ToolBar is overlapping on my RelativeLayout when i use By default toolBar in android

Question

I've added Default Toolbar in my current application.

But when I added this toolBar my "Hello world" textview is not appearing.

How to resolve this problem!?

activity_main.xml:-

 <?xml version="1.0" encoding="utf-8"?>
    <android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true"
        tools:context="com.example.venkat.actionbarapp.MainActivity">

        <android.support.design.widget.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/AppTheme.AppBarOverlay">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimary"
                app:popupTheme="@style/AppTheme.PopupOverlay" >

            </android.support.v7.widget.Toolbar>

        </android.support.design.widget.AppBarLayout>

        <include layout="@layout/content_main" />

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|end"
            android:layout_margin="@dimen/fab_margin"
            android:src="@android:drawable/ic_dialog_email" />

    </android.support.design.widget.CoordinatorLayout>

content_main.xml:-

 <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:background="@android:color/holo_blue_dark"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/toolbar"
        android:layout_marginTop="10dp">

        <TextView
            android:layout_width="wrap_content"
            android:textColor="@android:color/holo_red_dark"
            android:layout_height="wrap_content"
            android:text="Hello World!" />

    </RelativeLayout>

Answer 1

Try this -

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:background="@android:color/holo_blue_dark"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="10dp"

        app:layout_behavior="@string/appbar_scrolling_view_behavior" >

        <TextView
            android:layout_width="wrap_content"
            android:textColor="@android:color/holo_red_dark"
            android:layout_height="wrap_content"
            android:text="Hello World!" />

    </RelativeLayout>