Java GUI：如何在JFrame上的JPanel中设置JButton的焦点？ [英] Java GUI: How to Set Focus on JButton in JPanel on JFrame?

问题描述

我已经进行了实验和搜索，我似乎无法弄清楚我认为什么是简单的东西，当我的小GUI应用程序启动时，让我的START按钮有焦点，所以用户所要做的就是按下他们的Enter / Return键，这与他们用鼠标点击START按钮的效果相同。这是我的代码。感谢您的帮助：）

I've experimented and searched and I can't seem to figure out what I thought would be something simple, which is having my START button have focus when my little GUI app launches I.e., so all the user has to do is press their Enter/Return key, which will have the same effect as if they had clicked the START button with their mouse. Here is my code. Thanks for your help :)

private void initialize() {

   // Launch the frame:
   frame = new JFrame();
   frame.setTitle("Welcome!");
   frame.setSize(520, 480);
   frame.setLocationRelativeTo(null);
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

   // Add the image:
   ImageIcon heroShotImage = new ImageIcon("heroShot.jpg");
   JPanel heroShotPanel = new JPanel();
   JLabel heroShot = new JLabel(heroShotImage);
   heroShotPanel.add(heroShot);

   // Create a panel to hold the "Start" button:
   JPanel submitPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));

   // Create the "Start" button, which launches business logic and dialogs:
   JButton start = new JButton("Start");
   start.setToolTipText("Click to use library");
   start.setFocusable(true); // How do I get focus on button on App launch?
   start.requestFocus(true); // Tried a few things and can't get it to work.

   // Listen for user actions and do some basic validation:
   start.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
      // THE APP's LOGIC GOES HERE...
      }

   // Finish setting up the GUI and its components, listeners, and actions:
   submitPanel.add(start);

   frame.getContentPane().add(heroShotPanel, BorderLayout.NORTH);
       frame.getContentPane().add(submitPanel, BorderLayout.SOUTH);

}

推荐答案

试试这段代码..我所做的就是最后移动 requestFocus（）方法。

Try out this code.. All I have done is moving the requestFocus() method at the end.

基本上这些是你需要做的两件事在按下回车键的同时进行响应并默认聚焦。

Basically these are the two things you have to do for it to respond while pressing enter key and for it to be focused by default.

frame.getRootPane().setDefaultButton(start);
start.requestFocus();

package sof;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class TestFrame {

    public static void main(String[] args) {
        // Launch the frame:
        JFrame frame = new JFrame();
        frame.setTitle("Welcome!");
        frame.setSize(520, 480);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // Add the image:
        ImageIcon heroShotImage = new ImageIcon("heroShot.jpg");
        JPanel heroShotPanel = new JPanel();
        JLabel heroShot = new JLabel(heroShotImage);
        heroShotPanel.add(heroShot);

        // Create a panel to hold the "Start" button:
        JPanel submitPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));

        JButton start = new JButton("Start");
        start.setToolTipText("Click to use library");

        start.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("I AM PRESSED");
            }
        });

        submitPanel.add(start);

        frame.getContentPane().add(heroShotPanel, BorderLayout.NORTH);
        frame.getContentPane().add(submitPanel, BorderLayout.SOUTH);
        frame.setVisible(true);
        frame.getRootPane().setDefaultButton(start);
        start.requestFocus();
    }
}

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