public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener,ViewSwitcher.ViewFactory {

    private Gallery gallery;

    private ImageSwitcher imageSwitcher;

    //数据源

    private int[] res = {R.drawable.item1,R.drawable.item2,R.drawable.item3,R.drawable.item4,

                        R.drawable.item5,R.drawable.item6, R.drawable.item7,R.drawable.item8,

                        R.drawable.item9,R.drawable.item10,R.drawable.item11,R.drawable.item12};

    private ImageAdapter adapter;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        gallery = (Gallery) findViewById(R.id.gallery);

        imageSwitcher = (ImageSwitcher) findViewById(R.id.imageswitch);

        adapter = new ImageAdapter(res,this);

        gallery.setAdapter(adapter);

        gallery.setOnItemSelectedListener(this);

        //imageSwitcher加载工厂factory

        imageSwitcher.setFactory(this);

        imageSwitcher.setInAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_in));

        imageSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this,android.R.anim.fade_out));

    }

    @Override

    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

        imageSwitcher.setBackgroundResource(res[position % res.length]);

    }

    @Override

    public View makeView() {

        ImageView image = new ImageView(this);

        //等比例 居中缩放

        image.setScaleType(ImageView.ScaleType.CENTER.FIT_CENTER);

        return image;

    }

public class ImageAdapter extends BaseAdapter {

    private int[] res;

    private Context context;

    public ImageAdapter(int[] res,Context context){

        this.res        =   res;

        this.context    = context;

    }

    //获取数量

    @Override

    public int getCount() {

        return res.length;

//        return Integer.MAX_VALUE;  约等于无限数量

    }

    //获取项目

    @Override

    public Object getItem(int position) {

        return res[position];

    }

    //获取在适配器中的位置

    @Override

    public long getItemId(int position) {

        return position;

    }

    //获取单个的View

    @Override

    public View getView(int position, View convertView, ViewGroup parent) {

        //new出一个新的View

        ImageView image = new ImageView(context);

        //给ImageView加载对应的图像资源

        image.setBackgroundResource(res[position]);

        //利用取余 无限图片位置 不受数目限制了 res[position % res.length]

        //设置view在Gallery中缩略图的大小

        image.setLayoutParams(new Gallery.LayoutParams(200,150));

        //设置缩放模式

        image.setScaleType(ImageView.ScaleType.FIT_XY);

        return image;

    }

}

<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:orientation="vertical"

    tools:context=".MainActivity">

    <Gallery

        android:id="@+id/gallery"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"/>

    <ImageSwitcher

        android:layout_gravity="center_vertical"

        android:layout_below="@id/gallery"

        android:id="@+id/imageswitch"

        android:layout_width="match_parent"

        android:layout_height="wrap_content">

    </ImageSwitcher>

</LinearLayout>