java - 在Java主窗口上画线

我试图在主窗口上画线而不创建新窗口，因为在我发现的大多数示例中都是如此。我在NetBeans 8.1中创建了一个新项目，添加了新的JPanel并将两个按钮置于“设计”模式。像这样：

public class NewJPanel extends javax.swing.JPanel {

    /**
     * Creates new form NewJPanel
     */
    public NewJPanel() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    . . . .
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
    }

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
    }


    // Variables declaration - do not modify
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    // End of variables declaration
}

我想按Buttom1画线（10,10,100,100），按Bottom2画线。我将不胜感激最简单的例子。
非常感谢！

最佳答案

您可以使用paint方法在JPanel中绘制2D图形，为实现您的功能，请创建一个布尔变量drawLine并将其对button1设置为true，对button2设置为false，如下所示：

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
        drawLine = true;
        repaint();
    }

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        drawLine = false;
        repaint();
    }

    // Variables declaration - do not modify
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private boolean drawLine = false;

现在，覆盖面板中的paint方法，并添加以下代码以显示line并在drawLine为false时将其清除：

@Override
    public void paint(Graphics arg0) {
        super.paint(arg0);
        Graphics2D gd = (Graphics2D) arg0;
        if(drawLine){
            gd.setColor(Color.RED);
            gd.drawLine(10, 10, 100, 100);
        }else{
            super.paint(arg0);
        }
    }

这样，您可以通过按button1画线，并用button2清除它。