Android Studio 3 - Constraint layout editor is not working

Question

I recently installed android studio 3 but The constraint layout shows a grey window..I tried everything but I couldn't fix the the problem

Thanks in advance for any help provided:

XML code:

<?xml version="1.0" encoding="utf-8"?> 
<android.support.constraint.ConstraintLayout 
    xmlns:android="schemas.android.com/apk/res/android"; 
    xmlns:app="schemas.android.com/apk/res-auto"; 
    xmlns:tools="schemas.android.com/tools"; 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    tools:context="com.example.chihaoui.myapplication.MainActivi‌​ty"> 
</android.support.constraint.ConstraintLayout>

Answer 1

I just helped make the project and earned

example

Answer 2

I had a similar problem. My case is resolved by adding the following lines on app/build.gradle:

implementation 'com.android.support.constraint:constraint-layout:1.1.3'
implementation('com.android.support:appcompat-v7:28.0.0') {
    force = true
}

Note the force = true part.