Pointers 谷歌+；android中的登录按钮。这些是我的java文件和错误日志

JAVA:

    package com.example.api_test;

    import android.app.Activity;
    import android.content.Intent;
    import android.content.IntentSender.SendIntentException;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.Toast;

    import com.google.android.gms.common.ConnectionResult;
    import  com.google.android.gms.common.GooglePlayServicesClient.OnConnectionFailedListener;
    import com.google.android.gms.common.api.GoogleApiClient;
    import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks;
    import com.google.android.gms.plus.Plus;


    public class MainActivity extends Activity implements       OnClickListener,ConnectionCallbacks, OnConnectionFailedListener{

    Button bSignIn;
    private static final int RC_SIGN_IN=1;

    private GoogleApiClient mGoogleApiClient;

    private boolean mIntentInProgress, mSignInClicked;
    private ConnectionResult mConnectionResult;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main); 

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

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

    @Override
    public void onClick(View view) {
          if (view.getId() == R.id.sign_in_button
            && !mGoogleApiClient.isConnecting()) {
            mSignInClicked = true;
            resolveSignInError();
          }
        }


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

    private void resolveSignInError() {
          if (mConnectionResult.hasResolution() && mGoogleApiClient != null) {
            try {
              mIntentInProgress = true;
              startIntentSenderForResult(mConnectionResult.getResolution().getIntentSender(),
                  RC_SIGN_IN, null, 0, 0, 0);
            } catch (SendIntentException e) {
              mIntentInProgress = false;
              mGoogleApiClient.connect();
            }
          }
        }





    protected void onStop(){
        super.onStop();
        if (mGoogleApiClient.isConnected()){
        mGoogleApiClient.disconnect();
    }
}





    @Override
    public void onConnectionFailed(ConnectionResult result) {
        if (!mIntentInProgress && result.hasResolution()){
            try{
                mIntentInProgress = true;
                startIntentSenderForResult(result.getResolution().getIntentSender(), RC_SIGN_IN ,null ,0 ,0 , 0);
            } catch (SendIntentException e){
                mIntentInProgress =false;
                mGoogleApiClient.connect();
            }
        }

        if (mSignInClicked){
            resolveSignInError();
        }
    }


    @Override
    public void onConnected(Bundle connectionHint) {
      mSignInClicked = false;
      Toast.makeText(this, "User is connected!", Toast.LENGTH_LONG).show();
    }


    @Override
    public void onConnectionSuspended(int cause) {
        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();
        }
        }
    }


}

07-26 18:39:18.940: E/AndroidRuntime(888): FATAL EXCEPTION: main

错误日志：

    package com.example.api_test;

    import android.app.Activity;
    import android.content.Intent;
    import android.content.IntentSender.SendIntentException;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.Toast;

    import com.google.android.gms.common.ConnectionResult;
    import  com.google.android.gms.common.GooglePlayServicesClient.OnConnectionFailedListener;
    import com.google.android.gms.common.api.GoogleApiClient;
    import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks;
    import com.google.android.gms.plus.Plus;


    public class MainActivity extends Activity implements       OnClickListener,ConnectionCallbacks, OnConnectionFailedListener{

    Button bSignIn;
    private static final int RC_SIGN_IN=1;

    private GoogleApiClient mGoogleApiClient;

    private boolean mIntentInProgress, mSignInClicked;
    private ConnectionResult mConnectionResult;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main); 

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

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

    @Override
    public void onClick(View view) {
          if (view.getId() == R.id.sign_in_button
            && !mGoogleApiClient.isConnecting()) {
            mSignInClicked = true;
            resolveSignInError();
          }
        }


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

    private void resolveSignInError() {
          if (mConnectionResult.hasResolution() && mGoogleApiClient != null) {
            try {
              mIntentInProgress = true;
              startIntentSenderForResult(mConnectionResult.getResolution().getIntentSender(),
                  RC_SIGN_IN, null, 0, 0, 0);
            } catch (SendIntentException e) {
              mIntentInProgress = false;
              mGoogleApiClient.connect();
            }
          }
        }





    protected void onStop(){
        super.onStop();
        if (mGoogleApiClient.isConnected()){
        mGoogleApiClient.disconnect();
    }
}





    @Override
    public void onConnectionFailed(ConnectionResult result) {
        if (!mIntentInProgress && result.hasResolution()){
            try{
                mIntentInProgress = true;
                startIntentSenderForResult(result.getResolution().getIntentSender(), RC_SIGN_IN ,null ,0 ,0 , 0);
            } catch (SendIntentException e){
                mIntentInProgress =false;
                mGoogleApiClient.connect();
            }
        }

        if (mSignInClicked){
            resolveSignInError();
        }
    }


    @Override
    public void onConnected(Bundle connectionHint) {
      mSignInClicked = false;
      Toast.makeText(this, "User is connected!", Toast.LENGTH_LONG).show();
    }


    @Override
    public void onConnectionSuspended(int cause) {
        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();
        }
        }
    }


}

07-26 18:39:18.940: E/AndroidRuntime(888): FATAL EXCEPTION: main

07-26 18:39:18.940:E/AndroidRuntime（888）：进程：com.example.api_测试，PID:888 07-26 18:39:18.940:E/AndroidRuntime（888）：java.lang.NullPointerException 07-26 18:39:18.940:E/AndroidRuntime（888）：在com.example.api_test.MainActivity.ResolveSignError（MainActivity.java:61） 07-26 18:39:18.940:E/AndroidRuntime（888）：在com.example.api_test.MainActivity.onClick（MainActivity.java:50）上 07-26 18:39:18.940:E/AndroidRuntime（888）：在android.view.view.performClick（view.java:4438） 07-26 18:39:18.940:E/AndroidRuntime（888）：在android.view.view$PerformClick.run（view.java:18422） 07-26 18:39:18.940:E/AndroidRuntime（888）：在android.os.Handler.handleCallback（Handler.java:733）上 07-26 18:39:18.940:E/AndroidRuntime（888）：位于android.os.Handler.dispatchMessage（Handler.java:95） 07-26 18:39:18.940:E/AndroidRuntime（888）：在android.os.Looper.loop（Looper.java:136）上 07-26 18:39:18.940:E/AndroidRuntime（888）：位于android.app.ActivityThread.main（ActivityThread.java:5017） 07-26 18:39:18.940:E/AndroidRuntime（888）：位于java.lang.reflect.Method.Invokenactive（本机方法） 07-26 18:39:18.940:E/AndroidRuntime（888）：在java.lang.reflect.Method.invoke（Method.java:515） 07-26 18:39:18.940:E/AndroidRuntime（888）：在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:779） 07-26 18:39:18.940:E/AndroidRuntime（888）：位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:595）

---

07-26 18:39:18.940:E/AndroidRuntime（888）：在dalvik.system.NativeStart.main（本机方法）

看来您还没有将变量

MConnectionResult

初始化为任何内容，在第61行您得到了一个空指针异常。

您试图实现什么，什么时候出现此错误？