How to show an icon in the status bar when application is running, including in the background?

I want to put an icon in the status bar when ever my application is running, incl开发者_StackOverflow中文版uding when it is running in the background. How can I do this?

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You should be able to do this with Notification and the NotificationManager. However getting a guaranteed way to know when your application is not running is the hard part.

You can get the basic functionality of what you are desiring by doing something like:

Notification notification = new Notification(R.drawable.your_app_icon,
                                             R.string.name_of_your_app, 
                                             System.currentTimeMillis());
notification.flags |= Notification.FLAG_NO_CLEAR
                   | Notification.FLAG_ONGOING_EVENT;
NotificationManager notifier = (NotificationManager)
     context.getSystemService(Context.NOTIFICATION_SERVICE);
notifier.notify(1, notification);

This code must be somewhere where you are sure will get fired when your application starts. Possibly in your application's custom Application Object's onCreate() method.

However after that things are tricky. The killing of the application can happen at anytime. So you can try to put something in the onTerminate() of the Application class too, but it's not guaranteed to be called.

((NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE)).cancel(1);

will be what is needed to remove the icon.

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For new API you can use NotificationCompat.Builder -

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)
    .setSmallIcon(R.mipmap.ic_launcher)
    .setContentTitle("Title");
Intent resultIntent = new Intent(this, MyActivity.class);
PendingIntent resultPendingIntent = PendingIntent.getActivity(
this,
0,
resultIntent,
PendingIntent.FLAG_UPDATE_CURRENT);
mBuilder.setContentIntent(resultPendingIntent);
Notification notification = mBuilder.build();
notification.flags |= Notification.FLAG_NO_CLEAR | Notification.FLAG_ONGOING_EVENT;

mNotifyMgr = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
mNotifyMgr.notify(NOTIFICATION_ID, notification);

It will show as long as your application is running and someone manually closes your application. You can always cancel your notification by calling -

mNotifyMgr.cancel(NOTIFICATION_ID);

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Take a look at the Dev Guide "Creating Status Bar Notifications".

One way to achieve the goal of keeping the icon there only when the application is running is to initialize the notification in onCreate() and call cancel(int) in your onPause() method only if isFinishing() returns true.

An example:

private static final int NOTIFICATION_EX = 1;
private NotificationManager notificationManager;

@Override
public void onCreate() {
    super.onCreate();

    notificationManager = (NotificationManager) 
        getSystemService(Context.NOTIFICATION_SERVICE);

    int icon = R.drawable.notification_icon;
    CharSequence tickerText = "Hello";
    long when = System.currentTimeMillis();

    Notification notification = new Notification(icon, tickerText, when);

    Context context = getApplicationContext();
    CharSequence contentTitle = "My notification";
    CharSequence contentText = "Hello World!";
    Intent notificationIntent = new Intent(this, MyClass.class);
    PendingIntent contentIntent = PendingIntent.getActivity(this, 
        0, notificationIntent, 0);

    notification.setLatestEventInfo(context, contentTitle, 
        contentText, contentIntent);

    notificationManager.notify(NOTIFICATION_EX, notification);
}

@Override
protected void onPause() {
    super.onPause();
    if (isFinishing()) {
        notificationManager.cancel(NOTIFICATION_EX);
    }
}

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It really works. I created a method out of the example above:

private void applyStatusBar(String iconTitle, int notificationId) {
NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)
.setSmallIcon(R.mipmap.ic_launcher)
.setContentTitle(iconTitle);
Intent resultIntent = new Intent(this, ActMain.class);
PendingIntent resultPendingIntent = PendingIntent.getActivity(this, 0, resultIntent, PendingIntent.FLAG_UPDATE_CURRENT);
mBuilder.setContentIntent(resultPendingIntent);
Notification notification = mBuilder.build();
notification.flags |= Notification.FLAG_NO_CLEAR|Notification.FLAG_ONGOING_EVENT;

NotificationManager mNotifyMgr = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
mNotifyMgr.notify(notificationId, notification);}

It should be called like: applyStatusBar("Statusbar Test", 10);