透明背景清屏java

Question

我不确定这个问题是否出现在其他人身上，但我正在做一些简单的动画工作。我试图有一个透明的背景，这很容易用以下代码制作：

jf.setBackground(new Color(0,0,0,0));

问题是，每当我试图移动的东西移动时(在我的情况下是一张史莱克的照片)，它就会不断地画画，而不会清除之前的史莱克。我会把我所有的代码都贴在下面。

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
import java.io.*;
import java.util.logging.*;
import java.util.logging.*;
import javax.imageio.*;
public class MoveTest extends JPanel implements KeyListener {
double velX = 0;
double velY = 0;
double moveX = 0;
double moveY = 0;
double posX = 1;
double posY = 1;
double friction = 1.005;
BufferedImage image;
public void paintComponent(Graphics g) {
super.paintComponent(g);
try{                
image = ImageIO.read(new File("shrek.png"));
}catch (IOException ex){
System.out.println("Image Does Not Exist");
}
g.setColor(Color.RED);
moveX += velX;
moveY += velY;
posX += moveX;
posY += moveY;
g.drawImage(image,(int)posX,(int)posY,null);
}
public void keyPressed(KeyEvent e){
int key = e.getKeyCode();
int up = KeyEvent.VK_UP, w = KeyEvent.VK_W;
int down = KeyEvent.VK_DOWN, s = KeyEvent.VK_S;
int left = KeyEvent.VK_LEFT, a = KeyEvent.VK_A;
int right = KeyEvent.VK_RIGHT, d = KeyEvent.VK_D;
if(key == w || key == up)
velY = -.2;
if(key == s || key == down)
velY = .2;
if(key == a || key == left)
velX = -.2;
if(key == d || key == right)
velX = .2;
}
public void keyReleased(KeyEvent e){
int key = e.getKeyCode();
int up = KeyEvent.VK_UP, w = KeyEvent.VK_W;
int down = KeyEvent.VK_DOWN, s = KeyEvent.VK_S;
int left = KeyEvent.VK_LEFT, a = KeyEvent.VK_A;
int right = KeyEvent.VK_RIGHT, d = KeyEvent.VK_D;
if(key == w || key == up)
velY = 0;
if(key == s || key == down)
velY = 0;
if(key == a || key == left)
velX = 0;
if(key == d || key == right)
velX = 0;
}
public void keyTyped(KeyEvent e){}
public static void main(String[] args) {
MoveTest mt = new MoveTest();
JFrame jf = new JFrame();
jf.setTitle("Test one cladss");
jf.setSize(1440,900);
jf.setBackground(new Color(0,0,0,0));
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf.add(mt);
jf.setVisible(true);
mt.setOpaque(true);
mt.addKeyListener(mt);
mt.requestFocusInWindow();
while(true){
//jf.removeAll();
jf.repaint();
mt.collision();
mt.friction();
try {
Thread.sleep(16);
} catch(InterruptedException ex) {
Thread.currentThread().interrupt();
}
}
}
public void collision(){
if(posX >= 1440-50|| posX <= 0){
velX -= (2*velX);
moveX -= (2*moveX);
}
if(posY >= 900-50 || posY <= 0){
velY -= (2*velY);
moveY -= (2*moveY);
}
}
public void friction(){
moveX /= friction;
moveY /= friction;
}
}

如果你有更多的信息，请评论。任何帮助都将不胜感激！

Answer 1

我以前遇到过这种情况。从JFrame重写的paintComponent方法不同于从所有其他组件重写。由于您已经覆盖了JFrame的绘制代码，因此它不再擦除背景。有两种解决方案：

1. 添加您自己的JComponent(JPanel会很好地工作)并覆盖它的绘制方法，而不是JFrame

或

2. 调用super.paintComponent后，首先要自己清除画布

此外：

你不应该每次画画都阅读你的图像。由于在从任何线程调用重新绘制后不久就会进行绘制，因此图像可能会加载多次。如果您需要加载一次，请在类中创建一个无名实例块，如下所示：

{
try{                
image = ImageIO.read(new File("shrek.png"));
}catch (IOException ex){
System.out.println("Image Does Not Exist");
}
}

如果你只打算有一个副本，把它做成一个静态块：

static {
<load image here>
}

如果你想每帧都重新加载图像，因为它发生了变化，你需要找到一种不这样做的方法。相反，任何图像动画都应该通过在java中编辑BufferImage对象或加载sprite贴图来实现。