java - GoogleApiClient.Builder.enableAutoManage() 给我一个错误

Question

我正在尝试让 google 登录正常工作，但我遇到了这个错误:

mGoogleApiClient = new GoogleApiClient.Builder(this)
        .enableAutoManage(this /* FragmentActivity */,
                 this /* OnConnectionFailedListener */)
        .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
        .build();

this 是错误的，因为它需要一个 OnConnectionFailedListener 对象，而不是一个 Activity。

所以我将它转换为 OnConncetionFailedListener:

mGoogleApiClient = new GoogleApiClient.Builder(this)
        .enableAutoManage(this /* FragmentActivity */,
                (GoogleApiClient.OnConnectionFailedListener) this /* OnConnectionFailedListener */)
        .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
        .build();

这会移除红色波浪线。但是当我运行应用程序时，应用程序崩溃了，我得到的错误是:

09-02 13:01:37.937    2403-2403/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.android.googlelogin, PID: 2403
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.googlelogin/com.example.android.googlelogin.MainActivity}: java.lang.ClassCastException: com.example.android.googlelogin.MainActivity cannot be cast to com.google.android.gms.common.api.GoogleApiClient$OnConnectionFailedListener
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
            at android.app.ActivityThread.-wrap11(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
     Caused by: java.lang.ClassCastException: com.example.android.googlelogin.MainActivity cannot be cast to com.google.android.gms.common.api.GoogleApiClient$OnConnectionFailedListener
            at com.example.android.googlelogin.MainActivity.onCreate(MainActivity.java:35)
            at android.app.Activity.performCreate(Activity.java:6237)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
            at android.app.ActivityThread.-wrap11(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

这基本上是说我不能将 Activity 转换为 OnConncetionFailedListener。

我该怎么做才能纠正这个问题？

Answer 1

问题是您正在将 Activity 转换为 OnConnectionFailedListener，但它没有实现该接口(interface)。

要么使 FragmentActivity 实现 OnConnectionFailedListener(在这种情况下可以省略显式转换)，要么子类 OnConnectionFailedListener 并传递它的一个实例类而不是您的 Activity。

最简单的解决方案可能是使用匿名内部类:

mGoogleApiClient = new GoogleApiClient.Builder(this)
        .enableAutoManage(this, new GoogleApiClient.OnConnectionFailedListener() {
            @Override
            public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
                // connection failed, should be handled
            }
        })
        .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
        .build();