Call fragment from fragment

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http://stackoverflow.com – i have an activity with button on it and when a click i call the fragment with another button on fragment. but when click on fragment's button i cant call a second fragment. this is my source, pretty simple: activity_main.xml: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" tools:context=".MainActivity" > <Button android:id="@+id/btn_click" android:text="Call Fragment" android:layout_height="wra (HowTos)