尝试在空对象引用上调用虚拟方法 'android.app.Notification androidx.core.app.NotificationCompat$Builder.build()'

Question

我正在使用Firebase推送通知向应用程序发送通知。 通知在最新的安卓版本中有效，但是当我尝试在Lolipop版本中进行测试时。当我测试通知应用程序崩溃时.我不知道问题出在哪里。请帮我解决问题。提前谢谢.

public class MyFirebaseMessagingService extends FirebaseMessagingService {
@Override
public void onMessageReceived(@NonNull RemoteMessage remoteMessage) {
String title = Objects.requireNonNull(remoteMessage.getNotification()).getTitle();
String message = remoteMessage.getNotification().getBody();
//33
sendNotification(title,message);
}
private void sendNotification(String messageTitle,String messageBody) {
NotificationManager notificationManager =
(NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
Intent intent = new Intent(this, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_SINGLE_TOP);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_ONE_SHOT);
Uri soundUri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
@SuppressLint("WrongConstant")
NotificationChannel notificationChannel=new NotificationChannel("my_notification","n_channel",NotificationManager.IMPORTANCE_MAX);
notificationChannel.setDescription("description");
notificationChannel.setName("Channel Name");
assert notificationManager != null;
notificationManager.createNotificationChannel(notificationChannel);
}

NotificationCompat.Builder notificationBuilder = null;
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.N) {
notificationBuilder = new NotificationCompat.Builder(this)
.setSmallIcon(R.drawable.sicont)
.setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.sicont))
.setContentTitle(messageTitle)
.setContentText(messageBody)
.setAutoCancel(true)
.setSound(soundUri)
.setContentIntent(pendingIntent)
.setDefaults(Notification.DEFAULT_ALL)
.setPriority(NotificationManager.IMPORTANCE_MAX)
.setOnlyAlertOnce(true)
.setChannelId("my_notification")
.setColor(Color.parseColor("#3F5996"));
}
//.setProgress(100,50,false);
assert notificationManager != null;
int m = (int) ((new Date().getTime() / 1000L) % Integer.MAX_VALUE);
assert notificationBuilder != null;
//76 number line
notificationManager.notify(m, notificationBuilder.build());

}

}

日志猫：

java.lang.NullPointerException: Attempt to invoke virtual method 'android.app.Notification androidx.core.app.NotificationCompat$Builder.build()' on a null object reference
at p.MyFirebaseMessagingService.sendNotification(MyFirebaseMessagingService.java:76)
at p.MyFirebaseMessagingService.onMessageReceived(MyFirebaseMessagingService.java:33)
at com.google.firebase.messaging.FirebaseMessagingService.zzc(com.google.firebase:firebase-messaging@@20.0.0:68)
at com.google.firebase.messaging.zze.run(com.google.firebase:firebase-messaging@@20.0.0:2)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at com.google.android.gms.common.util.concurrent.zza.run(Unknown Source)

Answer 1

试试这个方法：

private void sendNotification(String messageTitle,String messageBody) {
NotificationManager notificationManager =
(NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
Intent intent = new Intent(this, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_SINGLE_TOP);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_ONE_SHOT);
Uri soundUri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
@SuppressLint("WrongConstant")
NotificationChannel notificationChannel=new NotificationChannel("my_notification","n_channel",NotificationManager.IMPORTANCE_MAX);
notificationChannel.setDescription("description");
notificationChannel.setName("Channel Name");
assert notificationManager != null;
notificationManager.createNotificationChannel(notificationChannel);
}

NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
.setSmallIcon(R.drawable.sicont)
.setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.sicont))
.setContentTitle(messageTitle)
.setContentText(messageBody)
.setAutoCancel(true)
.setSound(soundUri)
.setContentIntent(pendingIntent)
.setDefaults(Notification.DEFAULT_ALL)
.setOnlyAlertOnce(true)
.setChannelId("my_notification")
.setColor(Color.parseColor("#3F5996"));
//.setProgress(100,50,false);
assert notificationManager != null;
int m = (int) ((new Date().getTime() / 1000L) % Integer.MAX_VALUE);
notificationManager.notify(m, notificationBuilder.build());
}