Android自定義ScrollView

public class CustomScrollView extends ScrollView {

    private OnScrollChanged mOnScrollChanged;
    private int upHeight;

    public CustomScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
        upHeight = dpTopx(100);
    }

    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);
        if (mOnScrollChanged!=null){
            mOnScrollChanged.onScroll(l,t,oldl,oldt);
        }
    }

    /**
     *
     * @param onScrollChanged
     */
    public void setOnScrollChanged(OnScrollChanged onScrollChanged){
        this.mOnScrollChanged=onScrollChanged;
    }

    public interface OnScrollChanged{
        void onScroll(int l,int t,int oldl,int oldt);
    }

    /**
     *
     * @param dpValue
     * @return
     */
    private int dpTopx(int dpValue){
        final  float scale = this.getResources().getDisplayMetrics().density;
        return (int)(dpValue * scale + 0.5f);
    }
}
           

使用：

mCustomScrollView.setOnScrollChanged(new CustomScrollView.OnScrollChanged() {
            @Override
            public void onScroll(int l, int t, int oldl, int oldt) {
                //擷取控件高度
                int mHeight = (ivSingerDetailBg.getHeight() - llSingerDetailInfoBar.getHeight());

                if (t <= 0) {
                    //未滑動
                    llSingerDetailTitlebar.setBackgroundColor(Color.argb(0, 26, 26, 26));
                    tvSingerDetailTitle.setVisibility(View.GONE);
                    cbSingerDetailTitleAttention.setVisibility(View.GONE);
                } else if (t > 0 && t <= mHeight) {
                    //滑動過程中，并在mHeight内
                    // float alpha = (255 * (t / mHeight));
                    float scale = (float) t / mHeight;
                    float alpha = (255 * scale);
                    llSingerDetailTitlebar.setBackgroundColor(Color.argb((int) alpha, 26, 26, 26));
                    tvSingerDetailTitle.setVisibility(View.GONE);
                    cbSingerDetailTitleAttention.setVisibility(View.GONE);
                } else {
                    //超過标題欄
                    llSingerDetailTitlebar.setBackgroundColor(Color.argb(255, 26, 26, 26));
                    tvSingerDetailTitle.setVisibility(View.VISIBLE);
                    cbSingerDetailTitleAttention.setVisibility(View.VISIBLE);

                }
            }
        });