如何修复 Android Studio 上的 java.lang.RuntimeException？

Question

我正在尝试在应用程序中使用 Firebase 从我的设备中检索注册令牌，该应用程序具有一个 TextView，目的是在其中包含令牌的值，当我每次运行应用程序时获得 java.lang .RuntimeException 错误，我按照指示添加了此代码FirebaseApp.initializeApp(this);，但我仍然收到此类错误，我对 Android Studio 和 Firebase 还很陌生，我仍在尝试。

MainActivity.java

package com.gci.gestioncapteursincendie;

import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.widget.TextView;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.FirebaseApp;
import com.google.firebase.iid.FirebaseInstanceId;
import com.google.firebase.iid.InstanceIdResult;

public class MainActivity extends AppCompatActivity {

    private TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        FirebaseApp.initializeApp(this);

        textView= findViewById(R.id.textViewToken);
        FirebaseInstanceId.getInstance().getInstanceId()
                .addOnCompleteListener(new OnCompleteListener<InstanceIdResult>() {
                    @Override
                    public void onComplete(@NonNull Task<InstanceIdResult> task) {
                      if(task.isSuccessful()){
                          String token = task.getResult().getToken();
                          textView.setText("Token : " + token);
                        }
                        else
                      {
                          textView.setText("Token Not Generated");
                      }
                    }
                });
    }

}

日志跟踪：

03-31 19:10:19.203 11562-11562/com.gci.gestioncapteursincendie E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.gci.gestioncapteursincendie, PID: 11562
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gci.gestioncapteursincendie/com.gci.gestioncapteursincendie.MainActivity}: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.gci.gestioncapteursincendie. Make sure to call FirebaseApp.initializeApp(Context) first.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3319)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3415)
        at android.app.ActivityThread.access$1100(ActivityThread.java:229)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1821)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:148)
        at android.app.ActivityThread.main(ActivityThread.java:7406)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
     Caused by: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.gci.gestioncapteursincendie. Make sure to call FirebaseApp.initializeApp(Context) first.
        at com.google.firebase.FirebaseApp.getInstance(com.google.firebase:firebase-common@@16.0.1:219)
        at com.google.firebase.iid.FirebaseInstanceId.getInstance(Unknown Source)
        at com.gci.gestioncapteursincendie.MainActivity.onCreate(MainActivity.java:41)
        at android.app.Activity.performCreate(Activity.java:6904)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1136)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3266)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3415) 
        at android.app.ActivityThread.access$1100(ActivityThread.java:229) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1821) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:148) 
        at android.app.ActivityThread.main(ActivityThread.java:7406) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) 

build.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        google()
        jcenter()
        maven {
            url 'https://maven.fabric.io/public'
        }

    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.3.2'
        classpath 'com.google.gms:google-services:4.1.0'
        classpath 'io.fabric.tools:gradle:1.26.1'


        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()

    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

Answer 1

来自文档：

对于绝大多数应用程序，FirebaseInitProvider 将通过应用程序的 google-services.json 文件中包含的数据处理其配置为使用的默认项目的 Firebase 初始化。

如果应用需要访问默认项目之外的另一个 Firebase 项目，则必须使用 initializeApp(Context, FirebaseOptions, String) 以编程方式创建该关系。

如果您在两个不同的项目中使用这个应用程序，那么您需要使用initializeApp()。

https://firebase.google.com/docs/reference/android/com/google/firebase/FirebaseApp

还将您的 Google 服务版本更新为 4.2.0，因为 4.1.0 存在配置问题。

classpath 'com.google.gms:google-services:4.2.0'

Answer 2

在 app gradle 末尾添加应用插件：'com.google.gms.google-services'：

 dependencies {
     classpath 'com.android.tools.build:gradle:3.3.2'
     classpath 'com.google.gms:google-services:4.2.0'
     ...
 }
 apply plugin: 'com.google.gms.google-services'