Android ListView Initialization will instantiate how many item

The following is an analysis of the source flow parsing the ListView initialization.

Layoutchildren () is called in Abslistview.onlayout and is implemented by the ListView

@Overrideprotected voidOnLayout (BooleanChangedintLintTintRintb) {Super. OnLayout (Changed, L, T, R, b); Minlayout=true; Final intChildCount =Getchildcount (); if(changed) { for(inti = 0; i < ChildCount; i++) {Getchildat (i). Forcelayout ();        } mrecycler.markchildrendirty (); }            //Subclass ImplementationLayoutchildren (); Minlayout=false; Moverscrollmax= (B-T)/Overscroll_limit_divisor; //Todo:move somewhere sane. This doesn ' t belong in OnLayout ().        if(Mfastscroll! =NULL) {mfastscroll.onitemcountchanged (Getchildcount (), mitemcount); }    }

Listview.layoutchildren:

@Overrideprotected voidLayoutchildren () {Final BooleanBlocklayoutrequests =mblocklayoutrequests; if(blocklayoutrequests) {return; } mblocklayoutrequests=true; Try {            Super. Layoutchildren ();            Invalidate (); if(Madapter = =NULL) {resetlist ();                Invokeonitemscrolllistener (); return; }            Final intChildrentop =Mlistpadding.top; Final intChildrenbottom = Mbottom-mtop-Mlistpadding.bottom; Final intChildCount =Getchildcount (); .. .....default:                if(ChildCount = = 0) {                    if(!Mstackfrombottom) {                        Final intPosition = lookforselectableposition (0,true);                       Setselectedpositionint (position); //initialization will be performed hereSEL =fillfromtop (childrentop); } Else {                        Final intPosition = Lookforselectableposition (mItemCount-1,false);                        Setselectedpositionint (position); Sel= FillUp (mItemCount-1, Childrenbottom); }                } Else {                    if(mselectedposition >= 0 && Mselectedposition <Mitemcount) {sel=fillspecific (mselectedposition, Oldsel==NULL?ChildrenTop:oldSel.getTop ()); } Else if(Mfirstposition <Mitemcount) {sel=fillspecific (mfirstposition, Oldfirst==NULL?ChildrenTop:oldFirst.getTop ()); } Else{sel= fillspecific (0, Childrentop); }                }                 Break; }

Listview.fillfromtop:

Private View fillfromtop (int  nexttop) {        = math.min (mfirstposition, mselectedposition);         = Math.min (mfirstposition, mItemCount-1);         if (Mfirstposition < 0) {            = 0;        }         return FillDown (mfirstposition, nexttop);    }

Listview.filldown:

PrivateView FillDown (intPosintnexttop) {View Selectedview=NULL;
Height of the ListViewintEnd = (Mbottom-mtop); if((Mgroupflags & clip_to_padding_mask) = =clip_to_padding_mask) {End-=Mlistpadding.bottom; }        //when initializing pos = 0, if the total item count is less than one screen, execute mitemcount-pos times//If Item is extra a screen, perform end-nexttop times         while(Nexttop < end && Pos <Mitemcount) {            //Is this the selected item?            BooleanSelected = pos = =mselectedposition; View Child= Makeandaddview (pos, Nexttop,true, Mlistpadding.left, selected); Nexttop= Child.getbottom () +Mdividerheight; if(selected) {Selectedview=Child ; } POS++; } setvisiblerangehint (Mfirstposition, Mfirstposition+ Getchildcount ()-1); returnSelectedview; }

Android ListView Initialization will instantiate how many item