所以这个问题可能类似，但这不能回答我的问题＆＃34; why to import React＆＃34;
我们何时使用<layout 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">
<data>
<import type="android.view.View" />
<variable
name="viewmodel"
type="br.com.gzvr.zavipro.login.LoginViewModel" />
</data>
<ScrollView
android:id="@+id/scroll_root"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true"
android:focusableInTouchMode="true">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView
android:id="@+id/imageViewLogo"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="23dp"
android:contentDescription="@string/cd_app_logo"
app:layout_constraintBottom_toTopOf="@id/txtViewLayoutLoginMail"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.5"
app:layout_constraintVertical_chainStyle="packed"
app:srcCompat="@drawable/img_app_logo" />
<TextView
android:id="@+id/txtViewLayoutLoginMail"
android:layout_width="@dimen/login_fields_width"
android:layout_height="wrap_content"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
android:lineSpacingExtra="3sp"
android:paddingLeft="4dp"
android:paddingRight="4dp"
android:text="@string/edit_login_mail"
android:textAllCaps="true"
android:textColor="@color/accent_grey"
android:textSize="13sp"
app:fontFamily="@font/opensans_semibold"
app:layout_constraintBottom_toTopOf="@+id/inputLayoutLoginMail"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/imageViewLogo" />
<android.support.design.widget.TextInputLayout
android:id="@+id/inputLayoutLoginMail"
android:layout_width="@dimen/login_fields_width"
android:layout_height="wrap_content"
android:layout_marginBottom="32dp"
android:layout_marginEnd="16dp"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
android:layout_marginStart="16dp"
android:hint="@string/edit_login_mail_hint"
android:errorText="@{viewmodel.emailError}"
app:hintTextAppearance="@style/LoginTextInputLayoutAppearence"
app:layout_constraintBottom_toTopOf="@+id/txtViewLayoutLoginPass"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/txtViewLayoutLoginMail"
tools:hintEnabled="false"
tools:ignore="RtlSymmetry">
<AutoCompleteTextView
android:id="@+id/completeLoginMail"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/cd_empty"
android:imeOptions="flagNoExtractUi"
android:inputType="text"
android:items="@{viewmodel.cachedAccounts}"
android:text="@={viewmodel.email}"
app:fontFamily="@font/roboto_regular"
tools:text="user@mail.nil" />
</android.support.design.widget.TextInputLayout>
<TextView
android:id="@+id/txtViewLayoutLoginPass"
android:layout_width="@dimen/login_fields_width"
android:layout_height="wrap_content"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
android:lineSpacingExtra="3sp"
android:paddingLeft="4dp"
android:paddingRight="4dp"
android:text="@string/edit_login_pass"
android:textAllCaps="true"
android:textColor="@color/accent_grey"
android:textSize="13sp"
app:fontFamily="@font/opensans_semibold"
app:layout_constraintBottom_toTopOf="@+id/inputLayoutLoginPass"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/inputLayoutLoginMail"
app:layout_constraintVertical_chainStyle="packed" />
<android.support.design.widget.TextInputLayout
android:id="@+id/inputLayoutLoginPass"
android:layout_width="@dimen/login_fields_width"
android:layout_height="wrap_content"
android:layout_marginBottom="32dp"
android:layout_marginEnd="16dp"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
android:layout_marginStart="16dp"
android:errorText="@{viewmodel.passwordError}"
app:hintTextAppearance="@style/LoginTextInputLayoutAppearence"
app:layout_constraintBottom_toTopOf="@+id/buttonLoginMain"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/txtViewLayoutLoginPass"
tools:hintEnabled="false"
tools:ignore="RtlSymmetry">
<android.support.design.widget.TextInputEditText
android:id="@+id/editLoginPass"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:imeOptions="flagNoExtractUi|actionDone"
android:inputType="textPassword"
android:paddingEnd="45dp"
android:hint="@string/edit_login_pass_hint"
android:paddingRight="45dp"
android:text="@={viewmodel.password}"
app:fontFamily="@font/roboto_regular"
tools:ignore="RtlSymmetry"
tools:text="strong" />
</android.support.design.widget.TextInputLayout>
<ImageButton
android:id="@+id/imageButtonPasswordVisibility"
android:layout_width="38dp"
android:layout_height="38dp"
android:background="?android:attr/selectableItemBackground"
android:contentDescription="@string/cd_image_view_password_visibility"
android:padding="8dp"
app:layout_constraintEnd_toEndOf="@+id/inputLayoutLoginPass"
app:layout_constraintTop_toTopOf="@+id/inputLayoutLoginPass"
app:srcCompat="@drawable/ic_visibility_24dp" />
<ImageView
android:id="@+id/imageViewProgress"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_margin="2dp"
app:layout_constraintBottom_toBottomOf="@+id/buttonLoginMain"
app:layout_constraintLeft_toLeftOf="@+id/buttonLoginMain"
app:layout_constraintRight_toRightOf="@+id/buttonLoginMain"
app:layout_constraintTop_toTopOf="@+id/buttonLoginMain"
app:srcCompat="@drawable/ic_circle_progress_for_button" />
<Button
android:id="@+id/buttonLoginMain"
style="@style/GZVRNormalBlueButton"
android:layout_width="@dimen/login_fields_width"
android:layout_height="wrap_content"
android:layout_marginBottom="24dp"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
android:layout_marginTop="4dp"
android:enabled="@{viewmodel.validFields && !viewmodel.isPostingLogin}"
android:text="@string/button_login_main_text"
app:fontFamily="@font/opensans_semibold"
app:layout_constraintBottom_toTopOf="@+id/txtViewResetMyPass"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/inputLayoutLoginPass" />
<TextView
android:id="@+id/txtViewResetMyPass"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="?android:attr/selectableItemBackground"
android:focusable="true"
android:gravity="center_horizontal"
android:lineSpacingExtra="6sp"
android:padding="8dp"
android:text="@string/text_login_forgot_password"
android:textColor="@color/primary"
android:textSize="14sp"
app:fontFamily="@font/opensans_semibold"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/buttonLoginMain" />
</android.support.constraint.ConstraintLayout>
</ScrollView>
</layout>
？
我见过某些功能组件示例，其中人们传递道具并且不使用JSX。
道具可能从父母传给孩子，因此他们不需要编写导入但是JSX是使用导入功能组件的唯一原因吗？
类似地，当我们需要使用生命周期钩子并添加状态时，我们使用了有状态组件import React from react？
答案 0 :(得分：1)
React必须在Babel的范围内才能发挥其魔力，因此您必须导入React或以某种方式将其声明为全局变量。