使用Gallery制作图片浏览器

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>