Android TextInputLayout transitionName 和 transitionGroup - 目的是什么？

Question

我正在查看 firebaseUI auth project

我看到一些 TextInputLayouts 引用了 transitionName 和 transitionGroup 但我在网上找不到任何东西来帮助我理解如何使用它们以及真正的目的是什么:

这里有一个例子，请看android.support.design.widget.TextInputLayout的:

    <?xml version="1.0" encoding="utf-8"?>
<ScrollView
    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:fillViewport="true"
    android:layout_height="match_parent">

    <RelativeLayout
        style="@style/FirebaseUI.WrapperStyle">

        <TextView
            android:id="@+id/tv_title"
            fontPath="fonts/Medium-Extd.otf"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="30dp"
            android:layout_marginBottom="60dp"
            android:text="@string/fui_welcome"
            android:textAllCaps="true"
            android:focusable="false"
            android:clickable="false"
            android:textColor="#ffffff"
            android:layout_centerHorizontal="true"
            android:textSize="14sp"
            android:textStyle="bold"
            tools:ignore="MissingPrefix"
            tools:text="welcome" />

        <android.support.design.widget.TextInputLayout
            android:id="@+id/email_layout"
            style="@style/FirebaseUI.TextInputLayout.EmailField"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:transitionGroup="true"
            android:transitionName="@string/fui_email_field_name"
            android:layout_below="@+id/tv_title"
            app:errorEnabled="true"
            tools:ignore="UnusedAttribute">

            <android.support.design.widget.TextInputEditText
                android:id="@+id/email"
                android:textColor="@color/fui_white"
                tools:text="johndoe@msn.com"
                style="@style/FirebaseUI.TextInputEditText.EmailField" />

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

        <android.support.design.widget.TextInputLayout
            android:id="@+id/name_layout"
            android:layout_below="@+id/email_layout"
            style="@style/FirebaseUI.TextInputLayout.NameField"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="30dp"
            app:errorEnabled="true">

            <android.support.design.widget.TextInputEditText
                android:id="@+id/name"
                style="@style/FirebaseUI.TextInputEditText.NameField"
                android:layout_width="match_parent"
                tools:text="john doe"
                android:maxLines="1"
                android:layout_height="wrap_content" />

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

        <android.support.design.widget.TextInputLayout
            android:id="@+id/password_layout"
            style="@style/FirebaseUI.TextInputLayout.PasswordField"
            android:layout_width="match_parent"
            android:layout_below="@id/name_layout"
            android:layout_height="wrap_content"
            android:layout_marginTop="@dimen/fui_field_padding_vert"
            app:errorEnabled="true"
            app:passwordToggleTint="@color/fui_white"
            app:passwordToggleEnabled="true">

            <android.support.design.widget.TextInputEditText
                android:id="@+id/password"
                tools:text="123456789"
                style="@style/FirebaseUI.TextInputEditText.PasswordField" />

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

        <TextView
            android:id="@+id/create_account_text"
            style="@style/FirebaseUI.Text.BodyText"
            android:focusable="false"
            android:layout_below="@+id/password_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="@dimen/fui_field_padding_vert"
            android:textIsSelectable="false"
            tools:text="@string/fui_create_account_preamble_tos_and_pp" />

        <Button
            android:id="@+id/button_create"
            style="@style/FirebaseUI.Button"
            android:layout_width="match_parent"
            android:layout_height="43dp"
            android:text="@string/fui_signup"
            tools:text="sign up"
            fontPath="fonts/Medium-Extd.otf"
            android:textColor="@color/fui_black"
android:layout_below="@id/create_account_text"
            tools:ignore="MissingPrefix,RtlHardcoded" />

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|center_horizontal"
            app:srcCompat="@drawable/fui_mylogo"
            android:layout_centerHorizontal="true"
            android:layout_alignParentBottom="true"
            />
    </RelativeLayout>

</ScrollView>

我试过不使用它们，但我仍然无法确定它的作用。

Answer 1

它们都处理共享元素转换。 Transition 包含有关在场景更改期间将在其目标上运行的动画的信息。基于文档:

transitionName

The name used of the View to be used to identify Views in Transitions or null if no name has been given.

它基本上是您的 View 的名称，将在转换期间用于识别目的。

是过渡组

Whether or not the ViewGroup should be treated as a unit in Activity transitions. If false, the ViewGroup won't transition, only its children. If true, the entire ViewGroup will transition together.

它确定是否应将 Transition 特性作为整个 ViewGroup 强加于该组的子级。