Android之拖拉功能

1：ColorBall 

package cn.itcast.dragdrop;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Point;

public class ColorBall  {
 private Bitmap img; // the image of the ball
 private int coordX = 0; // the x coordinate at the canvas
 private int coordY = 0; // the y coordinate at the canvas
 private int id; // gives every ball his own id, for now not necessary
 private static int count = 1;
 private boolean goRight = true;
 private boolean goDown = true;
 
	public ColorBall(Context context, int drawable) {

		BitmapFactory.Options opts = new BitmapFactory.Options();
        opts.inJustDecodeBounds = true;
        img = BitmapFactory.decodeResource(context.getResources(), drawable); 
        id=count;
		count++;

	}
	
	public ColorBall(Context context, int drawable, Point point) {

		BitmapFactory.Options opts = new BitmapFactory.Options();
        opts.inJustDecodeBounds = true;
        img = BitmapFactory.decodeResource(context.getResources(), drawable); 
        id=count;
		count++;
		coordX= point.x;
		coordY = point.y;

	}
	
	public static int getCount() {
		return count;
	}
	
	void setX(int newValue) {
        coordX = newValue;
    }
	
	public int getX() {
		return coordX;
	}

	void setY(int newValue) {
        coordY = newValue;
   }
	
	public int getY() {
		return coordY;
	}
	
	public int getID() {
		return id;
	}
	
	public Bitmap getBitmap() {
		return img;
	}
	
	public void moveBall(int goX, int goY) {
		// check the borders, and set the direction if a border has reached
		if (coordX > 270){
			goRight = false;
		}
		if (coordX < 0){
			goRight = true;
		}
		if (coordY > 400){
			goDown = false;
		}
		if (coordY < 0){
			goDown = true;
		}
		// move the x and y 
		if (goRight){
			coordX += goX;
		}else
		{
			coordX -= goX;
		}
		if (goDown){
			coordY += goY;
		}else
		{
			coordY -= goY;
		}
		
	}
	
}

 

2：DrawView

package cn.itcast.dragdrop;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Point;
import android.view.MotionEvent;
import android.view.View;

public class DrawView extends View {
   private ColorBall[] colorballs = new ColorBall[3]; // array that holds the balls
   private int balID = 0; // variable to know what ball is being dragged
    
    public DrawView(Context context) {
        super(context);
        setFocusable(true); //necessary for getting the touch events
        
        // setting the start point for the balls
        Point point1 = new Point();
        point1.x = 50;
        point1.y = 20;
        Point point2 = new Point();
        point2.x = 100;
        point2.y = 20;
        Point point3 = new Point();
        point3.x = 150;
        point3.y = 20;
        
                       
        // declare each ball with the ColorBall class
        colorballs[0] = new ColorBall(context,R.drawable.bol_groen, point1);
        colorballs[1] = new ColorBall(context,R.drawable.bol_rood, point2);
        colorballs[2] = new ColorBall(context,R.drawable.bol_blauw, point3);
        
        
    }
    
    // the method that draws the balls
    @Override protected void onDraw(Canvas canvas) {
        //canvas.drawColor(0xFFCCCCCC);     //if you want another background color       
        
    	//draw the balls on the canvas
    	for (ColorBall ball : colorballs) {
            canvas.drawBitmap(ball.getBitmap(), ball.getX(), ball.getY(), null);
          }

    }
    
    // events when touching the screen
    public boolean onTouchEvent(MotionEvent event) {
        int X = (int)event.getX(); 
        int Y = (int)event.getY(); 
        switch (event.getAction() ) { 
        case MotionEvent.ACTION_DOWN: // touch down so check if the finger is on a ball
        	balID = 0;
        	for (ColorBall ball : colorballs) {
        		// check if inside the bounds of the ball (circle)
        		// get the center for the ball
        		int centerX = ball.getX() + 25;
        		int centerY = ball.getY() + 25;
        		
        		// calculate the radius from the touch to the center of the ball
        		double radCircle  = Math.sqrt( (double) (((centerX-X)*(centerX-X)) + (centerY-Y)*(centerY-Y)));
        		
        		// if the radius is smaller then 23 (radius of a ball is 22), then it must be on the ball
        		if (radCircle < 23){
        			balID = ball.getID();
                    break;
        		}

        		// check all the bounds of the ball (square)
        		//if (X > ball.getX() && X < ball.getX()+50 && Y > ball.getY() && Y < ball.getY()+50){
                //	balID = ball.getID();
                //	break;
                //}
              }
             
             break; 


        case MotionEvent.ACTION_MOVE:   // touch drag with the ball
        	// move the balls the same as the finger
            if (balID > 0) {
            	colorballs[balID-1].setX(X-25);
            	colorballs[balID-1].setY(Y-25);
            }
        	
            break; 

        case MotionEvent.ACTION_UP: 
       		// touch drop - just do things here after dropping

             break; 
        } 
        // redraw the canvas
        invalidate(); 
        return true; 
	
    }
}

 

3：MainActivity

package cn.itcast.dragdrop;

import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new DrawView(this));
    }
}

 

4：

   
- 
- 
- 
-