Question

Java 里为什么画不出横线?

public class SleepMethodTest extends JFrame{
private static final long serialVersionUID = 1L;
private Thread t;
public static Color[]color ={Color.BLACK,Color.BLUE,Color.CYAN,Color.green,Color.ORANGE,
Color.YELLOW,Color.RED,Color.PINK,Color.LIGHT_GRAY};
private static final Random rand = new Random();
private static Color getC(){
return color[rand.nextInt(color.length)];

}
public SleepMethodTest(){
t = new Thread(new Runnable(){
int x =30;
int y =50;
public void run(){
while(true){
try{
Thread.sleep(100);

}catch (InterruptedException e){
e.printStackTrace();
}
Graphics graphics =getGraphics();
graphics.setColor(getC());
graphics.drawLine(x, y, 10, y++);
if(y<80){
y=50;
}
}
}
});
t.start();
}
public static void main(String[] args){
init(new SleepMethodTest(),100,100);
}

public static void init(JFrame frame,int width,int height){
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(width, height);
frame.setVisible(true);
}

}

Answer 1

得覆盖 paint 方法，在paint 方法中画。。。。。。。。。。

或者，先在BufferedImage中画好，再paint上去 。。。。。。。。