java - GridView Rearange switch by drag and drop -

i have program creates grid , rearranges drag-and-droping, first of functional not way wanted it. must common rearrange this, drag object , when drop falls position moving rest forward until find empty space, want more simple; want objects switch 1 that's in position dropped it. code of adapter:

@suppresslint("wrongcall")  public class draggridview extends viewgroup implements view.ontouchlistener, view.onclicklistener, view.onlongclicklistener {  public static float childratio = .9f; protected int colcount, childsize, padding, dpi, scroll = 0; protected float lastdelta = 0; protected handler handler = new handler();  protected int dragged = -1, lastx = -1, lasty = -1, lasttarget = -1; protected boolean enabled = true, touching = false;  public static int animt = 150; protected arraylist<integer> newpositions = new arraylist<integer>();  protected onrearrangelistener onrearrangelistener; protected onclicklistener secondaryonclicklistener; private onitemclicklistener onitemclicklistener;  public interface onrearrangelistener {  public abstract void onrearrange(int oldindex, int newindex); }  public draggridview(context context, attributeset attrs) { super(context, attrs); setlisteners(); handler.removecallbacks(updatetask); handler.postattime(updatetask, systemclock.uptimemillis() + 500); setchildrendrawingorderenabled(true);  displaymetrics metrics = new displaymetrics(); ((activity) context).getwindowmanager().getdefaultdisplay()         .getmetrics(metrics); dpi = metrics.densitydpi; }  protected void setlisteners() { setontouchlistener(this); super.setonclicklistener(this); setonlongclicklistener(this); }  @override public void setonclicklistener(onclicklistener l) { secondaryonclicklistener = l; }  protected runnable updatetask = new runnable() { public void run() {     if (dragged != -1) {         if (lasty < padding * 3 && scroll > 0)             scroll -= 20;         else if (lasty > getbottom() - gettop() - (padding * 3)                 && scroll < getmaxscroll())             scroll += 20;     } else if (lastdelta != 0 && !touching) {         scroll += lastdelta;         lastdelta *= .9;         if (math.abs(lastdelta) < .25)             lastdelta = 0;     }     clampscroll();     onlayout(true, getleft(), gettop(), getright(), getbottom());      handler.postdelayed(this, 25); } };  @override public void addview(view child) { super.addview(child); newpositions.add(-1); };  @override public void removeviewat(int index) { super.removeviewat(index); newpositions.remove(index); };  @override protected void onlayout(boolean changed, int l, int t, int r, int b) { // compute width of view, in dp float w = (r - l) / (dpi / 160f);  colcount = 2; int sub = 240; w -= 280; while (w > 0) {     colcount++;     w -= sub;     sub += 40; }  childsize = (r - l) / colcount; childsize = math.round(childsize * childratio); padding = ((r - l) - (childsize * colcount)) / (colcount + 1);  (int = 0; < getchildcount(); i++)     if (i != dragged) {         point xy = getcoorfromindex(i);         getchildat(i).layout(xy.x, xy.y, xy.x + childsize,                 xy.y + childsize);     } }  @override protected int getchilddrawingorder(int childcount, int i) { if (dragged == -1)     return i; else if (i == childcount - 1)     return dragged; else if (i >= dragged)     return + 1; return i; }  public int getindexfromcoor(int x, int y) { int col = getcolorrowfromcoor(x), row = getcolorrowfromcoor(y + scroll); if (col == -1 || row == -1)      return -1; int index = row * colcount + col; if (index >= getchildcount())     return -1; return index; }  protected int getcolorrowfromcoor(int coor) { coor -= padding; (int = 0; coor > 0; i++) {     if (coor < childsize)         return i;     coor -= (childsize + padding); } return -1; }  protected int gettargetfromcoor(int x, int y) { if (getcolorrowfromcoor(y + scroll) == -1)      return -1;   int leftpos = getindexfromcoor(x - (childsize / 4), y); int rightpos = getindexfromcoor(x + (childsize / 4), y); if (leftpos == -1 && rightpos == -1)      return -1; if (leftpos == rightpos)      return -1;  int target = -1; if (rightpos > -1)     target = rightpos; else if (leftpos > -1)     target = leftpos + 1; if (dragged < target)     return target - 1;  return target; }  protected point getcoorfromindex(int index) { int col = index % colcount; int row = index / colcount; return new point(padding + (childsize + padding) * col, padding         + (childsize + padding) * row - scroll); }  public int getindexof(view child) { (int = 0; < getchildcount(); i++)     if (getchildat(i) == child)         return i; return -1; }  public void onclick(view view) { if (enabled) {     if (secondaryonclicklistener != null)         secondaryonclicklistener.onclick(view);     if (onitemclicklistener != null && getlastindex() != -1)         onitemclicklistener.onitemclick(null,                 getchildat(getlastindex()), getlastindex(),                 getlastindex() / colcount); } }  public boolean onlongclick(view view) { if (!enabled)     return false; int index = getlastindex(); if (index != -1) {     dragged = index;     animatedragged();     return true; } return false; }  @suppresslint("wrongcall") public boolean ontouch(view view, motionevent event) { int action = event.getaction(); switch (action & motionevent.action_mask) { case motionevent.action_down:     enabled = true;     lastx = (int) event.getx();     lasty = (int) event.gety();     touching = true;     break; case motionevent.action_move:     int delta = lasty - (int) event.gety();     if (dragged != -1) {         // change draw location of dragged visual         int x = (int) event.getx(), y = (int) event.gety();         int l = x - (3 * childsize / 4), t = y - (3 * childsize / 4);         getchildat(dragged).layout(l, t, l + (childsize * 3 / 2),                 t + (childsize * 3 / 2));          // check new target hover         int target = gettargetfromcoor(x, y);         if (lasttarget != target) {             if (target != -1) {                 animategap(target);                 lasttarget = target;             }         }     } else {         scroll += delta;         clampscroll();         if (math.abs(delta) > 2)             enabled = false;         onlayout(true, getleft(), gettop(), getright(), getbottom());     }     lastx = (int) event.getx();     lasty = (int) event.gety();     lastdelta = delta;     break; case motionevent.action_up:     if (dragged != -1) {         view v = getchildat(dragged);         if (lasttarget != -1)             reorderchildren();         else {             point xy = getcoorfromindex(dragged);             v.layout(xy.x, xy.y, xy.x + childsize, xy.y + childsize);         }         v.clearanimation();         if (v instanceof imageview)             ((imageview) v).setalpha(255);         lasttarget = -1;         dragged = -1;     }     touching = false;     break; } if (dragged != -1)     return true; return false; }  protected void animatedragged() { view v = getchildat(dragged); int x = getcoorfromindex(dragged).x + childsize / 2, y = getcoorfromindex(dragged).y         + childsize / 2; int l = x - (3 * childsize / 4), t = y - (3 * childsize / 4); v.layout(l, t, l + (childsize * 3 / 2), t + (childsize * 3 / 2)); animationset animset = new animationset(true); scaleanimation scale = new scaleanimation(.667f, 1, .667f, 1,         childsize * 3 / 4, childsize * 3 / 4); scale.setduration(animt); alphaanimation alpha = new alphaanimation(1, .5f); alpha.setduration(animt);  animset.addanimation(scale); animset.addanimation(alpha); animset.setfillenabled(true); animset.setfillafter(true);  v.clearanimation(); v.startanimation(animset); }  protected void animategap(int target) { (int = 0; < getchildcount(); i++) {     view v = getchildat(i);     if (i == dragged)         continue;     int newpos = i;     if (dragged < target && >= dragged + 1 && <= target)         newpos--;     else if (target < dragged && >= target && < dragged)         newpos++;      int oldpos = i;     if (newpositions.get(i) != -1)         oldpos = newpositions.get(i);     if (oldpos == newpos)         continue;      point oldxy = getcoorfromindex(oldpos);     point newxy = getcoorfromindex(newpos);     point oldoffset = new point(oldxy.x - v.getleft(), oldxy.y             - v.gettop());     point newoffset = new point(newxy.x - v.getleft(), newxy.y             - v.gettop());      translateanimation translate = new translateanimation(             animation.absolute, oldoffset.x, animation.absolute,             newoffset.x, animation.absolute, oldoffset.y,             animation.absolute, newoffset.y);     translate.setduration(animt);     translate.setfillenabled(true);     translate.setfillafter(true);     v.clearanimation();     v.startanimation(translate);      newpositions.set(i, newpos); } }  protected void reorderchildren() { if (onrearrangelistener != null)     onrearrangelistener.onrearrange(dragged, lasttarget); arraylist<view> children = new arraylist<view>(); (int = 0; < getchildcount(); i++) {     getchildat(i).clearanimation();     children.add(getchildat(i)); } removeallviews(); while (dragged != lasttarget)     if (lasttarget == children.size())      {         children.add(children.remove(dragged));         dragged = lasttarget;     } else if (dragged < lasttarget)      {         collections.swap(children, dragged, dragged + 1);         dragged++;     } else if (dragged > lasttarget)      {         collections.swap(children, dragged, dragged - 1);         dragged--;     } (int = 0; < children.size(); i++) {     newpositions.set(i, -1);     addview(children.get(i)); } onlayout(true, getleft(), gettop(), getright(), getbottom()); }  @suppresslint("wrongcall") public void scrolltotop() { scroll = 0; }  public void scrolltobottom() { scroll = integer.max_value; clampscroll(); }  protected void clampscroll() { int stretch = 3, overreach = getheight() / 2; int max = getmaxscroll(); max = math.max(max, 0);  if (scroll < -overreach) {     scroll = -overreach;     lastdelta = 0; } else if (scroll > max + overreach) {     scroll = max + overreach;     lastdelta = 0; } else if (scroll < 0) {     if (scroll >= -stretch)         scroll = 0;     else if (!touching)         scroll -= scroll / stretch; } else if (scroll > max) {     if (scroll <= max + stretch)         scroll = max;     else if (!touching)         scroll += (max - scroll) / stretch; } }  protected int getmaxscroll() { int rowcount = (int) math.ceil((double) getchildcount() / colcount), max = rowcount         * childsize + (rowcount + 1) * padding - getheight(); return max; }  public int getlastindex() { return getindexfromcoor(lastx, lasty); }  public void setonrearrangelistener(onrearrangelistener l) { this.onrearrangelistener = l; }  public void setonitemclicklistener(onitemclicklistener l) { this.onitemclicklistener = l; } } 

the methods think have change animategap , reorderchildren, don't know how exactly.