看到有人在问如何实现淘宝商品详情页效果，手痒了就撸了一个，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

 icon.setImageAlpha(0);

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);}@Overrideprotected 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

  @Overrideprotected 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）

 @Overrideprotected 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() {@Overridepublic 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);}@Overridepublic void onChangedFirstColor(float percentage) {}@Overridepublic void onChangedSecondColor(float percentage) {}});ideaScrollView.setOnSelectedIndicateChangedListener(new IdeaScrollView.OnSelectedIndicateChangedListener() {@Overridepublic 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