powercamera.java

《j2me开发精解〉（詹健飞）CD-rom附带源码。用netbeans

package com.j2medev.ch8.mmapi;

import java.io.IOException;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.media.*;
import javax.microedition.media.control.VideoControl;

public class PowerCamera extends MIDlet implements CommandListener{
    
    private Display display = null;
    private Displayable resume = null;
    private List main = null;
    private PowerModel pm = null;
    private Player player = null;
    private VideoControl vc = null;
    private Command exitCommand = new Command("退出",Command.EXIT, 1);
    private Command captureCommand = new Command("拍照",Command.OK, 1);
    private Command backCommand = new Command("返回",Command.BACK, 1);
    
    public void startApp() {
        if(display == null){
            display = Display.getDisplay(this);
            pm = new PowerModel(this);
            main = new List("主菜单", List.IMPLICIT, new String[]{"手机拍照","我的相册"}, null);
            main.addCommand(exitCommand);
            main.setCommandListener(this);
            resume = main;
        }
        display.setCurrent(resume);
    }
    
    public void setCurent(Displayable current){
        display.setCurrent(current);
    }
    public void pauseApp() {
        resume = display.getCurrent();
    }
    
    public void destroyApp(boolean unconditional) {
        //退出程序,释放资源
        pm.release();
        releasePlayer(); 
    }
    
    private void showCamera(){
        try{
            //创建播放器
            if(player == null){
                player = Manager.createPlayer("capture://video");
            }
            player.realize();
            //获得VideoControl
            vc = (VideoControl)player.getControl("VideoControl");
            //将捕获的数据绘制到Canvas上
            CameraCanvas cc = new CameraCanvas(this, vc);
            cc.addCommand(captureCommand);
            cc.addCommand(backCommand);
            cc.setCommandListener(this);
            display.setCurrent(cc);
            player.start();
        }catch(IOException ex){
            ex.printStackTrace();
            player =null;
            vc = null;
        } catch(MediaException ex){
            ex.printStackTrace();
            player =null;
            vc = null;
        }
    }
    
    public void capture(){
        try{
            //捕获数据 可以通过参数定制编码类型以及图片的长度和高度
            byte[] imgData = vc.getSnapshot("encoding=jpeg&width=160&height=120");
            ViewImageUI vimage = new ViewImageUI(this, imgData);
            //显示图片，并让用户输入标题
            display.setCurrent(vimage);
            player.close();
            player = null;
            vc = null;
        }catch(MediaException ex){
            showInfo(ex.toString(),AlertType.ERROR);
        }
    }
    
    public void back(){
        display.setCurrent(main);
    }
    public void savePicture(Picture pic){
        pm.savePicture(pic);
        showInfo("成功保存图片到我的相册", AlertType.CONFIRMATION);
    }
    //错误提示
    public void showInfo(String message,AlertType type){
        Alert alert = new Alert("系统提示");
        alert.setString(message);
        alert.setTimeout(2000);
        alert.setType(type);
        display.setCurrent(alert, main);
    }
    //处理和用户交互的逻辑
    public void commandAction(Command cmd,Displayable displayable){
        if(cmd == exitCommand){
            destroyApp(false);
            notifyDestroyed();
        }else if(cmd == List.SELECT_COMMAND){
            String label = main.getString(main.getSelectedIndex());
            if(label.equals("手机拍照")){
                //判断是否支持MMAPI
                String support = PowerModel.isVideoCapture();
                if(support.equals("true")){
                    showCamera();
                }else{
                    showInfo("您的手机不支持拍照功能",AlertType.WARNING);
                }
            }else if(label.equals("我的相册")){
                //一次读取Picture[]数组，这里对内存消耗很大
                Picture[] pic = pm.getAllPicture();
                if(pic == null){
                    showInfo("相册为空", AlertType.INFO);
                }else{
                    ImageList list = new ImageList(this);
                    list.initTitle(pic);
                    display.setCurrent(list);
                }
            }
        }else if(cmd == captureCommand){
            capture();
        }else if(cmd == backCommand){
            releasePlayer();
            back();
        }
    }
    //把播放器资源释放，系统可能需要使用
    private void releasePlayer(){
        if(player != null){
            player.close();
            player = null;
        }if(vc != null){
            vc = null;
        }
    }
}