<?xml version="1.0" encoding="utf-8"?>
<framelayout android:layout_height="fill_parent" android:layout_width="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/FrameLayout01">
<imageview android:layout_height="fill_parent" android:layout_width="fill_parent" android:id="@+id/ImageView01" android:src="@drawable/wallpaper_0">
</imageview>

<gallery android:layout_height="wrap_content" android:layout_width="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/Gallery01" android:spacing="5dp">
</gallery>
</framelayout>

<?xml version="1.0" encoding="UTF-8"?>
<resources>
  <declare -styleable="" name="HelloGallery">
    <attr name="android:galleryItemBackground">
  </attr></declare>
</resources>

package android.basic.lesson13;

import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;

import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.Toast;

public class MainHelloGallery extends Activity {

  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    //定义UI组件
    final ImageView iv= (ImageView)findViewById(R.id.ImageView01);
    Gallery g = (Gallery) findViewById(R.id.Gallery01);

    //设置图片匹配器
    g.setAdapter(new ImageAdapter(this));

    //设置AdapterView点击监听器，Gallery是AdapterView的子类
    g.setOnItemClickListener(new OnItemClickListener() {

      @Override
      public void onItemClick(AdapterView<?> parent, View view,
          int position, long id) {
        //显示点击的是第几张图片
        Toast.makeText(MainHelloGallery.this, "" + position,
            Toast.LENGTH_LONG).show();
        //设置背景部分的ImageView显示当前Item的图片
        iv.setImageResource(((ImageView)view).getId());
      }
    });
  }

  //定义继承BaseAdapter的匹配器
  public class ImageAdapter extends BaseAdapter {

    //Item的修饰背景
    int mGalleryItemBackground;

    //上下文对象
    private Context mContext;

    //图片数组
    private Integer[] mImageIds = { R.drawable.wallpaper_0,
        R.drawable.wallpaper_1, R.drawable.wallpaper_2,
        R.drawable.wallpaper_3, R.drawable.wallpaper_4,
        R.drawable.wallpaper_5, R.drawable.wallpaper_6,
        R.drawable.wallpaper_7, R.drawable.wallpaper_8,
        R.drawable.wallpaper_9 };

    //构造方法
    public ImageAdapter(Context c){
      mContext = c;
      //读取styleable资源
    TypedArray a = obtainStyledAttributes(R.styleable.HelloGallery);
    mGalleryItemBackground = a.getResourceId(
      R.styleable.HelloGallery_android_galleryItemBackground, 0);
    a.recycle();

    }

    //返回项目数量
    @Override
    public int getCount() {
      return mImageIds.length;
    }

    //返回项目
    @Override
    public Object getItem(int position) {
      return position;
    }

    //返回项目Id
    @Override
    public long getItemId(int position) {
      return position;
    }

    //返回视图
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

      ImageView iv = new ImageView(mContext);
      iv.setImageResource(mImageIds[position]);
      //给生成的ImageView设置Id，不设置的话Id都是-1
      iv.setId(mImageIds[position]);
      iv.setLayoutParams(new Gallery.LayoutParams(120, 160));
      iv.setScaleType(ImageView.ScaleType.FIT_XY);
      iv.setBackgroundResource(mGalleryItemBackground);
      return iv;
    }

  }
}