Gallery自动循环滚动以及手动滚动的平滑切换（一）

@Gallery配合dot使用时，如果放在RelativeLayout中，则手动滑动有反弹现象，其他layout没问题，现在还没弄清原因。
首先继承Gallery重写OnFling函数，去除gallery的滚动惯性

public class MyGallery extends Gallery {

    public MyGallery(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
    }

    private boolean isScrollingLeft(MotionEvent e1, MotionEvent e2) {

        return e2.getX() > e1.getX();

    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
            float velocityY) {
        int keyCode;

        if (isScrollingLeft(e1, e2)) {

            keyCode = KeyEvent.KEYCODE_DPAD_LEFT;

        } else {

            keyCode = KeyEvent.KEYCODE_DPAD_RIGHT;

        }

        onKeyDown(keyCode, null);

        return true;
    }

}

@注 OnFling直接返回false也能实现类似效果，但那样需要滑动很大距离，图片才会切换，用户体验不好

 

第二步，构造adapter

要想平滑的实现循环滚动，可以让getCount返回一个很大的值，这样gallery就认为是有多个item,item之间的切换动画是平滑的

public class GalleryAdapter extends BaseAdapter {

    private LayoutInflater mInflater;
    private Context mContext;
    private int width;
    private int count;
    private int[] mImageIds;

    public GalleryAdapter(Context context, int[] ids) {
        mContext = context;
        mImageIds = ids;
        mInflater = LayoutInflater.from(mContext);
        DisplayMetrics dm = mContext.getApplicationContext().getResources()
                .getDisplayMetrics();
        width = dm.widthPixels;
        count = mImageIds.length;
    }

    @Override
    public int getCount() {
        return Integer.MAX_VALUE;//用于循环滚动
    }

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

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        position = position % count;
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.gallery_item, null);
        }
        ImageView v = (ImageView) convertView.findViewById(R.id.img);
        v.setLayoutParams(new Gallery.LayoutParams(width, 200));
        v.setScaleType(ImageView.ScaleType.FIT_XY);
        v.setBackgroundResource(mImageIds[position]);
        return v;
    }

}