我从 https://developers.google.com/+/mobile/android/getting-started

当我启动我的应用程序时，会出现一条消息“用户已连接!” 然后我按 G+ 登录按钮我的应用强制关闭。

这是logcat的消息形式

04-08 18:31:21.680  24231-24231/app.umitems.test.testgoogleplus1.app D/﹕ onClick()
04-08 18:31:21.680  24231-24231/app.umitems.test.testgoogleplus1.app D/AndroidRuntime﹕ Shutting down VM
04-08 18:31:21.680  24231-24231/app.umitems.test.testgoogleplus1.app W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41f99ce0)
04-08 18:31:21.685  24231-24231/app.umitems.test.testgoogleplus1.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: app.umitems.test.testgoogleplus1.app, PID: 24231
    java.lang.NullPointerException
        at app.umitems.test.testgoogleplus1.app.ExampleActivity.resolveSignInError(ExampleActivity.java:68)
        at app.umitems.test.testgoogleplus1.app.ExampleActivity.onClick(ExampleActivity.java:166)
        at com.google.android.gms.common.SignInButton.onClick(Unknown Source)
        at android.view.View.performClick(View.java:4445)
        at android.view.View$PerformClick.run(View.java:18446)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5081)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
        at dalvik.system.NativeStart.main(Native Method)

这是我的代码

package app.umitems.test.testgoogleplus1.app;
import android.app.Activity;
import android.content.Intent;
import android.content.IntentSender;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesClient.ConnectionCallbacks;
import com.google.android.gms.common.GooglePlayServicesClient.OnConnectionFailedListener;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.plus.Plus;

public class ExampleActivity extends Activity implements
                                          ConnectionCallbacks, 
                                          OnConnectionFailedListener,
                                          GoogleApiClient.ConnectionCallbacks,
                                          GoogleApiClient.OnConnectionFailedListener, 
                                          View.OnClickListener  {

  /* Request code used to invoke sign in user interactions. */
  private static final int RC_SIGN_IN = 0;

  /* Client used to interact with Google APIs. */
  private GoogleApiClient mGoogleApiClient;

  /* A flag indicating that a PendingIntent is in progress and prevents
   * us from starting further intents.
   */
  private boolean mIntentInProgress;

  /* Track whether the sign-in button has been clicked so that we know to resolve
   * all issues preventing sign-in without waiting.
   */
  private boolean mSignInClicked;

  /* Store the connection result from onConnectionFailed callbacks so that we can
   * resolve them when the user clicks sign-in.
   */
  private ConnectionResult mConnectionResult;
  View btn;

  public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.activity_example);

     mGoogleApiClient = new GoogleApiClient.Builder(this)
           .addConnectionCallbacks(this)
           .addOnConnectionFailedListener(this)
           .addApi(Plus.API, null)
           //.addScope(Plus.SCOPE_PLUS_LOGIN)
           .build();

        btn = findViewById(R.id.sign_in_button);
        btn.setOnClickListener(this);
  }

  protected void onStart() {
     super.onStart();
     mGoogleApiClient.connect();
  }

  /* A helper method to resolve the current ConnectionResult error. */
  public void resolveSignInError() {
     Log.d("","resolveSignInError()");
     if (mConnectionResult.hasResolution()) {
        Log.d("","resolveSignInError() mConnectionResult.hasResolution()");
        try {
           mIntentInProgress = true;
           /*startIntentSenderForResult(mConnectionResult.getIntentSender(),
                                      RC_SIGN_IN, null, 0, 0, 0);*/

           mConnectionResult.startResolutionForResult(this, // your activity
                                           RC_SIGN_IN);
        } catch (IntentSender.SendIntentException e) {
           // The intent was canceled before it was sent.  Return to the default
           // state and attempt to connect to get an updated ConnectionResult.
           Log.d("","resolveSignInError() mConnectionResult.hasResolution() catch");
           mIntentInProgress = false;
           mGoogleApiClient.connect();
        }
     }
  }

  protected void onStop() {
     super.onStop();

     if (mGoogleApiClient.isConnected()) {
        mGoogleApiClient.disconnect();
     }
  }

  @Override public void onConnected(Bundle bundle){
     // We've resolved any connection errors.  mGoogleApiClient can be used to
     // access Google APIs on behalf of the user.
     mSignInClicked = false;
     Toast.makeText(this, "User is connected!", Toast.LENGTH_LONG).show();
  }

  @Override public void onConnectionSuspended(int i){
     mGoogleApiClient.connect();
  }

  @Override public void onDisconnected(){

  }

  @Override
  public void onConnectionFailed(ConnectionResult result) {
     if (!mIntentInProgress) {
        // Store the ConnectionResult so that we can use it later when the user clicks
        // 'sign-in'.
        mConnectionResult = result;

        if (mSignInClicked) {
           // The user has already clicked 'sign-in' so we attempt to resolve all
           // errors until the user is signed in, or they cancel.
           resolveSignInError();
        }
     }
  }
  /*@Override
  public void onConnectionFailed(ConnectionResult result){
     if (!mIntentInProgress && result.hasResolution()) {
        try {
           mIntentInProgress = true;*//*
           startIntentSenderForResult(result.getIntentSender(),
                                      RC_SIGN_IN, null, 0, 0, 0);*//*

           result.startResolutionForResult(this, // your activity
                                           RC_SIGN_IN);
        } catch (IntentSender.SendIntentException e) {
           // The intent was canceled before it was sent.  Return to the default
           // state and attempt to connect to get an updated ConnectionResult.
           mIntentInProgress = false;
           mGoogleApiClient.connect();
        }
     }
  }*/

  protected void onActivityResult(int requestCode, int responseCode, Intent intent) {
     if (requestCode == RC_SIGN_IN) {
        if (responseCode != RESULT_OK) {
           mSignInClicked = false;
        }

        mIntentInProgress = false;

        if (!mGoogleApiClient.isConnecting()) {
           mGoogleApiClient.connect();
        }
     }
  }

  @Override public void onClick(View view){

     Log.d("","onClick()");
     if (view.getId() == R.id.sign_in_button
         && !mGoogleApiClient.isConnecting()) {
        mSignInClicked = true;
        resolveSignInError();
     }
  }
}

我刚刚发现该应用程序会在未经任何许可的情况下自动连接到 Google+。我不需要按登录按钮，但我可以通过我的帐户发帖。这是关于隐私的错误吗？

最佳答案

好的!因此，toast 是因为您已登录，当您单击时，您正在尝试再次登录:因为您没有需要解决错误的连接结果，所以您得到了 NPE。

它是这样工作的:

1. 您的登录状态存储在 Google Play 服务中。
2. 连接后，您的应用会连接到 Google Play 服务，并且 尝试查看您之前是否登录过。
3. 如果有，它会回调 onConnected。
4. 如果没有，它会回调 onConnectionFailed 并给出 你是一个 ConnectionResult。
5. 当用户点击登录时，您在 ConnectionResult - 这只是一个未决的 Intent，它会触发 帐户选择器和同意屏幕。
6. 当用户同意后，您的应用会被回调 onActivityResult，然后您重新连接(并且流程再次开始，这 时间在第 3 步结束)。

因此，如果您获得 onConnected，您应该隐藏登录按钮 - 用户已登录!

现在，也许出于某种原因您希望用户必须单击按钮才能开始。那也没关系。在onClick 中，只需要测试mPlusClient 是否已连接。如果是，请直接转到登录后您想执行的任何操作。如果不是，则解决连接结果。

关于Android 在 mConnectionResult.hasResolution() 上实现 Google plus 登录错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22935861/