Center, there are two different layout of the center! They are LinearLayout and RelativeLayout.

1. The first thing to say is the center under LinearLayout layout:

Note: In the android: layout_width= “fill_parent” android: layout_height= “fill_parent” attribute, if the level is centered, it will occupy at least the full screen in width; If vertically centered, it occupies full screen in height

<LinearLayout
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:gravity="center|center_horizontal|center_vertical" >
  //  Above gravity Parameters of the property: center For the center, center_horizontal Is horizontally centered, center_vertical Is vertically centered
  <Button
    android:id="@+id/Binding_button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text=" Associate a new account " />
</LinearLayout>

2. Then we talk about the center under the RelativeLayout layout:

<RelativeLayout xmlns:Android="http://schemas.android.com/apk/res/android"
  Android:layout_width="fill_parent" Android:layout_height="fill_parent">
  <Button Android:id="@+id/btngal" Android:layout_width="wrap_content"
    Android:layout_height="wrap_content" Android:gravity="center_horizontal"
    Android:textSize="20sp" Android:layout_alignParentBottom="true"
    Android:layout_centerHorizontal="true" Android:text=" Return to the main interface " />
</RelativeLayout>

Brief description

Android: gravity= “CENTER_VERTICAL”: This is vertical center alignment

Android: gravity= “BOTTOM”: At the bottom of the container

Android: gravity= “CENTER”: In the center of the container

3. 1 Method with two buttons in the center of the row

Method 1:

<LinearLayout android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal"
  style="@android:style/ButtonBar">

<Button android:id="@+id/btn_listview"
  android:layout_height="wrap_content"
  android:layout_width="0dp"
  android:layout_weight="1"
  android:text="ListView"/>

<Button android:id="@+id/btn_emptyview"
  android:layout_height="wrap_content"
  android:layout_width="0dp"
  android:layout_weight="1"
  android:text="EmptyView"/>
</LinearLayout>

Method 2:

<RelativeLayout android:id="@+id/relativeTop"
  android:layout_width="fill_parent" android:layout_height="wrap_content"
  android:layout_centerHorizontal="true" >
  <Button
    android:id="@+id/btnGetMp3s"
    android:text="@string/strGetMp3List"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:layout_toLeftOf="@id/txtHide" />
  <TextView android:id="@+id/txtHide" android:layout_width="25" android:layout_height="1"
    android:layout_centerHorizontal="true" />
  <Button
    android:id="@+id/btnExitSys"
    android:text="@string/strExitSys"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_toRightOf="@id/txtHide" />
</RelativeLayout>