[Android] uses BaseAdapter as the adapter's ListView and Its Performance Optimization

Java class of the adapter

Package com. app. adapter; import org. json. JSONArray; import org. json. JSONObject; import android. r. integer; import android. content. context; import android. view. layoutInflater; import android. view. view; import android. view. viewGroup; import android. widget. baseAdapter; import android. widget. imageView; import android. widget. textView; import com. app. test01.R; public class MyWeixinJSON extends BaseAdapter {private LayoutInflater mInflater; // Dynamic Layout ING private JSONArray list; private Context context Context; private int I = 0; public MyWeixinJSON (JSONArray list, context Context) {this. list = list; this. context = context; this. mInflater = LayoutInflater. from (context) ;}@ Overridepublic int getCount () {// TODO Auto-generated method stubreturn list. length () ;}@ Overridepublic Object getItem (int position) {// TODO Auto-generated method stubreturn null;} @ Overridepublic long getItemId (int position) {// TODO Auto-generated method stubreturn 0;} @ Overridepublic View getView (int position, View convertView, ViewGroup parent) {// TODO Auto-generated method stubconvertView = mInflater. inflate (R. layout. item_weixin, null); // instantiate viewtry {JSONObject jObject = list based on the layout file. getJSONObject (position); TextView title = (TextView) convertView. findViewById (R. id. title); // find the title of a control. setText (jObject. get ("title "). toString (); // set data for the control (data from the Collection class) TextView time = (TextView) convertView. findViewById (R. id. time); time. setText (jObject. get ("time "). toString (); TextView info = (TextView) convertView. findViewById (R.id.info); info. setText (jObject. get ("info "). toString (); ImageView img = (ImageView) convertView. findViewById (R. id. img); img. setBackgroundResource (Integer) jObject. get ("img");} catch (Exception e) {// TODO: handle exception} return convertView ;}}

Activity Type

Package com. app. test01; import java. util. arrayList; import java. util. hashMap; import java. util. list; import org. json. JSONArray; import org. json. JSONObject; import android. app. activity; import android. OS. bundle; import android. widget. listView; import com. app. adapter. myWeixinJSON; import com. app. adapter. myWeixinList; public class ListViewBase extends Activity {private ListView lv; @ Overrideprotected void onCreate (Bundle savedInstanceState) {// TODO Auto-generated method stubsuper. onCreate (savedInstanceState); setContentView (R. layout. weixin); lv = (ListView) findViewById (R. id. lv); MyWeixinJSON mJson = new MyWeixinJSON (getJSONArray (), this); lv. setAdapter (mJson);} private JSONArray getJSONArray () {JSONArray jsonArray = new JSONArray (); try {for (int I = 1; I <= 30; I ++) {JSONObject jsonObject = new JSONObject (); jsonObject. put ("title", "name" + I); jsonObject. put ("time", "September 29"); jsonObject. put ("info", "I have passed your friend verification request, now we can start to talk"); jsonObject. put ("img", R. drawable. special_spring_head2); jsonArray. put (jsonObject) ;}} catch (Exception e) {// TODO: handle exception} return jsonArray ;}}

ListView Performance Optimization

@ Overridepublic View getView (int position, View convertView, ViewGroup parent) {// TODO Auto-generated method stubSystem. out. println ("rendering the nth" + position + "Row ++" + I ++); OneView oneView; if (convertView = null) {convertView = mInflater. inflate (R. layout. item_weixin, null); // viewoneView = new OneView (); oneView is instantiated Based on the layout file. title = (TextView) convertView. findViewById (R. id. title); // find a widget oneView. time = (TextView) convertView. findViewById (R. id. time); oneView.info = (TextView) convertView. findViewById (R.id.info); oneView. img = (ImageView) convertView. findViewById (R. id. img); convertView. setTag (oneView); // associate View with an object} else {oneView = (OneView) convertView. getTag ();} JSONObject jObject = null; try {jObject = list. getJSONObject (position); // obtain the oneView of a row in the Collection class based on the position. title. setText (jObject. get ("title "). toString (); // set data for the control (data comes from the Collection class) oneView. time. setText (jObject. get ("time "). toString (); oneView.info. setText (jObject. get ("info "). toString (); oneView. img. setBackgroundResource (Integer) jObject. get ("img");} catch (Exception e) {// TODO: handle exception} return convertView ;} /** wrap each control of each layout file in each row into an object */private class OneView {TextView title; TextView time; TextView info; ImageView img ;}