java - 为什么我的应用程序在尝试从 Firebase 检索数据时崩溃？

Question

我是 Firebase 的新手，我正在尝试从我的项目的 Firebase 实时数据库中检索数据，但是每当它到达获取数据时onClickFunction 应用程序崩溃不知道为什么。我很确定它与 Firebase 代码有关

我正在学习这里的教程 https://www.youtube.com/watch?v=LpWhAz3e1sI

我尝试使用实现 'com.android.support:multidex:1.0.3'，但它仍然崩溃

Firebase 数据

myfirebase-fbc55
|
|
    Movies
    |
    |
      movie1
          movieName: "The Angry Birds Movie 2"
          plot: "The Angry Birds Movie 2 (also referred to as An..."
      movie2
          movieName: "Good Boys" 
          plot: "Good Boys is a 2019 American comedy film co-wri..."
      movie3
          movieName: "Where'd You Go, Bernadette"
          plot: "Where'd You Go, Bernadette is a 2012 comedy nov..."

安卓工作室Java

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



        Button but1 = (Button) findViewById(R.id.button);
        but1.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view){
                Log.d("working", "working ");
               db = FirebaseDatabase.getInstance().getReference().child("Movies").child("movie1");
               db.addValueEventListener(new ValueEventListener() {
                   @Override
                   public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        String movie = dataSnapshot.child("movieName").getValue().toString();
                       String plot = dataSnapshot.child("plot").getValue().toString();

                       Log.d("movie", movie);
                       Log.d("plot", plot);
                   }

                   @Override
                   public void onCancelled(@NonNull DatabaseError databaseError) {

                   }
               });
            }
        });
    }

Android Studio Gradle

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.0"
    defaultConfig {
        applicationId "com.example.firebasedemo"
        minSdkVersion 21
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        multiDexEnabled true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.0.2'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'com.google.firebase:firebase-database:16.0.4'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    implementation 'com.google.firebase:firebase-core:17.0.0'
    implementation 'com.android.support:multidex:1.0.3'
}

apply plugin: 'com.google.gms.google-services'

我希望数据至少在 movie1 中显示在日志中，因此我知道该应用正在正确检索数据。

这是错误日志

08-17 14:00:26.316 10148-10148/com.example.firebasedemo I/art: Rejecting re-init on previously-failed class java.lang.Class<com.google.firebase.database.android.AndroidAuthTokenProvider$3>
08-17 14:00:26.317 10148-10148/com.example.firebasedemo I/art: Rejecting re-init on previously-failed class java.lang.Class<com.google.firebase.database.android.AndroidAuthTokenProvider$3>
08-17 14:00:26.374 10148-10230/com.example.firebasedemo I/art: Rejecting re-init on previously-failed class java.lang.Class<com.google.firebase.database.android.AndroidAuthTokenProvider$3>
08-17 14:00:26.376 10148-10230/com.example.firebasedemo E/RunLoop: Uncaught exception in Firebase Database runloop (3.0.0). Please report to firebase-database-client@google.com
    java.lang.NoClassDefFoundError: com.google.firebase.database.android.AndroidAuthTokenProvider$3
        at com.google.firebase.database.android.AndroidAuthTokenProvider.produceIdTokenListener(com.google.firebase:firebase-database@@16.0.4:85)
        at com.google.firebase.database.android.AndroidAuthTokenProvider.addTokenChangeListener(com.google.firebase:firebase-database@@16.0.4:80)
        at com.google.firebase.database.core.Repo.deferredInitialization(com.google.firebase:firebase-database@@16.0.4:109)
        at com.google.firebase.database.core.Repo.access$000(com.google.firebase:firebase-database@@16.0.4:55)
        at com.google.firebase.database.core.Repo$1.run(com.google.firebase:firebase-database@@16.0.4:94)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:422)
        at java.util.concurrent.FutureTask.run(FutureTask.java:237)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:152)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:265)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
        at java.lang.Thread.run(Thread.java:818)
08-17 14:00:26.381 10148-10148/com.example.firebasedemo D/AndroidRuntime: Shutting down VM
08-17 14:00:26.382 10148-10148/com.example.firebasedemo E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.firebasedemo, PID: 10148
    java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask@2736e3ff rejected from com.google.firebase.database.core.utilities.DefaultRunLoop$1@210f5cc[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 1]
        at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2011)
        at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:793)
        at java.util.concurrent.ScheduledThreadPoolExecutor.delayedExecute(ScheduledThreadPoolExecutor.java:298)
        at java.util.concurrent.ScheduledThreadPoolExecutor.schedule(ScheduledThreadPoolExecutor.java:503)
        at java.util.concurrent.ScheduledThreadPoolExecutor.execute(ScheduledThreadPoolExecutor.java:592)
        at com.google.firebase.database.core.utilities.DefaultRunLoop.scheduleNow(com.google.firebase:firebase-database@@16.0.4:105)
        at com.google.firebase.database.core.Repo.scheduleNow(com.google.firebase:firebase-database@@16.0.4:276)
        at com.google.firebase.database.Query.addEventRegistration(com.google.firebase:firebase-database@@16.0.4:233)
        at com.google.firebase.database.Query.addValueEventListener(com.google.firebase:firebase-database@@16.0.4:149)
        at com.example.firebasedemo.MainActivity$1.onClick(MainActivity.java:36)
        at android.view.View.performClick(View.java:4756)
        at android.view.View$PerformClick.run(View.java:19749)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
08-17 14:00:28.418 10148-10148/? I/Process: Sending signal. PID: 10148 SIG: 9

Answer 1

确保在 Firebase 数据库的“规则”部分中，“读”和“写”权限为真，如果不是，则将其设置为真。在此之前，您通过检查 dataSnapshot 是否为空来获取您的值。如下所示:

db.addValueEventListener(new ValueEventListener() {
                   @Override
                   public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                       if(dataSnapshot != null) {
                           String movie = dataSnapshot.child("movieName").getValue().toString();
                           String plot = dataSnapshot.child("plot").getValue().toString();

                           Log.d("movie", movie);
                           Log.d("plot", plot);
                       } else {
                           Log.d(TAG, "Data Snapshot is null");
                       }

                   }

                   @Override
                   public void onCancelled(@NonNull DatabaseError databaseError) {

                   }
               });

通过这样做，您将知道您是否正在接收任何数据。并且不要忘记检查 Firebase 数据库的“规则”部分中的权限。