原理:就是自定义scrollview实现对滑动高度的监听而已，如此实现对搜索框的渐变

//自定义ScrollViewpublic class CustomView extends ScrollView { public interface ScrollViewListener { void onScrollChanged(CustomView customView, int x, int y, int oldx, int oldy); } private ScrollViewListener scrollViewListener = null; public CustomView(Context context) { super(context); } public CustomView(Context context, AttributeSet attrs,   int defStyle) { super(context, attrs, defStyle); } public CustomView(Context context, AttributeSet attrs) { super(context, attrs); } public void setScrollViewListener(ScrollViewListener scrollViewListener) { this.scrollViewListener = scrollViewListener; } @Override protected void onScrollChanged(int x, int y, int oldx, int oldy) { super.onScrollChanged(x, y, oldx, oldy); if (scrollViewListener != null) {  scrollViewListener.onScrollChanged(this, x, y, oldx, oldy); } }}

好了，接下来就直接在逻辑代码中调用就行了！

@Override public void onViewCreated(View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); //搜索框在布局最上面 line.bringToFront(); mScrollview.setScrollViewListener(new CustomView.ScrollViewListener() {  @Override  public void onScrollChanged(CustomView customView, int x, int y, int oldx, int oldy) {  if (y <= 0) {   line.setBackgroundColor(Color.argb((int) 0, 227, 29, 26));//AGB由相关工具获得，或者美工提供  } else if (y > 0 && y <= imageHeight) {   //获取ScrollView向下滑动图片消失的比例   float scale = (float) y / imageHeight;   //更加这个比例,让标题颜色由浅入深   float alpha = (255 * scale);   // 只是layout背景透明   line.setBackgroundColor(Color.argb((int) alpha, 255, 255, 255));  }  } });