[英]Please explain the working of repaint() method in java?
我見過很多類似的問題但我不明白為什么重繪不能正常工作
在我的程序中,在退出框架之前,我調用了 repaint() 使用 Thread.sleep 來延遲退出,然后消息“鼠標退出”也不會顯示。
你能解釋一下為什么會發生這種情況或提供相同的鏈接嗎
public void mouseExited(MouseEvent me)
{
msg="Mouse Exited";
repaint();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
System.exit(0);
}
完整的程序
/**Write a program to create a frame using AWT. Implement mouseClicked( ),
mouseEntered( ) and mouseExited( ) events. Frame should become visible when
mouse enters it. */
import java.awt.*;
import java.awt.event.*;
class Question8 extends Frame{
static Dimension original;
String msg;
Question8(String s)
{
msg=s;
addMouseListener(new MouseAdapter()
{
public void mouseClicked(MouseEvent me)
{
msg="Mouse Clicked";
setSize(original);
repaint();
}
public void mouseEntered(MouseEvent me)
{
msg="Mouse Entered";
setSize(original.height*3,original.width*3);
repaint();
}
public void mouseExited(MouseEvent me)
{
msg="Mouse Exited";
repaint();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
System.exit(0);
}
});
addWindowListener(new WindowAdapter()
{
public void windowClosing(Window ev)
{
System.exit(0);
}
});
}
public void paint(Graphics g)
{
g.drawString(msg, 50, 50);
}
public static void main(String agrs[])
{
Question8 obj=new Question8("Hello");
original=new Dimension(300,300);
obj.setSize(original);
obj.setTitle("Question 8");
obj.setVisible(true);
}
}
正如maloomeister 所指出的, Thread.sleep()
正在阻塞事件線程,因此您需要創建一個新線程。
如果你用這個替換你的mouseExited
方法,它會像你期望的那樣工作:
public void mouseExited(MouseEvent me) {
msg = "Mouse Exited";
repaint();
new Thread(() -> {
try {
Thread.sleep(1000);
System.exit(0);
} catch (InterruptedException e) {
}
}
).start();
}
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