final View view = findViewById(R.id.fixation_title_bar); // 需要透明的view
final View totalTitle = findViewById(R.id.total_title);
CompatNestedScrollView scrollView = findViewById(R.id.scrollView);
scrollView.setOnScrollChangedListener(new CompatNestedScrollView.OnScrollChangedListener() {
      @Override
       public void onScrollChanged(NestedScrollView scrollView, int x, int y, int oldx, int oldy) {
           float totalTitleHeight = totalTitle.getHeight(); // 目标高度
           float alphaValue = y / totalTitleHeight;
           view.setAlpha(alphaValue);
       }
});