滚动屏幕

最新推荐文章于 2020-03-31 22:32:47 发布

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#import #thread #scroll #image #class #null

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本文介绍了一个使用Java ME的Canvas组件来实现图片滚动显示的方法。通过不断更新图片的显示位置并利用线程定时刷新画布，可以创建出平滑的图片滚动效果。该实现包括了图片加载、滚动方向控制及启动停止等功能。

import java.io.IOException;

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;

class ScrollImageCanvas
extends Canvas
implements Runnable {
Image pic;

int drawX, drawY; //原点座标

int scrollleft; //左右移动最大距离

boolean isleft = true; //是否往左移动

boolean isStop = false;
ScrollImageCanvas() {
    try {
      //装入png图片文件
      pic = Image.createImage("/ScrollPic.png");
    }
    catch (IOException e) {
      //需要import java.io.*;
      System.out.println("load png resource error " + e.getMessage());
      pic = null;
    }

scrollleft = this.getWidth() - pic.getWidth();

drawX = 0; //getWidth();
drawY = getHeight();
}

protected void paint(Graphics g) {

g.translate(drawX, 0);
g.drawImage(pic, 0, drawY, Graphics.BOTTOM | Graphics.LEFT);

}

public void run() {

    while (true) {
      this.scroll();
      repaint();
      try {
        Thread.sleep(50);
      }
      catch (InterruptedException e) {
        System.out.println("sleep error : " + e.getMessage());
      }
      if (isStop) {
        break;
      }
    }

}

public void start() {
    isStop = false;
    Thread t = new Thread(this);
    t.start();
}

public void stop() {
isStop = true;
}

//滚动屏幕
protected void scroll() {
    if (isleft) {
      //如果往左滚动完整个图片则往右滚动
      if (drawX >= scrollleft) {
        drawX = drawX - 1;
      }
      else {
        isleft = false;
      }
    }
    else {
      if (drawX <= 0) {
        drawX = drawX + 1;
      }
      else {
        isleft = true;
      }
    }
}
}