修改TabLayout下滑指导线的宽度和高度

修改TabLayout下滑指导线的宽度
如果是和你设置的字体宽度一样宽，可以直接写该类 Reflex
然后在TabLayout初始化的地方调用该方法

 mReflex = new Reflex();
 mReflex.reflex(mTabLayout);

public class Reflex {
    public void reflex(final TabLayout tabLayout){
        //了解源码得知 线的宽度是根据 tabView的宽度来设置的
        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                try {
                    //拿到tabLayout的mTabStrip属性
                    LinearLayout mTabStrip = (LinearLayout) tabLayout.getChildAt(0);

                    int dp10 = dip2px(tabLayout.getContext(), 10);

                    for (int i = 0; i < mTabStrip.getChildCount(); i++) {
                        View tabView = mTabStrip.getChildAt(i);

                        //拿到tabView的mTextView属性  tab的字数不固定一定用反射取mTextView
                        Field mTextViewField = tabView.getClass().getDeclaredField("mTextView");
                        mTextViewField.setAccessible(true);

                        TextView mTextView = (TextView) mTextViewField.get(tabView);

                        tabView.setPadding(0, 5, 0, 5);

                        //因为我想要的效果是   字多宽线就多宽，所以测量mTextView的宽度
                        int width = 0;
                        width = mTextView.getWidth()+20;
                        if (width == 0) {
                            mTextView.measure(0, 0);
                            width = mTextView.getMeasuredWidth();
                        }

                        //设置tab左右间距为10dp  注意这里不能使用Padding 因为源码中线的宽度是根据 
                        tabView的宽度来设置的
                        LinearLayout.LayoutParams params = (LinearLayout.LayoutParams)  
                        tabView.getLayoutParams();
                        params.width = width ;
                        params.leftMargin = dp10;
                        params.rightMargin = dp10;
                        tabView.setLayoutParams(params);


                        tabView.invalidate();
                    }

                } catch (NoSuchFieldException e) {
                    e.printStackTrace();
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            }
        });

    }
}

修改TabLayout的下划线高度
可通过xml代码修改app:tabIndicatorHeight="3dp"

<android.support.design.widget.TabLayout
        android:id="@+id/tablayout"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="@color/colorWhite"
        app:layout_constraintDimensionRatio="W,0.1:1"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@+id/iv_down"
        app:layout_constraintTop_toBottomOf="@+id/toolbar"
        app:tabIndicatorColor="@color/colorPrimary"
        app:tabMode="scrollable"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        app:tabPaddingEnd="15dp"
        app:tabIndicatorHeight="3dp"
        app:tabPaddingStart="15dp"
        app:tabSelectedTextColor="@color/colorPrimary"
        app:tabTextColor="@color/colorNormalText"/>