我的应用无法在 Android 模拟器中运行

【问题标题】：My app doesnt run in the Android simulator我的应用无法在 Android 模拟器中运行
【发布时间】：2020-01-28 03:19:53
【问题描述】：

所以我正在开发一个聊天应用程序，并且我一直在 Android 模拟器中对其进行测试（像素 3 选项）。但是现在我正试图让它在另一个模拟器中运行（这次我选择了一个像素 2）并且没有运行。

我会传递一些代码，包括 MainActivity。

这是来自 LogCat

2020-01-28 01:47:27.799 10456-10456/com.example.textmefinal E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.textmefinal, PID: 10456
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.textmefinal/com.example.textmefinal.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3270)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
    at android.os.Handler.dispatchMessage(Handler.java:107)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7356)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference
    at com.example.textmefinal.MainActivity.onCreate(MainActivity.java:44)
    at android.app.Activity.performCreate(Activity.java:7802)
    at android.app.Activity.performCreate(Activity.java:7791)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409) 
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016) 
    at android.os.Handler.dispatchMessage(Handler.java:107) 
    at android.os.Looper.loop(Looper.java:214) 
    at android.app.ActivityThread.main(ActivityThread.java:7356) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930) 

2020-01-28 01:47:57.456 10456-10494/com.example.textmefinal E/FirebaseInstanceId：令牌检索失败：SERVICE_NOT_AVAILABLE

主要活动

package com.example.textmefinal;

公共类 MainActivity 扩展 AppCompatActivity {

private Toolbar mToolbar;
private ViewPager myViewPager;
private TabLayout myTabLayout;
private TabsAccessorAdapter myTabsAccessorAdapter;

private FirebaseUser currentUser;
private FirebaseAuth mAuth;
private DatabaseReference RootRef;
private String currentUserID;

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

    mAuth = FirebaseAuth.getInstance();
    currentUser  = mAuth.getCurrentUser();
    currentUserID = mAuth.getCurrentUser().getUid();
    RootRef = FirebaseDatabase.getInstance().getReference();

    mToolbar = (Toolbar) findViewById(R.id.main_page_toolbar);
    setSupportActionBar(mToolbar);
    getSupportActionBar().setTitle("TextMe");

    myViewPager = (ViewPager) findViewById(R.id.main_tabs_pager);
    myTabsAccessorAdapter =  new TabsAccessorAdapter(getSupportFragmentManager());
    myViewPager.setAdapter(myTabsAccessorAdapter);

    myTabLayout = (TabLayout) findViewById(R.id.main_tabs);
    myTabLayout.setupWithViewPager(myViewPager);
}


@Override
protected void onStart() {
    super.onStart();

    if (currentUser == null){
        SendUserToLoginActivity();
    }
    else {
        VerifyUserExistance();
    }
}

private void VerifyUserExistance() {
    String currentUserId = mAuth.getCurrentUser().getUid();

    RootRef.child("Users").child(currentUserId).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if ((dataSnapshot.child("name").exists())){
                Toast.makeText(MainActivity.this, "Welcome", Toast.LENGTH_SHORT).show();
            }
            else {
                SendUserToSettingsActivity();
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    super.onCreateOptionsMenu(menu);

    getMenuInflater().inflate(R.menu.options_menu, menu);

    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    super.onOptionsItemSelected(item);
    if (item.getItemId() == R.id.main_logout_option){
        mAuth.signOut();
        SendUserToLoginActivity();
    }
    if (item.getItemId() == R.id.main_settings_option){

        SendUserToSettingsActivity();

    }
    if (item.getItemId() == R.id.main_find_friends_option){
        SendUserToFindFriendsActivity();
    }

    return true;
}

private void SendUserToLoginActivity() {

    Intent loginIntent = new Intent(MainActivity.this, LoginActivity.class);
    loginIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
    startActivity(loginIntent);
    //finish();
}

private void SendUserToSettingsActivity() {

    Intent settingsIntent = new Intent(MainActivity.this, SettingsActivity.class);
    startActivity(settingsIntent);
}


private void SendUserToFindFriendsActivity() {

    Intent findFriendsIntent = new Intent(MainActivity.this, FindFriendsActivity.class);
    startActivity(findFriendsIntent);
}

}

登录活动

package com.example.textmefinal;

公共类 LoginActivity 扩展 AppCompatActivity {

private FirebaseAuth mAuth;
private ProgressDialog loadingBar;


private Button LoginButton, PhoneLoginButton;
private EditText UserEmail, UserPassword;
private TextView NeedNewAccountLink, ForgetPasswordLink;

private DatabaseReference UsersRef;


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

    mAuth = FirebaseAuth.getInstance();
    UsersRef = FirebaseDatabase.getInstance().getReference().child("Users");

    InitializeFields();

    NeedNewAccountLink.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            SendUserToRegisterActivity();
        }
    });

    LoginButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            AllowUserToLogin();
        }
    });
}

@Override
protected void onStart()
            {
                super.onStart();

                FirebaseUser currentUser = mAuth.getCurrentUser();
                if (currentUser != null)
                    {
                        SendUserToMainActivity();
                    }
            }

private void AllowUserToLogin() {
    String email = UserEmail.getText().toString();
    String password = UserPassword.getText().toString();

    if (TextUtils.isEmpty(email)){
        Toast.makeText(this, "Please enter email...", Toast.LENGTH_SHORT).show();
    }
    if (TextUtils.isEmpty(password)){
        Toast.makeText(this, "Please enter password...", Toast.LENGTH_SHORT).show();
    }
    else {

        loadingBar.setTitle("Sign In");
        loadingBar.setMessage("Please wait...");
        loadingBar.setCanceledOnTouchOutside(true);
        loadingBar.show();

        mAuth.signInWithEmailAndPassword(email, password)
                .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()){

                            String currentUserId = mAuth.getCurrentUser().getUid();
                            String deviceToken = FirebaseInstanceId.getInstance().getToken();

                            UsersRef.child(currentUserId).child("device_token")
                                    .setValue(deviceToken)
                                    .addOnCompleteListener(new OnCompleteListener<Void>() {
                                        @Override
                                        public void onComplete(@NonNull Task<Void> task) {
                                            if (task.isSuccessful())  {
                                                SendUserToMainActivity();
                                                Toast.makeText(LoginActivity.this, "Logged in Successful", Toast.LENGTH_SHORT).show();
                                                loadingBar.dismiss();
                                            }
                                        }
                                    });
                        }
                        else {
                            String message = task.getException().toString();
                            Toast.makeText(LoginActivity.this, "Error: " + message, Toast.LENGTH_SHORT).show();
                            loadingBar.dismiss();
                        }
                    }
                });
    }
}

private void InitializeFields() {
    LoginButton = (Button) findViewById(R.id.login_button);
    PhoneLoginButton = (Button) findViewById(R.id.phone_login_button);
    UserEmail = (EditText) findViewById(R.id.login_email);
    UserPassword = (EditText) findViewById(R.id.login_password);
    NeedNewAccountLink = (TextView) findViewById(R.id.need_new_account_link);
    ForgetPasswordLink = (TextView) findViewById(R.id.forget_password_link);
    loadingBar = new ProgressDialog(this);

}


private void SendUserToMainActivity() {
    Intent mainIntent = new Intent(LoginActivity.this, MainActivity.class);
    mainIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
    startActivity(mainIntent);
    finish();
}

private void SendUserToRegisterActivity() {
    Intent registerIntent = new Intent(LoginActivity.this, RegisterActivity.class);
    startActivity(registerIntent);
}

}

注册活动

package com.example.textmefinal;

公共类 RegisterActivity 扩展 AppCompatActivity {

private Button CreateAccountButton;
private EditText UserEmail, UserPassword;
private TextView AlreadyHaveAccountLink;

private FirebaseAuth mAuth;
private DatabaseReference RootRef;

private ProgressDialog loadingBar;

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

    mAuth = FirebaseAuth.getInstance();
    RootRef = FirebaseDatabase.getInstance().getReference();


    InitializeFields();


    AlreadyHaveAccountLink.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            SendUserToLoginActivity();
        }
    });

    CreateAccountButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            CreateNewAccount();
        }
    });
}

private void CreateNewAccount() {
    String email = UserEmail.getText().toString();
    String password = UserPassword.getText().toString();

    if (TextUtils.isEmpty(email)){
        Toast.makeText(this, "Please enter email...", Toast.LENGTH_SHORT).show();
    }
    if (TextUtils.isEmpty(password)){
        Toast.makeText(this, "Please enter password...", Toast.LENGTH_SHORT).show();
    }
    else {

        loadingBar.setTitle("Creating New Account");
        loadingBar.setMessage("Please wait, while we are creating new account for you...");
        loadingBar.setCanceledOnTouchOutside(true);
        loadingBar.show();

        mAuth.createUserWithEmailAndPassword(email, password)
                .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()){

                            String deviceToken = FirebaseInstanceId.getInstance().getToken();


                            String currentUserID = mAuth.getCurrentUser().getUid();
                            RootRef.child("Users").child(currentUserID).setValue("");

                            RootRef.child("Users").child(currentUserID).child("device_token")
                                    .setValue(deviceToken);

                            SendUserToMainActivity();
                            Toast.makeText(RegisterActivity.this, "Account Created Successfully...", Toast.LENGTH_SHORT).show();
                            loadingBar.dismiss();
                        }
                        else {
                            String message = task.getException().toString();
                            Toast.makeText(RegisterActivity.this, "Error: " + message, Toast.LENGTH_SHORT).show();
                            loadingBar.dismiss();
                        }
                    }
                });
    }
}

private void InitializeFields() {
    CreateAccountButton = (Button) findViewById(R.id.register_button);
    UserEmail = (EditText) findViewById(R.id.register_email);
    UserPassword = (EditText) findViewById(R.id.register_password);
    AlreadyHaveAccountLink = (TextView) findViewById(R.id.already_have_account_link);

    loadingBar = new ProgressDialog(this);
}

private void SendUserToLoginActivity() {
    Intent loginIntent = new Intent(RegisterActivity.this, LoginActivity.class);
    startActivity(loginIntent);
}

private void SendUserToMainActivity() {
    Intent mainIntent = new Intent(RegisterActivity.this, MainActivity.class);
    mainIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
    startActivity(mainIntent);
    finish();
}

}

谁能帮助我？

enter image description here

【问题讨论】：

  • 分享 logcat 消息。

标签： android android-studio android-emulator


【解决方案1】：

如果您单击编辑器底部的“运行”选项卡，如果应用遇到异常，您通常应该会看到一条以红色书写的消息。此消息应该告诉您遇到了哪个错误。

【讨论】：

  • 嗨，感谢您的回复，是的，我已经添加了一个新的 ss，但问题是它没有显示任何错误
【解决方案2】：

您的应用 TextMe 在启动器活动中有一些问题，为什么它在启动时崩溃，请修复该问题...或分享 logcat 的日志，以便我们提供帮助。

【讨论】：

  • 很抱歉缺少更多信息，我已经用更多信息更新了帖子。但是logcat的日志没有显示任何错误，实际上是应用程序没有打开，它被安装了但就是这样
  • mAuth.getCurrentUser() 正在重新调整 null 这就是为什么在应用程序启动时调用 mAuth.getCurrentUser().getUid() 时会出现空指针异常；
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