How to Set Focus on JTextField?

问题:

I make my game run without mouse so using pointer is not a choice. High Score menu will show when player lose.

this is my code

    highScore=new MyTextField("Your Name");
    highScore.addKeyListener(this);
    highScore.setFont(font);
    highScore.requestFocusInWindow();

I have tried

highScore.setFocusable(true);
highScore.requestFocusInWindow();
highScore.requestFocus(true);
highScore.requestFocus();

but still not gained focus on my JTextField.

How to focus it?

回答1:

If you want your JTextField to be focused when your GUI shows up, you can use this:

in = new JTextField(40);
f.addWindowListener( new WindowAdapter() {
    public void windowOpened( WindowEvent e ){
        in.requestFocus();
    }
}); 

Where f would be your JFrame and in is your JTextField.

回答2:

if is there only one Top-Level Container then last lines in GUI constructor would be for example

.
.
.
myFrame.setVisible(true);
EventQueue.invokeLater(new Runnable() {

   @Override
     public void run() {
         myComponent.grabFocus();
         myComponent.requestFocus();//or inWindow
     }
});

回答3:

public void actionPerformed(ActionEvent arg0)
{
    if (arg0.getSource()==clearButton)
    {
        enterText.setText(null);
        enterText.grabFocus();  //Places flashing cursor on text box        
    }       
}

回答4:

Try this one,

myFrame.setVisible(true);
EventQueue.invokeLater(new Runnable() {

   @Override
     public void run() {
         myComponent.grabFocus();
         myComponent.requestFocus();//or inWindow
     }
});

回答5:

If the page contains multiple item and like to set the tab sequence and focus I will suggest to use FocusTraversalPolicy.

grabFocus() will not work if you are using FocusTraversalPolicy.

Sample code

int focusNumber = 0;
Component[] focusList;
focusList = new Component[] { game, move, amount, saveButton,
            printButton, editButton, deleteButton, newButton,
            settingsButton };

frame.setFocusTraversalPolicy(new FocusTraversalPolicy() {

        @Override
        public Component getLastComponent(Container aContainer) {
            return focusList[focusList.length - 1];
        }

        @Override
        public Component getFirstComponent(Container aContainer) {
            return focusList[0];
        }

        @Override
        public Component getDefaultComponent(Container aContainer) {
            return focusList[1];
        }

        @Override
        public Component getComponentAfter(Container focusCycleRoot,
                Component aComponent) {
            focusNumber = (focusNumber + 1) % focusList.length;
            if (focusList[focusNumber].isEnabled() == false) {
                getComponentAfter(focusCycleRoot, focusList[focusNumber]);
            }
            return focusList[focusNumber];
        }

        @Override
        public Component getComponentBefore(Container focusCycleRoot,
                Component aComponent) {
            focusNumber = (focusList.length + focusNumber - 1)
                    % focusList.length;
            if (focusList[focusNumber].isEnabled() == false) {
                getComponentBefore(focusCycleRoot, focusList[focusNumber]);
            }
            return focusList[focusNumber];
        }
    });

回答6:

In my case nothing above worked untill I called requestFocus() AFTER my constructor has returned.

MyPanel panel = new MyPanel(...);
frame.add(panel);
panel.initFocus();

MyPanel.initFocus() would have:

myTextField.requestFocus();

And it works.

回答7:

This code mouse cursor “jtextfield” “Jcombobox” location focused

 try {
     Robot  robot = new Robot();
        int x = Jtextfield.getLocationOnScreen().x;
        int y=  Jtextfield.getLocationOnScreen().y;
       JOptionPane.showMessageDialog(null, x+"x< - y>"+y);// for I location see
        robot.mouseMove(x, y);
    } catch (AWTException ex) { 
        ex.printStackTrace();
    } 

回答8:

It was not working for me when tried to use:

JOptionPane.showConfirmDialog(...)

But - I found a solution ! Very primitive, but works.

Just jump to the field by java.awt.Robot using key "Tab". For example:

Robot robot = new Robot();
robot.keyPress(KeyEvent.VK_TAB);
robot.delay(100);
robot.keyRelease(KeyEvent.VK_TAB);

If you should press multiple times on "Tab" to get your Component you can use below method:

GUIUtils.pressTab(3);

Definition:

public static void pressTab(int amountOfClickes)
{
    SwingUtilities.invokeLater(new Runnable()
    {
        public void run()
        {
            try
            {
                Robot robot = new Robot();
                int i = amountOfClickes;
                while (i-- > 0)
                {
                    robot.keyPress(KeyEvent.VK_TAB);
                    robot.delay(100);
                    robot.keyRelease(KeyEvent.VK_TAB);
                }
            }
            catch (AWTException e)
            {
                System.out.println("Failed to use Robot, got exception: " + e.getMessage());
            }
        }
    });
}

If your Component location is dynamic, you can run over the while loop without limitation, but add some focus listener on the component, to stop the loop once arrived to it.

回答9:

While yourTextField.requestFocus() is A solution, it is not the best since in the official Java documentation this is discourage as the method requestFocus() is platform dependent.

The documentation says:

Note that the use of this method is discouraged because its behavior is platform dependent. Instead we recommend the use of requestFocusInWindow().

Use yourJTextField.requestFocusInWindow() instead.