Set width to match constraints in ConstraintLayout

Solution 1:

match_parent is not allowed. But you can actually set width and height to 0dp and set either top and bottom or left and right constraints to "parent".

So for example if you want to have the match_parent constraint on the width of the element, you can do it like this:

<TextView
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintEnd_toEndOf="parent"/>

Solution 2:

match_parent is not supported, so use android:layout_width="0dp". With 0dp, you can think of your constraints as 'scalable' rather than 'filling whats left'.

Also, 0dp can be defined by a position, where match_parent relies on it's parent for it's position (x,y and width, height)

Solution 3:

Apparently match_parent is :

• NOT OK for views directly under ConstraintLayout
• OK for views nested inside of views that are directly under ConstraintLayout

So if you need your views to function as match_parent, then:

1. Direct children of ConstraintLayout should use 0dp
2. Nested elements (eg, grandchild to ConstraintLayout) can use match_parent

Example:

<android.support.constraint.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingBottom="16dp">

    <android.support.design.widget.TextInputLayout
        android:id="@+id/phoneNumberInputLayout"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent">

        <android.support.design.widget.TextInputEditText
            android:id="@+id/phoneNumber"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

    </android.support.design.widget.TextInputLayout>

Solution 4:

From the official doc:

Important: MATCH_PARENT is not recommended for widgets contained in a ConstraintLayout. Similar behavior can be defined by using MATCH_CONSTRAINT with the corresponding left/right or top/bottom constraints being set to "parent".

So if you want achieve MATCH_PARENT effect, you can do this:

<TextView
    android:id="@+id/textView"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text="TextView"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent" />