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Android仿淘宝商品详情页

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看到有人在问如何实现淘宝商品详情页效果，献上效果图

Android仿淘宝商品详情页

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);
 }

 @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。