画廊视图(Gallery)的功能和用法

Gallery与Spinner组件有共同的父类：AbsSpinner，表明Gallery和Spinner都是一个列表框。它们之间的区别在于Spinner显示的是一个垂直的列表选择框吗，而Gallery显示的是一个水平的列表选择框。

下面以一个例子来说明：

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
	<ImageView 
	    android:id="@+id/imageView"
	    android:layout_width="match_parent"
	    android:layout_height="0dip"
	    android:layout_weight="1"/>
	<Gallery 
	    android:id="@+id/gallery"
	    android:layout_width="match_parent"
	    android:layout_height="wrap_content"
	    android:layout_marginTop="25dip"
	    android:unselectedAlpha="0.6"
	    android:spacing="2pt"/>
</LinearLayout>

MainActivity.java

package com.example.testgallary;

import android.app.Activity;
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.OnItemSelectedListener;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;

public class MainActivity extends Activity {

	private int[] imageIds = new int[]{
			R.drawable.img1, R.drawable.img2,
			R.drawable.img3, R.drawable.img4,
			R.drawable.img5, R.drawable.img6,
	};
	
	private Gallery gallery;
	private ImageView imageView;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		gallery = (Gallery) findViewById(R.id.gallery);
		imageView = (ImageView) findViewById(R.id.imageView);
		
		BaseAdapter adapter = new BaseAdapter() {
			
			@Override
			public View getView(int position, View convertView, ViewGroup parent) {
				// 创建一个ImageView
				ImageView imageView = new ImageView(MainActivity.this);
				imageView.setImageResource(imageIds[position]);
				// 设置ImageView的缩放类型
				imageView.setScaleType(ImageView.ScaleType.FIT_XY);
				// 为imageView设置布局参数
				imageView.setLayoutParams(new Gallery.LayoutParams(75, 100));
				TypedArray typedArray = obtainStyledAttributes(
						R.styleable.Gallery);
				imageView.setBackgroundResource(typedArray.getResourceId(
						R.styleable.Gallery_android_galleryItemBackground, 0));
				return imageView;
			}
			
			@Override
			public long getItemId(int position) {
				// TODO Auto-generated method stub
				return position;
			}
			
			@Override
			public Object getItem(int item) {
				// TODO Auto-generated method stub
				return item;
			}
			
			@Override
			public int getCount() {
				// TODO Auto-generated method stub
				return imageIds.length;
			}
		};
		
		gallery.setAdapter(adapter);
		gallery.setOnItemSelectedListener(new OnItemSelectedListener() {

			@Override
			public void onItemSelected(AdapterView<?> parent, View view,
					int position, long id) {
				imageView.setImageResource(imageIds[position]);
				
			}

			@Override
			public void onNothingSelected(AdapterView<?> view) {
				
				
			}
		});
	}

}

运行结果：