android Adapter的用法說明

在使用ListView或是GridView時，會使用到Adapter來定義View的內容，最簡單的方式如下：

	ListView listview = (ListView) findViewById(R.id.listview);
	//ListView 要顯示的內容
	String[] str = {"新北市","台北市","台中市","台南市","高雄市"};
	//android.R.layout.simple_list_item_1 為內建樣式，還有其他樣式可自行研究
	ArrayAdapter adapter = new ArrayAdapter(this,
	android.R.layout.simple_list_item_1,
	str);
	listview.setAdapter(adapter);

view raw adatper_example1.java hosted with ❤ by GitHub

但我們通常不會只想要List或是Grid裡面只有一個TextView的，所以這邊必須要自定義一個Adapter來使用。

例如：

	package com.example.mp3list;
	import com.example.mp3list.R;
	import android.content.Context;
	import android.content.res.Resources;
	import android.graphics.Bitmap;
	import android.graphics.BitmapFactory;
	import android.media.MediaMetadataRetriever;
	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 java.util.ArrayList;
	import java.util.List;
	public class MusicGridAdapter extends BaseAdapter {
	private Context context;
	private List<MusicInfo> musicInfos;
	private MusicInfo musicInfo;
	private ArrayList<Bitmap> album_cover_list;
	/**
	* 构造函数
	* @param context 上下文
	* @param mp3Infos 集合对象
	*/
	public MusicGridAdapter(Context context, List<MusicInfo> mp3Infos, ArrayList<Bitmap> bit) {
	this.context = context;
	this.musicInfos = mp3Infos;
	this.album_cover_list = bit;
	}
	@Override
	public int getCount() {
	// TODO Auto-generated method stub
	return musicInfos.size();
	}
	@Override
	public MusicInfo getItem(int position) {
	// TODO Auto-generated method stub
	return this.musicInfos.get(position);
	}
	@Override
	public long getItemId(int position) {
	// TODO Auto-generated method stub
	return 0;
	}
	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
	MusicGridAdapter.ViewHolder viewHolder = null;
	if(convertView == null)
	{
	viewHolder = new MusicGridAdapter.ViewHolder();
	convertView = LayoutInflater.from(context).inflate(R.layout.grid, null);
	viewHolder.musicTitle = (TextView) convertView.findViewById(R.id.grid_title);
	viewHolder.albumImage = (ImageView) convertView.findViewById(R.id.grid_cd);
	viewHolder.musicArtist = (TextView) convertView.findViewById(R.id.grid_art);
	convertView.setTag(viewHolder); //表示给View添加一个格外的数据，
	} else {
	viewHolder = (MusicGridAdapter.ViewHolder)convertView.getTag();//通过getTag的方法将数据取出来
	}
	musicInfo = musicInfos.get(position);
	viewHolder.musicTitle.setText(musicInfo.getTitle()); //显示标题
	viewHolder.musicArtist.setText(musicInfo.getArtist()); //显示艺术家
	viewHolder.albumImage.setImageBitmap(album_cover_list.get(position));//显示bit
	return convertView;
	}
	/**
	* 定义一个内部类
	* 声明相应的控件引用
	*
	*/
	public class ViewHolder {
	//所有控件对象引用
	public ImageView albumImage; //专辑图片
	public TextView musicTitle; //音乐标题
	public TextView musicDuration; //音乐时长
	public TextView musicArtist; //音乐艺术家
	}
	}

view raw MusicGridAdapter.java hosted with ❤ by GitHub

最基本的adapter必須具備這樣的一個架構，而我們可以從convertView = LayoutInflater.from(context).inflate(R.layout.grid, null);

去定義R.layout.grid去修改顯示的內容

	<?xml version="1.0" encoding="utf-8"?>
	<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:background="#ffffff">
	<ImageView
	android:id="@+id/grid_cd"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:adjustViewBounds="true"
	android:src="@drawable/cd_example"/>
	<TextView
	android:id="@+id/grid_title"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:layout_below="@+id/grid_cd"
	android:singleLine="true"
	android:text="title"
	android:textSize="15dp" />
	<TextView
	android:id="@+id/grid_art"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:layout_below="@+id/grid_title"
	android:textSize="10dp"
	android:singleLine="true"
	android:text="art" />
	</RelativeLayout>

view raw grid.xml hosted with ❤ by GitHub

最後的結果：