android TabLayout下标随文字长度变化长宽。

代码如下：

public static void setIndicator(final TabLayout tabs, final List<BaseFragment> fragments){
        tabs.post(new Runnable() {
            @Override
            public void run() {
                int screenWidth = RxDeviceTool.getScreenWidth(tabs.getContext());
                int textlength = 0;
                int length = 0;
                try {
                    //拿到tabLayout的mTabStrip属性
                    Field mTabStripField = tabs.getClass().getDeclaredField("mTabStrip");
                    mTabStripField.setAccessible(true);
                    LinearLayout mTabStrip = (LinearLayout) mTabStripField.get(tabs);
                    int dp10 = DimenUtil.dip2px(10);
                    int dp2 = DimenUtil.dip2px(2);
                    for(int i = 0; i < mTabStrip.getChildCount(); i++){
                        View tabView = mTabStrip.getChildAt(i);

                        //拿到tabView的mTextView属性
                        Field mTextViewField = tabView.getClass().getDeclaredField("mTextView");
                        mTextViewField.setAccessible(true);

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

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

                        //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();
                        if (width == 0) {
                            mTextView.measure(0, 0);
                            width = mTextView.getMeasuredWidth();
                        }
                        textlength = width+textlength;
                    }

                    //当不满一屏幕的时候间距平均分配
                    length = fragments.size()*dp10+dp10+textlength;
                    if(screenWidth>length){
                        dp10 = (screenWidth-textlength)/(fragments.size()+1);
                    }
                    for (int i = 0; i < mTabStrip.getChildCount(); i++) {
                        View tabView = mTabStrip.getChildAt(i);

                        //拿到tabView的mTextView属性
                        Field mTextViewField = tabView.getClass().getDeclaredField("mTextView");
                        mTextViewField.setAccessible(true);

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

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

                        //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();
                        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;
                        params.bottomMargin = dp2;
                        tabView.setLayoutParams(params);
                        tabView.invalidate();
                    }

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

另外一个方法：

//改变tablayout的下划线宽度
    public static void setTabWidth(final TabLayout tabLayout,final int padding){
        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                try {
                    //拿到tabLayout的mTabStrip属性
                    LinearLayout mTabStrip = (LinearLayout) tabLayout.getChildAt(0);
                    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, 0, 0, 0);
                        //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();
                        if (width == 0) {
                            mTextView.measure(0, 0);
                            width = mTextView.getMeasuredWidth();
                        }
                        //设置tab左右间距 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 = padding;
                        params.rightMargin = padding;
                        tabView.setLayoutParams(params);
                        tabView.invalidate();
                    }
                } catch (NoSuchFieldException e) {
                    e.printStackTrace();
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            }
        });
    }

有bug，记录一下。有好的方法欢迎大家建议。