tablayout较全的用法（会陆续补充）

<android.support.design.widget.TabLayout
            android:id="@+id/tablayout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            //背景颜色
            android:background="@color/gray_new"
            app:tabGravity="fill"
            //下划线颜色
            app:tabIndicatorColor="@color/blue"
            //下划线高度
            app:tabIndicatorHeight="@dimen/pad_3"
            app:tabMode="fixed"
            //字体样式（下边会补充）
            app:tabTextAppearance="@style/MyTabLayoutTextAppearance"
           //选中时的字体颜色             
            app:abTextColor="#000000" />

tablayout 标题文字样式

<style name="MyTabLayoutTextAppearance" parent="TextAppearance.AppCompat.Widget.ActionBar.Title">
    <item name="android:textSize">20sp</item>
    <item name="android:textColor">@android:color/black</item>
    <item name="android:textStyle">bold</item>
</style>

改变下划线长度（通过反射的方法）

 public void setIndicator(TabLayout tabs, int leftDip, int rightDip) {
    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();
    }

    int left = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, leftDip, Resources.getSystem().getDisplayMetrics());
    int right = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, rightDip, Resources.getSystem().getDisplayMetrics());

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

在oncreate中调用修改长度

tabLayout.post(new Runnable() {
        @Override
        public void run() {
            setIndicator(tabLayout, 10, 10);
        }
    });