java - 在 Activity 之间移动

Question

我有 2 个 Activity ，一个是我的应用程序主页，另一个是注册页面。我主页的正文是这样的:

 public void onCreate(Bundle savedInstanceState)
 {
     registerOperation();

     super.onCreate(savedInstanceState);
     setContentView(R.layout.main);

     System.out.println("Already logged in");
 }
 public void registerOperation()
 {
     //checks if I did logged in already. if true start a new Intent of my Registeration page and stop the current Intent.
 }

在我的测试中，我还没有注册，所以 registerOperation 中的条件为真，新 Activity 即将出现，但几秒钟后应用程序停止。我已经使用了注册页面，但我以不同的方式调用它，一切都很好，所以我猜我调用它的方式有问题。在注册 Activity 运行时，我调用 registerOperation 后的输出行也会被执行。

编辑如果您想查看特定代码，请告诉我，我会更新帖子。

传递 Activity 代码。

    public void registerOperation()
    {
        SharedPreferences pref = getSharedPreferences("MyKid",MODE_PRIVATE);
        String email = pref.getString("email", null);
        String password = pref.getString("password", null);
        if(email == null && password == null)
        {
            this.stopService(this.getIntent());
            Intent register = new Intent(getBaseContext(), Register.class);
            startActivity(register);
        }
    }

编辑日志:

12-31 11:27:38.610: E/AndroidRuntime(28903): java.lang.RuntimeException: Unable to stop activity {com.example.android.location/com.example.android.location.Track}: java.lang.NullPointerException

Answer 1

//这是第二个问题

public void onCreate(Bundle savedInstanceState)
     {
         if (registerOperation()){
             System.out.println("Already logged in");
             return;
         } 

         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);


     }
     public void registerOperation()
     {
         //checks if I did logged in already. if true start a new Intent of my Registeration page and stop the current Intent.
     }

//和

public boolean registerOperation()
    {
        SharedPreferences pref = getSharedPreferences("MyKid",MODE_PRIVATE);
        String email = pref.getString("email", null);
        String password = pref.getString("password", null);
        if(email == null && password == null)
        {
            this.stopService(this.getIntent());
            Intent register = new Intent(getBaseContext(), Register.class);
            startActivity(register);
            return true;
        }
        return false;
    }