imagecanvas.java

Java编写的GUI聊天工具

package com.jeeva.chatclient;

import java.awt.Dimension;
import java.awt.Canvas;
import java.util.ArrayList;
import java.awt.Graphics;
import java.awt.Event;
import java.awt.Image;
import java.awt.Color;
import java.awt.Font;
import java.awt.Cursor;
public class ImageCanvas extends Canvas implements CommonSettings
{
	/**********Constructor Of Image Canvas *************/
	ImageCanvas(ChatClient Parent)
	{
		chatclient = Parent;		
		dimension = this.size();
		IconArray = new ArrayList();								
	}
	
	protected void AddIconsToMessageObject()
	{
		int StartX = IMAGE_CANVAS_START_POSITION;					
		int StartY = IMAGE_CANVAS_START_POSITION;
		for(G_ILoop = 1; G_ILoop <= chatclient.IconCount;G_ILoop++)
		{
			messageobject = new MessageObject();
			messageobject.Message = (G_ILoop - 1)+"";
			messageobject.StartX  = StartX;
			messageobject.StartY  = StartY;
			messageobject.IsImage = true;
			messageobject.Width   = DEFAULT_ICON_WIDTH;
			messageobject.Height  = DEFAULT_ICON_HEIGHT;
			IconArray.add(messageobject);			
			if(G_ILoop % 3 == 0)
			{
				StartX	= IMAGE_CANVAS_START_POSITION;
				StartY	+= DEFAULT_ICON_HEIGHT+DEFAULT_IMAGE_CANVAS_SPACE;
			}
			else
			{
				StartX 	+=	DEFAULT_ICON_WIDTH+DEFAULT_IMAGE_CANVAS_SPACE;	
			}
		}
		
		scrollview.setValues(dimension.width,StartY);
		scrollview.setScrollPos(1,1);
		scrollview.setScrollSteps(2,1,DEFAULT_SCROLLING_HEIGHT);
		repaint();		
	}
	
	private void PaintFrame(Graphics graphics)
	{
		int m_iconListSize = IconArray.size();		
		for(G_ILoop = 0; G_ILoop < m_iconListSize; G_ILoop++)
		{			
			messageobject = (MessageObject) IconArray.get(G_ILoop);			
			if((messageobject.StartY + messageobject.Height) >= YOffset)
			{				
				PaintImagesIntoCanvas(graphics,messageobject);	
			}
		}
	}
	
	private void PaintImagesIntoCanvas(Graphics graphics, MessageObject messageObject)
	{
		int m_StartY = messageObject.StartY - YOffset;
		if(messageobject.Message.equals(SelectedImage))
			graphics.draw3DRect(messageObject.StartX-2,m_StartY-2,DEFAULT_ICON_WIDTH+2,DEFAULT_ICON_HEIGHT+2, true);			
		graphics.drawImage(chatclient.IconArray[Integer.parseInt(messageObject.Message)],messageObject.StartX,m_StartY,DEFAULT_ICON_WIDTH,DEFAULT_ICON_HEIGHT,this);		
		graphics.setColor(Color.black);
		graphics.drawString(ICON_NAME+messageObject.Message,messageObject.StartX-1,m_StartY+DEFAULT_ICON_HEIGHT+10);
	}
	
	public boolean handleEvent(Event event)
    {
        if(event.id == 1001 && event.arg == scrollview)
        {
            if(event.modifiers == 1)
                XOffset = event.key;
            else
                YOffset = event.key;                                    
            repaint();
            return true;
        } 
        else
        {
            return super.handleEvent(event);
        }			
    }
    
    public boolean 	mouseEnter(Event event, int i, int j)
	{
		setCursor(new Cursor(Cursor.HAND_CURSOR));
		return true;
	}

	public boolean 	mouseExit(Event event, int i, int j)
	{
		setCursor(new Cursor(Cursor.DEFAULT_CURSOR)); 
		return true;
	}

    public boolean mouseMove(Event event, int i, int j)
	{
		int CurrentY = j + YOffset;
		int m_iconListSize = IconArray.size();
		for(G_ILoop = 0; G_ILoop <  m_iconListSize; G_ILoop++)
		{
			messageobject = (MessageObject) IconArray.get(G_ILoop);
			if((CurrentY <= messageobject.StartY+messageobject.Height) && (i <= messageobject.StartX+messageobject.Width))
			{
				SelectedImage = messageobject.Message;
				repaint();
				break;
			}
			SelectedImage = null;
		}					
		return true;
	}
	
	public boolean mouseDown(Event event, int i , int j)
	{
		int CurrentY = j + YOffset;
		int m_iconListSize = IconArray.size();
		for(G_ILoop = 0; G_ILoop <  m_iconListSize; G_ILoop++)
		{
			messageobject = (MessageObject) IconArray.get(G_ILoop);
			if((CurrentY <= messageobject.StartY+messageobject.Height) && (i <= messageobject.StartX+messageobject.Width))
			{
				chatclient.AddImageToTextField(messageobject.Message);
				break;
			}			
		}			
		return true;				
	}
	
	public void paint(Graphics graphics)
	{			
		/*************Double Buffering**************/		
		dimension = size();

		/*********** Create the offscreen graphics context**************/
		if ((offGraphics == null) || (dimension.width != offDimension.width)|| (dimension.height != offDimension.height)) 
		{
	    	offDimension = dimension;
	    	offImage = createImage(dimension.width, dimension.height);
	    	offGraphics = offImage.getGraphics();	    		    		    		    	
		}

		/********* Erase the previous image*********/
		offGraphics.setColor(Color.white);
		offGraphics.fillRect(0, 0, dimension.width, dimension.height);	

		/*************** Paint the frame into the image*****************/
		PaintFrame(offGraphics);

		/****************** Paint the image onto the screen*************/
		graphics.drawImage(offImage, 0, 0, null);
	}
	
	public void update(Graphics graphics)	
	{
		paint(graphics);	
	}
	
	/***********Global Variable Declarations****************/
	Dimension offDimension,dimension;
    Image offImage;
    Graphics offGraphics;  	
    ChatClient chatclient;    
    ArrayList IconArray;
    int G_ILoop,XOffset,YOffset;
    MessageObject messageobject;
    ScrollView scrollview;
    String SelectedImage;
}