Typical wording for optimizing custom adapter using Viewholder in Android

public class Markeritemadapter extends baseadapter{private Context mcontext = null;    Private list<markeritem> mmarkerdata = null;        Public Markeritemadapter (context context, list<markeritem> markeritems) {mcontext = context;    Mmarkerdata = Markeritems;    } public void Setmarkerdata (list<markeritem> markeritems) {mmarkerdata = Markeritems;        } @Override public int getcount () {int count = 0;        if (null! = Mmarkerdata) {count = Mmarkerdata.size ();    } return count;        } @Override public Markeritem getItem (int position) {Markeritem item = NULL;        if (null! = Mmarkerdata) {item = Mmarkerdata.get (position);    } return item;    } @Override public long getitemid (int position) {return position; } @Override public View getView (int position, view Convertview, ViewGroup parent) {Viewholder Viewholder = NULL;            if (null = = Convertview) {Viewholder = new Viewholder ();            Layoutinflater minflater = Layoutinflater.from (Mcontext);            Convertview = minflater.inflate (R.layout.item_marker_item, NULL);            Viewholder.name = (TextView) Convertview.findviewbyid (r.id.name);            Viewholder.description = (TextView) convertview. Findviewbyid (r.id.description);            Viewholder.createtime = (TextView) convertview. Findviewbyid (R.id.createtime);        Convertview.settag (Viewholder);        } else {Viewholder = (Viewholder) convertview.gettag ();        }//Set item values to the Viewholder:markeritem Markeritem = GetItem (position);            if (null! = Markeritem) {ViewHolder.name.setText (Markeritem.getname ());            ViewHolder.description.setText (Markeritem.getdescription ()); ViewHolder.createTime.setText (Markeritem.getcreaTedate ());    } return Convertview;        } private static class Viewholder {TextView name;        TextView description;    TextView Createtime; }}

Where Markeritem is a custom class that contains fields such as Name,description,createtime and has the appropriate get and set methods.

　　Viewholder is an internal class that contains individual controls in a single project layout.

The layout of individual items, namely R.layout.item_marker_item, is as follows:

<?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:o rientation= "vertical"     android:padding= "5DP" >    <textview        android:id= "@+id/name"        android: Layout_width= "Match_parent"        android:layout_height= "wrap_content"        android:text= "Name"        android: Textsize= "20SP"        android:textstyle= "bold"/>    <textview        android:id= "@+id/description        " Android:layout_width= "Match_parent"        android:layout_height= "wrap_content"        android:text= "Description"        android:textsize= "18sp"/>    <textview        android:id= "@+id/createtime"        android:layout_ Width= "Match_parent"        android:layout_height= "wrap_content"        android:text= "Createtime"        android: Textsize= "16SP"/></linearlayout>

This example is also available in the official API demos:

List14 in the package Com.example.android.apis.view:

/* Copyright (C) The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License") ; * You are not a use this file except in compliance with the License. * Obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * unless required by appli Cable law or agreed into writing, software * Distributed under the License is distributed on a "as is" BASIS, * without Warranties or CONDITIONS of any KIND, either express OR implied. * See the License for the specific language governing permissions and * limitations under the License. */package Com.example.android.apis.view;import Android.app.listactivity;import Android.content.Context;import Android.os.bundle;import Android.view.layoutinflater;import Android.view.view;import Android.view.ViewGroup; Import Android.widget.baseadapter;import Android.widget.textview;import Android.widget.imageview;import Android.graphics.bitmapfactory;import Android.graphics.bitmap;import Com.example.android.apis.r;/** * Demonstrates how to write a efficient list adapter. The adapter used in this example binds * to an ImageView and to a TextView for each row in the list. * To work efficiently The adapter implemented here uses a techniques: *-It reuses the Convertview passed to GetView (  ) to avoid inflating View when it's not necessary *-it uses the Viewholder pattern to avoid calling Findviewbyid () when It is not necessary * * The Viewholder pattern consists in storing a data structure in the tag of the view returned by * GetView (). This data structures contains references to the views we want to bind data to, thus * avoiding calls to Findviewbyid () Eve Ry Time GetView () is invoked.  */public class List14 extends Listactivity {private static class Efficientadapter extends Baseadapter {private        Layoutinflater Minflater;        Private Bitmap MIcon1;        Private Bitmap MIcon2; Public Efficientadapter (Context context) {//Cache the LayoutiNflate to avoid asking for a new one each time.            Minflater = Layoutinflater.from (context);            Icons bound to the rows.            MIcon1 = Bitmapfactory.decoderesource (Context.getresources (), r.drawable.icon48x48_1);        MIcon2 = Bitmapfactory.decoderesource (Context.getresources (), r.drawable.icon48x48_2);         /** * The number of the items in the list are determined by the number of speeches * in our array. * * @see Android.widget.listadapter#getcount () */public int getcount () {return D        Ata.length; }/** * Since The data comes from a array, just returning the index is * sufficent-get at the D Ata.         If we were using a more complex data * structure, we would return whatever object represents one row in the         * list.            * * @see android.widget.listadapter#getitem (int) */public Object getItem (int position) { RetuRN position;         }/** * Use the array index as a unique ID.            * * @see android.widget.listadapter#getitemid (int) */public long getitemid (int position) {        return position;         }/** * Make a view to hold each row.         * * @see android.widget.listadapter#getview (int, Android.view.View, * android.view.ViewGroup) */Public View getView (int position, View Convertview, ViewGroup parent) {//A Viewholder keeps Refere            NCEs to children views to avoid unneccessary calls//to Findviewbyid () on each row.            Viewholder Holder; When convertview are not NULL, we can reuse it directly, there are no need//to reinflate it.            We only inflate a new View when the Convertview supplied//by ListView is null. if (Convertview = = null) {Convertview = minflater.inflate (R.layout.list_item_icon_text, NULL);               Creates a viewholder and store references to the other children views//We want to bind Da                Ta to.                Holder = new Viewholder ();                Holder.text = (TextView) Convertview.findviewbyid (R.id.text);                Holder.icon = (ImageView) Convertview.findviewbyid (R.id.icon);            Convertview.settag (holder);                 } else {//Get the Viewholder back-to-get fast access to the TextView//and the ImageView.            Holder = (viewholder) convertview.gettag ();            }//Bind the data efficiently with the holder.            Holder.text.setText (Data[position]);            Holder.icon.setImageBitmap ((position & 1) = = 1? micon1:micon2);        return convertview;            } static class Viewholder {TextView text;        ImageView icon; }} @Override public void OnCreate (Bundle savedinstancestate) {super.oncreate (SavedinstaNcestate);    Setlistadapter (New Efficientadapter (this)); } private static Final string[] DATA = cheeses.scheesestrings;}

Which layout:

<?xml version= "1.0" encoding= "Utf-8"?><!--Copyright (C) The Android Open Source Project Licensed under     The Apache License, Version 2.0 (the "License");     You are not a use of this file except in compliance with the License. Obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 unless required by app Licable law or agreed to in writing, software distributed under the License are distributed on a "as is" BASIS, WI     Thout warranties or CONDITIONS of any KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.--><linearlayo UT xmlns:android= "http://schemas.android.com/apk/res/android" android:orientation= "Horizontal" android:layout_ Width= "Match_parent" android:layout_height= "match_parent" > <imageview android:id= "@+id/icon" Android:la Yout_width= "48dip" android:layout_height= "48dip"/> <textview Android:id= "@+id/text" android:layout_gravity= "center_vertical" android:layout_width= "0dip" Android: Layout_weight= "1.0" android:layout_height= "Wrap_content"/></linearlayout>

More articles on adapter optimization:

Http://www.cnblogs.com/over140/archive/2011/03/23/1991100.html

Http://www.cnblogs.com/halzhang/archive/2010/12/05/1896791.html

Reprint: http://www.cnblogs.com/mengdd/p/3254323.html

Typical wording for optimizing custom adapter using Viewholder in Android