tablayout doesn’t show dots in android

I want to show my viewPager pages with dots that carries with TabLayout. but tablayout doesn’t show anything.

my java code:

public class MainActivity extends AppCompatActivity  {
private ViewPager viewPager;
private ViewPagerAdapter adapter;

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

         //adapter + view pager
    adapter = new ViewPagerAdapter(getSupportFragmentManager());

    viewPager = (ViewPager) findViewById(R.id.container);
    viewPager.setAdapter(adapter);
    viewPager.setOnPageChangeListener(this);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_dots);
    tabLayout.setupWithViewPager(viewPager,true);
}

my xml code:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/lib/com.app.chasebank"    android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/main_color"
tools:context="zekrshomargouya.maxsoft.com.zekrshomargouya.MainActivity">

<android.support.v7.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:fitsSystemWindows="true"
    android:minHeight="?attr/actionBarSize"
    app:navigationIcon="?attr/homeAsUpIndicator"
    style="@style/toolbar">
</android.support.v7.widget.Toolbar>


<android.support.v4.view.ViewPager
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    android:layout_marginBottom="50dp"
    android:layout_marginLeft="25dp" android:layout_marginRight="25dp"
    android:layout_marginTop="30dp"
    android:layout_gravity="top"
    android:layout_below="@id/toolbar"/>

<android.support.design.widget.TabLayout
    android:id="@+id/tab_dots"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    app:tabBackground="@drawable/tab_selector"
    app:tabGravity="center"
    app:tabIndicatorHeight="2dp"
    android:background="#ff55ff"
    android:layout_marginTop="0dp"
    android:layout_gravity="center"
    android:layout_alignParentBottom="true"/>

my build.gradle code:

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:25.0.1'
compile 'com.android.support:support-v4:25.0.1'
testCompile 'junit:junit:4.12'
compile 'com.android.support:design:25.0.1'
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
})

as you can see in this image, TabLayout is just a line (but i use dots)
tabLayout

tablayout doesn’t show dots in android