Some records of Android adapter

I. Summary

　　An Adapter object acts as a bridge between AdapterView an And the underlying data for that view. The Adapter provides access to the data items. The Adapter is also responsible for making a for each item in the View data set.

This is the official Android definition of adapter. This relationship can be described as the following diagram,

　　

Ii. the inheritance relationship of adapter

Three, examples

Attached here is an example of the "Android programming Treasure" of the Beihang University, paired with a ListView to show how adapter plays the middleman and provides data for the view layer.

1, the definition of 3 layout files, respectively, is activity_main.xml,fragment_main.xml,my_listitem.xml.

Activity_main.xml

<Framelayoutxmlns:android= "Http://schemas.android.com/apk/res/android"Xmlns:tools= "Http://schemas.android.com/tools"Android:id= "@+id/container"Android:layout_width= "Match_parent"Android:layout_height= "Match_parent"Tools:context= "So.byj.example.mytestapp.MainActivity"Tools:ignore= "Mergerootframe" />

Fragment_main.xml

<LinearLayoutxmlns:android= "Http://schemas.android.com/apk/res/android"Android:id= "@+id/linearlayout01"android:baselinealigned= "false"android:orientation= "vertical"Android:layout_width= "Fill_parent"Android:layout_height= "Fill_parent">    <ListViewAndroid:id= "@+id/mylistview"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content">    </ListView>    </LinearLayout>

My_listitem.xml

<?XML version= "1.0" encoding= "Utf-8"?><LinearLayoutxmlns:android= "Http://schemas.android.com/apk/res/android"Android:id= "@+id/mylistitem"Android:paddingbottom= "3dip"Android:paddingleft= "10dip"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"android:orientation= "vertical" >        <TextViewAndroid:id= "@+id/itemtitle"Android:layout_width= "Wrap_content"Android:layout_height= "Fill_parent"android:textsize= "30SP" />        <TextViewAndroid:id= "@+id/itemtext"Android:layout_width= "Fill_parent"Android:layout_height= "Wrap_content"/></LinearLayout>

2, write mainactivity, the code is as follows

 PackageSo.byj.example.mytestapp;Importjava.util.ArrayList;ImportJava.util.HashMap;Importandroid.support.v7.app.ActionBarActivity;ImportAndroid.support.v7.app.ActionBar;Importandroid.support.v4.app.Fragment;ImportAndroid.os.Bundle;ImportAndroid.view.LayoutInflater;ImportAndroid.view.Menu;ImportAndroid.view.MenuItem;ImportAndroid.view.View;ImportAndroid.view.ViewGroup;ImportAndroid.webkit.WebView.FindListener;ImportAndroid.widget.ArrayAdapter;ImportAndroid.widget.AutoCompleteTextView;ImportAndroid.widget.ListView;ImportAndroid.widget.RatingBar;ImportAndroid.widget.SimpleAdapter;ImportAndroid.widget.RatingBar.OnRatingBarChangeListener;ImportAndroid.widget.SeekBar;ImportAndroid.widget.TextView;ImportAndroid.widget.SeekBar.OnSeekBarChangeListener;ImportAndroid.os.Build; Public classMainactivityextendsactionbaractivity {@Overrideprotected voidonCreate (Bundle savedinstancestate) {Super. OnCreate (savedinstancestate);        Setcontentview (R.layout.activity_main); if(Savedinstancestate = =NULL) {Getsupportfragmentmanager (). BeginTransaction (). Add (R.id.container,Newplaceholderfragment ()). commit (); }} @Override Public BooleanOncreateoptionsmenu (Menu menu) {//inflate the menu; This adds items to the action bar if it is present.getmenuinflater (). Inflate (R.menu.main, menu); return true; } @Override Public Booleanonoptionsitemselected (MenuItem item) {//Handle Action Bar item clicks here. The Action Bar would//automatically handle clicks on the Home/up button, so long//As you specify a the parent activity in Androidmanifest.xml.        intID =Item.getitemid (); if(id = =r.id.action_settings) {            return true; }        return Super. onoptionsitemselected (item); }    /*** A placeholder fragment containing a simple view. */     Public Static classPlaceholderfragmentextendsFragment { Publicplaceholderfragment () {} @Override PublicView Oncreateview (layoutinflater inflater, ViewGroup container, Bundle savedinstancestate) { View Rootview= Inflater.inflate (R.layout.fragment_main, container,false); ListView list = (ListView) Rootview.findviewbyid (R.id.mylistview); ArrayListNewArraylist();  for(inti=0;i<30;i++) {HashMap<string, string> map =NewHashmap<string, string>(); Map.put ("Itemtitle", "This is the Title ..."); Map.put ("Itemtext", "This is text ...");            Mylist.add (map); } simpleadapter Mschedule = new  Simpleadapter (getactivity (), MyList,                                                        R.layout.my_listitem,//This defines the style of the data fill                                                          New string[] {"Itemtitle", "Itemtext"},                         new int[] {r.id.itemtitle,r.id.itemtext});                        List.setadapter (Mschedule); returnRootview; }    }}

As in the bold section above, the ListView to be populated will be taken out first, and then an instance of adapter is populated with data from the ListView.