问题
I am gone through some of code java applet and animation, i write the following code :
import java.applet.*;
import java.awt.*;
/*<applet code="AppletDemo" width = 200 height = 100></applet>
*/
public class AppletDemo extends Applet implements Runnable
{
String msg = "Text Animating from right to left...";
Thread t = null;
int state;
boolean stopFlag;
int msgX = 200;
String s;
boolean diff;
public void init()
{
setBackground(Color.cyan);
setForeground(Color.black);
}
public void start()
{
t = new Thread(this);
stopFlag = false;
t.start();
s = "abc";
diff = s.equalsIgnoreCase("abc");
}
public void run()
{
while (true)
{
try{
if(msgX>=-150)
msgX--;
else
msgX =200;
Thread.sleep(10);
repaint();
}
catch(Exception e)
{}
}
}
public void paint(Graphics g)
{
g.drawString(msg,msgX,20);
showStatus(diff+"Text at "+msgX+",20");
}
}
What is happening is that when i put Thread.sleep(100), it works fine but when i try to animate faster that is Thread.sleep(10) it starts flickering , i couldn't understand what is happening can anyone help.
回答1:
- Don't directly paint over top level container. Use
JPanel
to paint on it. - Don't use
Thread.sleep()
. It's better to useSwing
Timer for animation. - Override
paintComponent()
method ofJPanel
for custom painting. - Don't forget to call
super.paintComponent()
inside overriddenpaintComponent
method.
Instead of infinite loop try with Swing Timer.
Please have a look at How to Use Swing Timers
sample code:
import java.applet.Applet;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JPanel;
import javax.swing.Timer;
/*
* <applet code="AppletDemo" width = 200 height = 100></applet>
*/
public class AppletDemo extends Applet {
String msg = "Text Animating from right to left...";
int state;
boolean stopFlag;
int msgX = 200;
String s;
boolean diff;
JPanel panel;
public void init() {
setBackground(Color.cyan);
setForeground(Color.black);
panel = new JPanel() {
@Override
public void paintComponent(Graphics g) {
super.paintComponents(g);
g.drawString(msg, msgX, 20);
showStatus(diff + "Text at " + msgX + ",20");
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 40);
}
};
add(panel);
int delay = 10; // milliseconds
ActionListener taskPerformer = new ActionListener() {
public void actionPerformed(ActionEvent evt) {
if (msgX >= -150)
msgX--;
else
msgX = 200;
repaint();
}
};
Timer timer = new Timer(delay, taskPerformer);
timer.setRepeats(true);
timer.start();
}
}
Find a Sample code here
回答2:
Yes it will flicker. You will have to solve this problem using the concept of DoubleBuffering. It means that the image to be drawn is already buffered before its drawn on screen. It will remove the flickering effect.
来源:https://stackoverflow.com/questions/25092903/java-applet-thread-animation