确保首先调用FirebaseApp.initializeApp（Context）
其他问题可能已经完全相同，但是我真的不知道这里有什么问题。在此先感谢您的帮助。
build.gradle（项目）
// Top-level build file where you can add configuration options common to all sub-projects/modules.buildscript {
repositories {
jcenter()
}
dependencies {
classpath 'com.android.tools.build:gradle:2.3.3'
classpath 'com.google.gms:google-services:3.1.0'
// NOTE: Do not place your application dependencies here; they belong
// in the individual module build.gradle files
}
}
allprojects {
repositories {
jcenter()
maven {
url "https://maven.google.com" // Google's Maven repository
}
}
}
task clean(type: Delete) {
delete rootProject.buildDir
}
build.gradle（模块）
apply plugin: 'com.android.application'android {
compileSdkVersion 25
buildToolsVersion "25.0.3"
defaultConfig {
applicationId "com.bustracker.usc.myapplication"
minSdkVersion 21
targetSdkVersion 25
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:25.3.1'
compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha7'
compile 'com.google.android.gms:play-services-maps:10.2.6'
compile 'com.google.android.gms:play-services-location:10.2.6'
compile 'com.google.firebase:firebase-database:10.2.6'
testCompile 'junit:junit:4.12'
}
apply plugin: 'com.google.gms.google-services'
MainActivity.java
@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FirebaseApp.initializeApp(this);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
firebaseDatabase = FirebaseDatabase.getInstance();
mRootReference = firebaseDatabase.getReference();
mheadingReference = mRootReference.child("users");
错误：
FATAL EXCEPTION: main Process: com.bustracker.sample.myapplication, PID: 2658
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.bustracker.sample.myapplication/com.bustracker.sample.myapplication.MainActivity}: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.bustracker.sample.myapplication. Make sure to call FirebaseApp.initializeApp(Context) first.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.bustracker.sample.myapplication. Make sure to call FirebaseApp.initializeApp(Context) first.
at com.google.firebase.FirebaseApp.getInstance(Unknown Source)
at com.google.firebase.database.FirebaseDatabase.getInstance(Unknown Source)
at com.bustracker.sample.myapplication.MainActivity.onCreate(MainActivity.java:53)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
其他问题可能已经完全相同，但是我真的不知道这里有什么问题。在此先感谢您的帮助。
回答：
根据文档：
如文档中所述：
任何FirebaseApp初始化必须仅在应用程序的主要过程中发生。不支持在主流程以外的其他流程中使用Firebase，这可能会导致与资源争用相关的问题。
您无需在活动中初始化它。
将应用程序类添加到清单示例中：
<applicaton android:name="MyApplication"
然后这样做：
public class MyApplication extends Application { @Override
public void onCreate() {
super.onCreate();
FirebaseApp.initializeApp(this);
}
并从活动中删除初始化。您需要在作为基类的应用程序类中对其进行初始化。
编辑（关于应用程序）：
用于维护全局应用程序状态的基类。您可以通过创建一个子类并在AndroidManifest.xml的标签中将该子类的标准名称指定为“
android：name”属性来提供自己的实现。创建应用程序/包的过程时，将在任何其他类之前实例化Application类或Application类的子类。
有用的链接：https
:
//developer.android.com/reference/android/app/Application.html
以上是 确保首先调用FirebaseApp.initializeApp（Context） 的全部内容， 来源链接： utcz.com/qa/425042.html
