Java Swing Frame有點落后嗎？

Question

我有一個簡單的動畫代碼，可以創建一個儀表類型的矩形效果。 我想創建它，使其完全填充面板。 我很近，但它延伸到底部的框架之外。 我想念什么？

public class Main {

public static void main(String[] args) {

    JFrame frame = new JFrame("Pong");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLayout(new GridLayout(1,2));
    frame.setSize(500, 500);

    //MouseTest test = new MouseTest();
    Test test2 = new Test(frame.getWidth(), frame.getHeight(), frame.getHeight(), 50);
    //frame.add(test);
    frame.add(test2);

    frame.setVisible(true);

    }
}

public class Test extends JPanel implements ActionListener, MouseListener{

int y = 0, width, height, dy=0, maxHeight;
int BOTTOM;
Timer timer;

public Test(int width, int height, int BOTTOM, int SPEED){
    setBackground(Color.BLUE);
    this.width = width;
    maxHeight = height;
    this.BOTTOM = BOTTOM;

    addMouseListener(this);

    timer = new Timer(1000/SPEED, this);
    timer.start();

   }
 public void move(){

    if(y>=maxHeight){
        dy = -1;
    }
    if(y<=0)
    {
        dy = 1;
    }
    y+=dy;
    height+=dy;
    //System.out.println(y);
    repaint();

}

public void paintComponent(Graphics g){

    super.paintComponent(g);
    if(y<=maxHeight/2) {
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM - y, width, height);
    }
    if(y>=maxHeight/2 && y<(maxHeight/10)*9){
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM-(maxHeight/2), width, maxHeight/2);
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM - y, width, height-(maxHeight/2));
    }
    if(y>=(maxHeight/10)*9){
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM-(maxHeight/2), width, maxHeight/2);
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM-(9*(maxHeight/10)), width, (4*maxHeight)/10);
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM - y, width, height-(9*(maxHeight)/10));
    }
        for(int i = 1; i<6; i++)
            g.fillRect(0, BOTTOM - (i*(maxHeight/5)), width, 10);

    System.out.println(y);



}

Answer 1

面板占用的空間少於JFrame ，因為您的框架具有標題欄和窗口邊框。 您可以在paint方法中查詢JPanel使用的JPanel的getWidth()和getHeight()正確的寬度和高度（換句話說，JFrame的寬度和高度與JPanel的寬度不同）和高度，即使JPanel在邊框之間視覺上占據了框架中的所有空間）。

另外，如果您確實有邏輯無法做到這一點，則可以查詢幀的插入大小，然后從寬度中減去左右插入值，然后將其作為寬度傳遞，並對頂部和底部插入值的高度。

Answer 2

• 覆蓋JPanel getPreferredSize ，這將幫助布局管理器確定布局組件的最佳方法
• 使用JFrame#pack將框架邊框包裹在視圖周圍
• 使用getWidth和getHeight獲取面板的實際大小。 每當您需要了解這些值時都應該這樣做，不要長時間存儲它們，因為這些值可能會發生變化
• 您還應該通讀我是否應該避免在Java Swing中使用set（Preferred | Maximum | Minimum）Size方法？

這是基於您的代碼的基本示例...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test1 {

    public static void main(String[] args) {
        new Test1();
    }

    public Test1() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private int yPos;
        private int dy = 1;
        private int bottom = 50;

        public TestPane() {
            Timer timer = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    move();
                }
            });
            timer.start();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(500, 500);
        }

        public void move() {

            if (yPos >= getHeight()) {
                dy = -1;
            }
            if (yPos <= 0) {
                dy = 1;
            }
            yPos += dy;
            repaint();

        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            int maxHeight = getHeight();
            int width = getWidth();
            int height = maxHeight;
            if (yPos <= maxHeight / 2) {
                g.setColor(Color.green);
                g.fillRect(0, bottom - yPos, width, height);
            }
            if (yPos >= maxHeight / 2 && yPos < (maxHeight / 10) * 9) {
                g.setColor(Color.green);
                g.fillRect(0, bottom - (maxHeight / 2), width, maxHeight / 2);
                g.setColor(Color.green);
                g.fillRect(0, bottom - yPos, width, height - (maxHeight / 2));
            }
            if (yPos >= (maxHeight / 10) * 9) {
                g.setColor(Color.green);
                g.fillRect(0, bottom - (maxHeight / 2), width, maxHeight / 2);
                g.setColor(Color.green);
                g.fillRect(0, bottom - (9 * (maxHeight / 10)), width, (4 * maxHeight) / 10);
                g.setColor(Color.green);
                g.fillRect(0, bottom - yPos, width, height - (9 * (maxHeight) / 10));
            }
            for (int i = 1; i < 6; i++) {
                g.fillRect(0, bottom - (i * (maxHeight / 5)), width, 10);
            }

        }
    }

}

Answer 3

另一種方法是使用pack（）。 它將框架的大小設置為框架內容的大小。 在您的代碼中，它看起來像這樣：

frame.add(test2);
frame.pack();

如果以這種方式進行操作，則不需要frame.setSize（）調用。 您可以添加.add（）或添加以下內容來添加面板：

frame.setContentPane(test2);

Answer 4

因此，我結合了您的評論並使其正常工作。 這是有效的代碼。

public class Main {

public static void main(String[] args) {

    JFrame frame = new JFrame("Pong");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLayout(new GridLayout(1,2));
    Insets inset = frame.getInsets();


    Test test2 = new Test(200-(inset.right + inset.left), 200 -(inset.top + inset.bottom), 200, 50);
    frame.setContentPane(test2);
    frame.pack();

    frame.setVisible(true);

}
}

public class Test extends JPanel implements ActionListener, MouseListener{

int y = 0, width, height, dy=0, maxHeight;
int BOTTOM;
Timer timer;
Dimension size;
Insets inset;

public Test(int width, int height, int BOTTOM, int SPEED){
    size = new Dimension(width, height);
    setBackground(Color.BLUE);
    setPreferredSize(size);
    inset = this.getInsets();
    this.width = width-(inset.right+inset.left);
    maxHeight = height;
    this.BOTTOM = BOTTOM - (inset.bottom+inset.top);

    addMouseListener(this);

    timer = new Timer(1000/SPEED, this);
    timer.start();

   }
public void move(){

    if(y>=maxHeight){
        dy = -1;
    }
    if(y<=0)
    {
        dy = 1;
    }
    y+=dy;
    height+=dy;
    //System.out.println(y);
    repaint();

}

public void paintComponent(Graphics g){

    super.paintComponent(g);
    if(y<=maxHeight/2) {
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM - y, width, height);
    }
    if(y>=maxHeight/2 && y<(maxHeight/10)*9){
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM - (maxHeight / 2), width, maxHeight / 2);
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM - y, width, height-(maxHeight/2));
    }
    if(y>=(maxHeight/10)*9){
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM-(maxHeight/2), width, maxHeight/2);
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM-(9*(maxHeight/10)), width, (4*maxHeight)/10);
        g.setColor(Color.green);
        g.fillRect(0, BOTTOM - y, width, height-(9*(maxHeight)/10));
    }

    g.setColor(Color.white);
        for(int i = 1; i<6; i++)
            g.fillRect(0, BOTTOM - (i*(maxHeight/5)), width, 5);

    }