按钮不在RelativeLayout内，其中gravity = center

Question

I have a button inside relative layout that I want to center along with input edit text. I added android:gravity="center" to relative layout, every was centered correctly other than the button, I even tried to add android:layout_centerInParent="true" to the button but it didn't work. What could be the issue?

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent" android:layout_gravity="bottom">

<ImageView
    android:id="@+id/imageView"
    android:src="@drawable/logo"
    android:layout_weight=".3"
    android:layout_width="wrap_content"
    android:layout_height="0dp"
    android:layout_marginTop="10dp"
    android:layout_gravity="center_horizontal"/>


<RelativeLayout
    android:layout_weight=".1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center">

    <EditText
        android:id="@+id/et_email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:inputType="textEmailAddress"
        android:ems="10"
        android:hint="Email"/>

    <EditText
        android:id="@+id/et_password"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et_email"
        android:inputType="textPassword"
        android:hint="Password"
        android:ems="10"
        android:layout_marginBottom="20dp"
        android:imeOptions="actionDone"/>

    <Button
        android:id="@+id/b_login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et_password"
        android:text="Login"/>

</RelativeLayout>


<View
    android:layout_weight=".1"
    android:layout_width="match_parent"
    android:layout_height="0dp"/>

Button is not centered:

Answer 1

android:gravity="center" is a property of LinearLayout so its direct child (the RelativeLayout ) inside of it. You still need to center the children inside the RelativeLayout . To center the Button inside of its parent RelativeLayout use android:layout_centerHorizontal="true"

<Button
    android:id="@+id/b_login"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/et_password"
    android:text="Login"
    android:layout_centerHorizontal="true"/>   // here

Docs

Update

Center each View inside of the RelativeLayout

 <RelativeLayout
android:layout_weight=".1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center">

<EditText
    android:id="@+id/et_email"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="10dp"
    android:inputType="textEmailAddress"
    android:ems="10"
    android:hint="Email"
    android:layout_centerHorizontal="true"/>

<EditText
    android:id="@+id/et_password"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/et_email"
    android:inputType="textPassword"
    android:hint="Password"
    android:ems="10"
    android:layout_marginBottom="20dp"
    android:imeOptions="actionDone"
    android:layout_centerHorizontal="true"/>

<Button
    android:id="@+id/b_login"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/et_password"
    android:text="Login"
    android:layout_centerHorizontal="true"/>

Answer 2

Try this.. Use LinearLayout instead of RelativeLayout

<LinearLayout
    android:layout_weight=".1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:gravity="center">

    <EditText
        android:id="@+id/et_email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:inputType="textEmailAddress"
        android:ems="10"
        android:hint="Email"/>

    <EditText
        android:id="@+id/et_password"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et_email"
        android:inputType="textPassword"
        android:hint="Password"
        android:ems="10"
        android:layout_marginBottom="20dp"
        android:imeOptions="actionDone"/>

    <Button
        android:id="@+id/b_login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et_password"
        android:text="Login" />

</LinearLayout>

OR in Your same layout just remove android:gravity="center" add android:layout_centerHorizontal="true" for each EditText and Button

<RelativeLayout
    android:layout_weight=".1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <EditText
        android:id="@+id/et_email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:inputType="textEmailAddress"
        android:layout_centerHorizontal="true"
        android:ems="10"
        android:hint="Email"/>

    <EditText
        android:id="@+id/et_password"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et_email"
        android:inputType="textPassword"
        android:hint="Password"
        android:layout_centerHorizontal="true"
        android:ems="10"
        android:layout_marginBottom="20dp"
        android:imeOptions="actionDone"/>

    <Button
        android:id="@+id/b_login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et_password"
        android:layout_centerHorizontal="true"
        android:text="Login" />

</RelativeLayout>

Answer 3

Try this code:

    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent" android:layout_gravity="bottom">

<ImageView
    android:id="@+id/imageView"
    android:src="@drawable/logo"
    android:layout_weight=".3"
    android:layout_width="wrap_content"
    android:layout_height="0dp"
    android:layout_marginTop="10dp"
    android:layout_gravity="center_horizontal"/>


<RelativeLayout
    android:layout_weight=".1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center">

    <EditText
        android:id="@+id/et_email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:inputType="textEmailAddress"
        android:ems="10"
        android:hint="Email"/>

    <EditText
        android:id="@+id/et_password"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et_email"
        android:inputType="textPassword"
        android:hint="Password"
        android:ems="10"
        android:layout_marginBottom="20dp"
        android:imeOptions="actionDone"/>

    <Button
        android:id="@+id/b_login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et_password"
    android:layout_gravity="center"
        android:text="Login"/>

</RelativeLayout>


<View
    android:layout_weight=".1"
    android:layout_width="match_parent"
    android:layout_height="0dp"/>