android - ClassCastException android.widget.Button 到 com.google.android.gms.common.SignInButton

Question

我不知道我做错了什么，但我的 Google+ 登录按钮一直出现以下错误

09-02 19:26:56.245  12537-12537/com.ferdiseegers.klantenbestand E/AndroidRuntime: FATAL EXCEPTION: main
        java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ferdiseegers.klantenbestand/com.ferdiseegers.klantenbestand.Activities.LoginActivity}: java.lang.ClassCastException: android.widget.Button cannot be cast to com.google.android.gms.common.SignInButton
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2339)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2389)
        at android.app.ActivityThread.access$600(ActivityThread.java:153)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1269)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:5289)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:525)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:739)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:555)
        at dalvik.system.NativeStart.main(Native Method)
        Caused by: java.lang.ClassCastException: android.widget.Button cannot be cast to com.google.android.gms.common.SignInButton
        at com.ferdiseegers.klantenbestand.Activities.LoginActivity.onCreate(LoginActivity.java:81)
        at android.app.Activity.performCreate(Activity.java:5133)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2293)
        ... 11 more

我在示例项目的布局 XML 中使用了按钮

<com.google.android.gms.common.SignInButton
     android:id="@+id/sign_in_button"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_marginBottom="30dip"/>

这就是我在 Activity 中使用它的方式

    public class LoginActivity extends Activity implements View.OnClickListener,
            PlusClient.ConnectionCallbacks, PlusClient.OnConnectionFailedListener,
            PlusClient.OnAccessRevokedListener {

        private static final int DIALOG_GET_GOOGLE_PLAY_SERVICES = 1;

        private static final int REQUEST_CODE_SIGN_IN = 1;
        private static final int REQUEST_CODE_GET_GOOGLE_PLAY_SERVICES = 2;

        private TextView mSignInStatus;
        private PlusClient mPlusClient;
        private SignInButton mSignInButton;
        private View mSignOutButton;
        private View mRevokeAccessButton;
        private ConnectionResult mConnectionResult;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_login);

            mPlusClient = new PlusClient.Builder(this, this, this)
                    .setVisibleActivities("http://schemas.google.com/AddActivity", "http://schemas.google.com/BuyActivity")
                    .setScopes(Scopes.PLUS_LOGIN, Scopes.PLUS_PROFILE)
                    .build();

            mSignInStatus = (TextView) findViewById(R.id.sign_in_status);
            mSignInButton = (SignInButton) findViewById(R.id.sign_in_button);
            mSignInButton.setOnClickListener(this);
            mSignOutButton = findViewById(R.id.sign_out_button);
            mSignOutButton.setOnClickListener(this);
            mRevokeAccessButton = findViewById(R.id.revoke_access_button);
            mRevokeAccessButton.setOnClickListener(this);
        }

    //some other methods not worth pasting here

}

它可能很简单，但我已经为它苦苦挣扎了 2 个小时。希望有人能帮帮我!

Answer 1

如果您在布局文件中将 Button 替换为 SignInButton，请尝试刷新并清除项目。还要检查布局文件中是否有另一个 Button @+id/sign_in_button