There is an error popping when i am trying to set layout width and height in xml file

Question

When setting the layout height and width, android studio is showing an error that attribute

android:layout_height and android:layout_width is not allowed here respectively.

And also setting TextView is showing error:-

Element TextView is not allowed here.

I have read and tried the answers of Element LinearLayout is not allowed in CardView but it did not helped.

I have checked for any extra opening or closing brackets but there is none. Is there problem in the gradle.build file? I have checked but it looks fine.

Here is the code in activity__main.xml file.

<?xml version="1.0" encoding="utf-8"?>

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="16dp"
        android:textSize="20sp" />

</FrameLayout>

Here is the code of build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25

    defaultConfig {
        applicationId "com.android.example.favoritetoys"
        minSdkVersion 10
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:25.1.0'
}