snappermidlet.java

《精通JAVA手机游戏与应用程序设计》随书光盘

/*
 * 抓图
 */

package snapper;

import java.io.IOException;
import java.io.InputStream;

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 {
	private Display display;

	private Form mainForm;

	private Command exitCommand, cameraCommand;

	private Command backCommand, captureCommand;

	private Player player;

	private VideoControl videoControl;

	public SnapperMidlet() {
		exitCommand = new Command("退出", Command.EXIT, 0);
		cameraCommand = new Command("播放", Command.SCREEN, 0);
		backCommand = new Command("返回", Command.BACK, 0);
		captureCommand = new Command("抓图", Command.SCREEN, 0);

		mainForm = new Form("抓图");
		mainForm.addCommand(exitCommand);
		//判断设备是否支持抓图
		String supports = System.getProperty("video.snapshot.encodings");
		if (supports != null && supports.length() > 0) {
			mainForm.append("设备允许播放视频的时候抓图");
			mainForm.addCommand(cameraCommand);
		} else
			mainForm.append("设备不支持抓图 ");
		mainForm.setCommandListener(this);
	}

	public void startApp() {
		display = Display.getDisplay(this);

		display.setCurrent(mainForm);
	}

	public void pauseApp() {
	}

	public void destroyApp(boolean unconditional) {
	}

	public void commandAction(Command c, Displayable s) {
		if (c.getCommandType() == Command.EXIT) {
			destroyApp(true);
			notifyDestroyed();
		}
		if (c == cameraCommand) {
			Thread t = new Thread() {
				public void run() {

					showCamera();
				}
			};
			t.start();

		}
		if (c == backCommand)
			display.setCurrent(mainForm);
		if (c == captureCommand) {

			Thread t = new Thread() {
				public void run() {

					capture();
				}
			};
			t.start();
		}
	}

	private void showCamera() {

		Form f = new Form("视频演示程序");
		f.addCommand(backCommand);
		f.addCommand(captureCommand);
		f.setCommandListener(this);

		try {
			InputStream ins = getClass().getResourceAsStream("/test-mpeg.mpg");

			player = Manager.createPlayer(ins, "video/mpeg");

			player.realize();

			Item videoItem = null;

			if ((videoControl = (VideoControl) player
					.getControl("VideoControl")) != null)
				videoItem = (Item) videoControl.initDisplayMode(
						VideoControl.USE_GUI_PRIMITIVE, null);

			display.setCurrent(f);
			player.start();

			f.append(videoItem);

		} catch (IOException ioe) {
			handleException(ioe);
		} catch (MediaException me) {
			handleException(me);
		}
	}

	public void capture() {
		try {
			// 获得Image对象，参数尾null表示格式为png类型
			byte[] raw = videoControl.getSnapshot(null);
			Image image = Image.createImage(raw, 0, raw.length);

			Image thumb = createThumbnail(image);

			//放置到mainForm中
			if (mainForm.size() > 0 && mainForm.get(0) instanceof StringItem)
				mainForm.delete(0);
			mainForm.append(thumb);

			//返回mainForm
			display.setCurrent(mainForm);

			//关闭Player.
			player.close();
			player = null;
			videoControl = null;
		} catch (MediaException me) {
			handleException(me);
		}
	}

	private void handleException(Exception e) {
		Alert a = new Alert("Exception", e.toString(), null, null);
		a.setTimeout(Alert.FOREVER);
		display.setCurrent(a, mainForm);
	}

	//绘制缩小的图片
	private Image createThumbnail(Image image) {
		int sourceWidth = image.getWidth();
		int sourceHeight = image.getHeight();
		//设置缩小图的宽度
		int thumbWidth = 64;
		int thumbHeight = -1;
		//如果为－1则表示长宽按照比例缩小，计算缩小图的高度
		if (thumbHeight == -1)
			thumbHeight = thumbWidth * sourceHeight / sourceWidth;
		//创建一个空的离屏Image对象
		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;
				//按照比例计算源图片中的象素
				g.drawImage(image, x - dx, y - dy, Graphics.LEFT
								| Graphics.TOP);
			}
		}

		Image immutableThumb = Image.createImage(thumb);
		return immutableThumb;

	}
}