修改監聽器上的文本字段

Question

我已經添加上文本字段修改監聽器，當我嘗試打開它觸發的修改監聽事件，並給出了對話框打開

這裏之前，空指針異常的對話是我的代碼

UserNameDialog dialog = new UserNameDialog(PlatformUI.getWorkbench().getActiveWorkbenchWindow().getShell(), true); 
    dialog.init("", userSession.hasAdminRights(), false, true, false, ""); 
    dialog.open(); 
    if (dialog.getReturnCode() == Window.CANCEL) { 
     return; 
    } 

對話框類

public class UserNameDialog extends TitleAreaDialog { 
private Text txtUsername; 
@Override 
protected Control createDialogArea(Composite parent) { 
    setMessage("Enter user information and press OK"); 
    setTitle("User Information"); 
    Composite area = (Composite) super.createDialogArea(parent); 
    Composite container = new Composite(area, SWT.NONE); 
    container.setLayout(new GridLayout(2, false)); 
    container.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true, 1, 1)); 

    Label lblUserName = new Label(container, SWT.NONE); 
    lblUserName.setText("User name"); 

    txtUsername = new Text(container, SWT.BORDER); 
    txtUsername.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false, 1, 1)); 
    txtUsername.addListener(SWT.Modify, new Listener() 
    { 
     @Override 
     public void handleEvent(Event event) 
     { 
      getButton(IDialogConstants.OK_ID).setEnabled(isValidUsername()); 
      // As I try to open the dialog the handler comes here and throws exception on 
      // getButton(IDialogConstants.OK_ID) 
     } 

    }); 
    if(newUser || currentUserisAdmin) 
     txtUsername.setEditable(true); 
    else 
     txtUsername.setEditable(false); 
    txtUsername.setText(name); 

    new Label(container, SWT.NONE); 
    new Label(container, SWT.NONE); 

    return area; 
} 

/** 
* Create contents of the button bar. 
* @param parent 
*/ 
@Override 
protected void createButtonsForButtonBar(Composite parent) { 
    okButton = createButton(parent, IDialogConstants.OK_ID, IDialogConstants.OK_LABEL, true); 
    createButton(parent, IDialogConstants.CANCEL_ID, IDialogConstants.CANCEL_LABEL, false); 
    okButton.setEnabled(false); 
} 

private boolean isValidUsername() 
{ 
    String username = txtUsername.getText(); 
    return username != null && username.trim().length() > 0; 
} 
}  

這是一個對話框內，但其創造的對話框我想之前調用因爲okButton是空

Answer 1

首先感謝巴茲對他的幫助。我發佈了所有相關的代碼，但我無法弄清楚爲什麼你的解決方案無法正常工作。我做了什麼，對我的工作是如下

txtUsername.addKeyListener(new KeyAdapter() { 
     @Override 
     public void keyReleased(KeyEvent e) { 
      updateOKButton(); 
     } 
    }); 


@Override 
protected void createButtonsForButtonBar(Composite parent) { 
    okButton = createButton(parent, IDialogConstants.OK_ID, IDialogConstants.OK_LABEL, true); 
    createButton(parent, IDialogConstants.CANCEL_ID, IDialogConstants.CANCEL_LABEL, false); 
    okButton.setEnabled(false); 
} 


private void updateOKButton() { 
    if(newUser){  
     if(txtUsername.getText() == null || txtUsername.getText().isEmpty()){ 
      this.setMessage("Username can not be empty!"); 
      okButton.setEnabled(false); 
     } 
     else if(txtPassword.getText().isEmpty() && txtPassword_1.getText().isEmpty()){ 
      this.setMessage("Passwords cannot be null!"); 
      okButton.setEnabled(false); 
     } 
     else if (!(txtPassword.getText().equals(txtPassword_1.getText()))) { 
      this.setMessage("Password do not match!"); 
      okButton.setEnabled(false);  
     }else { 
      this.setMessage(null); 
      okButton.setEnabled(true); 
     } 
    } 
    else{ 
     if(txtUsername.getText() == null || txtUsername.getText().isEmpty()){ 
      this.setMessage("Username can not be empty!"); 
      okButton.setEnabled(false); 
     } 
     else { 
      this.setMessage(null); 
      okButton.setEnabled(true); 
     } 
    } 
} 

感謝

Answer 2

好吧，這裏是一個對話框，如果用戶名是至少一個字符長，將只啓用OK按鈕的例子：

private Text text; 

protected UsernameDialog(Shell parentShell) 
{ 
    super(parentShell); 
} 

@Override 
protected void configureShell(Shell newShell) 
{ 
    super.configureShell(newShell); 
    newShell.setText("Dialog"); 
} 

@Override 
protected Control createDialogArea(Composite parent) 
{ 
    Composite container = (Composite) super.createDialogArea(parent); 
    text = new Text(container, SWT.BORDER); 
    text.setLayoutData(new GridData(SWT.BEGINNING, SWT.CENTER, false, false)); 
    text.addListener(SWT.Modify, new Listener() 
    { 
     @Override 
     public void handleEvent(Event event) 
     { 
      getButton(IDialogConstants.OK_ID).setEnabled(isValidUsername()); 
     } 
    }); 

    return container; 
} 

private boolean isValidUsername() 
{ 
    String username = text.getText(); 
    return username != null && username.trim().length() > 0; 
} 

@Override 
protected void okPressed() 
{ 
    if (isValidUsername()) 
     super.okPressed(); 
    else 
     System.out.println("Invalid username"); 
} 

@Override 
protected void createButtonsForButtonBar(Composite parent) 
{ 
    createButton(parent, IDialogConstants.OK_ID, IDialogConstants.OK_LABEL, true); 
    createButton(parent, IDialogConstants.CANCEL_ID, IDialogConstants.CANCEL_LABEL, false); 

    getButton(IDialogConstants.OK_ID).setEnabled(false); 
} 

public static void main(String[] args) 
{ 
    new UsernameDialog(new Shell()).open(); 
}