在 Lollipop 上使用 Xamarin Android 无法正确显示通知图标

Question

I have problem setting up a notification image to display properly.

Below is the original image, with file path:

myApp\\Resources\\drawable\\Icon.png

Dimensions: 72x72pixels, 32bit depths

The problem:

It displays like below.

Below is the code. The code seems working correctly for previous version which displays it properly.

public class MyServiceConnection : Java.Lang.Object, IServiceConnection
{
    private string _appName;
    public MyServiceConnection(string appName)
    {
        _appName = appName;
    }
    public void OnServiceConnected(ComponentName name, IBinder service)
    {
        var intent = new Intent(Application.Context, typeof(ManifestActivity));
        intent.AddFlags(ActivityFlags.ClearTop);
        var pendingIntent = PendingIntent.GetActivity(Application.Context, 0, intent, PendingIntentFlags.UpdateCurrent);
        var notificationBuilder = new NotificationCompat.Builder(Application.Context)

            .SetSmallIcon(Resource.Drawable.Icon)
            .SetContentTitle(_appName)
            .SetAutoCancel(true)
            .SetContentIntent(pendingIntent);
        var notificationManager = NotificationManager.FromContext(Application.Context);
        var notification = notificationBuilder.Build();
        notificationManager.Notify(1, notification);
        var serviceBinder = service as MyService.Binder;
        serviceBinder.StartForeground(1, notification);
    }
    public void OnServiceDisconnected(ComponentName name)
    {
    }
}

Environments:

android:minSdkVersion="15" android:targetSdkVersion="27" 

Update

As I mentioned, the same code and same png file are used and working now on a separate apk. Once the code was created for a second branch, the issue occurs on the second branch.

Update 2

I fixed it by changing below

Project Properties -> Android Manifest -> Target Android Version to "Use Compile using SDK version"

which results in below:

android:minSdkVersion="15" 

What does it mean by "Use Compile using SDK version"? What target version is being used when installed on Lollipop?

Answer 1

Because Google has made restrictions on android5.0 and above (not including 5.0), in order to unify the system style. After that, the icon in the status bar can't use a picture with rich colors at will. It can only appear in two colors, white and transparent.

You can do it two ways：

1.Color icons are displayed by lowering the targetSdkVersion method, but lowering the targetSdkVersion method is not supported.(not recommended)

2.Set setSmallIcon, respectively(Make another white icon with a transparent background)

 if(Android.OS.Build.VERSION.SdkInt> BuildVersionCodes.Lollipop){         
     // white icon with a transparent background
     notificationBuilder.SetSmallIcon(Resource.Drawable.ic_aphla_logo);
  } else {
     // icon image
     notificationBuilder.SetSmallIcon(Resource.Drawable.ic_logo);
 }

You can refer to this： Notification bar icon turns white in Android 5 Lollipop