java - 出现在同一帧

Question

我希望两个不同的图像出现在两个不同的帧中。问题是这段代码不显示这两个图像(圆圈)，而只显示最后一个。任何帮助将不胜感激!谢谢。

public class MyCanvas extends JPanel {


private static final long serialVersionUID = 1L;
static int paint=0;

public MyCanvas(){              
}

public void paintComponent(Graphics graphics){  


    System.out.println("mpika!!!"); 
    //  super.paintComponent(graphics);
        if(paint==0){
            graphics.setColor(Color.blue);
            graphics.drawOval(250,250,250,250);                        
        }
        else{       
            graphics.setColor(Color.red);       
            graphics.drawOval(150,150,150,150);                        
        }
}


public static void other(){
    JFrame frame2 = new JFrame();
    MyCanvas canvas2 = new MyCanvas();
    frame2.setSize(700, 700);
    frame2.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame2.add(canvas2);
    frame2.setVisible(true);
    Graphics graph2 = canvas2.getGraphics();
    canvas2.paintComponent(graph2); 

}
public static void main(String[] args){
    double t;
    JFrame frame = new JFrame();
    MyCanvas canvas = new MyCanvas();
    frame.setSize(700, 700);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(canvas);
    frame.setVisible(true);
    Scanner input = new Scanner(System.in);
    Graphics graph = canvas.getGraphics();
    canvas.paintComponent(graph);   
//      t = input.nextInt();

    paint=1;
    other();

}
}

Answer 1

你从不打电话setVisible在 frame2 .

也为 paint是静态的:

静态 int 油漆 = 0;

你只会看到一种颜色。

解决办法是把它变成MyCanvas中的成员变量，类似于:

public void setColorFlag(int color)

或者最好还是传入圆圈颜色(!)。