[英]Java Applet: painted ball does not appear in the hard-coded position. Applet does not maintain constant size
我正在制作一个由在屏幕上移动的球组成的applet。 我将球的初始X和Y坐标设置为0,但是在距这些点一定距离处绘制了椭圆形(参见图片)。 另一个问题是,有时当我运行应用程序时,会得到一个具有所需宽度和高度的小程序,但有时它会更小。 我不确定为什么会这样。
我粘贴了以下代码:
import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Timer;
public class StartingPoint extends Applet implements ActionListener
{
final int DELAY = 10;
final int APPLET_WIDTH = 400;
final int APPLET_HEIGHT = 300;
int x=0;
int y=0;
int ballRadius = 20;
int movementX = 10;
int movementY = 10;
private Image appletImage;
private Graphics appletGraphics;
public void init()
{
super.init();
//StartingPoint.this.setSize( APPLET_WIDTH, APPLET_HEIGHT );
}
public void start()
{
Timer animationTimer = new Timer(60, this);
animationTimer.start();
}
public void stop()
{
super.stop();
}
public void destroy()
{
super.destroy();
}
public void update(Graphics g)
{
if(appletImage == null)
{
appletImage = createImage( this.getSize().width, this.getSize().height );
appletGraphics = appletImage.getGraphics();
}
//draw applet background
appletGraphics.setColor(getBackground());
appletGraphics.fillRect(0, 0, this.getSize().width, this.getSize().height);
//draw applet foreground
appletGraphics.setColor(getForeground());
this.paint( appletGraphics );
//draw images on the applet
g.drawImage(appletImage, 0, 0, this);
}
public void paint(Graphics g)
{
super.paint(g);
this.setBackground(Color.BLUE);
g.setColor(Color.RED);
g.fillOval(this.x, this.y, ballRadius, ballRadius);
}
@Override
public void actionPerformed(ActionEvent e)
{
if( (x+movementX) > (this.getWidth()-ballRadius))
{
this.x = this.getWidth()-ballRadius;
this.movementX = -movementX;
}else if( x+movementX < ballRadius)
{
this.x = ballRadius;
this.movementX = -movementX;
}
else
this.x += movementX;
if( (y+movementY) > this.getHeight()-ballRadius)
{
this.y = this.getHeight()-ballRadius;
this.movementY = -movementY;
}else if( y+movementY < ballRadius)
{
this.y = ballRadius;
this.movementY = -movementY;
}
else
this.y += movementY;
this.repaint();
}
}
我弄清楚哪里出了问题,这确实有点愚蠢。
actionPerformed()方法中的以下代码行偏移了x和y位置:
else
this.x += movementX;
//....
else
this.y += movementY;
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