Android Adapter的一些记录

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.

　　这是Android官方对Adapter的定义。这个关系可以描述为下面一个关系图，

二、Adapter的继承关系

三，样例

　　这里附上北航《Android编程宝典》的一个例子，搭配ListView说明Adapter怎么样去扮演这个中间人，为View层提供数据。

　　1，定义3个layout文件，分别是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，编写MainActivity，代码如下

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, // 这里定义了数据填充的样式

                                                        new String[] {"ItemTitle", "ItemText"},

                                                        new int[] {R.id.itemTitle,R.id.itemText});

list.setAdapter(mSchedule);
return rootView;

        }

    }
}

　　如上面黑体部分，先把待填充数据的ListView拿出来，然后实例一个Adapter对ListView进行数据填充。

Android Adapter的一些记录