android监听sd卡挂载状态,onReceive无法被调用问题

MyExternalStorageReceiver

package com.rishiqing.receiver;

import android.app.AlertDialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.IntentFilter;
import android.content.DialogInterface.OnDismissListener;
import android.content.Intent;
import android.os.Environment;
import android.util.Log;

import com.rishiqing.activity.LuncherActivity;
import com.rishiqing.utils.LogUtil;

public class MyExternalStorageReceiver extends BroadcastReceiver {

private static String TAG = MyExternalStorageReceiver.class.getName();
private Context mContext;

public MyExternalStorageReceiver(Context c) {
LogUtil.e(TAG, "MyExternalStorageReceiver~~~~");
this.mContext = c;
IntentFilter intentFilter = new IntentFilter(
Intent.ACTION_MEDIA_MOUNTED);
intentFilter.addAction(Intent.ACTION_MEDIA_SCANNER_STARTED);
intentFilter.addAction(Intent.ACTION_MEDIA_SCANNER_FINISHED);
intentFilter.addAction(Intent.ACTION_MEDIA_REMOVED);
intentFilter.addAction(Intent.ACTION_MEDIA_UNMOUNTED);
intentFilter.addAction(Intent.ACTION_MEDIA_BAD_REMOVAL);
mContext.registerReceiver(this, intentFilter);
}

@Override
public void onReceive(Context context, Intent intent) {
LogUtil.e(TAG, "onReceive~~~~");
ifSDStateFalse();
}

public void ifSDStateFalse() {
AlertDialog mAlertDialog = null;
// TODO Auto-generated method stub
if (!Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED) == true) {
mAlertDialog = new AlertDialog.Builder(mContext)
.setMessage("系统未检测到sd卡,将强制退出").show();
mAlertDialog.setOnDismissListener(new OnDismissListener() {
@Override
public void onDismiss(DialogInterface dialog) {
Intent i = new Intent();
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
i.setClass(mContext, LuncherActivity.class);
i.putExtra("isFinish", 1);
mContext.startActivity(i);
}
});
}
else if(Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED) == true){
if(mAlertDialog!=null && mAlertDialog.isShowing())
mAlertDialog.dismiss();
}
}

public void unregister() {
Log.d(TAG, "unregister()");
mContext.unregisterReceiver(this);
}
}

以上代码看起来，感觉已经很完整了，但是onReceive怎么都无法被调用。

最后发现在intentFilter中加上了intentFilter.addDataScheme("file");这样才起作用(line 30)