Android Adapter的一些記錄

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 一、摘要

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

　　這是Android官方對Adapter的定義。這個關係可以描述為下面一個關係圖，

　　

 

二、Adapter的繼承關係

　　 

 

三，範例

　　這裡附上北航《Android編程寶典》的一個例子，搭配ListView說明Adapter怎麼樣去扮演這個中間人，為View層提供資料。

　　1，定義3個layout檔案，分別是activity_main.xml，fragment_main.xml，my_listitem.xml。

　　activity_main.xml

<FrameLayout xmlns: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

<LinearLayout xmlns: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">    <ListView android: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"?><LinearLayout xmlns: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" >        <TextView android:id="@+id/itemTitle"        android:layout_width="wrap_content"        android:layout_height="fill_parent"        android:textSize="30sp" />        <TextView android:id="@+id/itemText"        android:layout_width="fill_parent"        android:layout_height="wrap_content"/></LinearLayout>

 

　　2，編寫MainActivity，代碼如下

package so.byj.example.mytestapp;import java.util.ArrayList;import java.util.HashMap;import android.support.v7.app.ActionBarActivity;import android.support.v7.app.ActionBar;import android.support.v4.app.Fragment;import android.os.Bundle;import android.view.LayoutInflater;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.ViewGroup;import android.webkit.WebView.FindListener;import android.widget.ArrayAdapter;import android.widget.AutoCompleteTextView;import android.widget.ListView;import android.widget.RatingBar;import android.widget.SimpleAdapter;import android.widget.RatingBar.OnRatingBarChangeListener;import android.widget.SeekBar;import android.widget.TextView;import android.widget.SeekBar.OnSeekBarChangeListener;import android.os.Build;public class MainActivity extends ActionBarActivity {        @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        if (savedInstanceState == null) {            getSupportFragmentManager().beginTransaction()                    .add(R.id.container, new PlaceholderFragment()).commit();        }    }    @Override    public boolean onCreateOptionsMenu(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 boolean onOptionsItemSelected(MenuItem item) {        // Handle action bar item clicks here. The action bar will        // automatically handle clicks on the Home/Up button, so long        // as you specify a parent activity in AndroidManifest.xml.        int id = item.getItemId();        if (id == R.id.action_settings) {            return true;        }        return super.onOptionsItemSelected(item);    }    /**     * A placeholder fragment containing a simple view.     */    public static class PlaceholderFragment extends Fragment {                public PlaceholderFragment() {        }        @Override        public View 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);                        ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();            for(int i=0;i<30;i++)            {                HashMap<String, String> map = new HashMap<String, String>();                map.put("ItemTitle", "This is Title.....");                map.put("ItemText", "This is text.....");                mylist.add(map);            }                        SimpleAdapter mSchedule = new SimpleAdapter(getActivity(),                                                        mylist,                                                        R.layout.my_listitem, // 這裡定義了資料填充的樣式                                                        new String[] {"ItemTitle", "ItemText"},                                                         new int[] {R.id.itemTitle,R.id.itemText});                        list.setAdapter(mSchedule);                        return rootView;        }    }}

　　如上面黑體部分，先把待填充資料的ListView拿出來，然後執行個體一個Adapter對ListView進行資料填充。