bird_canvas.java

本光盘是《J2ME无线移动游戏开发》一书的配套光盘

package ch08;

import java.util.*;
import javax.microedition.lcdui.*;

public class Bird_Canvas
    extends Canvas {

  //声明一个Display对象
  private Display display;

  //代表前景图像
  private Image offscreen;

  //代表背景图像
  private Image back;

  //用于承载组成动画的一组图片
  private Vector images = new Vector();

  /*
   8.构造器
   */
  public Bird_Canvas(Display display) {
    this.display = display;
    //装载图片
    try {
      back = Image.createImage("/icons/bird/cloud.png");
    }
    catch (Exception e) {
      System.out.println(e.toString());
    }
    if (!isDoubleBuffered()) {
      offscreen = Image.createImage(getWidth(), getHeight());
    }
  }

  /*
   9.添加图片
   */
  public void add(Bird_Image image) {
    images.addElement(image);
  }

  /*
   10.绘制图像
   */
  protected void paint(Graphics g) {
    Graphics saved = g;
    g.drawImage(back, 0, 0, Graphics.LEFT | Graphics.TOP);

    if (offscreen != null) {
      g = offscreen.getGraphics();
    }

    int n = images.size();
    for (int i = 0; i < n; ++i) {
      Bird_Image img = (Bird_Image) images.elementAt(i);
      img.draw(g);
    }

    if (g != saved) {
      saved.drawImage(offscreen, 0, 0, Graphics.LEFT | Graphics.TOP);
    }
  }
}