尝试在空对象引用上调用虚拟方法“void com.google.android.gms.common.SignInButton.setSize（int）”

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package design.nxn.login_template_01;


import android.app.ProgressDialog;

import android.content.Intent;

import android.os.Bundle;

import android.support.annotation.NonNull;

import android.support.v4.app.Fragment;

import android.util.Log;

import android.view.View;

import android.widget.Toast;


import com.google.android.gms.auth.api.Auth;

import com.google.android.gms.auth.api.signin.GoogleSignIn;

import com.google.android.gms.auth.api.signin.GoogleSignInAccount;

import com.google.android.gms.auth.api.signin.GoogleSignInClient;

import com.google.android.gms.auth.api.signin.GoogleSignInOptions;

import com.google.android.gms.auth.api.signin.GoogleSignInResult;

import com.google.android.gms.common.ConnectionResult;

import com.google.android.gms.common.SignInButton;

import com.google.android.gms.common.api.ApiException;

import com.google.android.gms.common.api.GoogleApiClient;

import com.google.android.gms.tasks.OnCompleteListener;

import com.google.android.gms.tasks.Task;


import java.text.BreakIterator;

import java.util.Objects;


import design.nxn.login_template_01.Tools.CustomViewPager;

import design.nxn.login_template_01.Tools.ViewPagerAdapter;


public class LoginActivity extends BaseActivity implements GoogleApiClient.OnConnectionFailedListener, View.OnClickListener {

    private static final String TAG = BaseActivity.class.getSimpleName();

    private static final int RC_SIGN_IN = 420;

    private GoogleApiClient mGoogleApiClient;

    private ProgressDialog mProgressDialog;

    private SignInButton btnSignIn;

    private GoogleSignInClient mGoogleSignInClient;

    private String personPhotoUrl;

    GoogleSignInOptions gso;

    BreakIterator mStatusTextView;

    private static final int LOGIN_FRAGMENT = 0;

    private static final int SIGNUP_FRAGMENT = 1;

    private static final int RESET_PASSWORD_FRAGMENT = 2;

    private Fragment newFragment;

    private CustomViewPager viewPager;

    private ViewPagerAdapter viewPagerAdapter;



    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_login);


        btnSignIn = (SignInButton)findViewById(R.id.sign_in_button);

        initializeGPlusSettings();

        initializeControls();

        findViewById(R.id.sign_in_button).setOnClickListener(this);


        viewPager = findViewById(R.id.viewpager);

        viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());

        viewPager.setAdapter(viewPagerAdapter);

        viewPager.setPagingEnabled(false);

        changeFragment(LOGIN_FRAGMENT);



        mGoogleSignInClient = GoogleSignIn.getClient(this, gso);


    }

    private void initializeControls() {

        btnSignIn.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View view) {

                Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);

                startActivityForResult(signInIntent, RC_SIGN_IN);


            }

        });

    }


    public void onStart() {

        super.onStart();

        GoogleSignInAccount account = 
GoogleSignIn.getLastSignedInAccount(this);

        updateUI(account);

    }

    @Override

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == RC_SIGN_IN) {

            Task<GoogleSignInAccount> task = 
GoogleSignIn.getSignedInAccountFromIntent(data);

            handleSignInResult(task);

        }

    }

    private void handleGPlusSignInResult(GoogleSignInResult result) {

        Log.d(TAG,"handleSignInResult:" +result.isSuccess());

        if (result.isSuccess()){

            GoogleSignInAccount acct = result.getSignInAccount();

            String personname = acct.getDisplayName();

            personPhotoUrl = Objects.requireNonNull(acct.getPhotoUrl()).toString();

            String personEmail = acct.getEmail();

            Intent intent = new Intent(LoginActivity.this,SecondActivity.class);

            intent.putExtra("personname",personname);

            intent.putExtra("email",personEmail);

            intent.putExtra("personphotoUrl",personPhotoUrl);

            startActivity(intent);

            finish();

        }

    }

    private void handleSignInResult(Task<GoogleSignInAccount> task) {

        try {

            GoogleSignInAccount account = task.getResult(ApiException.class);

            // Signed in successfully, show authenticated UI.

            updateUI(account);

        } 

catch (ApiException e) {
            // The ApiException status code indicates the detailed failure reason.
            // Please refer to the GoogleSignInStatusCodes class reference for more information.

            Log.w(TAG, "signInResult:failed code=" + e.getStatusCode());

            updateUI(null);

        }

    }


    private void initializeGPlusSettings() {
        // Configure sign-in to request the user's ID, email address, and basic
// profile. ID and basic profile are included in DEFAULT_SIGN_IN.
        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN).requestEmail().build();
        // Build a GoogleSignInClient with the options specified by gso.

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

        btnSignIn.setSize(SignInButton.SIZE_STANDARD);



    }

    private void changeFragment(int fragmentType) {

        switch (fragmentType) {

            case LOGIN_FRAGMENT:

                viewPager.setCurrentItem(LOGIN_FRAGMENT);

                break;

            case SIGNUP_FRAGMENT:

                viewPager.setCurrentItem(SIGNUP_FRAGMENT);

                break;

            case RESET_PASSWORD_FRAGMENT:

                viewPager.setCurrentItem(RESET_PASSWORD_FRAGMENT);

                break;

            default:

                viewPager.setCurrentItem(LOGIN_FRAGMENT);

                break;

        }


    }

    public void signUpClick(View view) {

        changeFragment(SIGNUP_FRAGMENT);

    }

    public void signInClick(View view) {

        changeFragment(LOGIN_FRAGMENT);

    }

    public void resetPasswordClick(View view) {

        changeFragment(RESET_PASSWORD_FRAGMENT);

    }

    public void backClick(View view){

        changeFragment(LOGIN_FRAGMENT);

    }

    @Override

    public void onBackPressed() {


        if (viewPager.getCurrentItem() == LOGIN_FRAGMENT)

            super.onBackPressed();

        else {

            changeFragment(LOGIN_FRAGMENT);

        }

    }

    public void logInButtonClicked() {

        Toast.makeText(this, R.string.login_button_click, Toast.LENGTH_SHORT).show();

    }

    public void signUpButtonClicked() {

        Toast.makeText(this, R.string.signup_button_click, Toast.LENGTH_SHORT).show();

    }

    public void resetPasswordButtonClicked() {

        Toast.makeText(this, R.string.reset_password_button_clicked, Toast.LENGTH_SHORT).show();

    }

    @Override

    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) 

   {

    }

    @Override

    public void onClick(View view) {

     switch (view.getId()) {

            case R.id.sign_in_button:

                signIn();

            case R.id.logout:

                signOut();

                break;

        }


    }

    private void signOut() {

        mGoogleSignInClient.signOut()
                .addOnCompleteListener(this, new OnCompleteListener<Void>() {

                    @Override

                    public void onComplete(@NonNull Task<Void> task) {
                        // ...

                    }

                });

    }

    private void revokeAccess() {

        mGoogleSignInClient.revokeAccess()
                .addOnCompleteListener(this, new OnCompleteListener<Void>() {

                    @Override

                    public void onComplete(@NonNull Task<Void> task) {
                        // ...

                    }

                });

    }




    private void signIn() {

        Intent signInIntent = mGoogleSignInClient.getSignInIntent();

        startActivityForResult(signInIntent, RC_SIGN_IN);


    }


    private void updateUI(GoogleSignInAccount account) {

        if (account != null) {

            mStatusTextView.setText(getString(R.string.signed_in_fmt, account.getDisplayName()));

            findViewById(R.id.sign_in_button).setVisibility(View.GONE);

            findViewById(R.id.logout).setVisibility(View.VISIBLE);

        } 

    else {
            mStatusTextView.setText(String.valueOf(R.string.signed_out));

            findViewById(R.id.sign_in_button).setVisibility(View.VISIBLE);

         findViewById(R.id.logout).setVisibility(View.GONE);

        }

    }

}

根据此代码，您需要使用

switch (view.getId()) {

            case R.id.sign_in_button:

                signIn();

而不是

 btnSignIn.setOnClickListener(this);

---

可能重复所做的更改。但是我的应用程序在USB调试后崩溃了调试中的问题是什么，在没有调试的情况下是否工作正常错误是：尝试在空对象引用上调用虚拟方法'void com.google.android.gms.common.SignInButton.setOnClickListenerandroid.view.view$OnClickListener'。在渐变类路径中使用此方法'com.android.tools.build:gradle:2.1.0'classpath'com.google.gms:google services:3.0.0'我已在项目的登录屏幕中添加了使用谷歌按钮登录。在使用谷歌按钮添加登录之前，我的项目已成功运行。但添加该按钮后，我的应用程序崩溃。

findViewById(R.id.sign_in_button).setOnClickListener(this);