带圆角的Android Material Tab布局指示器

<!-- res/layout/activity_main.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tab_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:tabIndicatorFullWidth="false"
        app:tabIndicatorGravity="center"
        app:tabIndicatorHeight="4dp"
        app:tabIndicatorCornerRadius="8dp"
        app:tabIndicatorColor="#FF0000"
        app:tabMode="fixed"
        app:tabGravity="fill"/>

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

// MainActivity.java
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;
import com.google.android.material.tabs.TabLayout;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TabLayout tabLayout = findViewById(R.id.tab_layout);
        ViewPager viewPager = findViewById(R.id.view_pager);

        // Set up the ViewPager with the sections adapter.
        viewPager.setAdapter(new SectionsPagerAdapter(getSupportFragmentManager()));
        tabLayout.setupWithViewPager(viewPager);
    }

    public static class SectionsPagerAdapter extends FragmentPagerAdapter {
        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            // Return a new instance of the fragment for the given section.
            return PlaceholderFragment.newInstance(position + 1);
        }

        @Override
        public int getCount() {
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return "Tab " + (position + 1);
        }
    }
}

app:tabIndicatorCornerRadius="8dp"
app:tabIndicatorHeight="4dp"

app:tabIndicatorColor="#FF0000"