constraint doesn't show in the activity_main.xml（solution added）

Question

Solution: Android Studio does not show layout preview

Hi there！I created a new project and the constraint as well as the textfild("hello world") didn't show in activity_main.xml. Is there something special need to setup？

Thanks guys!Finally,I found the solution here: Android Studio does not show layout preview

<?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"
tools:context=".MainActivity">

<TextView
    android:id="@+id/textView"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:text="Hello World"
    android:textAppearance="@android:style/TextAppearance.DeviceDefault.Widget.TextView"
    android:textColor="@color/colorAccent"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

click to view the image

There is a yellow (!) mark next to your TextView, I think there might be some 'missing constraint'. Of course it will be better if you can paste your xml code — Wesely, Jun 20 '18 at 03:57
Please show that XML file to more understand. Otherwise restart the android studio. — Prince Dholakiya, Jun 20 '18 at 04:42

manitaz · Answer 1 · 2018-06-20T04:18:43.297

In your xml layout_width = "0dp" please use it to value or change it to android:layout_width="wrap_content" like below

<?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"
tools:context=".MainActivity">

<TextView
    android:id="@+id/textView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World"
    android:textAppearance="@android:style/TextAppearance.DeviceDefault.Widget.TextView"
    android:textColor="@color/colorAccent"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

score -1 · Answer 2 · answered Jun 20 '18 at 10:42

<?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"
    tools:context=".MainActivity">

     <TextView
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="Hello World!"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintLeft_toLeftOf="parent"
         app:layout_constraintRight_toRightOf="parent"
         app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

above code is main_activity.xml

and theme look like....

<resources>

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
</style>

constraint doesn't show in the activity_main.xml（solution added）

2 Answers2