我想讓球知道他們在一個JPanel中的矩形內

我正在製作一個小程序，其中一些球在一個盒子裏彈跳。這個邏輯已經在一個名爲Ball.java的類中完成，球正在彈跳並正常移動。我想讓球知道他們在一個JPanel中的矩形內

我想更進一步，在Jframe內部繪製一個矩形，並在內部有兩個球的時候讓球表現出特定的方式。應該只有2個球在矩形的邊界內移動。其他進入長方形的球應該凍結，直到當前移動的球中的一個離開它爲止。從矩形中移出的移動球應該凍結，除非框中存在另一個球，意味着該矩形永遠不應該是空的。

下面是我的邏輯，這應該實施，我在paincomponents（）方法中繪製了帶有g.drawRect(75, 75, 200, 200);的矩形，我很難讓球知道它們在矩形內。

package bouncingball; 

import bouncingball.Ball; 
import java.awt.Graphics; 
import java.awt.event.MouseAdapter; 
import java.awt.event.MouseEvent; 
import java.util.ArrayList; 
import javax.swing.JPanel; 

public class BallPanel extends JPanel { 

private Ball ball; 
private ArrayList<Ball> balls = new ArrayList(); 
private int ballsInside = 0; 

public BallPanel() { 
    addMouseListener(new Mouse()); 
} 

//method for creating a new ball 
private void newBall(MouseEvent click) { 
    ball = new Ball(this); 
    balls.add(ball); 
    Thread t = new Thread(ball); 
    t.setPriority(Thread.NORM_PRIORITY); 
    t.start(); 
    System.out.println("New ball created"); 
} 

public void animate() { 
    while (true) { 
     repaint(); 
} 

/* public synchronized void countIn() throws InterruptedException { 
while (ballsInside < 2){ 
wait(); 
} 
ballsInside++; 
notifyAll(); 

} 

public synchronized void countMaxIn() throws InterruptedException { 
while (ballsInside == 2){ 
wait(); 
} 
ballsInside--; 
notifyAll(); 

}*/ 
private class Mouse extends MouseAdapter { 

    @Override 
    public void mousePressed(final MouseEvent event) { 
     newBall(event); 
    } 
} 

@Override 
public void paintComponent(Graphics g) { 
    super.paintComponent(g); 
    g.drawRect(75, 75, 200, 200); 
    for (Ball ball : balls) { 
     if (ball != null) { 
      ball.draw(g); 
     } 
    } 
} 
}

和我的球類

package bouncingball; 

import java.awt.Color; 
import java.awt.Graphics; 
import java.awt.event.MouseEvent; 
import java.util.Random; 
import java.lang.Runnable; 
import javax.swing.JPanel; 
import java.util.ArrayList; 

public class Ball implements Runnable { 

public final static Random random = new Random(); 

final static int SIZE = 30; 
final static int MAX_SPEED = 5; 

BallPanel panel = new BallPanel(); 

private int x; 
private int y; 

private int dx; 
private int dy; 

private Color color = Color.BLUE; 
//private ArrayList<Ball> balls ; 


@Override 
public void run() { 
    while (true) { 
     move(); 
     try { 
      Thread.sleep(40); // wake up roughly 25 frames per second 
     } catch (InterruptedException exception) { 
      exception.printStackTrace(); 
     } 
    } 
} 

public Ball(BallPanel panel) { 
    this.panel = panel; 
    x = random.nextInt(panel.getWidth()); 
    y = random.nextInt(panel.getHeight()); 
    dx = random.nextInt(2 * MAX_SPEED) - MAX_SPEED; 
    dy = random.nextInt(2 * MAX_SPEED) - MAX_SPEED; 
} 

public void draw(Graphics g) { 
    g.setColor(color); 
    g.fillOval(x, y, SIZE, SIZE); 
} 

public void move() { 

    // check for bounce and make the ball bounce if necessary 
    // 
    if (x < 0 && dx < 0) { 
     //bounce off the left wall 
     x = 0; 
     dx = -dx; 
    } 
    if (y < 0 && dy < 0) { 
     //bounce off the top wall 
     y = 0; 
     dy = -dy; 
    } 
    if (x > panel.getWidth() - SIZE && dx > 0) { 
     //bounce off the right wall 
     x = panel.getWidth() - SIZE; 
     dx = -dx; 
    } 
    if (y > panel.getHeight() - SIZE && dy > 0) { 
     //bounce off the bottom wall 
     y = panel.getHeight() - SIZE; 
     dy = -dy; 
    } 

    //make the ball move 
    x += dx; 
    y += dy; 
} 
}

來源

2015-10-02 answerSeeker

看看答案爲[這個問題]（http://stackoverflow.com/questions/32746683/ball-sometimes-bounces-sometimes-doesnt/32748251＃32748251） - 這不完全像你的情況，但它可能會幫助你開始。 –

使用一個整數semaphore，讓2個球，直到進入其他球擋住。

private final Semaphore entryTickets = new Semaphore(2, true);

中一球：

entryTickets.acquire(); // Enter 
... 
entryTickets.release(); // Leave

來源

2015-10-02 17:34:16

我想讓球知道他們在一個JPanel中的矩形內

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