Getting started with Android: listview

1. Introduction to listview

 

Listview is similar to dividing an interface into one line, for example:

 

Listview is only a view. To display data in this list view, you must use "adapter". We usually have three types of adapters:

(1) arrayadapter: each line can only be one text;

(2) simpleadapter: This method is not very good. After testing, only one row of data can be displayed;

(3) inherit baseadapter: This method is flexible and can be customized to correspond each line to different layout XML;

(4) simplecursoradapter: the incoming data is not a list, but a cursor returned by the database query;

 

Ii. listview instance

 

This instance implements the use of three listview types;

The project hierarchy is as follows:

 

Listview interface:

 

The arrayadapter display interface is as follows:

 

The simpleadapter interface is as follows:

 

The extendbaseadapter interface is as follows:

 

 

1. Main interface module:

 

Listviewactivity. Java

 

Package Org. xiazdong; import android. app. activity; import android. content. intent; import android. OS. bundle; import android. view. view; import android. view. view. onclicklistener; import android. widget. arrayadapter; import android. widget. button; public class listviewactivity extends activity implements onclicklistener {private button btn1; private button btn2; private button btn3; @ override public void oncreate (bundle savedinstancestate) {super. oncreate (savedinstancestate); setcontentview (R. layout. main); // you must first setcontentview before findviewbyid btn1 = (button) This. findviewbyid (R. id. arrayadapter); btn2 = (button) This. findviewbyid (R. id. simpleadapter); btn3 = (button) This. findviewbyid (R. id. baseadapter); btn1.setonclicklistener (this); btn2.setonclicklistener (this); btn3.setonclicklistener (this);} @ overridepublic void onclick (view v) {If (V = btn1) {intent = new intent (listviewactivity. this, arrayadapteractivity. class); this. startactivity (intent);} else if (V = btn2) {intent = new intent (listviewactivity. this, simpleadapteractivity. class); this. startactivity (intent);} else if (V = btn3) {intent = new intent (listviewactivity. this, extendbaseadapteractivity. class); this. startactivity (intent );}}}

Main. xml

 

<? XML version = "1.0" encoding = "UTF-8"?> <Relativelayout xmlns: Android = "http://schemas.android.com/apk/res/android" Android: layout_width = "fill_parent" Android: layout_height = "fill_parent" Android: Orientation = "vertical"> <textview Android: id = "@ + ID/TV" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content" Android: layout_centerhorizontal = "true" Android: TEXT = "listview usage" Android: textsize = "50px"/> <button Android: Id = "@ + ID/arrayadapter" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content" Android: layout_below = "@ ID/TV" Android: text = "arrayadapter"> </button> <button Android: id = "@ + ID/simpleadapter" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content" Android: layout_below = "@ ID/arrayadapter" Android: TEXT = "simpleadapter"> </button> <button Android: Id = "@ + ID/baseadapter" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content" Android: layout_below = "@ ID/simpleadapter" Android: text = "extendbaseadapter"> </button> <textview Android: Id = "@ + ID/textview1" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: Rule = "true" Android: layout_alignparentright = "true" Android: layout_marginbottom = "142dp" Android: layout_marginright = "16dp" Android: text = "by xiazdong" Android: textsize = "20px"/> </relativelayout>

 

2. arrayadapter Module

 

Arrayadapteractivity. Java

 

Package Org. xiazdong; import Java. util. arraylist; import Java. util. list; import android. app. activity; import android. OS. bundle; import android. widget. arrayadapter; import android. widget. listview;/** each time an activity is created, it must be stored in androidmanifest. * arrayadapter can only display basic strings * simpleadapter can display custom views */public class arrayadapteractivity extends activity {private listview lv; @ overrideprotected void oncreate (bundle savedinstancestate) {super. oncreate (savedinstancestate); Lv = new listview (this); // listview inherits viewlist <string> List = new arraylist <string> (); For (INT I = 0; I <10; I ++) {list. add ("xiazdong-" + I);} arrayadapter <string> SA = new arrayadapter <string> (this, // assign list to arrayadapter and use simple_item_1 style android. r. layout. simple_list_item_1, list); LV. setadapter (SA); // map the value of arrayadapter to listview this. setcontentview (LV );}}

 

3. simpleadapter Module

 

Generally, listview is used to display the list. Generally, the data in the list comes from the database. Therefore, we assume that a dbservice class has been implemented before, and pagequery (INT offset, int length) exists in it );

For example, dbservice. pagequery (3, 5); indicates that three records are skipped and five records are inserted;

Main. xml

<? XML version = "1.0" encoding = "UTF-8"?> <Linearlayout xmlns: Android = "http://schemas.android.com/apk/res/android" Android: layout_width = "fill_parent" Android: layout_height = "fill_parent" Android: Orientation = "vertical"> <linearlayout Android: layout_width = "wrap_content" // note that wrap_content Android: layout_height = "wrap_content" // note that wrap_content Android: Orientation = "horizontal"> <textview Android: layout_width = "100dp" Android: layout_height = "wrap_content" Android: text = "ID"/> <textview Android: layout_width = "100dp" Android: layout_height = "wrap_content" Android: TEXT = "name"/> <textview Android: layout_width = "100dp" Android: layout_height = "wrap_content" Android: text = "Age"/> </linearlayout> <listview Android: id = "@ + ID/listview" Android: layout_width = "wrap_content" Android: layout_height = "fill_parent"> </listview> </linearlayout>

Item. xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="horizontal" >    <TextView        android:id="@+id/id1"        android:layout_width="100dp"        android:layout_height="wrap_content"        />    <TextView        android:id="@+id/name"        android:layout_width="100dp"        android:layout_height="wrap_content"        />    <TextView        android:id="@+id/age"        android:layout_width="100dp"        android:layout_height="wrap_content"        /></LinearLayout>

Mainactivity. Java

Package Org. xiazdong. DB; import Java. util. arraylist; import Java. util. hashmap; import Java. util. list; import Java. util. map; import Org. xiazdong. DB. domain. person; import Org. xiazdong. DB. service. dbservice; import android. app. activity; import android. OS. bundle; import android. util. log; import android. widget. listview; import android. widget. simpleadapter; public class mainactivity extends activity {private listview; @ override public void oncreate (bundle savedinstancestate) {super. oncreate (savedinstancestate); setcontentview (R. layout. main); listview = (listview) This. findviewbyid (R. id. listview); dbservice service = new dbservice (this); List <person> Persons = service. pagequery (0, 10); List 
Conclusion: simpleadapter does not need to implement the adapter internally. It can only implement a list with the same layout for each item;

 
4. inherit the baseadapter class
 
Extendbaseadapteractivity. Java
 
Package Org. xiazdong; import Java. util. arraylist; import Java. util. list; import android. app. activity; import android. OS. bundle; import android. widget. arrayadapter; import android. widget. listview; public class extendbaseadapteractivity extends activity {private listview lv; @ overrideprotected void oncreate (bundle savedinstancestate) {super. oncreate (savedinstancestate); Lv = new listview (this); myadapter MA = new myadapter (this, new int [] {R. layout. sub1, R. layout. sub2}); // display the layout of sub1 and the layout of sub2 in each row. setadapter (MA); this. setcontentview (LV );}}
 
Myadapter. Java
 
Package Org. xiazdong; import android. content. context; import android. view. layoutinflater; import android. view. view; import android. view. view. onclicklistener; import android. view. viewgroup; import android. widget. baseadapter; import android. widget. button; import android. widget. checkbox; import android. widget. compoundbutton; import android. widget. compoundbutton. oncheckedchangelistener; import android. widget. toast; public class myadapter extends baseadapter {private context; private int layoutid []; private layoutinflater inflator; Public myadapter (context, int layoutid []) {This. context = context; this. layoutid = layoutid; inflator = layoutinflater. from (context) ;}@ overridepublic int getcount () {// a layout occupies a row return layoutid. length ;}@ overridepublic object getitem (INT position) {return NULL ;}@ overridepublic long getitemid (INT position) {return 0 ;} @ override // position indicates the row to be displayed, and 0 indicates the first row. // convertview indicates the public view getview (INT position, view convertview, viewgroup parent) to be displayed) {convertview = inflator. inflate (layoutid [position], null); // map a layout XML to one if (convertview. findviewbyid (R. id. checkbox1) instanceof checkbox) {checkbox CB1 = (checkbox) convertview. findviewbyid (R. id. checkbox1); cb1.setoncheckedchangelistener (New oncheckedchangelistener () {@ overridepublic void oncheckedchanged (compoundbutton buttonview, Boolean ischecked) {toast T = toast. maketext (context, "click the check box", toast. length_short); T. show () ;}}) ;}if (convertview. findviewbyid (R. id. button1) instanceof button) {button b1 = (button) convertview. findviewbyid (R. id. button1); b1.setonclicklistener (New onclicklistener () {@ overridepublic void onclick (view v) {toast T = toast. maketext (context, "click", toast. length_short); T. show () ;}}) ;}return convertview ;}}
 
Sub1.xml
 
<? XML version = "1.0" encoding = "UTF-8"?> <Relativelayout xmlns: Android = "http://schemas.android.com/apk/res/android" Android: layout_width = "match_parent" Android: layout_height = "match_parent"> <textview Android: Id = "@ + ID/textview1" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: layout_alignbaseline = "@ + ID/checkbox1" Android: layout_alignbottom = "@ + ID/checkbox1" Android: layout_alignparentleft = "true" Android: text = "click to bring up the prompt"/> <checkbox Android: Id = "@ + ID/checkbox1" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: layout_alignparentright = "true" Android: layout_alignparenttop = "true" Android: text = ""/> </relativelayout>
 
Sub2.xml
 
<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent" > <TextView     android:id="@+id/textView2"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_alignBaseline="@+id/button1"     android:layout_alignBottom="@+id/button1"     android:layout_alignParentLeft="true"     android:text="TextView" /><Button     android:id="@+id/button1"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_alignParentRight="true"     android:layout_alignParentTop="true"     android:text="Button" /></RelativeLayout>
5. simplecursoradapter
Note: To use simplecursoradapter, the primary key of the result set of cursor is required to be named _ id. Therefore, we must use as _ id for alias during query;


For example, select ID, name from person; select ID as _ id, name from person;



Main steps:
Cursor cursor = query ();
Simplecursoradapter adapter = new simplecursoradapter (this,/* cotnext */
R. layout. Item,/* layout of an item */
Cursor,
New String [] {"name", "Age"},/* name, age are the attributes of tables in the database */
New int [] {R. Id. Name, R. Id. Age});/* R. Id. Name, R. Id. Age can display data */
Listview. setadapter (adapter );




Summary:
 
There are many listview applications, such
(1) List rankings in general games;
(2) Multiple seed settings are listed in "Settings;
(3) list words in the dictionary;
 
 
 
(4) Address Book list;