getfiles_form.java

j2me的数据库系统开发的经典案例

package connectpacket;

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.Item;
import javax.microedition.io.*;//yao yong dao httpconnection 
import java.io.*;//yao  yong dao  inputstream outputstream
import javax.microedition.lcdui.*;

public class GetFiles_Form extends Form implements CommandListener {

	private GetFiles_MIDlet gfm;
	private Command exitCommand;
	private HttpConnection http_con=null;
	private InputStream is=null;
	private OutputStream os=null;
	private Image img1=null;
	private Image img2=null;
	public GetFiles_Form(String str_URL,GetFiles_MIDlet gfm) {
		super("HttpGetFiles_Form");
		// TODO 自动生成构造函数存根
		this.gfm=gfm;
		exitCommand=new Command("Exit",Command.EXIT,1);
		this.addCommand(exitCommand);
		this.setCommandListener(this);
		try
		{
			if(http_con==null)
			{
				
				http_con=(HttpConnection)javax.microedition.io.Connector.open(str_URL);
				http_con.setRequestMethod(HttpConnection.GET);
				System.out.print("http_con::");
				System.out.println(http_con);
				//http_con.setRequestProperty(HttpConnection., arg1)
			
			}
			if(is==null||os==null)
			{
				is=http_con.openInputStream();
				//int length=is.available();
				//os=http_con.openOutputStream();
				System.out.print("is::");
				System.out.println(is);
				System.out.print("is.length::");//is.length=buf.length
				//System.out.println(length);//is.length=buf.length
				
			}
			int length=is.available();
			byte[]buf=new byte[length];
			is.read(buf,0,buf.length);
			////当然我么也可以采取简洁转移法，就是假如我们无法得到该流的大小，
			//那我们就先把该流写进一个字节数组输出流中，进而见解得到一个该输入流的大小，
			//我们称这种见解方法为字节分流.....
			/*int byte_code=0;
			ByteArrayOutputStream baos=new ByteArrayOutputStream();
			while((byte_code=is.read())!=-1)
			{
				baos.write(byte_code);
				//baos可以直接向字节数组输出流中写入一个整形或者字节数组
			}
			byte buf[]=baos.toByteArray();*/
			System.out.print("buf.length::");//is.length=buf.length
			System.out.println(buf.length);//is.length=buf.length
			//ByteArrayInputStream bis=new ByteArrayInputStream(buf);
			//DataInputStream dis=new DataInputStream(bis);
			//System.out.println(dis.readUTF());
			//is.read(buf,0, buf.length);
			//既然可以从输入流中判断字节码的长度，在这里我们尝试以下，
			//根据它的长度直接生成一个字节数组缓存区，来读去输入流中的字节码//
			/*int length=is.available();
			byte img_buf[]=new byte[1688];
			is.read(img_buf,0,img_buf.length);
			img2=Image.createImage(img_buf,0, img_buf.length);
			this.append(img2);
			//实验结果是不行的,但不知道为什么会这样?????????
			*/
			img1=Image.createImage(buf,0, buf.length);
			this.append(img1);
			
			//
			
			
		}
		catch(Exception e)
		{
			e.printStackTrace();
		}
		finally
		{
			try
			{
				if(is!=null)
				{
			      is.close();
				}
				if(http_con!=null)
				{
					
			       http_con.close();
				}
			}
			catch(Exception e)
			{
				e.printStackTrace();
			}
		}
		
	}

	public GetFiles_Form(String arg0, Item[] arg1) {
		super(arg0, arg1);
		// TODO 自动生成构造函数存根
	}

	public void commandAction(Command c, Displayable d) {
		// TODO 自动生成方法存根
		if(c==exitCommand)
		{
			gfm.quitApp();
		}

	}

}