downloadfromurlform.java

相册是J2me MIDLet 的一个demo程序

/*  
 *	Filename: DownloadFromURLForm.java
 *  - contains definition of the class DownloadFromURLForm, which is a Form used as user interface in downloading
 *  and saving images/descriptions into persistent storage on phone, it is also the corresponding CommandListener 
 *  handling image download using HTTP protocol and images/descriptions save using methods defined in class 
 *  RMSOperations.
 *  
 *
 *  Application Name: Image Album Demo 
 *  Version: 2.0
 *  Release Date: 27th September, 2002
 *  Author:	Edmund Wong, Application Engineer, Metrowerks Hong Kong
 *
 *  
 *  (c) Copyright. 2002. Metrowerks Corp. ALL RIGHTS RESERVED.
 *	This code is provided "AS IS" without warranty of any kind and subject to Metrowerks Sample Application
 *  End User License Agreement. NO EXTERNAL DISTRIBUTION OR COMMERCIALIZATION OF THE SOFTWARE IS PERMITTED 
 *  EXCEPT BY WRITTEN AGREEMENT OF METROWERKS."
 */

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

public class DownloadFromURLForm extends Form implements CommandListener{


    /**
     * Create Items and Command for DownloadFromURLForm
     */
		 
	//for DownloadFromURLForm	
	Command downloadCommand = new Command("Get Image",Command.SCREEN,0); 
	
	TextField URLtextField = new TextField("Download from URL:", "http://localhost/samples/1.png"/*"http://www2.comp.polyu.edu.hk/~c1415307/1.png"*/, 60, TextField.URL);
    
	
	
	//for downloadImageCanvas which display downloaded image
	Command backCommand = new Command("Back",Command.BACK,0); // going back to DownloadFromURLForm
				
	Command saveImageCommand = new Command("Save Image",Command.SCREEN,0); //for saving downloaded image to phone
	
	
	//for saveOKForm which display 'Save image OK' information
	Command saveEditedDescriptionsCommand = new Command("Save Description",Command.SCREEN,0); // for saving edited description
	
	Command downloadAgainCommand = new Command("Download again", Command.BACK, 0); //for going back to DownloadFromURLForm
	        
    TextField descriptionsEntryField = null;	// for user to enter of new description on Save Image OK screen
    
    
    
    byte [] downloadedImageData;    // data buffer for storing downloaded data
    
    int addedDescriptionDBRecordID;	// for storing the recordID of the new record created for storing description of newly 
    								// saved image
    
    Image img = null;				// reference for image created
    

  	ImageAlbum imageAlbumReference;	// reference for main object ImageAlbum
  	
	

	/**
     * Constructor of DownloadFromURLForm
     */
	
	public DownloadFromURLForm(ImageAlbum imageAlbumReference) {
	
	
		super("Please input URL:");
	
		this.imageAlbumReference = imageAlbumReference;
		
	
	   /**
     	* Add items for the Download URL Input Form
     	*/
     	
		append(URLtextField);		
		
										
		
	   /**
     	* Add command and set CommandListener for the DownloadFromURLForm
     	*/
     	
     	addCommand(downloadCommand);
     	
     	addCommand(ImageAlbum.mainMenuCommand);
     	
     	setCommandListener(this);
     		
	}
	
	
	
	/**
     * Implementation for CommandListener
     */
     
    public void commandAction(Command c, Displayable s) {

		/** 
    	 *	download and display image from specified URL when download Command is chosen from downloadFromURLForm
    	 */	
    	 	
		if (c==downloadCommand) {
		
				try{				
				
				// download byte data and store in byte array						
					downloadedImageData = HttpDownloader.httpDownload(URLtextField.getString());
								
				}
								
				catch (IOException e){
        		
        			System.out.println("IO Exception" + e.toString());
        		
        		}
				
				// create image from byte array							
				img = Image.createImage(downloadedImageData, 0, downloadedImageData.length);
											 
				
				// create downloadImageCanvas for displaying downloaded image, with description field showing URL 
				PhotoCanvas downloadImageCanvas = new PhotoCanvas(img, URLtextField.getString(), downloadedImageData.length);
				
				downloadImageCanvas.downloadImageCanvasFlag = true;	// set flag to stop drawing string 'image x of y'
							
				downloadImageCanvas.addCommand(saveImageCommand);  
				
				downloadImageCanvas.addCommand(backCommand);
				
				downloadImageCanvas.addCommand(ImageAlbum.mainMenuCommand);
				
				downloadImageCanvas.setCommandListener(this);
				
				ImageAlbum.myDisplay.setCurrent(downloadImageCanvas);
				
				downloadImageCanvas = null;
								
					
		}
		
		
		/** 
    	 *	add image data to RecordStore when saveImageCommand is chosen from downloadImageCanvas 
    	 */
		
		if (c==saveImageCommand) {
		
		
				// open the RecordStore "ImageDB"
     	 		imageAlbumReference.rmsOperations.openRecordStore("ImageDB", false);
     	 		
					
				// add downloaded image data to the opened ImageDB RecordStore
				imageAlbumReference.rmsOperations.addRecord(downloadedImageData);
				
				
				//update variable storing total no. of images 				
				ImageAlbum.totalImageNumber++; 
				
				//update variable storing no. of images in RecordStore  
				ImageAlbum.imageNumberInRecordStore++;
				
				
				System.out.println(" total image no.: "+ImageAlbum.totalImageNumber);
				
				// store the image into the vector imageVector in main ImageAlbum object for immediate showing use
				imageAlbumReference.imageVector.addElement(img);
						
						
				// create Form for showing Image Save OK notification and allow user to enter user's description 										
				Form saveOKForm = new Form("Image Save OK!");
				
				// text field for entering user's description
				descriptionsEntryField = new TextField("To change default description -\nEnter your own description in text box below and choose 'Save Description' Command. (max. 100 characters):", URLtextField.getString(), 100, TextField.ANY);
								
				saveOKForm.append(new StringItem("Image saved as Image number " + ImageAlbum.totalImageNumber +"!\nURL has been saved as default description for this image!", null));
				
				saveOKForm.append(descriptionsEntryField);
				
				saveOKForm.addCommand(saveEditedDescriptionsCommand);
								
				saveOKForm.addCommand(ImageAlbum.mainMenuCommand);
				
				saveOKForm.addCommand(downloadAgainCommand);
								
				saveOKForm.setCommandListener(this);
				
				ImageAlbum.myDisplay.setCurrent(saveOKForm); 
				
				saveOKForm = null;
				
				// close RecordStore "ImageDB"
        		
        		imageAlbumReference.rmsOperations.closeRecordStore();
				
				
				img = null;
							
				
				
				/**
				 * Saving default description of this image to Description database 
				 */	
							
				byte [] byteArray = null;
				
								
				// open the RecordStore "DescriptionsDB"
				
				imageAlbumReference.rmsOperations.openRecordStore("DescriptionsDB", false);
								
				
				// convert default description string into byte array 
				try {
		
					byteArray = StringByteOperations.stringToByteConvertion(URLtextField.getString());
				
				}
				
				catch(Exception e) {
					
					System.out.println("Exception: "+e.toString());
		
				}
				
				// write the byte array of the string into RecordStore "DescriptionsDB"
				addedDescriptionDBRecordID = imageAlbumReference.rmsOperations.addRecord(byteArray);
							
				System.out.println("added description record #" + addedDescriptionDBRecordID);
											
				
				// store the description into the Vector descriptionVector in main ImageAlbum for immediate showing use
				imageAlbumReference.descriptionsVector.addElement(descriptionsEntryField.getString());
				
				
				// close RecordStore "DescriptionsDB"
        		
        		imageAlbumReference.rmsOperations.closeRecordStore();
					
									
				byteArray = null; 				
				
		}
		
		
		
		/** 
    	 *	jump back to DownloadFromURLForm when backCommand is chosen from downloadImageCanvas
    	 */
		
		if (c==backCommand) { 			
		
		img = null;
			
		ImageAlbum.myDisplay.setCurrent(this);	
					
		
		}
		
		
		/** 
    	 *	jumping back to Main Menu when mainMenuCommand is chosen from DownloadFromURLForm,
    	 *	downloadImageCanvas or saveOKForm
    	 */	
		
		if (c==ImageAlbum.mainMenuCommand) {	
		
			img = null;
	
			ImageAlbum.myDisplay.setCurrent(imageAlbumReference.selectList);
	
		}	
		
		 
		/** 
    	 *	jump back to DownloadFromURLForm when downloadAgainCommand is chosen from saveOKForm
    	 */
    	 
		if (c == downloadAgainCommand) {
		
			ImageAlbum.myDisplay.setCurrent(this);
		
		} 
		
		
		/** 
    	 *	store user's edited description when saveEditedDescriptionsCommand is chosen from saveOKForm
    	 */
		
		if (c==saveEditedDescriptionsCommand) { 
		
			byte [] byteArray = null;
			
				
			// open the RecordStore "DescriptionsDB"				
				imageAlbumReference.rmsOperations.openRecordStore("DescriptionsDB", false);
						
			
			// convert edited description string into byte array 			
			try{
		
				byteArray = StringByteOperations.stringToByteConvertion(descriptionsEntryField.getString());
		
			}
			
			catch(Exception e) {
			
				System.out.println("Exception: " + e.toString());
		
			}
								
									
			imageAlbumReference.rmsOperations.setRecord(addedDescriptionDBRecordID, byteArray, "Edited Description Save OK!", this);
				
			
			System.out.println("edited description record #" + addedDescriptionDBRecordID);
							
			System.out.println("total description record #" + ImageAlbum.totalImageNumber);
										
			
			// store the description into the Vector descriptionVector for immediate showing use
			imageAlbumReference.descriptionsVector.setElementAt(descriptionsEntryField.getString(), (imageAlbumReference.descriptionsVector.size() - 1));
						
			
			// close RecordStore "DescriptionsDB"         		
        	imageAlbumReference.rmsOperations.closeRecordStore();
						
									
			byteArray = null; 					
		
		}
	
	}
}