JFrame repaint()问题 - Java

Question

我希望能够在JFrame上使用Java的paint()进行绘制.当我点击的JFrame(任何地方现在)我想的JFrame与点击的坐标重新绘制-类似这样的Java小程序http://www.realapplets.com/tutorial/MouseClickExample.html

正在工作:

• 最初绘制所有内容并正确显示JFrame

不工作:

• 即使声明了repaint(),JFrame也不会重新绘制和更新

这是我的代码 - 请尽可能严格 - 我希望改进我的Java编程技术(如果你有时间)指出我可以改进的每个方面.

任何帮助将非常感谢.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class AreaForText extends JPanel implements MouseListener {

int xpos; 
int ypos;

JFrame myJFrame = new JFrame();

public void setJFrame() {

    myJFrame.setSize(300, 150);
    myJFrame.setTitle("Bigger Text!");
    myJFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    myJFrame.setVisible(true);
    myJFrame.getContentPane().add(new AreaForText());
    myJFrame.addMouseListener(new AreaForText());

}

public void mouseClicked(MouseEvent me) {
    //Save the coordinates of the click lke this. 
    xpos = MouseInfo.getPointerInfo().getLocation().x; 
    ypos = MouseInfo.getPointerInfo().getLocation().y;
    System.out.print("Click" + "  x: " + xpos + "  y: " + ypos);
    myJFrame.invalidate();
    repaint();
    revalidate();
}


public void mouseEntered(MouseEvent e){
}

public void mouseReleased(MouseEvent e) { 
}

public void mousePressed(MouseEvent e) {
}

public void mouseExited(MouseEvent e) { 
}

public void paint(Graphics g) {

    System.out.print("hello");
    g.drawString("Hello World", 30, 80);
    g.fillRect(20,20,20,20);        
    g.drawString("("+xpos+","+ypos+")",xpos,ypos);

    }
}

class EnlargeText {

    public static void main(String args[]) {

       AreaForText test = new AreaForText();

       test.setJFrame();

    }

 } 

Answer 1

您正在创建2个AreaForText实例,这不是您想要做的.一个添加到JFrame,一个添加到侦听器.因此实际获取鼠标事件并且正在调用重绘的那个与正在显示的对象不同.

你的一些代码组织并不是最好的.你有一个JPanel子类,它构建自己的JFrame并将自己放入面板中.如果你真的需要它,你应该传入JFrame.我在下面做了一些改动.

编辑.我定了一些的鼠标侦听器的东西,你得到错误的X/Y坐标,而且,你应该只添加监听到面板直接,而不是JFrame的,这样你就不必翻译坐标.

编辑我将paint方法更改为paintComponent,这是在此处覆盖的首选方法.有关更多信息,请查看Swing Paint Tutorial.

import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.MouseInfo;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JFrame;
import javax.swing.JPanel;

class AreaForText extends JPanel implements MouseListener {

    private int xpos;
    private int ypos;


    public AreaForText() {
        super();
        this.addMouseListener(this);
    }

    public void mouseClicked(MouseEvent me) {
        // Save the coordinates of the click lke this.
        xpos = me.getX();
        ypos = me.getY();
        System.out.print("Click" + "  x: " + xpos + "  y: " + ypos);
        repaint();
    }

    public void mouseEntered(MouseEvent e) {
    }

    public void mouseReleased(MouseEvent e) {
    }

    public void mousePressed(MouseEvent e) {
    }

    public void mouseExited(MouseEvent e) {
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        System.out.print("hello");
        g.drawString("Hello World", 30, 80);
        g.fillRect(20, 20, 20, 20);
        g.drawString("(" + xpos + "," + ypos + ")", xpos, ypos);

    }
}

class EnlargeText {

    public static void main(String args[]) {

        EventQueue.invokeLater(new Runnable() {
            public void run() {
                JFrame myJFrame = new JFrame("Bigger Text!");
                myJFrame.setSize(300, 150);
                myJFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                myJFrame.getContentPane().add(new AreaForText());
                myJFrame.setVisible(true);
            }
        });
    }

}

Answer 2

您没有调用 JFrame，repaint()您正在调用JPanel重绘方法（您所在的类）

尝试：

myJFrame.repaint();