java - 将 repaint() 方法与 actionPerformed 一起使用

Question

当按下按钮并且图形 p 必须从头开始重新绘制所有内容时，如何使用 repaint() 方法？

谢谢。

  import javax.swing.Box;
  import javax.swing.JButton;
  import javax.swing.JTextField;
  import java.awt.*;
  import java.awt.event.*;
  import javax.swing.*;

  class fares extends JPanel{

    private static final long serialVersionUID = 1L;
    public static int xaxis1,xaxis2,yaxis3,yaxis4;

public ControlsB(square) {

    final JButton btn1 = new JButton("Resize");

    final Box b = Box.createHorizontalBox();
    b.add(new JLabel("Please enter range:  "));
    Box b0 = Box.createVerticalBox();//create a vertical box to stack the controls

    Box b1 = Box.createHorizontalBox(); // create a horizontal box for the x-axis

    //x-axis
    b1.add(new JLabel("mark "));
    b1.add(new JLabel("for"));

    f1.setMaximumSize(new Dimension(100,30));

    b1.add(f1);
    b1.add(new JLabel("till"));

    f2.setMaximumSize(new Dimension(100,30));
    b1.add(f2);

    //y-axis
    //this code is not in use at the moment

    f4.setMaximumSize(new Dimension(100,30));
    b2.add(f4);

    b0.add(b1);

    add(b);

    btn1.addActionListener(new ActionListener(){

        public void actionPerformed(ActionEvent event){

            f = Integer.parseInt(f1.getText());

            invalidate();
            validate();
            paint(p);//this is not working...
        }
    });
 b.add(btn1);
  }
}

这是必须调用和重绘的代码:

import java.awt.*;

import javax.swing.*;

class Graph extends JPanel {

public static Graphics p;
private static final long serialVersionUID = 1L;
public static int f;
public static int g;

@Override
public Dimension getPreferredSize()
{   
    return (new Dimension(560,560));
}

public void paintComponent(Graphics p) {

    super.paintComponent(p);

    Graphics2D graph = (Graphics2D)p;

    Dimension appletSize = this.getSize();
    int appletHeight = (int)(appletSize.height);
    int appletWidth = appletSize.width;

    //change -ve num to +ve
    int g3 = Math.abs(g);

    int a1 = g3 + f;
    int b1 = a1;


    int d = (appletWidth / a1);
    int e = (appletHeight / b1);

    //draw y-axis numbers 
    //(+ve)
    while(f != 0){
        String s = String.valueOf(f);

        m = m + b;
        f = f - 1;
    }
    //(-ve)
    m2 = y;
    while(f2 != g-1)
        m2 = m2 + b;
        f2 = f2 - 1;
    }
    //draw x-axis numbers.
    //(-ve)
    while(g != 0){
        String hy = String.valueOf(g);

        n = n + a;
        g = g + 1;
    }
    //(+ve)
    n2 = x + a;
    while(g2 != g3+1){
        String w = String.valueOf(g2);
        n2 = n2 + a;
        g2 = g2 + 1;
    }

    BasicStroke aLine2 = new BasicStroke(1.0F,
                                         BasicStroke.CAP_ROUND,BasicStroke.JOIN_ROUND);
    graph.setStroke(aLine2);

    //notch on numbers and grid lines
    //left to right, top to bottom notches
    int v2 = -5;
    int v5 = 0;
    while(i <= a1-1){
        p.setColor(Color.lightGray);//lightgray line
        a = a + d;
        b = b + e;
        i = i + 1;
    }

  }
}

目前，调整大小按钮可以使用，但我需要调整窗口大小，以便图表响应给定的输入。基本上在调整图形大小时正在重新绘制/重新绘制...现在我需要自动完成此操作。

Answer 1

很难根据代码片段判断出什么问题，但看起来您的图表是在 Graph 对象上绘制的，称为 graph (如果我错了请纠正我)，并且您似乎正在尝试重新绘制(或绘画——永远不要直接调用它!)你的 ControlsB 面板。如果是这样，那么您可能在错误的对象上调用了方法。也许您需要执行以下操作:

// graph is final so it may be used in an inner class
public ControlsB(Box box2, final Graph graph) {

     // .....

      btn1.addActionListener(new ActionListener(){

        public void actionPerformed(ActionEvent event){

            f = Integer.parseInt(f1.getText());
            g = Integer.parseInt(f2.getText());
            System.out.println(f + "  " + g);

            // invalidate();
            // validate();
            //  paint(p); ***** NEVER do this

            graph.repaint();
        }
    });
}

还有:

• 切勿直接在组件上调用 paint(...)，除非在非常特殊的情况下(不是这样)。
• 永远不要试图捕获一个组件的 Graphics 对象并用它来绘制，因为这通常会导致 NullPointerException 发生，而且它肯定不会起作用。
• 一定要阅读标准 Swing 教程中有关如何在 Swing 中绘图的内容。您可能会从中学到很多东西。
• 同样，如果您不能很快得到满意的答案，请考虑创建并发布一个 sscce .