尝试在空对象引用上调用虚拟方法com.google.firebase.iid.FirebaseInstanceId.getInstanceId()' [英] Attempt to invoke virtual method com.google.firebase.iid.FirebaseInstanceId.getInstanceId()' on a null object reference

问题描述

我要使用firebase-messaging库，并尝试在应用启动时使用以下方法获取令牌.

I am to using firebase-messaging library and trying to fetch the token using below method on app launch.

FirebaseInstanceId.getInstance().getInstanceId().addOnSuccessListener(new OnSuccessListener() {
           @Override
           public void onSuccess(InstanceIdResult instanceIdResult) {
               String token = instanceIdResult.getToken();
               // print token
           }
       });

应用在投放本身时崩溃

java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.tasks.Task com.google.firebase.iid.FirebaseInstanceId.getInstanceId()' on a null object reference

AndroidManifest

AndroidManifest

<service
      android:name=".MyFirebaseMessageService">
      <intent-filter>
            <action android:name="com.google.firebase.MESSAGING_EVENT"/>
      </intent-filter>
</service>

Build.gradle:

Build.gradle :

implementation 'com.google.android.gms:play-services-analytics:16.0.5'
implementation 'com.google.firebase:firebase-messaging:17.3.4'

此外，我尝试将令牌存储在SharedPreferences中，但似乎从未调用过onNewToken().

Also, i have tried to cache the token in SharedPreferences but it seems onNewToken() is never called.

@Override
    public void onNewToken(String token) {
        super.onNewToken(token);
        SharedPreferences preference = PreferenceManager.getDefaultSharedPreferences(this);
        SharedPreferences.Editor editor = preference.edit();
        editor.putString("TOKEN",token);
        editor.apply();
    }

可能是什么问题?

推荐答案

合并清单中存在问题，合并清单中缺少以下服务. 在AndroidManifest.xml中添加了相同内容，就像是一种魅力.

There was problem in merged manifest, following service was missing from the merged manifest. Added same to AndroidManifest.xml it worked like a charm.

 <service android:name="com.google.firebase.components.ComponentDiscoveryService" >
            <meta-data
                android:name="com.google.firebase.components:com.google.firebase.iid.Registrar"
                android:value="com.google.firebase.components.ComponentRegistrar" />
 </service>

现在一切正常.

这篇关于尝试在空对象引用上调用虚拟方法com.google.firebase.iid.FirebaseInstanceId.getInstanceId()'的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！