Android adds checkbox implementation to listview

The main interface CheckBoxinListViewActivity. the java code is as follows: [java] public class CheckBoxinListViewActivity extends Activity {/** Called when the activity is first created. */private MyAdapter adapter; private ListView; private Button checkAll; private Button noCheckAll; @ Override public void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. main); listview = (L IstView) findViewById (R. id. listview); checkAll = (Button) findViewById (R. id. button1); noCheckAll = (Button) findViewById (R. id. button2); adapter = new MyAdapter (); listview. setAdapter (adapter); checkAll. setOnClickListener (new OnClickListener () {@ Override public void onClick (View v) {adapter. checkAll () ;}}); noCheckAll. setOnClickListener (new OnClickListener () {@ Override public void onClick (View v) {Adapter. noCheckAll () ;}});} private class MyAdapter extends BaseAdapter {private ArrayList <Message> list = new ArrayList <Message> (); public MyAdapter () {for (int I = 1; I <= 100; I ++) {list. add (new Message ("item _" + I) ;}} public void checkAll () {for (Message msg: list) {msg. isCheck = true;} policydatasetchanged ();} public void noCheckAll () {for (Message msg: list) {msg. isCheck = false;} policydat ASetChanged () ;}@ Override public int getCount () {return list. size () ;}@ Override public Object getItem (int position) {return null ;}@ Override public long getItemId (int position) {return 0 ;} @ Override public View getView (int position, View convertView, ViewGroup parent) {ViewHolder viewHolder; if (convertView = null) {LayoutInflater inflater = LayoutInflater. from (CheckBoxinListViewActivity. t His); convertView = inflater. inflate (R. layout. listview_item, null); viewHolder = new ViewHolder (); viewHolder. checkBox = (CheckBox) convertView. findViewById (R. id. checkBox1); convertView. setTag (viewHolder);} else {viewHolder = (ViewHolder) convertView. getTag ();} final Message msg = list. get (position); viewHolder. checkBox. setText (msg. str); viewHolder. checkBox. setChecked (msg. isCheck); // note that onChe is not set here CkedChangListener is worth thinking about viewHolder. checkBox. setOnClickListener (new OnClickListener () {@ Override public void onClick (View v) {if (msg. isCheck) {msg. isCheck = false;} else {msg. isCheck = true ;}}); return convertView ;}} private class ViewHolder {CheckBox checkBox ;}} the Message adapted by the adapter. java: [java] public class Message {public boolean isCheck; public String str; public Message (String str) {This. str = str ;}} the main. xml Code is as follows: [html] <? Xml version = "1.0" encoding = "UTF-8"?> <LinearLayout xmlns: android = "http://schemas.android.com/apk/res/android" android: orientation = "vertical" android: layout_width = "fill_parent" android: layout_height = "fill_parent"> <LinearLayout android: layout_width = "wrap_content" android: layout_height = "wrap_content"> <Button android: text = "select all" android: id = "@ + id/button1" android: layout_width = "wrap_content" android: layout_height = "wrap_content"> </Button> <Button android: text = "undo" android: id = "@ + id/button2" android: layout_width = "wrap_content" android: layout_height = "wrap_content"> </Button> </LinearLayout> <ListView android: id = "@ + id/listview" android: layout_height = "fill_parent" android: layout_width = "fill_parent"/> </LinearLayout> the listview_item.xml code is as follows: [html] <? 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 = "wrap_content" android: descendantFocusability = "blocksDescendants"> <LinearLayout android: layout_width = "fill_parent" android: layout_height = "wrap_content" android: gravity = "center"> <CheckBox android: text = "CheckBox" android: id = "@ + id/checkBox1" android: layout_width = "wrap_content" android: layout_height = "wrap_content"/> </LinearLayout>