Java上边界图形 [英] Java Upper Boundary Graphics
问题描述
关于基本碰撞检测的短片：
https://www.youtube.com/watch?v=ptqhnmP8FY0&list=PL6E90696571998DC2
有人可以告诉我为什么上限需要是球的大小？我认为椭圆形是从左上角开始绘制一个边界矩形。如果是这样的话，看起来y == 0将是上限，但显然不是这种情况。
总结问题：为什么上层如果边界三角形从左上角开始，则不是0。
以下是代码：
public class JavaGame extends JFrame {
int x，y，sizeX = 350，sizeY = 350;
// boolean erase = false;
private Image dbImage;
私人图形dbg;
public class AL extends KeyAdapter {
public void keyPressed（KeyEvent e）{
int keyCode = e.getKeyCode（）;
if（keyCode == e.VK_LEFT）{
if（x <= 0）
x = 0;
else
x- = 5; （keyCode == e.VK_RIGHT）{
if（x == sizeX-20）
x = sizeX-20;
}
;
else
x + = 5;
if（keyCode == e.VK_UP）{
if（y == 20）
y = 20;
else
y- = 5;
if（keyCode == e.VK_DOWN）{
if（y == sizeY-20）
y = sizeY-20;
else
y + = 5;
}
/ * if（keyCode == e.VK_S）{
erase = true;
public void keyReleased（KeyEvent e）{
$ b}
}
public JavaGame（） {
addKeyListener（new AL（））;
x = y = 150;
setTitle（Java Game）;
setBackground（Color.WHITE）;
setSize（sizeX，sizeY）;
setResizable（false）;
setVisible（true）;
setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;
$ b public void paint（Graphics g）{
dbImage = createImage（getWidth（），getHeight（））;
dbg = dbImage.getGraphics（）;
paintComponent（dbg）;
g.drawImage（dbImage，0，0，this）;
$ b public void paintComponent（Graphics g）{
g.fillOval（x，y，20，20）;
/ * if（erase）{
g.setColor（Color.WHITE）;
g.fillRect（0，0，500，500）;
erase = false;
} * /
repaint（）;
$ b}
public static void main（String [] args）{
new JavaGame（）;
$ b
它的标题栏高度 JFrame 这就是为什么 y 在22之后开始可见
与 JFrame x >外边框宽度。
下面是示例代码以及快照
g.setColor（Color.RED）;
g.drawRect（3，22，200，200）;
- 编辑 -
我从来不建议您使用它。阅读下面的评论，因为它的缺点。
Regarding this short video of basic collision detection:
https://www.youtube.com/watch?v=ptqhnmP8FY0&list=PL6E90696571998DC2
Can someone tell me why the upper boundary needs to be the size of the ball? I thought that an oval was drawn with a bounding rectangle starting from the upper left. If that is the case then it would seem that y==0 would be the upper boundary, but that is obviously not the case.
Summary question: why is the upper boundary 20 and not 0 if the bounding triangle starts in the upper left.
Here is the code:
public class JavaGame extends JFrame {
int x,y,sizeX = 350,sizeY=350;
//boolean erase = false;
private Image dbImage;
private Graphics dbg;
public class AL extends KeyAdapter{
public void keyPressed(KeyEvent e){
int keyCode = e.getKeyCode();
if (keyCode == e.VK_LEFT){
if(x<= 0)
x=0;
else
x-=5;
}
if (keyCode == e.VK_RIGHT){
if(x==sizeX-20)
x=sizeX-20;
else
x+=5;
}if (keyCode == e.VK_UP){
if(y==20)
y=20;
else
y-=5;
}if (keyCode == e.VK_DOWN){
if(y==sizeY-20)
y=sizeY-20;
else
y+=5;
}
/*if (keyCode == e.VK_S){
erase = true;
}*/
}
public void keyReleased(KeyEvent e){
}
}
public JavaGame(){
addKeyListener(new AL());
x=y=150;
setTitle("Java Game");
setBackground(Color.WHITE);
setSize(sizeX,sizeY);
setResizable(false);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void paint(Graphics g){
dbImage = createImage(getWidth(), getHeight());
dbg = dbImage.getGraphics();
paintComponent(dbg);
g.drawImage(dbImage, 0, 0, this);
}
public void paintComponent(Graphics g){
g.fillOval(x, y, 20, 20);
/*if(erase){
g.setColor(Color.WHITE);
g.fillRect(0, 0, 500, 500);
erase = false;
}*/
repaint();
}
public static void main(String[] args) {
new JavaGame();
}
}
Its the height of title bar of JFrame that's why y starts visible after 22.
Same for x that starts visible from 2 due to JFrame outer border width.
Here is the sample code along with snapshot
g.setColor(Color.RED);
g.drawRect(3, 22, 200, 200);
--EDIT--
I never suggest you to use it. Read below comments for it's drawbacks.
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