Android Open Source - BounceMe Sling

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Back to project page BounceMe.
License

The source code is released under:
MIT License
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Java Source Code

package com.example.bounceme;
//from   w  w  w . j av  a 2  s.  com
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.Log;

public class Sling {
  private int size = 5;
  private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
  private int leftX, rightX, Y;
  private int midX, midY, midX2, midY2;
  private int x, y;
  private int width;
  private double bounce = .0025;
  boolean above = true;
  boolean forced = false;
  private final Type[] types = {new Type(200, .0025, 0xFF4989C8), new Type(500, .001, 0xFFF2642F)};
  private Type type;

  public Sling(int x, int y, int typeNum) {
    type = types[typeNum];
    width = type.width;
    bounce = type.bounce;
    mPaint.setColor(type.color);
    
    midX = midX2= this.x = x;
    Y = midY = midY2 = this.y =  y;
    leftX = midX - width / 2;
    rightX = midX + width / 2;
    
    mPaint.setStrokeWidth(size);
  }

  public void draw(Canvas can) {
    //Log.d("OUTPUT", "left:(" + midX + "," + midY + ")");
    //Log.d("OUTPUT", "right:(" + midX2 + "," + midY2 + ")");
    can.drawLine(leftX, Y, midX, midY, mPaint);
    can.drawLine(midX2, midY2, rightX, Y, mPaint);
    can.drawCircle(leftX, Y, 10, mPaint);
    can.drawCircle(rightX, Y, 10, mPaint);
  }

  public boolean update(Ball ball){
    /*x -= 1;
    midX -= 1;
    midX2 -= 1;
    leftX -= 1;
    rightX -= 1;*/
    
    int radius = ball.getRadius() - 2;
    int centerX = ball.getX();
    int centerY = ball.getY();
    double a1, a2, d1, d2;
    a1 =  a2 = d1 = d2 = 0;
    
    //detecting if the ball is above the sling
    if (centerY + radius < Y + 20){
      above = true;
    }else{
      above = false;
    }
    
    
    if(centerY + radius > Y){
      if((centerX > leftX && centerX < rightX) || forced){
        if(forced || above){
          forced = true;
          
          //Mathematical logic for physics on the sling can be found here - "http://www.emanueleferonato.com/2007/08/13/throw-a-ball-with-a-sling-physics-flash-tutorial/"
                  double x1 = centerX - leftX;
          double y1 = centerY - Y;
          double x2 = rightX - centerX;
          double y2 = Y - centerY;
          
          
          d1 = Math.sqrt(x1*x1 + y1*y1);
          d2 = Math.sqrt(x2*x2 + y2*y2);
          
          a1 = Math.atan2(y1, x1);
          a2 = Math.atan2(y2, x2);
          
          midX = (int) (centerX + Math.cos(a1 + Math.PI/2)*radius);
          midY = (int) (centerY + Math.sin(a1 + Math.PI/2)*radius);
          midX2 = (int) (centerX + Math.cos(a2 + Math.PI/2)*radius);
          midY2 = (int) (centerY + Math.sin(a2 + Math.PI/2)*radius);
          
          a1 += Math.sin(radius/d1);
          a2 += Math.sin(radius/d2)*-1.0;
        }
      }
    }else{
      forced = false;
      midX = midX2 = x;
      midY = midY2 = y;
    }
    
    double xacc = 0;
    double yacc = 0;
    
    if(forced){
      Log.d("OUPUT", "into acc change");
      xacc += d1*Math.sin(a2)*bounce;
          yacc -= d1*Math.cos(a1)*bounce;
          xacc += d2*Math.sin(a1)*bounce;
          yacc -= d2*Math.cos(a2)*bounce;
          
          Log.d("OUPUT", "(" + xacc + "," + yacc + ")");
          ball.setAcc(xacc, yacc);
    }
    
    return true;
  }
  
  public class Type{
    public int width;
    public double bounce;
    public int color;
    
    public Type(int w, double b, int green){
      width = w;
      bounce = b;
      color = green;
    }
  }
}
Java Source Code List
