问题描述

我将使用 firebase-messaging 库并尝试在应用启动时使用以下方法获取令牌.

应用程序在启动时崩溃

java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法 'com.google.android.gms.tasks.Task com.google.firebase.iid.FirebaseInstanceId.getInstanceId()'

AndroidManifest

构建.gradle:

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

另外，我尝试在 SharedPreferences 中缓存令牌，但似乎从未调用过 onNewToken().

@Override公共无效onNewToken(字符串令牌){super.onNewToken(token);SharedPreferences 首选项 = PreferenceManager.getDefaultSharedPreferences(this);SharedPreferences.Editor 编辑器 = preference.edit();editor.putString("TOKEN",token);editor.apply();}

可能是什么问题?

合并清单出现问题，合并清单中缺少以下服务.在 AndroidManifest.xml 中添加了相同的内容，它就像一个魅力.

 <service android:name="com.google.firebase.components.ComponentDiscoveryService" ><元数据android:name="com.google.firebase.components:com.google.firebase.iid.Registrar"android:value="com.google.firebase.components.ComponentRegistrar"/></服务>

现在一切正常.

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
           }
       });

App crashes on the launch itself giving

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

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

Build.gradle :

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

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();
    }

What could be the problem?

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>

Everything is working fine now.