public class MyReceiver extends BroadcastReceiver {

     @Override

     public void onReceive(final Context context, Intent intent) {

         AlertDialog.Builder builder = new AlertDialog.Builder(context);

         builder.setTitle("提示");

         builder.setMessage("确定打开主界面吗？");

         builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {

             @Override

             public void onClick(DialogInterface dialog, int which) {

                 Intent intent1 = new Intent(context, MainActivity.class);

                 //在广播接收器中启动活动，一定要给Intent加入FLAG_ACTIVITY_NEW_TASK标志

                 intent1.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

                 context.startActivity(intent1);

             }

         });

         AlertDialog dialog = builder.create();

         //需要把对话框的类型设为TYPE_SYSTEM_ALERT，否则对话框无法在广播接收器里弹出

         dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);

         dialog.show();

     }

 }