Android expandablelist extension usage (based on baseexpandablelistadapter)

1. Introduction

Based on the baseexpandablelistadapter extension's expandablelist usage, there are currently two popular online methods: the first is to input two arrays to the baseexpandablelistadapter, and the first is a one-dimensional array that represents the group (directory header) information, the second is a two-dimensional array that represents the child (directory sub-item); the second is to construct two classes, one is the groupinfo class that represents the directory information, and the other is the ChildInfo class that represents the Sub-item information, input baseexpandablelistadapter. Through comparison, it is found that the first method is not useful because the array is fixed, while the actual project usually needs dynamically changed directories and subitems. The second method has too many files and is complicated to implement. Here we provide a method to transfer two dynamic two-dimensional arrays to implement directory structure.

2. Case studies

 Package  Com. Devin;  Import  Java. util. arraylist;  Import  Android. App. activity;  Import  Android. Graphics. color;  Import Android. Graphics. drawable. colordrawable;  Import  Android. OS. Bundle;  Import  Android. View. gravity;  Import  Android. View. view;  Import  Android. View. View. onclicklistener;  Import  Android. View. viewgroup;  Import  Android. widget. baseexpandablelistadapter;  Import Android. widget. expandablelistadapter;  Import  Android. widget. expandablelistview;  Import  Android. widget. imageview;  Import  Android. widget. linearlayout;  Import  Android. widget. textview;  Public   Class Padtestactivity Extends  Activity {  Protected  Void  Oncreate (bundle savedinstancestate ){  Super  . Oncreate (savedinstancestate); arraylist <String> grouplist = New Arraylist <string> ();  For ( Int I = 0; I <3; I ++ ) {Grouplist. Add ( "Title" );} Arraylist <String> itemlist1 = New Arraylist <string>(); Itemlist1.add ( "Item1" ); Itemlist1.add ( "Item2" ); Arraylist <String> itemlist2 = New Arraylist <string> (); Itemlist2.add ( "Item1" ); Itemlist2.add ( "Item21" ); Itemlist2.add ( "Item3" ); Arraylist <String> itemlist3 = New Arraylist <string> (); Itemlist3.add ( "Item1"); Itemlist3.add ( "Item2" ); Itemlist3.add ( "Item3" ); Itemlist3.add ( "Item4" ); Arraylist <Arraylist <string> childlist = New Arraylist <string> (); Childlist. Add (itemlist1); childlist. Add (itemlist2); childlist. Add (itemlist3); expandablelistview list = New Expandablelistview ( This  ); Expandablelistadapter madapter =New  Myexpandablelistadapter (grouplist, childlist); list. setadapter (madapter); list. setcachecolorhint ( Zero X 00000000 ); List. setselector (  New  Colordrawable (color. Transparent); list. setgroupindicator (  Null  );  For ( Int I = 0; I <madapter. getgroupcount (); I ++ ) {List. expandgroup (I);} setcontentview (list );}  Private  Class Myexpandablelistadapter Extends  Baseexpandablelistadapter {  Private Arraylist <string> Grouplist;  Private Arraylist <string> Childlist; myexpandablelistadapter (arraylist <String> grouplist, arraylist <string> Childlist ){  This . Grouplist = Grouplist;  This . Childlist = Childlist ;}  Public Object getchild ( Int Groupposition, Int  Childposition ){  Return  Childlist. Get (groupposition). Get (childposition );}  Private   Int Selectedgroupposition =-1 ;  Private   Int Selectedchildposition =-1;  Public   Void Setselectedposition ( Int Selectedgroupposition, Int  Selectedchildposition ){  This . Selectedgroupposition = Selectedgroupposition;  This . Selectedchildposition = Selectedchildposition ;}  Public   Long Getchildid ( Int Groupposition, Int  Childposition ){  Return  Childposition ;}  Public   Int Getchildrencount ( Int  Groupposition ){  Return  Childlist. Get (groupposition). Size ();}  Public View getchildview ( Final   Int Groupposition,Final   Int Childposition, Boolean  Islastchild, view convertview, viewgroup parent) {textview = Null  ;  If (Convertview = Null  ) {Textview = New Textview (padtestactivity. This  ); Textview. setpadding ( 32, 10, 0, 10); Convertview = Textview ;}  Else  {Textview = (Textview) convertview;} textview. settext (getchild (groupposition, childposition). tostring ());  If (Groupposition = Selectedgroupposition ){  If (Childposition = Selectedchildposition) {textview. setbackgroundcolor ( 0xffb6ddee );} Else  {Textview. setbackgroundcolor (color. Transparent) ;}} textview. setonclicklistener (  New  Onclicklistener (){  Public   Void  Onclick (view v) {setselectedposition (groupposition, childposition); yydatasetchanged ();}});  Return  Textview ;}  Public Object getgroup ( Int Groupposition ){  Return  Grouplist. Get (groupposition );}  Public   Int  Getgroupcount (){  Return  Grouplist. Size ();}  Public   Long Getgroupid ( Int  Groupposition ){  Return  Groupposition ;} Public View getgroupview ( Int Groupposition, Boolean  Isexpanded, view convertview, viewgroup parent) {linearlayout cotain = New Linearlayout (padtestactivity. This  ); Cotain. setpadding ( 0, 10, 0, 10 ); Cotain. setgravity (gravity. center_vertical); imageview imgindicator = New Imageview (padtestactivity. This ); Textview = New Textview (padtestactivity. This  ); Textview. settext (getgroup (groupposition). tostring (); textview. setpadding ( 5, 0, 0, 0 );  If  (Isexpanded) {imgindicator. setbackgroundresource (R. drawable. macro_minus );}  Else  {Imgindicator. setbackgroundresource (R. drawable. macro_plus);} cotain. addview (imgindicator); cotain. addview (textview ); Return  Cotain ;}  Public   Boolean  Hasstableids (){  Return   True  ;}  Public   Boolean Ischildselectable ( Int Groupposition, Int  Childposition ){  Return   True ;}}} 

AboveCodeTo baseexpandablelistadapter, two dynamic arrays grouplist (indicating the directory header information) and childlist (representing the Sub-item information) are passed to build a directory. On the one hand, the directory can be dynamically added, while on the other hand, the implementation is simplified, two birds in one fell swoop. In addition, if the baseexpandablelistadapter is used in the actual project, you need to cache the getgroupview () and getchildview () methods (the same as the listview build ), to optimize performance and prevent memory leakage. You can build it on your own.