尝试调用虚拟方法'int java.lang.Object.hashCode()'facebook集成

Question

我按照Facebook教程集成SDK,刚刚在我的.xml文件中添加了登录到Facebook按钮.

当我运行我的应用程序时,我的应用程序显示如下错误.

我正在开发完全更新的Android Studio.

我还添加了Facebook app id和string.xml文件,并在manifesto文件中添加了元数据.

为什么我收到此错误？

请帮我.

logcat的:

FATAL EXCEPTION: AsyncTask #2
    Process: com.example.venkat.sampleapplication, PID: 23130
    java.lang.RuntimeException: An error occurred while executing doInBackground()
    at android.os.AsyncTask$3.done(AsyncTask.java:309)
    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
    at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
    at java.util.concurrent.FutureTask.run(FutureTask.java:242)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
    at java.lang.Thread.run(Thread.java:818)
    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Object.hashCode()' on a null object reference
    at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:772)
    at java.util.concurrent.ConcurrentHashMap.containsKey(ConcurrentHashMap.java:800)
    at com.facebook.internal.Utility.queryAppSettings(Utility.java:802)
    at com.facebook.login.widget.LoginButton$1.doInBackground(LoginButton.java:502)
    at com.facebook.login.widget.LoginButton$1.doInBackground(LoginButton.java:499)
    at android.os.AsyncTask$2.call(AsyncTask.java:295)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
    at java.lang.Thread.run(Thread.java:818) 

AndroidMenifesto文件: -

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.venkat.sampleapplication">

    <uses-permission android:name="android.permission.INTERNET"/>

    <meta-data
        android:name="com.facebook.sdk.ApplicationId"
        android:value="@string/facebook_app_id"/>

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

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

string.xml

<resources>
    <string name="app_name">SampleApplication</string>
    <string name="action_settings">Settings</string>
    <string name="facebook_app_id">xxxxxxxxxxx</string>
</resources>

主要活动:-

public class MainActivity extends AppCompatActivity {

    // Create, automatically open (if applicable), save, and restore the
    // Active Session in a way that is similar to Android UI lifecycles.

    private LoginButton loginButton;
    private CallbackManager callbackManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        FacebookSdk.sdkInitialize(this.getApplicationContext());
        setContentView(R.layout.content_main);
        callbackManager = CallbackManager.Factory.create();
        loginButton = (LoginButton) findViewById(R.id.loginFaceBook_button);
        List<String> permissionNeeds = Arrays.asList("user_photos", "email", "user_birthday", "public_profile");
        loginButton.setReadPermissions(permissionNeeds);
        loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                System.out.println("onSuccess");
            }

            @Override
            public void onCancel() {
                System.out.println("onCancel");
            }

            @Override
            public void onError(FacebookException exception) {
                Log.v("LoginActivity", exception.getCause().toString());
            }
        });
}
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        callbackManager.onActivityResult(requestCode, resultCode, data);
    }
}

Answer 1

你的Meta Data标签应该在ApplicationTag of Manifest.

改变这个.

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

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

      <meta-data
        android:name="com.facebook.sdk.ApplicationId"
        android:value="@string/facebook_app_id"/>

    </application>