Inspired from Twitter iOS App and modified from CircleIndicator.

• Add the JitPack repository to your root build.gradle:

repositories {
    maven { url "https://jitpack.io" }
}

• Add the dependency to your sub build.gradle:

dependencies {
    compile 'com.github.nekocode:ToolbarIndicator:{latest-version}'
}

• Set the target ViewPager for ToolbarIndicator:

ToolbarIndicator toolbarIndicator = (ToolbarIndicator) this.findViewById(R.id.indicator);
toolbarIndicator.setViewPager(viewPager);

ToolbarIndicator get titles from FragmentPagerAdapter's getPageTitle function, check the sample project for more detail.