看到有人在问如何实现淘宝商品详情页效果，献上效果图
大致梳理一下思路，这里不提供源码
状态栏透明使用开源库StatusBarCompat，为了兼容手机4.4
dependencies { compile ('com.github.niorgai:StatusBarCompat:2.1.4', { exclude group: 'com.android.support' }) }allprojects { repositories { ... maven { url "https://jitpack.io" } } } 标题栏图标透明度变化参考Api setAlpha()已过时
Banner控件为ViewPager,淘宝显示为正方形，这里需要修改ViewPager measure函数
public class IdeaViewPager extends ViewPager { private Point point; public IdeaViewPager(Context context) { this(context,null); } public IdeaViewPager(Context context, AttributeSet attrs) { super(context, attrs); WindowManager windowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE); point = new Point(); windowManager.getDefaultDisplay().getSize(point); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); setMeasuredDimension(point.x,point.x); }} 测量View高度，获取到高度集合绑定到ScrollView,根据ScrollView滑动距离判断是属于哪一个Tab选项
public int getMeasureHeight(View view){ int width = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED); int height = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED); view.measure(width, height); return view.getMeasuredHeight(); } 重新onScrollChanged函数，实现ViewPager滑动速度比其他View慢
@Override protected void onScrollChanged(int l, int t, int oldl, int oldt) { super.onScrollChanged(l, t, oldl, oldt); if (viewPager != null && t != oldt) { viewPager.setTranslationY(t/2); } } 根据限定距离（Banner）计算百分比偏移量，实现颜色渐变、透明度渐变（淘宝商品详情页有二次颜色渐变）
@Override protected void onScrollChanged(int l, int t, int oldl, int oldt) { super.onScrollChanged(l, t, oldl, oldt); if(viewPager!=null&&t<=point.x-headerHeight&&getOnScrollChangedColorListener()!=null){ getOnScrollChangedColorListener().onChanged(Math.abs(t)/Float.valueOf(point.x-headerHeight)); if(t<=(point.x-headerHeight)/2){ getOnScrollChangedColorListener().onChangedFirstColor(t/(point.x-headerHeight)/2); }else{ getOnScrollChangedColorListener().onChangedSecondColor((t-(point.x-headerHeight)/2)/(point.x-headerHeight)/2); } } int currentPosition = getCurrentPosition(t,arrayDistance); if(currentPosition!=position&&getOnSelectedIndicateChangedListener()!=null){ getOnSelectedIndicateChangedListener().onSelectedChanged(currentPosition); } this.position = currentPosition; } 单一颜色渐变透明度，还原argb通道，修改a值
ideaScrollView.setOnScrollChangedColorListener(new IdeaScrollView.OnScrollChangedColorListener() { @Override public void onChanged(float percentage) { int color = getAlphaColor(percentage>0.9f?1.0f:percentage); header.setBackgroundDrawable(new ColorDrawable(color)); radioGroup.setBackgroundDrawable(new ColorDrawable(color)); icon.setImageAlpha((int) ((percentage>0.9f?1.0f:percentage)*255)); radioGroup.setAlpha((percentage>0.9f?1.0f:percentage)*255); setRadioButtonTextColor(percentage); } @Override public void onChangedFirstColor(float percentage) { } @Override public void onChangedSecondColor(float percentage) { } }); ideaScrollView.setOnSelectedIndicateChangedListener(new IdeaScrollView.OnSelectedIndicateChangedListener() { @Override public void onSelectedChanged(int position) { isNeedScrollTo = false; radioGroup.check(radioGroup.getChildAt(position).getId()); isNeedScrollTo = true; } }); public int getAlphaColor(float f){ return Color.argb((int) (f*255),0x09,0xc1,0xf4); } Tab选项属性不能太频繁，会有颜色值闪烁情况出现，这里需要策略
public void setRadioButtonTextColor(float percentage){ if(Math.abs(percentage-currentPercentage)>=0.1f){ for(int i=0;i<radioGroup.getChildCount();i++){ RadioButton radioButton = (RadioButton) radioGroup.getChildAt(i); radioButton.setTextColor(radioButton.isChecked()?getRadioCheckedAlphaColor(percentage):getRadioAlphaColor(percentage)); } this.currentPercentage = percentage; } } 判断当前属于哪个选项，根据滑动距离与传入绑定的View高度集合来计算
private int getCurrentPosition(int t, ArrayList<Integer> arrayDistance) { int index = 0; for (int i=0;i<arrayDistance.size();i++){ if(i==arrayDistance.size()-1){ index = i; }else { if(t>=arrayDistance.get(i)&&t<arrayDistance.get(i+1)){ index = i; break; } } } return index; } 切换选项卡以及回到顶部按钮的具体实现参考scrollTo函数
private void scrollToPosition(int position){ scrollTo(0,arrayDistance.get(position)); } 以上代码实现了上图效果，当然也可以使用RecyclerView AbsListView做容器。
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