waitcanvas.java

《精通JAVA手机游戏与应用程序设计》随书光盘

package WaitDemo;

import java.util.*;

import javax.microedition.lcdui.*;

public class WaitCanvas
    extends Canvas {
  private int mCount, mMaximum;
  private int mInterval;
  
  private int mWidth, mHeight, mX, mY, mRadius;
  private String mMessage;
  
  public WaitCanvas() {
    mCount = 0;
    mMaximum = 36;
    mInterval = 100;
    
    mWidth = getWidth();
    mHeight = getHeight();
    
    //计算角度.
    int halfWidth = (mWidth - mRadius) / 2;
    int halfHeight = (mHeight - mRadius) / 2;
    mRadius = Math.min(halfWidth, halfHeight);
    
    // 计算坐标.
    mX = halfWidth - mRadius / 2;
    mY = halfHeight - mRadius / 2;

    // 创建一个定时器.
    TimerTask task = new TimerTask() {
      public void run() {
        mCount = (mCount + 1) % mMaximum;
        repaint();
      }
    };
    Timer timer = new Timer();
    timer.schedule(task, 0, mInterval);
  }
  
  public void setMessage(String s) {
    mMessage = s;
    repaint();
  }
  
  public void paint(Graphics g) {
    int theta = -(mCount * 360 / mMaximum);
    
    //清除屏幕
    g.setColor(255, 255, 255);
    g.fillRect(0, 0, mWidth, mHeight);
    
    //画图案
    g.setColor(0x00ff0000);
    g.drawArc(mX, mY, mRadius, mRadius, 0, 360);
    g.setColor(0x000000ff);
    g.fillArc(mX, mY, mRadius, mRadius, theta +  90, 90);
    g.fillArc(mX, mY, mRadius, mRadius, theta + 270, 90);
    
    // 如果有信息则显示信息
    if (mMessage != null)
      g.drawString(mMessage, mWidth / 2, mHeight,
          Graphics.BOTTOM | Graphics.HCENTER);
  }
}