln">                </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">String</span><span class="pun">[]</span><span class="pln"> </span><span class="pun">{</span><span class="pln"> file</span><span class="pun">.</span><span class="pln">toString</span><span class="pun">()</span><span class="pln"> </span><span class="pun">},</span><span class="pln"> </span><span class="kwd">null</span><span class="pun">,</span><span class="pln">                </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">MediaScannerConnection</span><span class="pun">.</span><span class="typ">OnScanCompletedListener</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">            </span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">void</span><span class="pln"> onScanCompleted</span><span class="pun">(</span><span class="typ">String</span><span class="pln"> path</span><span class="pun">,</span><span class="pln"> </span><span class="typ">Uri</span><span class="pln"> uri</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">                </span><span class="typ">Log</span><span class="pun">.</span><span class="pln">i</span><span class="pun">(</span><span class="str">"ExternalStorage"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"Scanned "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> path </span><span class="pun">+</span><span class="pln"> </span><span class="str">":"</span><span class="pun">);</span><span class="pln">                </span><span class="typ">Log</span><span class="pun">.</span><span class="pln">i</span><span class="pun">(</span><span class="str">"ExternalStorage"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"-> uri="</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> uri</span><span class="pun">);</span><span class="pln">            </span><span class="pun">}</span><span class="pln">        </span><span class="pun">});</span><span class="pln">    </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">catch</span><span class="pln"> </span><span class="pun">(</span><span class="typ">IOException</span><span class="pln"> e</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">        </span><span class="com">// Unable to create file, likely because external storage is</span><span class="pln">        </span><span class="com">// not currently mounted.</span><span class="pln">        </span><span class="typ">Log</span><span class="pun">.</span><span class="pln">w</span><span class="pun">(</span><span class="str">"ExternalStorage"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"Error writing "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> file</span><span class="pun">,</span><span class="pln"> e</span><span class="pun">);</span><span class="pln">    </span><span class="pun">}</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">void</span><span class="pln"> deleteExternalStoragePublicPicture</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">    </span><span class="com">// Create a path where we will place our picture in the user's</span><span class="pln">    </span><span class="com">// public pictures directory and delete the file.  If external</span><span class="pln">    </span><span class="com">// storage is not currently mounted this will fail.</span><span class="pln">    </span><span class="typ">File</span><span class="pln"> path </span><span class="pun">=</span><span class="pln"> </span><span class="typ">Environment</span><span class="pun">.</span><span class="pln">getExternalStoragePublicDirectory</span><span class="pun">(</span><span class="pln">            </span><span class="typ">Environment</span><span class="pun">.</span><span class="pln">DIRECTORY_PICTURES</span><span class="pun">);</span><span class="pln">    </span><span class="typ">File</span><span class="pln"> file </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">File</span><span class="pun">(</span><span class="pln">path</span><span class="pun">,</span><span class="pln"> </span><span class="str">"DemoPicture.jpg"</span><span class="pun">);</span><span class="pln">    file</span><span class="pun">.</span><span class="kwd">delete</span><span class="pun">();</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">boolean</span><span class="pln"> hasExternalStoragePublicPicture</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">    </span><span class="com">// Create a path where we will place our picture in the user's</span><span class="pln">    </span><span class="com">// public pictures directory and check if the file exists.  If</span><span class="pln">    </span><span class="com">// external storage is not currently mounted this will think the</span><span class="pln">    </span><span class="com">// picture doesn't exist.</span><span class="pln">    </span><span class="typ">File</span><span class="pln"> path </span><span class="pun">=</span><span class="pln"> </span><span class="typ">Environment</span><span class="pun">.</span><span class="pln">getExternalStoragePublicDirectory</span><span class="pun">(</span><span class="pln">            </span><span class="typ">Environment</span><span class="pun">.</span><span class="pln">DIRECTORY_PICTURES</span><span class="pun">);</span><span class="pln">    </span><span class="typ">File</span><span class="pln"> file </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">File</span><span class="pun">(</span><span class="pln">path</span><span class="pun">,</span><span class="pln"> </span><span class="str">"DemoPicture.jpg"</span><span class="pun">);</span><span class="pln">    </span><span class="kwd">return</span><span class="pln"> file</span><span class="pun">.</span><span class="pln">exists</span><span class="pun">();</span><span class="pln"></span><span class="pun">}</span>

Parameters

typeThe type of storage directory to return. Should be one ofDIRECTORY_MUSIC,DIRECTORY_PODCASTS,DIRECTORY_RINGTONES,DIRECTORY_ALARMS,DIRECTORY_NOTIFICATIONS,DIRECTORY_PICTURES,DIRECTORY_MOVIES,DIRECTORY_DOWNLOADS, orDIRECTORY_DCIM. May not be null.

Returns

• Returns the File path for the directory. Note that this directory may not yet exist, so you must make sure it exists before using it such as withFile.mkdirs().

                                                                                                                                                                                                                            以上内容摘自google android开发文档。

2012-04-06 10:14:19)

转载▼

标签： 

android

 

sd

 

状态

 

大小

分类： 手机世界

1、讲述 Environment 类
Environment 是一个提供访问环境变量的类。Environment 包含常量：
MEDIA_BAD_REMOVAL
解释：返回getExternalStorageState() ，表明SDCard 被卸载前己被移除
MEDIA_CHECKING
解释：返回getExternalStorageState() ，表明对象正在磁盘检查。
MEDIA_MOUNTED
解释：返回getExternalStorageState() ，表明对象是否存在并具有读/写权限
MEDIA_MOUNTED_READ_ONLY
解释：返回getExternalStorageState() ，表明对象权限为只读
MEDIA_NOFS
解释：返回getExternalStorageState() ，表明对象为空白或正在使用不受支持的文件系统。
MEDIA_REMOVED
解释：返回getExternalStorageState() ，如果不存在 SDCard 返回
MEDIA_SHARED
解释：返回getExternalStorageState() ，如果 SDCard 未安装 ，并通过 USB 大容量存储共享 返回
MEDIA_UNMOUNTABLE
解释：返回getExternalStorageState() ，返回 SDCard 不可被安装 如果 SDCard 是存在但不可以被安装
MEDIA_UNMOUNTED
解释：返回getExternalStorageState() ，返回 SDCard 已卸掉如果 SDCard 是存在但是没有被安装

Environment 常用方法：
方法：getDataDirectory()
解释：返回 File ，获取 Android 数据目录。
方法：getDownloadCacheDirectory()
解释：返回 File ，获取 Android 下载/缓存内容目录。
方法：getExternalStorageDirectory()
解释：返回 File ，获取外部存储目录即 SDCard
方法：getExternalStoragePublicDirectory(String type)
解释：返回 File ，取一个高端的公用的外部存储器目录来摆放某些类型的文件
方法：getExternalStorageState()
解释：返回 File ，获取外部存储设备的当前状态
方法：getRootDirectory()
解释：返回 File ，获取 Android 的根目录
2、讲述 StatFs 类
StatFs 一个模拟linux的df命令的一个类,获得SD卡和手机内存的使用情况
StatFs 常用方法:
getAvailableBlocks()
解释：返回 Int ，获取当前可用的存储空间
getBlockCount()
解释：返回 Int ，获取该区域可用的文件系统数
getBlockSize()
解释：返回 Int ，大小，以字节为单位，一个文件系统
getFreeBlocks()
解释：返回 Int ，该块区域剩余的空间
restat(String path)
解释：执行一个由该对象所引用的文件系统

 

 

* 1 在AndroidManifest文件中加入sdcard操作权限
　　* <!--在SDCard中创建与删除文件权限 -->
　　* <uses-permissioandroid:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/> 
　　* <!--往SDCard写入数据权限 --> 
　　* <uses-permissionandroid:name="android.permission.WRITE_EXTERNAL_STORAGE"/> 
* 2 确认sdcard的存在
　　* android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED)

检查当前内存卡是否可用

1. if (Environment.getExternalStorageState().equals(     
2.                     Environment.MEDIA_MOUNTED)) {     
3.                 // sd card 可用     
4.                          
5.                 }else {     
6. // 当前不可用     
7. }  

* 3 获取扩展存储设备的文件目录
　　* android.os.Environment.getExternalStorageDirectory();

 

* 4 获取扩展存储设备的大小

 

   String sdcard = Environment.getExternalStorageDirectory().getPath();
   StatFs statFs = new StatFs(sdcard);

   long blockSize = statFs.getBlockSize();//返回以字节为单位的一个文件系统大小

   long blockCount = statFs.getBlockCount() ;
   long blocks = statFs.getAvailableBlocks();//获取当前可用的存储空间
   long availableSpare = (blocks * blockSize) / (1024 * 1024);