android 格式化ＳＤ卡

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1,在设置界面点击>存储->格式化内部存储将会执行
packages/apps/Settings/src/com/android/settings/deviceinfo/Memory.java
if (preference == mSdFormat) { 
            Intent intent = new Intent(Intent.ACTION_VIEW); 
            intent.setClass(this, com.android.settings.MediaFormat.class); 
            startActivity(intent); 
            return true; 
} 
 
2,packages/apps/Settings/src/com/android/settings/MediaFormat.java
下面将会跳到onCreate方法的establishInitialState();
protected void onCreate(Bundle savedState) { 
@Override     protected void onCreate(Bundle savedState) {         super.onCreate(savedState);         establishInitialState();     } 
3,构造第一个含有一个按钮(格式化内部大容量存储设备)的页面,并为按钮添加事件
private void establishInitialState() { 
       if (mInitialView == null) { 
           mInitialView = mInflater.inflate(R.layout.media_format_primary, null); 
           mInitiateButton = 
                   (Button) mInitialView.findViewById(R.id.initiate_media_format); 
           mInitiateButton.setOnClickListener(mInitiateListener); 
       } 
    } 
4,当点击这个按钮时将会跳到确认页面,防止误操作
private Button.OnClickListener mInitiateListener = new Button.OnClickListener() { 
        public void onClick(View v) { 
            if (!runKeyguardConfirmation(KEYGUARD_REQUEST)) { 
                establishFinalConfirmationState(); 
            } 
        } 
    }; 
5,确认格式化大容量存储设备的时候将会发送一个Intent,并将要格式化的路径传入
Intent intent = new Intent(ExternalStorageFormatter.FORMAT_ONLY); 
intent.setComponent(ExternalStorageFormatter.COMPONENT_NAME); 
String strPath = Environment.getExternalStorageDirectory().getPath(); 
intent.putExtra("path", strPath); 
startService(intent); 
6,frameworks/base/core/java/com/android/internal/os/storage/ExternalStorageFormatter.java
执行ExternalStorageFormatter类中的public int onStartCommand(Intent intent, int flags, int startId)方法
接收路径并执行updateProgressState()方法
7,在updateProgressState()方法中判断路径是否存在,将卸载存储卡,
if (Environment.MEDIA_MOUNTED.equals(status) 
                || Environment.MEDIA_MOUNTED_READ_ONLY.equals(status)) { 
            updateProgressDialog(mIsSdcard? R.string.progress_unmounting : R.string.progress_unmounting_nand); 
            SystemProperties.set("sys.storage.state","formating"); 
            IMountService mountService = getMountService(); 
            try { 
                /* 
                 * For mount point of external sdcard is: /mnt/sdcard/external_sd, 
                 * unmount sdcard first. 
                 */ 
                if (mPath.equals(Environment.getFlashStorageDirectory().toString())) { 
                    updateProgressDialog(R.string.progress_unmounting_nand); 
                    mountService.unmountVolume(Environment.getActExternalStorageDirectory().toString(),true); 
                } 
                mountService.unmountVolume(mPath, true); 
            } 
8,成功卸载SD卡会激发StorageEventListener mStorageListener = new StorageEventListener()事件
mStorageListener会重新执行updateProgressState()方法
9,再次执行updateProgressState()方法的时候SD卡已经卸载将会执行格式化操作
if (Environment.MEDIA_NOFS.equals(status) 
               || Environment.MEDIA_UNMOUNTED.equals(status) 
               || Environment.MEDIA_UNMOUNTABLE.equals(status)) { 
           updateProgressDialog(mIsSdcard? R.string.progress_erasing : R.string.progress_erasing_nand); 
           SystemProperties.set("sys.storage.state","ready"); 
           final IMountService mountService = getMountService(); 
           final String extStoragePath = mPath;//Environment.getExternalStorageDirectory().toString(); 
           if (mountService != null) { 
               new Thread() { 
                   public void run() { 
                       boolean success = false; 
                       try { 
                           mountService.formatVolume(extStoragePath); 
                           success = true; 
                       } catch (Exception e) { 
                           Toast.makeText(ExternalStorageFormatter.this, mIsSdcard? 
                                   R.string.format_error : R.string.format_error_nand, Toast.LENGTH_LONG).show(); 
                       } 
                       if (success) { 
                           if (mFactoryReset) { 
                               android.os.SystemProperties.set("ctl.start","bootanim"); 
                               sendBroadcast(new Intent("android.intent.action.MASTER_CLEAR")); 
                               // Intent handling is asynchronous -- assume it will happen soon. 
                               stopSelf(); 
                               return; 
                           } 
                       } 
                       // If we didn't succeed, or aren't doing a full factory 
                       // reset, then it is time to remount the storage. 
                       if (!success && mAlwaysReset) { 
                           sendBroadcast(new Intent("android.intent.action.MASTER_CLEAR")); 
                       } 
10,success等于真的话会会清楚缓存,语句mountService.formatVolume(extStoragePath);是格式化操作
public int formatVolume(String mountPoint) throws RemoteException { 
    Parcel _data = Parcel.obtain(); 
    Parcel _reply = Parcel.obtain(); 
    int _result; 
    try { 
        _data.writeInterfaceToken(DESCRIPTOR); 
        _data.writeString(mountPoint); 
        mRemote.transact(Stub.TRANSACTION_formatVolume, _data, _reply, 0); 
        _reply.readException(); 
        _result = _reply.readInt(); 
    } finally { 
        _reply.recycle(); 
        _data.recycle(); 
    } 
    return _result; 
}

本文出自 “背着重重壳的蜗牛” 博客，请务必保留此出处http://zchengdong.blog.51cto.com/3363091/845863

如果需要自己格式化某一个指定ＳＤ卡路径，如下：

　　Intent intent = new Intent(ExternalStorageFormatter.FORMAT_ONLY);
        intent.setComponent(ExternalStorageFormatter.COMPONENT_NAME);
　　 //String strPath = Environment.getExternalStorageDirectory().getPath();
　　 intent.putExtra("path", extStoragePath);
   　 Bundle bundle = new Bundle();
　   bundle.putParcelable(StorageVolume.EXTRA_STORAGE_VOLUME,getDvrVolume());
　　 intent.putExtras(bundle);
　　 startService(intent);

public StorageVolume getDvrVolume() {
        return getPrimaryVolume(getVolumeList());
    }

    /** {@hide} */
    public static StorageVolume getPrimaryVolume(StorageVolume[] volumes) {
        for (StorageVolume volume : volumes) {
            if (volume.getPath().equals("/mnt/extsd2")) {
           Log.w(TAG, "volume is :"+volume.getPath());
                return volume;
            }
        }
        Log.w(TAG, "No primary storage defined");
        return null;
    }　　

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