snappermidlet.java

Java ME手机应用开发大全一书的配套光盘上的源码

import javax.microedition.lcdui.*;
import javax.microedition.media.*;
import javax.microedition.media.control.*;
import javax.microedition.midlet.MIDlet;

public class SnapperMIDlet extends MIDlet implements CommandListener,Runnable {
  private Display mDisplay;
  private Form mMainForm;
  private Command mExitCommand, mCameraCommand;
  private Command mBackCommand, mCaptureCommand;
  //创建播放器对象
  private Player mPlayer;
  //创建视频控制器接口
  private VideoControl mVideoControl;
  
  public SnapperMIDlet() {
    mExitCommand = new Command("Exit", Command.EXIT, 0);
    mCameraCommand = new Command("Camera", Command.SCREEN, 0);
    mBackCommand = new Command("Back", Command.BACK, 0);
    mCaptureCommand = new Command("Capture", Command.SCREEN, 0);
    
    mMainForm = new Form("Snapper");
    mMainForm.addCommand(mExitCommand);
    String supports = System.getProperty("video.snapshot.encodings");
    if (supports != null && supports.length() > 0) {
      mMainForm.append("Ready to take pictures.");
      mMainForm.addCommand(mCameraCommand);
    }
    else
      mMainForm.append("Snapper cannot use this " + "device to take pictures.");
    mMainForm.setCommandListener(this);
  }
  
  public void startApp() {
    mDisplay = Display.getDisplay(this);   
    mDisplay.setCurrent(mMainForm);
  }
    
  public void pauseApp() {}
  
  public void destroyApp(boolean unconditional) {
  }
  
  public void commandAction(Command c, Displayable s) {
    if (c.getCommandType() == Command.EXIT) {
      destroyApp(true);
      notifyDestroyed();
    }
    else if (c == mCameraCommand)
	  //启动摄像头
      showCamera();
    else if (c == mBackCommand)
	  //显示主屏幕届面
      mDisplay.setCurrent(mMainForm);
    else if (c == mCaptureCommand) {
      //创建摄像头捕获图像的线程
	  new Thread(this).start();
    }
  }

  private void showCamera() {
    try {
      //创建播放器对象
      mPlayer = Manager.createPlayer("capture://video");
	  //使摄像头处于就绪状态
      mPlayer.realize();
      //创建视频控制器接口
      mVideoControl = (VideoControl)mPlayer.getControl("VideoControl");
      //新建Canvas画布对象
      Canvas canvas = new CameraCanvas(this, mVideoControl);
      canvas.addCommand(mBackCommand);
      canvas.addCommand(mCaptureCommand);
      canvas.setCommandListener(this);
      mDisplay.setCurrent(canvas);
	  //启动摄像头
      mPlayer.start();
    }
    catch (IOException ioe) { handleException(ioe); }
    catch (MediaException me) { handleException(me); }
  }
  //捕获图像的线程中的方法定义
  public void run(){
  capture();
 }
  public void capture() {
    try {
      // 得到摄像头拍照的图像的字节数组
      byte[] raw = mVideoControl.getSnapshot(null);
	  //将摄像头获取的图像二进制字节数组转换成Image对象
      Image image = Image.createImage(raw, 0, raw.length);
      //调用图像转换方法
      Image thumb = createThumbnail(image);
      
      //将图像显示在屏幕上 
      if (mMainForm.size() > 0 && mMainForm.get(0) instanceof StringItem)
        mMainForm.delete(0);
      mMainForm.append(thumb);
      mDisplay.setCurrent(mMainForm);
      // 关闭播放器
      mPlayer.close();
      mPlayer = null;
      mVideoControl = null;
    }
    catch (MediaException me) { handleException(me); }
  }
  
  private void handleException(Exception e) {
    Alert a = new Alert("Exception", e.toString(), null, null);
    a.setTimeout(Alert.FOREVER);
    mDisplay.setCurrent(a, mMainForm);
  }
  //图像转换方法
  private Image createThumbnail(Image image) {
    int sourceWidth = image.getWidth();
    int sourceHeight = image.getHeight();  
    int thumbWidth = 64;
    int thumbHeight = -1;   
    if (thumbHeight == -1)
      thumbHeight = thumbWidth * sourceHeight / sourceWidth;
    Image thumb = Image.createImage(thumbWidth, thumbHeight);
    Graphics g = thumb.getGraphics();
    
    for (int y = 0; y < thumbHeight; y++) {
      for (int x = 0; x < thumbWidth; x++) {
        g.setClip(x, y, 1, 1);
        int dx = x * sourceWidth / thumbWidth;
        int dy = y * sourceHeight / thumbHeight;
        g.drawImage(image, x - dx, y - dy, Graphics.LEFT | Graphics.TOP);
      }
    }
    Image immutableThumb = Image.createImage(thumb);
    return immutableThumb;
  }
}