Gallery的使用

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener,ViewSwitcher.ViewFactory{
    private int[] res={R.mipmap.ic_launcher,R.mipmap.ic_launcher,R.mipmap.ic_launcher,R.mipmap.ic_launcher,R.mipmap.ic_launcher};;
    private Gallery gallery;
    private ImageAdapter imageAdapter;
    private ImageSwitcher imageSwitcher;
    @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.imageswitcher);
        imageAdapter=new ImageAdapter(res,this);
        gallery.setAdapter(imageAdapter);
        //设定gallery的监听器
        gallery.setOnItemSelectedListener(this);
        //通过Viewfactory的接口为imageswitcher创建一个视图
        imageSwitcher.setFactory(this);

    }
    //给imageswitcher设定选中的图片的资源
    @Override
    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
        imageSwitcher.setBackgroundResource(res[i]);
    }

    @Override
    public void onNothingSelected(AdapterView<?> adapterView) {

    }
    //设定所要设计的接口视图返回imageview的对象；适用于设置viewswitcher
    @Override
    public View makeView() {
        ImageView imageView= new ImageView(this);
        imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
        return imageView;
    }
}

public class ImageAdapter extends BaseAdapter {
    private Context context;
    private int[] res;
    //通过构造函数来传递数据
    public ImageAdapter(int[]res, Context context){
        this.context=context;
        this.res=res;
    }
    @Override
    public int getCount() {
        return res.length;
    }

    @Override
    public Object getItem(int i) {
        return res[i];
    }

    @Override
    public long getItemId(int i) {
        return i;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        ImageView imageView= new ImageView(context);
        imageView.setBackgroundResource(res[i]);
        imageView.setLayoutParams(new Gallery.LayoutParams(300,400));
        imageView.setScaleType(ImageView.ScaleType.FIT_XY);
        return imageView;
    }
}