为什么我不能在jpanel上创建一个形状？

Question

我正在研究带有套接字编程的java gui。我想在jframe上使用我从服务器发送的参数创建jpanel，并在jpanel中创建随机形状。我用这个资源绘制形状：

https://github.com/AugustBrenner/Random-Draw-Shape/blob/master/DrawPanel.java

我在jframe中的代码是;

 public void starteGame(String received) {
    gamers.setText(received);



    String[] mParsed = received.split(" ");
    boolean filled = true;
    int width = Integer.parseInt(mParsed[2]);
    int height = Integer.parseInt(mParsed[1]);
    int x1 = Integer.parseInt(mParsed[3]);
    int y1 = Integer.parseInt(mParsed[4]);
    int x2 = Integer.parseInt(mParsed[5]);
    int y2 = Integer.parseInt(mParsed[6]);
    int randomShape = Integer.parseInt(mParsed[7]);
    Color firstColor = new Color(Integer.parseInt(mParsed[8]), true);
    Color secondColor = new Color(Integer.parseInt(mParsed[9]), true);
    boolean cyclic = Boolean.parseBoolean(mParsed[10]);
    switch (randomShape) {
        case 1:
            // add the line to the list of lines to be displayed
            shape = new MyPolygon(x1, y1, x2, y2, firstColor, filled);
            break;
        case 2:
            shape = new MyRectangle(x1, y1, x2, y2, firstColor, filled);
            break;
        case 3:
            shape = new MyOval(x1, y1, x2, y2, firstColor, filled);
            break;
    }

 jPanel2=new PanelDraw(width,height,x1,y1,x2,y2,firstColor,secondColor,
randomShape,shape,cyclic);

}

And my PanelDraw is;
public class PanelDraw extends JPanel implements MouseMotionListener {

private Random randomNumbers;
private MyShape shape;
int x1;
int y1;
int x2;
int y2;
Color firstColor;
Color secondColor;
int width;
int height;
// generate random shape
int randomShape;
 boolean cyclic ;
// constructor, creates a panel with random shapes
public PanelDraw(int width, int height, int x1, int y1, int x2, int y2, 
Color first, Color second, int randomS,MyShape shape ,boolean cyclic) {
    this.width = width;
    this.height = height;
    // generate random coordinates      
    this.x1 = x1;
    this.y1 = y1;
    this.x2 = x2;
    this.y2 = y2;
    // generate a random color
    this.firstColor = first;
    this.secondColor = second;
    // generate random shape
    randomShape = randomS;
    this.shape=shape;
    this.cyclic=cyclic;
    //setBackground( Color.BLACK ); 
} // end DrawPanel constructor

   public void mouseMoved(MouseEvent event) {

}// end mouseMoved

public void mouseDragged(MouseEvent event) {
} // end method

// for each shape array, draw the individual shapes
   @Override
   public void paintComponent(Graphics g) {

    //initialize filled boolean to true;
    boolean filled = true;

    // initialize random cyclic boolean


    // draw the shape
    Graphics2D g2d = (Graphics2D) g; // cast g to Graphics2D
    g2d.setPaint(new GradientPaint(x1, y1, firstColor, x2, y2,
            secondColor, cyclic));
    shape.draw(g2d);
    g2d.dispose();
   // shapeCount++;

    try {
        Thread.sleep(700);
    } catch (Exception e) {
    }

    repaint();

} // end method paintComponent

} // end class DrawPanel

当我的功能运行并且没有出现随机形状时，面板不会出现。你能帮助我吗？

Answer 1

Problem #1...

try {
    Thread.sleep(700);
} catch (Exception e) {
}

在你的paintComponent方法内：/

Swing是单线程的（而不是线程安全的），在你的paintComponent中执行此操作将阻止绘制所有内容，直到sleep返回之后，它还将阻止所有用户交互发生。

有关详细信息，请参阅Concurrency in Swing

问题＃1.1 ......

Graphics2D g2d = (Graphics2D) g; // cast g to Graphics2D
//...
g2d.dispose();

传递给您的Graphics上下文由系统创建，并在绘制过程中绘制的所有组件之间共享。像这样处理它会导致其他部件被涂漆

问题＃1.2 ......

repaint();

在你的paintComponent方法里面。

不要直接或间接地改变油漆通道中任何组件的状态。绘画应该描绘状态而不是其他。执行此操作将导致重绘管理器运行并消耗所有CPU周期

Problem #2....

jPanel2=new PanelDraw(width,height,x1,y1,x2,y2,firstColor,secondColor, randomShape,shape,cyclic);

是的，但你没有将组件添加到任何东西，那么它是如何被绘制的？

Answer 2

Thread.sleep(700);

不要在绘画方法中使用Thread.sleep（）。

这将导致事件调度线程进入休眠状态，这意味着GUI无法重新绘制自身或响应事件。

也：

1. 永远不要在绘画方法中调用reapint（）。如果你需要动画，可以使用Swing Timer。
2. paintComponent（）方法中的第一个语句应该是super.paintComponent(g)，以确保在执行自定义绘制之前清除面板的背景。