如何显示通知栏？

<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

NotificationCompat.Builder builder = new NotificationCompat.Builder(context)
        .setSmallIcon(R.drawable.notification_icon)
        .setContentTitle("通知标题")
        .setContentText("通知内容")
        .setPriority(NotificationCompat.PRIORITY_DEFAULT);

Intent intent = new Intent(context, MainActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
builder.setContentIntent(pendingIntent);

NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify(notificationId, builder.build());