java - 使用线程移动图形 2d 对象

Question

我不太清楚为什么我的船不动。如果有人能详细解释一下那就太好了。

这就是创建并显示船的内容:

import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JApplet;


@SuppressWarnings("serial")
public class boatApplet extends JApplet{

    public void paint(Graphics g) {
        setBackground(Color.blue);
        // Xposition, YPosition, widthofboat, hieght of boat
        SailBoat boat = new SailBoat(25,500, 350, 400);
        boat.draw(g);
    } //ends method
}

这是我的帆船类(class)，它用多段线绘制一艘船。

import java.applet.Applet;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.GeneralPath;
import java.awt.geom.Rectangle2D;


@SuppressWarnings("serial")
/*
 * sailboat class extends applet intx is starting x position inty is starting y
 * position boatW is the length of the boat boatH is the boat height - the boat
 * and cabin height polyline is used to draw the boat
 */
public class SailBoat extends Applet implements Runnable{
    public int x;
    public int y;
    public int boatW;
    public int boatH;
    private GeneralPath polyline;

    // constructor takes in x pos, y pos, width of boat, height of boat
    public SailBoat(int xx, int yy, int w, int h) {
        setBackground(Color.blue);
        boatW = w;
        boatH = h;
        x = xx;
        y = yy;
        Thread t = new Thread(this);
        t.start();
    }

    public void draw(Graphics g) {
        /*
         * This method builds the boat from various polyline actionscreaes a
         * graphics 2d object anduses to build the boatrectangle with width of
         * 200 for skybuild the boat basebuild the cabinbuild themastbuild the
         * front sailbuild the backsail
         */
        Graphics2D g2d = (Graphics2D) g;
        // sky
        g2d.setColor(new Color(135, 206, 250));
        // color light blue
        Rectangle2D.Double sky = new Rectangle2D.Double(0, 0, 2000, 520);
        // draws a regtangle
        g2d.draw(sky);
        // draws it to g2d
        g2d.fill(sky);
        // fills with color

        g2d.setColor(Color.BLACK);
        // change color to black
        g2d.setStroke(new BasicStroke(2));
        // set stroke size 2

        // boat base
        int[] xBoat = { x, x + boatW, x + boatW - 25, x + 25, x };
        // x pos array
        int[] yBoat = { y, y, y + 50, y + 50, y };
        // y pos array
        polyline = new GeneralPath(GeneralPath.WIND_EVEN_ODD, xBoat.length);
        polyline.moveTo(xBoat[0], yBoat[0]);
        // moves polyline to first position of array x.y
        for (int index = 1; index < yBoat.length; index++) {
            // for each pos
            polyline.lineTo(xBoat[index], yBoat[index]);
            // draw the lines
        }
        ; // ends loop
        polyline.closePath();
        // closes poly
        g2d.draw(polyline);
        // draws it
        g2d.setColor(Color.white);
        // colors the boat base white
        g2d.fill(polyline);
        // fills the poly shape

        // cabin
        g2d.setColor(Color.black);
        // change color to black
        // cabins x position is x + 60% of the boats length on -1 y to
        // compensate for stroke size
        int[] xCabin = { (int) (x + (boatW * .6)) - 10,
                (int) (x + (boatW * .6)),
                (int) ((x + (boatW * .6)) + (boatW * .15)),
                (int) ((x + (boatW * .6)) + (boatW * .15)) + 10,
                (int) (x + boatW * .6) };
        // cabin y pos
        int[] yCabin = { y - 1, y - 25, y - 25, y - 1, y - 1 };
        polyline = new GeneralPath(GeneralPath.WIND_EVEN_ODD, xCabin.length);// gp
        polyline.moveTo(xCabin[0], yCabin[0]);
        // move poly line
        for (int index = 1; index < yCabin.length; index++) {
            // for each pos
            polyline.lineTo(xCabin[index], yCabin[index]);
            // draws lines
        }
        ; // ends loop
        polyline.closePath();
        // close path
        g2d.draw(polyline);
        // draws the poly to g2d
        g2d.setColor(Color.WHITE);
        // sets color white
        g2d.fill(polyline);
        // fills cabin

        // mast
        g2d.setColor(Color.BLACK);
        // set color black
        g2d.setStroke(new BasicStroke(4));
        // set stroke size for mast to 4
        g2d.drawLine((int) (x + (boatW * .65)), y - 28,
                (int) (x + (boatW * .65)), (int) (y - boatH + 50));
        // draws a line from top of cabin to the remainder of boats height

        // frontsail
        g2d.setStroke(new BasicStroke(2));
        // set stroke to size 2
        // front sail x position is based on mast pos - 5
        int[] xFSail = { (int) (x + (boatW * .65) - 5), x,
                (int) (x + (boatW * .65) - 5), (int) (x + (boatW * .65) - 5) };
        // front sail y position is set to height to 30 from boat base
        int[] yFSail = { (y - boatH + 50), y - 35, y - 35, (y - boatH + 50) };
        // poly gp
        polyline = new GeneralPath(GeneralPath.WIND_EVEN_ODD, xFSail.length);
        polyline.moveTo(xFSail[0], yFSail[0]);
        // moves fs poly line
        for (int index = 1; index < yFSail.length; index++) {
            // for each pos
            polyline.lineTo(xFSail[index], yFSail[index]);
            // draw line to
        }
        ; // ends loop
        polyline.closePath();
        // closes path
        g2d.draw(polyline);
        // draws path to g2d
        g2d.setPaint(new GradientPaint(x, y, Color.white, 450, y, Color.black));
        // set paint as gradient
        // fills sail
        g2d.fill(polyline);

        // backsail
        g2d.setColor(Color.BLACK);
        g2d.setStroke(new BasicStroke(2));
        int[] xBSail = { (int) (x + (boatW * .65) + 5),
                (int) (x + (boatW * .65) + 5), x + boatW,
                (int) (x + (boatW * .65) + 5) };
        int[] yBSail = { (y - boatH + 50), y - 35, y - 35, (y - boatH + 50) };
        polyline = new GeneralPath(GeneralPath.WIND_EVEN_ODD, xBSail.length);
        polyline.moveTo(xBSail[0], yBSail[0]);
        for (int index = 1; index < yBSail.length; index++) {
            polyline.lineTo(xBSail[index], yBSail[index]);
        }
        ; // ends loop
        polyline.closePath();
        g2d.draw(polyline);
        g2d.setPaint(new GradientPaint(x, y, Color.white, 300, 200, Color.black));
        g2d.fill(polyline);
    }

    @Override
    public void run() {
        for(int time = 0; time < 1000; time += 10){
            x += 1;
            repaint();
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
            }
        }
    }
}

Answer 1

所以，根据我跳出来的两件事的代码片段......

1. 当您从 boatApplet 调用 SailBoat 的 draw 方法时，为什么 SailBoat 会扩展 Applet

2. 在 SailBoat 中调用 repaint 不会执行任何操作，因为它实际上不是可显示的组件(它不会“添加”到任何内容，并且基于您的尝试方式)使用，应该是)

   • 从 SailBoat 中删除 extends Applet，这只会让事情变得困惑
   • 将Thread移动到boatApplet，让它调用SailBoat上的move方法来更新对象的内部位置，然后让 boatApplet 对其自身调用 repaint
   • 在进行任何自定义绘画之前调用 super.paint
   • 使用 Swing Timer 而不是 Thread，它在 EDT 的上下文中更新，从而使更新 UI 状态更安全。请参阅Concurrency in Swing和 How to use Swing Timers了解更多详情
   • 如果可以的话，避免使用小程序，它们有很多自己的问题，您现在可能不需要处理这些问题
   • 将核心逻辑移至 JPanel 并重写其 paintComponent 方法(并调用 super.paintComponent)并免费获得双缓冲，然后您可以将此面板添加到您想要的任何顶级容器