近期在项目中须要对外部存储设备的状态进行监听，所以整理了此笔记，以便日后查看。

外部存储设备的状态变化时发出的广播

对照不同状态下的广播

1. 插入外部SD卡时：

2. 移除外部SD卡时：

3. 连接PC进入USB大容量存储模式时：

4. 连接PC退出USB大容量存储模式时：

代码实现监听

public void startListen(){    IntentFilter intentFilter = new IntentFilter(Intent.ACTION_MEDIA_MOUNTED);    intentFilter.setPriority(1000);      intentFilter.addAction(Intent.ACTION_MEDIA_UNMOUNTED);    intentFilter.addAction(Intent.ACTION_MEDIA_REMOVED);    intentFilter.addAction(Intent.ACTION_MEDIA_SHARED);    intentFilter.addAction(Intent.ACTION_MEDIA_BAD_REMOVAL);     intentFilter.addAction(Intent.ACTION_MEDIA_SCANNER_STARTED);    intentFilter.addAction(Intent.ACTION_MEDIA_SCANNER_FINISHED);     intentFilter.addAction(Intent.ACTION_MEDIA_CHECKING);    intentFilter.addAction(Intent.ACTION_MEDIA_EJECT);    intentFilter.addAction(Intent.ACTION_MEDIA_NOFS);    intentFilter.addAction(Intent.ACTION_MEDIA_BUTTON);    intentFilter.addAction(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);    intentFilter.addDataScheme("file");    registerReceiver(broadcastRec, intentFilter);}private final BroadcastReceiver broadcastRec = new BroadcastReceiver() {      @Override      public void onReceive(Context context, Intent intent) {          String action = intent.getAction();         Log.d("MediaAction", action);        if (action.equals("android.intent.action.MEDIA_MOUNTED"))        {          	//todo        } else if (action.equals(Intent.ACTION_MEDIA_UNMOUNTED))         {          	//todo        }else if (action.equals(Intent.ACTION_MEDIA_SCANNER_STARTED)){        }else if (action.equals(Intent.ACTION_MEDIA_SCANNER_FINISHED)){        }else if (action.equals(Intent.ACTION_MEDIA_SHARED)){        }else {         }      }  };