[英]stop applet flickering with double buffering Java Applet
很抱歉继续询问有关我的程序的问题,但是我想我已经快到了,而且我正在自学Java,所以请多多包涵。 我正在创建一个applet,当狗对象靠近绵羊时,它将绵羊对象在屏幕上随机移动。 让绵羊沿随机方向移动需要一些工作,并且在你们的帮助下,它现在可以工作了(但有些),但是我现在要做的是阻止我在屏幕上拖动对象时闪烁。 我已经读过有关双重缓冲的知识,我可以使它适用于在主类的paint方法中绘制的项目,但不能使其适用于在不同类中定义为单独对象的绵羊和狗对象。 任何帮助都感激不尽。 这是我的代码:
package mandAndDog;
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;
public class SheepDog extends Applet implements ActionListener, MouseListener, MouseMotionListener
{
/**
*
*/
private static final long serialVersionUID = 1L;
/**
*
*/
Dog dog;
Sheep sheep;
int[] directionNumbersLeft = {0, 1, 3};
int[] directionNumbersUp = {0, 1, 2};
int x;
int selection;
int xposR;
int yposR;
int sheepx;
int sheepy;
int sheepBoundsx;
int sheepBoundsy;
int MAX_DISTANCE = 50;
int direction;
int distance;
Boolean sheepisclosetodog;
public void init()
{
addMouseListener(this);
addMouseMotionListener(this);
dog = new Dog(10, 10);
sheepx = 175;
sheepy = 75;
sheep = new Sheep(sheepx, sheepy);
sheepBoundsx = 30;
sheepBoundsy = 30;
direction = (int)(Math.random()*4);
distance = (int) (Math.random() * MAX_DISTANCE) % MAX_DISTANCE;
sheepisclosetodog = false;
Random rand = new Random();
x = rand.nextInt(3);
selection = directionNumbersLeft[x];
}
public void paint(Graphics g)
{
dog.display(g);
sheep.display(g);
g.drawString(Integer.toString(distance), 85, 100);
g.drawString(Integer.toString(direction), 85, 125);
g.drawString(Integer.toString(selection), 85, 140);
}
public void actionPerformed(ActionEvent ev)
{}
public void mousePressed(MouseEvent e)
{}
public void mouseReleased(MouseEvent e)
{}
public void mouseEntered(MouseEvent e)
{}
public void mouseExited(MouseEvent e)
{}
public void mouseMoved(MouseEvent e)
{
}
public void mouseClicked(MouseEvent e)
{}
public void mouseDragged(MouseEvent e)
{
dog.setLocation(xposR, yposR);
sheep.setLocation(sheepx, sheepy);
if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
&& yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 0){
sheepx = sheepx + 50;
direction = (int)(Math.random()*4);
}
if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
&& yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 1){
sheepy = sheepy + 50;
direction = (int)(Math.random()*4);
}
if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
&& yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 2){
sheepx = sheepx - 50;
direction = (int)(Math.random()*4);
}
if (sheepx <= 5){
direction = directionNumbersLeft[x];
}
if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
&& yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 3){
sheepy = sheepy - 50;
direction = (int)(Math.random()*4);
}
if (sheepy <=5){
direction = directionNumbersUp[x];
}
xposR = e.getX();
yposR = e.getY();
repaint();
}
}
class Dog
{
int xpos;
int ypos;
int circleWidth = 30;
int circleHeight = 30;
public Dog(int x, int y)
{
xpos = x;
ypos = y;
}
public void setLocation(int lx, int ly)
{
xpos = lx;
ypos = ly;
}
public void display(Graphics g)
{
g.setColor(Color.blue);
g.fillOval(xpos, ypos, circleWidth, circleHeight);
}
}
class Sheep
{
int xpos;
int ypos;
int circleWidth = 10;
int circleHeight = 10;
public Sheep(int x, int y)
{
xpos = x;
ypos = y;
}
public void setLocation(int lx, int ly)
{
xpos = lx;
ypos = ly;
}
public void display(Graphics g)
{
g.setColor(Color.green);
g.fillOval(xpos , ypos, circleWidth, circleHeight);
g.drawOval(xpos - 20, ypos - 20, 50, 50);
}
}
首先,我不完全理解为什么在Sheep and Dog类中有显示方法。 与其相反,我建议您在SheepDog类中显示绵羊和狗。
另外,应该使用Graphics2D而不是Graphics。 为了使用这个简单地做
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
}
这是可能的,因为Graphics2D是Graphics的子类。 完成此操作后,我要做的就是覆盖update()方法并执行此操作
public void update(Graphics g) {
if (image == null) {
image = createImage(this.getWidth(), this.getHeight());
graphics = image.getGraphics();
}
graphics.setColor(getBackground());
graphics.fillRect(0, 0, this.getWidth(), this.getHeight());
graphics.setColor(getForeground());
paint(graphics);
g.drawImage(image, 0, 0, this);
}
当您调用repaint()时,它实际上首先调用了update()方法,该方法又调用了paint()方法。 在课堂上,您应该声明
Image image;
Graphics graphics;
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