firebase错误默认FirebaseApp在此进程中未初始化

Question

我正在开发一个Android程序，使用Firebase数据库，但我现在有问题。

这是我的代码主要活动：

public class MainActivity extends AppCompatActivity {

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

        FirebaseDatabase database = FirebaseDatabase.getInstance();
        DatabaseReference myRef = database.getReference("message");

        // Read from the database
        myRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String value = dataSnapshot.getValue(String.class);
                Log.d("TAG", "Value is: " + value);
            }

            @Override
            public void onCancelled(DatabaseError error) {
                Log.w("TAG", "Failed to read value.", error.toException());
            }
        });
    }

}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.google.firebase:firebase-database:16.0.6'
    implementation 'com.google.firebase:firebase-core:16.0.7'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

public class Application extends android.app.Application {

    @Override
    public void onCreate() {
        super.onCreate();
        FirebaseApp.initializeApp(this);
    }
}

Answer 1

似乎你在依赖项中缺少了谷歌服务插件。firebase android文档提到应该添加这些插件：

buildscript {
    // ...
    dependencies {
        // ...
        classpath 'com.google.gms:google-services:4.2.0' // google-services plugin
    }
}

allprojects {
    // ...
    repositories {
        google() // Google's Maven repository
        // ...
    }
}