Zugriff auf Arraylist außerhalb des Oncreate

Question

Hallo, ich bin neu in der Programmierung. Ich möchte Zugriff auf Arraylist außerhalb von onCreate, aber ich bekomme Fehler. Im Folgenden ist Code.

public class WelcomeOnFootActivity extends AppCompatActivity { 
    ImageButton next; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_welcome_on_foot); 
     Bundle bundle=getIntent().getExtra; 
     List<UserDate> data= new ArrayList(); 
     data.add((UserData)bundle.get("data")); 
     next=(ImageButton)findViewById(R.id.next); 

     next.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       handle(); 
      } 
     }); 
    } 
private void handle(){ 
     String info=data.getUserInfo;// here i get error 
} 
} 

Answer 1

public class WelcomeOnFootActivity extends AppCompatActivity { 
    ImageButton next; 
List<UserDate> data; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_welcome_on_foot); 
     Bundle bundle=getIntent().getExtra; 
     data= new ArrayList(); 
     data.add((UserData)bundle.get("data")); 
     next=(ImageButton)findViewById(R.id.next); 

     next.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       handle(); 
      } 
     }); 
    } 
private void handle(){ 
     String info=data.getUserInfo;// here i get error 
} 
} 

Answer 2

erklären Sie einfach die Liste global auf Klassenebene. In Ihrem Fall vor OnCreate.

List<UserDate> data= new ArrayList(); 
en@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_welcome_on_foot); 
    Bundle bundle=getIntent().getExtra; 
    data.add((UserData)bundle.get("data")); 
    next=(ImageButton)findViewById(R.id.next); 

    next.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      handle(); 
     } 
    }); 


    } 
    private void handle(){ 
     String info=data.getUserInfo; 
} 

Ich hoffe, es wird helfen.

Answer 3

public class WelcomeOnFootActivity extends AppCompatActivity { 
    ImageButton next; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_welcome_on_foot); 
     Bundle bundle=getIntent().getExtra; 
     final List<UserDate> data= new ArrayList(); 
     data.add((UserData)bundle.get("data")); 
     next=(ImageButton)findViewById(R.id.next); 

     next.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       handle(data); 
      } 
     }); 
    } 
private void handle(List<UserDate> listUD){ 
     String info=listUD.getUserInfo;// here i get error 
} 
}