Firebase ui recyclerview - 在使用 Firebase 之前需要使用 Firebase.setAndroidContext() 设置 Android 上下文

Question

我想要 firebase 数据库中的所有项目，所以我使用 recyclerview 来填充这些项目。当调用带有 recylerview 的 activity 时，应用程序崩溃并出现致命错误。

这是我的代码

我的java文件

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.ListView;
import android.widget.TextView;

import com.firebase.client.Firebase;
import com.firebase.geofire.GeoFire;
import com.firebase.ui.FirebaseListAdapter;
import com.firebase.ui.FirebaseRecyclerAdapter;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class RequestPendingActivity extends AppCompatActivity {

RecyclerView RequestListView;
Firebase ref = new Firebase("https://simplyparc.firebaseio.com/Valet Requests Location");
private DatabaseReference mDatabase;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_request_pending);
    RequestListView = (RecyclerView) findViewById(R.id.RequestListView);
    RequestListView.setHasFixedSize(true);
    RequestListView.setLayoutManager(new LinearLayoutManager(this));


    GeoFire geoFire = new GeoFire(mDatabase);


}

@Override
protected void onStart(){
    super.onStart();
    FirebaseRecyclerAdapter<String, MessageViewHolder> adapter = new FirebaseRecyclerAdapter<String, MessageViewHolder>(String.class, android.R.layout.two_line_list_item, MessageViewHolder.class, ref) {
        @Override
        protected void populateViewHolder(MessageViewHolder messageViewHolder, String s, int i) {
            messageViewHolder.mText.setText(s);
        }
    };
    RequestListView.setAdapter(adapter);

}

public static class MessageViewHolder extends RecyclerView.ViewHolder{
    TextView mText;

    public MessageViewHolder(View v){
        super(v);
        mText = (TextView) v.findViewById(android.R.id.text1);
    }
}

}

我的 android 清单文件

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity
        android:name=".FirstActivity"
        android:theme="@style/AppTheme.NoActionBar"
        android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".PendingSelectorActivity"
        android:label="Select Pending task"
        android:screenOrientation="portrait"/>
    <activity
        android:name=".RequestPendingActivity"
        android:label="Pending Request"
        android:screenOrientation="portrait"/>
    <!--
         The API key for Google Maps-based APIs is defined as a string resource.
         (See the file "res/values/google_maps_api.xml").
         Note that the API key is linked to the encryption key used to sign the APK.
         You need a different API key for each encryption key, including the release key that is used to
         sign the APK for publishing.
         You can define the keys for the debug and release targets in src/debug/ and src/release/. 
    -->
    <meta-data
        android:name="com.google.android.geo.API_KEY"
        android:value="@string/google_maps_key"/>

    <activity
        android:name=".RequestAcceptMapActivity"
        android:label="@string/title_activity_request_accept_map"
        android:screenOrientation="portrait"/>
    <activity
        android:name=".DropOffActivity"
        android:label="Drop-Off Request"
        android:screenOrientation="portrait"/>


</application>

运行时出现致命错误

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.example.zuke.zukevalet, PID: 9243
              java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.zuke.zukevalet/com.example.zuke.zukevalet.RequestPendingActivity}: java.lang.RuntimeException: You need to set the Android context using Firebase.setAndroidContext() before using Firebase.
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2548)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
                  at android.app.ActivityThread.-wrap12(ActivityThread.java)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6077)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
               Caused by: java.lang.RuntimeException: You need to set the Android context using Firebase.setAndroidContext() before using Firebase.
                  at com.firebase.client.core.Context.getPlatform(Context.java:45)
                  at com.firebase.client.core.Context.ensureLogger(Context.java:218)
                  at com.firebase.client.core.Context.initServices(Context.java:105)
                  at com.firebase.client.core.Context.freeze(Context.java:92)
                  at com.firebase.client.core.RepoManager.getLocalRepo(RepoManager.java:55)
                  at com.firebase.client.core.RepoManager.getRepo(RepoManager.java:19)
                  at com.firebase.client.Firebase.<init>(Firebase.java:172)
                  at com.firebase.client.Firebase.<init>(Firebase.java:177)
                  at com.firebase.client.Firebase.<init>(Firebase.java:155)
                  at com.example.zuke.zukevalet.RequestPendingActivity.<init>(RequestPendingActivity.java:21)
                  at java.lang.Class.newInstance(Native Method)
                  at android.app.Instrumentation.newActivity(Instrumentation.java:1078)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2538)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707) 
                  at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460) 
                  at android.os.Handler.dispatchMessage(Handler.java:102) 
                  at android.os.Looper.loop(Looper.java:154) 
                  at android.app.ActivityThread.main(ActivityThread.java:6077) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 
W/DynamiteModule: Local module descriptor class for com.google.firebase.auth not found.

我哪里错了？

Answer 1

在异常消息中：

You need to set the Android context using Firebase.setAndroidContext() before using Firebase

---

:

To quote (step 4 of) the Firebase quickstart documentation:

The Firebase library must be initialized once with an Android Context. This must happen before any Firebase reference is created or used.

创建MyApplication.java:

public class MyApplication extends android.app.Application {

    @Override
    public void onCreate() {
        super.onCreate();
        Firebase.setAndroidContext(this);
    }
}

并在 AndroidManifest.xml:

中更新 name 参数值

<application 
        android:label="@string/app_name"
        android:name=".MyApplication">
...
</application>