Using fragment to add the bottom navigation bar

Remember: Fragment must be placed in the framlayout, otherwise it will not be replaced completely (that is, the original fagment may exist after switching)

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:background= "#ffffff"
    android:orientation= "Vertical" >


    <framelayout
        Android:id= "@+id/content"
        Android:layout_width= "Match_parent"
        android:layout_height= "Match_parent"
>
        <fragment
            Android:name= "Com.liu25.asmallpark.Fragment.Fragment_1"
            Android:layout_width= "Match_parent"
            android:layout_height= "Match_parent"
            tools:layout= "@layout/fragment_1"/>
    </FrameLayout>

<linearlayout

Android:layout_width= "Match_parent"

android:layout_height= "Wrap_content" >
<!--four x button>

<LinearLayout/>

<LinearLayout/>

Fragment_1.xml (grey background)

<?xml version= "1.0" encoding= "Utf-8"?>
<linearlayout xmlns:android= "Http://schemas.android.com/apk/res/android"
    Android:layout_width= "Match_parent"
    android:layout_height= "Match_parent"
    Android:background= "#f3f3f3"
    android:orientation= "Vertical" >
</LinearLayout>

Fragment_2.xml (black background)

<?xml version= "1.0" encoding= "Utf-8"?>
<linearlayout xmlns:android= "Http://schemas.android.com/apk/res/android"
    Android:layout_width= "Match_parent"
    android:layout_height= "Match_parent"
    Android:background= "#000000"
    android:orientation= "Vertical" >
</LinearLayout>

Main.java
In the button click event:
　　

Fragmentmanager Fragmentmanager = Getfragmentmanager ();//
Fragmenttransaction transaction = Fragmentmanager.begintransaction ();
Transaction.replace (R.id.content, fragment_1);
Transaction.commit ();

Using fragment to add the bottom navigation bar