思想：运用反射的方式来实现

封装的方法如下：

  public voidsetIndicator(TabLayout tabs, intleftDip, intrightDip) {
     Class tabLayout = tabs.getClass();
     Field tabStrip =null;
     try{
         tabStrip = tabLayout.getDeclaredField("mTabStrip");
     }catch(NoSuchFieldException e) {
         e.printStackTrace();
     }
     tabStrip.setAccessible(true);
     LinearLayout llTab =null;
     try{
        llTab = (LinearLayout) tabStrip.get(tabs);
     }catch(IllegalAccessException e) {
        e.printStackTrace();
     }

     intleft = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,leftDip,Resources.getSystem().getDisplayMetrics());
     intright = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,rightDip,Resources.getSystem().getDisplayMetrics());

     for(inti =0;i < llTab.getChildCount();i++) {
          View child = llTab.getChildAt(i);
          child.setPadding(0,0,0,0);
          LinearLayout.LayoutParams params =newLinearLayout.LayoutParams(0,LinearLayout.LayoutParams.MATCH_PARENT,1);
          params.leftMargin= left;
          params.rightMargin= right;
          child.setLayoutParams(params);
          child.invalidate();
       }
    }

在tablayout渲染完成之后调用

tabLayout.post(newRunnable() {
  @Override
  public voidrun() {
    setIndicator(tabLayout,40,40);
  }
});