java - RotaryKnob using get progress value in text view -

i refereed website can't understand how can value rotary knob. given below tried sample code. need means when rotate right side knob want increase value in text view @ same time left side rotate means decrease value in text view. minimum value 0 , maximum value 25.

rotaryknobview class here

public class rotaryknobview extends imageview  {  private float angle = 0f; private float theta_old=0f;  private rotaryknoblistener listener;  public interface rotaryknoblistener {     public void onknobchanged(int arg); }  public void setknoblistener(rotaryknoblistener l ) {     listener = l; }  public rotaryknobview(context context) {     super(context);     initialize(); }  public rotaryknobview(context context, attributeset attrs) {     super(context, attrs);     initialize(); }  public rotaryknobview(context context, attributeset attrs, int defstyle) {     super(context, attrs, defstyle);     initialize(); }  private float gettheta(float x, float y) {     float sx = x - (getwidth() / 2.0f);     float sy = y - (getheight() / 2.0f);      float length = (float)math.sqrt( sx*sx + sy*sy);     float nx = sx / length;     float ny = sy / length;     float theta = (float)math.atan2( ny, nx );      final float rad2deg = (float)(180.0/math.pi);     float thetadeg = theta*rad2deg;      return (thetadeg < 0) ? thetadeg + 360.0f : thetadeg; }  public void initialize() {     this.setimageresource(r.drawable.ic_launcher);     setontouchlistener(new ontouchlistener()     {         @override         public boolean ontouch(view v, motionevent event) {             float x = event.getx(0);             float y = event.gety(0);             float theta = gettheta(x,y);              switch(event.getaction() & motionevent.action_mask)             {             case motionevent.action_pointer_down:                 theta_old = theta;                 break;             case motionevent.action_move:                 invalidate();                 float delta_theta = theta - theta_old;                 theta_old = theta;                 int direction = (delta_theta > 0) ? 1 : -1;                 angle += 3*direction;                 notifylistener(direction);                 break;             }             return true;         }     }); }  private void notifylistener(int arg) {     if (null!=listener)         listener.onknobchanged(arg); }  protected void ondraw(canvas c) {     c.rotate(angle,getwidth()/2,getheight()/2);        super.ondraw(c); } 

main activity class code here

final textview tview = (textview)findviewbyid(r.id.tv);     rotaryknobview jogview = (rotaryknobview)findviewbyid(r.id.knob);     jogview.setknoblistener(new rotaryknobview.rotaryknoblistener()     {         @override         public void onknobchanged(int progress) {              if (progress > 0){                 // rotate right                  tview.settext(""+progress);             } else{                 // rotate left                  tview.settext(""+progress);             }         }     }); 

mainactivity xml code here

<com.example.ghvhjf.rotaryknobview     android:id="@+id/knob"     android:layout_width="100dip"     android:layout_height="100dip" />  <textview     android:id="@+id/tv"     android:layout_width="wrap_content"     android:layout_height="wrap_content" /> 

your listener isn't informed total progress; turn direction, can seen here:

int direction = (delta_theta > 0) ? 1 : -1; notifylistener(direction); 

so track , sum changes in rotaryknoblistener:

new rotaryknobview.rotaryknoblistener() {      private int progress = 0;      @override     public void onknobchanged(int direction) {         progress += direction;         progress = math.max(0, math.min(25, progress));         tview.settext(integer.tostring(progress));     } }