问题描述
我有一个用于地理围栏的广播接收器。完全相同的代码在另一个应用程序中工作，我在一个活动中有一个完整的谷歌地图。在新应用中，我希望 Google 地图（片段）与其他按钮和文本一起作为一个活动的一部分。
当我将它添加到 Manifest.xml（见下文）时，应用程序打开，当我收到通知（我真的收到我想要的通知）时，应用程序崩溃。
<receiver
android:name=".GeofencebroadcastReceiver"
android:enabled="true"
android:exported="true"></receiver>
没有这个
所以在某些时候这部分很重要，但它可能会阻止其他东西？
这是 GeofencebroadcastReceiver.java：（最后是我调用通知的开关/案例）
public class GeofencebroadcastReceiver extends broadcastReceiver {
HauptActivity HA = new HauptActivity();
private static final String TAG = "GeofencebroadcastReceiv";
@Override
public void onReceive(Context context,Intent intent) {
// Todo: This method is called when the broadcastReceiver is receiving
// an Intent broadcast.
// Toast.makeText(context,"Geofence triggered...",Toast.LENGTH_SHORT).show();
NotificationHelper notificationHelper = new NotificationHelper(context);
GeofencingEvent geofencingEvent = GeofencingEvent.fromIntent(intent);
if (geofencingEvent.hasError()){
Log.d(TAG,"onReceive: Error receiving geofence event...");
return;
}
List<Geofence> geofenceList = geofencingEvent.getTriggeringGeofences();
for (Geofence geofence: geofenceList) {
Log.d(TAG,"onReceive: " + geofence.getRequestId());
}
// Location location = geofencingEvent.getTriggeringLocation();
int transitionType = geofencingEvent.getGeofenceTransition();
switch (transitionType) {
case Geofence.GEOFENCE_TRANSITION_ENTER:
Toast.makeText(context,"GEOFENCE_TRANSITION_ENTER",Toast.LENGTH_SHORT).show();
notificationHelper.sendHighPriorityNotification("GEOFENCE_TRANSITION_ENTER","",HauptActivity.class);
HA.changeMeldungGefahr();
break;
case Geofence.GEOFENCE_TRANSITION_DWELL:
Toast.makeText(context,"GEOFENCE_TRANSITION_DWELL",Toast.LENGTH_SHORT).show();
notificationHelper.sendHighPriorityNotification("GEOFENCE_TRANSITION_DWELL",HauptActivity.class);
break;
case Geofence.GEOFENCE_TRANSITION_EXIT:
Toast.makeText(context,"GEOFENCE_TRANSITION_EXIT",Toast.LENGTH_SHORT).show();
notificationHelper.sendHighPriorityNotification("GEOFENCE_TRANSITION_EXIT",HauptActivity.class);
break;
}
}
}
这是 NotificationHelper.java（我从网上得到的代码）
public class NotificationHelper extends Contextwrapper {
private static final String TAG = "NotificationHelper";
public NotificationHelper(Context base) {
super(base);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
createChannels();
}
}
private String CHANNEL_NAME = "High priority channel";
private String CHANNEL_ID = "com.example.notifications" + CHANNEL_NAME;
@RequiresApi(api = Build.VERSION_CODES.O)
private void createChannels() {
NotificationChannel notificationChannel = new NotificationChannel(CHANNEL_ID,CHANNEL_NAME,notificationmanager.IMPORTANCE_HIGH);
notificationChannel.enableLights(true);
notificationChannel.enableVibration(true);
notificationChannel.setDescription("this is the description of the channel.");
notificationChannel.setLightColor(Color.RED);
notificationChannel.setLockscreenVisibility(Notification.VISIBILITY_PUBLIC);
notificationmanager manager = (notificationmanager) getSystemService(Context.NOTIFICATION_SERVICE);
manager.createNotificationChannel(notificationChannel);
}
public void sendHighPriorityNotification(String title,String body,Class activityname) {
Intent intent = new Intent(this,activityname);
PendingIntent pendingIntent = PendingIntent.getActivity(this,267,intent,PendingIntent.FLAG_UPDATE_CURRENT);
Notification notification = new NotificationCompat.Builder(this,CHANNEL_ID)
// .setContentTitle(title)
// .setContentText(body)
.setSmallIcon(R.drawable.ic_launcher_background)
.setPriority(NotificationCompat.PRIORITY_HIGH)
.setStyle(new NotificationCompat.BigTextStyle().setSummaryText("Überwachungskamera").setBigContentTitle(title).bigText(body))
.setContentIntent(pendingIntent)
.setAutoCancel(true)
.build();
notificationmanagerCompat.from(this).notify(new Random().nextInt(),notification);
}
}
这与我之前在旧应用程序中使用的代码完全相同，并且一切正常。所以我真的不想改变代码太多，因为它应该完美无缺。也许我忘记了别的地方？也许问题不是代码...但我没有找到解决方案，也许你有。
编辑：这是“运行”下的红色文本
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.mapBox1,PID: 32082
java.lang.RuntimeException: Unable to start receiver com.example.mapBox1.GeofencebroadcastReceiver: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.app.ActivityThread.handleReceiver(ActivityThread.java:3399)
at android.app.ActivityThread.-wrap18(UnkNown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1780)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6944)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.content.Contextwrapper.getApplicationInfo(Contextwrapper.java:163)
at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:157)
at android.content.Context.obtainStyledAttributes(Context.java:655)
at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:839)
at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:806)
at androidx.appcompat.app.AppCompatDelegateImpl.findViewById(AppCompatDelegateImpl.java:630)
at androidx.appcompat.app.AppCompatActivity.findViewById(AppCompatActivity.java:223)
at com.example.mapBox1.HauptActivity.changeMeldungGefahr(HauptActivity.java:221)
at com.example.mapBox1.GeofencebroadcastReceiver.onReceive(GeofencebroadcastReceiver.java:47)
at android.app.ActivityThread.handleReceiver(ActivityThread.java:3392)
at android.app.ActivityThread.-wrap18(UnkNown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1780)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6944)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
并明确表示：应用程序启动后，我看到“HauptActivity”，然后根据需要收到通知。但是在通知之后应用立即崩溃。
解决方法
来自日志：调用
HauptActivity.changeMeldungGefahr(HauptActivity.java:221) 导致空指针。
您应该在 changeMeldungGefahr() 内修复 Nullpointer。