Android animation jumps to end -

hi trying simple listview expand animation work. animation working jumps end resumes animation.

gif of problem

this code animation class:

public class dropdownanimation extends animation { private int targetheight; private view view; private boolean down;  public dropdownanimation(view view, int targetheight, boolean down) {     this.view = view;     this.targetheight = targetheight;     this.down = down; }  public dropdownanimation(view view, int targetheight) {     this.view = view;     this.targetheight = targetheight;     this.setduration(350);     if(view.getvisibility() == view.invisible)         down = true;     else         down = false; }  @override protected void applytransformation(float interpolatedtime, transformation t) {     super.applytransformation(interpolatedtime,t);     int newheight;     if (down) {         newheight = (int) (targetheight * interpolatedtime);         view.setvisibility(view.visible);     } else {         newheight = (int) (targetheight * (1 - interpolatedtime));         view.setvisibility(view.invisible);     }     view.getlayoutparams().height = newheight;     view.requestlayout(); }  @override public void initialize(int width, int height, int parentwidth,                        int parentheight) {     super.initialize(width, height, parentwidth, parentheight); }  @override public boolean willchangebounds() {     return true; } } 

animation being called this:

dropdownanimation dropdownanimation = new dropdownanimation(toolbar,expandedheight);             toolbar.startanimation(dropdownanimation);             view parent = (view)test.getparent();             parent.invalidate();