implementation 'com.android.support:appcompat-v7:28.0.0' implementation 'com.android.support:design:28.0.0' implementation 'com.android.support:cardview-v7:28.0.0' <activity android:name=".MainActivity" android:theme="@style/Theme.AppCompat.Light.NoActionBar"> ... </activity> <android.support.v7.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize" android:background="?attr/colorPrimary" /> <android.support.v7.widget.RecyclerView android:id="@+id/recyclerView" android:layout_width="match_parent" android:layout_height="match_parent" /> <android.support.design.widget.FloatingActionButton android:id="@+id/fab" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/ic_add" Toolbar toolbar = findViewById(R.id.toolbar); setSupportActionBar(toolbar); RecyclerView recyclerView = findViewById(R.id.recyclerView); recyclerView.setLayoutManager(new LinearLayoutManager(this)); recyclerView.setAdapter(adapter); FloatingActionButton fab = findViewById(R.id.fab); fab.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { } });