downloadmidlet.java

Java手机程序开发-DownloadMIDlet

import javax.microedition.io.*;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.io.*;

public class DownloadMIDlet extends MIDlet implements CommandListener, Runnable{

	Display display;
	Command exitCmd;
	Command downloadCmd;
	Command backCmd;
	Command cancelCmd;
	TextBox inputURL;
	Form show;
	MyCanvas myCanvas;
	String defaultURL = "http://127.0.0.1:8080/JavaPowered-8.png";
	int dataInc = 0;
	int totalDataLength = 100;
	boolean isFinished = false;
	Thread connectThread;
	Image image;

	public DownloadMIDlet(){
		display = Display.getDisplay(this);
		inputURL = new TextBox("输入URL", defaultURL, 100, TextField.URL);
		show = new Form("下载图形");
		myCanvas = new MyCanvas();
		exitCmd = new Command("退出", Command.EXIT, 1);
		downloadCmd = new Command("下载", Command.SCREEN, 1);
		backCmd = new Command("返回", Command.BACK, 1);
		cancelCmd = new Command("取消", Command.CANCEL, 1);
		connectThread = new Thread(this);
		inputURL.addCommand(exitCmd);
		inputURL.addCommand(downloadCmd);
		inputURL.setCommandListener(this);
		show.addCommand(backCmd);
		show.setCommandListener(this);
		myCanvas.addCommand(cancelCmd);
		myCanvas.setCommandListener(this);
	}

	public void startApp(){
		display.setCurrent(inputURL);
	}

	public void pauseApp(){
	}

	public void destroyApp(boolean conditional){
	}

	public void commandAction(Command c, Displayable d){
		if( c == exitCmd){
			destroyApp(true);
			notifyDestroyed();
		}
		else if (c == downloadCmd){
			try{
				display.setCurrent(myCanvas);
				connectThread.start();
				myCanvas.t.start();
			}
			catch(Exception ex){}
		}
		else if(c == backCmd){
			display.setCurrent(inputURL);
		}
		else if(c == cancelCmd){
			isFinished = true;
			dataInc = 0;
			display.setCurrent(inputURL);
		}
	}

	public void run(){
		try{
			image = download(inputURL.getString());
			show.append(image);
			display.setCurrent(show);
		}
		catch(Exception ex){}
	}

	Image download(String url) throws IOException{

		ContentConnection con = (ContentConnection)Connector.open(url);
		InputStream ins = con.openInputStream();
		totalDataLength = (int)(con.getLength());


		Image image = null;
		int data = 0;
		byte[] imageData = new byte[totalDataLength];
		try{
			ByteArrayOutputStream baos = new ByteArrayOutputStream();
			while((data = ins.read()) != -1 || isFinished == true){
				baos.write(data);
				dataInc++;
			}
			imageData = baos.toByteArray();
			isFinished = true;
			baos.close();
			image = Image.createImage(imageData, 0, imageData.length);
		}
		finally{
			if(ins != null)
				ins.close();
			if(con != null)
				con.close();
		}
		return image;
	}

	class MyCanvas extends Canvas implements Runnable{

		Thread t;

		public MyCanvas(){
			t = new Thread(this);
		}

		public void run(){
			while(!isFinished){
				try{
					repaint();
				}
				catch(Exception ex){}
			}
		}

		public void paint(Graphics g){
			int startX = 20;
			int startY = getHeight()/2 - 2;
			int width = getWidth()-40;
			int height = 8;
			g.setColor(0xffffff);
			g.fillRect(0, 0, getHeight(), getHeight());
			g.setColor(0);
			g.drawString("下载中......", startX, startY - 20, Graphics.TOP|Graphics.LEFT);
			g.drawRect(startX, startY, width, height);
			g.setColor(0xff);
			g.fillRect(startX, startY ,(dataInc*width/totalDataLength), height);
		}

	}
}