Gallery和自定义Adapter配合使用，实现图片预览

Gallery是一个可以拖动的列表，正中对应的是选中的东西.他和spinner有共同的父类：AbsSpinner

属性：

android:animationDuration="1000" 　　图片切换动画持续时间
android:spacing="8dp" 　　　　　　     设置图片之间的间距
android:unselectedAlpha="0.6" 　　　  设置没有选择的图片的透明度

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.kale.gallery.MainActivity"
    android:orientation="vertical">

    <!--
        android:animationDuration="1000"    图片切换动画持续时间
        android:spacing="8dp"                 设置图片之间的间距
        android:unselectedAlpha="0.6"        设置没有选择的图片的透明度
     -->

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="用ImageView作预览图"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <ImageView
        android:id="@+id/imageView_id"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_gravity="center_horizontal"
        android:scaleType="fitXY"
        android:src="@drawable/ic_launcher" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="60dp"
        android:text="下方是gallery"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <Gallery
        android:id="@+id/gallery_id"
        android:layout_marginTop="10dp"
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:animationDuration="1000"
        android:spacing="8dp"
        android:unselectedAlpha="0.3"/>

</LinearLayout>

MainActivity.java

package com.kale.gallery;

import android.app.Activity;
import android.content.Context;
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.Gallery.LayoutParams;
import android.widget.ImageView;

@SuppressWarnings("deprecation")
public class MainActivity extends Activity {

    ImageView iV;
    Gallery gallery;

    int[] imageIds = new int [] {
            R.drawable.appstore,
            R.drawable.cydia,
            R.drawable.itunes,
            R.drawable.mail,
            R.drawable.safair
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewInit();
        gallery.setAdapter(new ImageAdapter(this));
        gallery.setOnItemSelectedListener(new OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> arg0, View arg1,
                    int arg2, long arg3) {
                // TODO 自动生成的方法存根
                iV.setImageResource(imageIds[arg2]);

            }

            @Override
            public void onNothingSelected(AdapterView<?> arg0) {
                // TODO 自动生成的方法存根

            }
        });
    }

    public class ImageAdapter extends BaseAdapter {
        private Context mContext;
            public ImageAdapter(Context context) {
            mContext = context;
        }

        public int getCount() {
            return imageIds.length;
        }

        public Object getItem(int position) {
            return position;
        }

        public long getItemId(int position) {
            return position;
        }

        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView image = new ImageView(mContext);
            image.setImageResource(imageIds[position]);
            //设置缩放类型
            image.setScaleType(ImageView.ScaleType.FIT_XY);
            image.setAdjustViewBounds(true);
            //设置布局参数
            image.setLayoutParams(new Gallery.LayoutParams(
                LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
            return image;
        }
    }

    private void viewInit() {
        // TODO 自动生成的方法存根
        gallery = (Gallery) findViewById(R.id.gallery_id);
        iV = (ImageView)findViewById(R.id.imageView_id);
    }

}