找不到元素“android.support.constraint.ConstraintLayout"的声明 [英] Cannot find the declaration of element 'android.support.constraint.ConstraintLayout'

问题描述

我创建了一个名为 activity_main(sw50dp) 的 xml 文件，但是当我尝试验证它时，它给了我错误:

<块引用>

错误:(4, 42) cvc-elt.1.a:找不到元素android.support.constraint.ConstraintLayout"的声明.

和

C:\Program Files\Android\Android Studio\lib\idea.jar!\standardSchemas\xhtml1.dtd错误:(26, 3) 文档中根元素之前的标记必须格式正确.

activity_main 文件

<按钮android:id="@+id/buttonDiv"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginStart="320dp"android:layout_marginTop="340dp"android:background="@drawable/circle"机器人:文本=÷"应用程序:layout_constraintEnd_toEndOf="父"应用程序:layout_constraintRight_toRightOf="parent"app:layout_constraintTop_toTopOf="parent"/><按钮android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginEnd="220dp"android:layout_marginStart="100dp"android:background="@drawable/椭圆"机器人:文本=2"应用程序:layout_constraintLeft_toRightOf="@+id/button1"应用程序:layout_constraintStart_toEndOf="@+id/button1"app:layout_constraintTop_toTopOf="@+id/button1"/><按钮android:id="@+id/button1"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginEnd="320dp"机器人:layout_marginRight="0dp"android:layout_marginTop="118dp"android:background="@drawable/椭圆"机器人:文本=1"应用程序:layout_constraintLeft_toLeftOf="parent"应用程序:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent"/><按钮android:id="@+id/buttonReset"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginEnd="320dp"机器人:layout_marginRight="0dp"android:layout_marginTop="45dp"android:background="@drawable/椭圆"机器人:文本=C"应用程序:layout_constraintLeft_toLeftOf="parent"应用程序:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent"/><文本视图android:id="@+id/textNum"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginEnd="100dp"android:layout_marginStart="100dp"<按钮android:id="@+id/button5"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginEnd="220dp"android:layout_marginStart="100dp"android:background="@drawable/椭圆"</android.support.constraint.ConstraintLayout>

activity_main(sw50dp) 文件

我还创建了其他布局文件，例如 activity_main(normal-land).我对他们没有任何问题.

解决方案

注意:如果资源目录名称不正确，可能会发生此错误.

创建目录名称的最佳过程:

1. 正在做:文件 -> 新建 -> Android 资源目录
2. 选择:最小屏幕宽度
3. 点击>>"并输入[浸入次数]

此外，将这一行添加到 Gradle 文件中可以解决类似的错误:

<预><代码>依赖{...实现 'com.android.support.constraint:constraint-layout:1.1.0'}

接着是重新同步.

I have created an xml file called activity_main(sw50dp), but when I try to validate it, it gives me the errors:

Error:(4, 42) cvc-elt.1.a: Cannot find the declaration of element 'android.support.constraint.ConstraintLayout'.

and

C:\Program Files\Android\Android Studio\lib\idea.jar!\standardSchemas\xhtml1.dtd

Error:(26, 3) The markup in the document preceding the root element must be well-formed.

activity_main file

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
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:layout_height="match_parent"
android:background="@drawable/images"
tools:context=".MainActivity">

<Button
    android:id="@+id/buttonDiv"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginStart="320dp"
    android:layout_marginTop="340dp"
    android:background="@drawable/circle"
    android:text="÷"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<Button

    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginEnd="220dp"
    android:layout_marginStart="100dp"
    android:background="@drawable/oval"
    android:text="2"
    app:layout_constraintLeft_toRightOf="@+id/button1"
    app:layout_constraintStart_toEndOf="@+id/button1"
    app:layout_constraintTop_toTopOf="@+id/button1" />

<Button
    android:id="@+id/button1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginEnd="320dp"
    android:layout_marginRight="0dp"
    android:layout_marginTop="118dp"
    android:background="@drawable/oval"
    android:text="1"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<Button
    android:id="@+id/buttonReset"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginEnd="320dp"
    android:layout_marginRight="0dp"
    android:layout_marginTop="45dp"
    android:background="@drawable/oval"
    android:text="C"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<TextView
    android:id="@+id/textNum"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginEnd="100dp"
    android:layout_marginStart="100dp"


<Button
    android:id="@+id/button5"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginEnd="220dp"
    android:layout_marginStart="100dp"
    android:background="@drawable/oval"


</android.support.constraint.ConstraintLayout>

activity_main(sw50dp) file

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">

I have created other layout files as well for example activity_main(normal-land). I didn't have any problems with them.

解决方案

Note: This error can happen if the resource directory name is incorrect.

Best procedure for creating the directory name:

1. Doing: File -> New -> Android Resource Directory
2. Choose: Smallest Screen Width
3. Tap ">>" and enter [The number of dips]

Also, adding this line to the Gradle file solves similar errors:

dependencies {
    ...
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
}

Followed by a resync.

Constraint Layout Versions

Google Constraint Layout Sample

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