间隙设置为零 

因为当我们引入TabLayout时就已经默认tabPaddingStart为12dp,tabPaddingEnd为12dp.才会导致不能填满的原因，这时我们只需要修改样式或者属性即可。

xmlns:app="http://schemas.android.com/apk/res-auto"

app:tabPaddingStart="0dp"
app:tabPaddingEnd="0dp"

间隙大小设置，下划线长度设置 

<com.google.android.material.tabs.TabLayoutandroid:layout_below="@+id/topli11"android:id="@+id/activity_tablayoutt"android:layout_width="match_parent"android:layout_height="@dimen/normal_110dp"android:background="@color/white"app:tabBackground="@null"app:tabRippleColor="@null"app:tabIndicatorColor="#4065E0"app:tabIndicatorHeight="@dimen/normal_5dp"app:tabIndicatorFullWidth="false"app:tabPaddingStart="@dimen/normal_70dp"app:tabPaddingEnd="@dimen/normal_70dp"app:tabMaxWidth="@dimen/normal_305dp"/>

 

<com.google.android.material.tabs.TabLayoutandroid:layout_below="@+id/topli11"android:id="@+id/activity_tablayoutt"android:layout_width="match_parent"android:layout_height="@dimen/normal_110dp"android:background="@color/white"app:tabBackground="@null"app:tabRippleColor="@null"app:tabIndicatorColor="#4065E0"app:tabIndicatorHeight="@dimen/normal_4dp"app:tabMaxWidth="@dimen/normal_180dp" />

 

方法二——api28以下使用

tabLayout.post(new Runnable() {@Overridepublic void run() {setIndicator(tabLayout);}
});

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/*** 设置tabLayout下划线的宽*/
public static void setIndicator(TabLayout tabs) {Class<?> tabLayout = tabs.getClass();Field tabStrip = null;try {tabStrip = tabLayout.getDeclaredField("slidingTabIndicator");} catch (NoSuchFieldException e) {e.printStackTrace();}tabStrip.setAccessible(true);LinearLayout llTab = null;try {llTab = (LinearLayout) tabStrip.get(tabs);} catch (IllegalAccessException e) {e.printStackTrace();}//因为我想要的效果是   字多宽线就多宽，所以测量mTextView的宽度for (int i = 0, count = llTab.getChildCount(); i < count; i++) {//获取tabViewView tabView = llTab.getChildAt(i);//拿到tabView的mTextView属性Field mTextViewField = null;try {//获取tabView的textView属性mTextViewField = tabView.getClass().getDeclaredField("textView");} catch (NoSuchFieldException e) {e.printStackTrace();}mTextViewField.setAccessible(true);TextView textView = null;try {textView = (TextView) mTextViewField.get(tabView);} catch (IllegalAccessException e) {e.printStackTrace();}tabView.setPadding(0, 0, 0, 0);//获取textview宽度int textWidth = 0;textWidth = textView.getWidth();if (textWidth == 0) {textView.measure(0, 0);textWidth = textView.getMeasuredWidth();}//获取tabview宽度int tabWidth = 0;tabWidth = tabView.getWidth();if (tabWidth == 0) {tabView.measure(0, 0);tabWidth = tabView.getMeasuredWidth();}//设置下划线margin值LinearLayout.LayoutParams tabViewParams = (LinearLayout.LayoutParams) tabView.getLayoutParams();int margin = (tabWidth - textWidth) / 2;tabViewParams.leftMargin = margin;tabViewParams.rightMargin = margin;tabView.setLayoutParams(tabViewParams);}}