约束布局中的 dp 和 wrap_content

Question

What is the difference between 0 dp and wrap_content when using Constraint Layout? Is it an efficiency problem? I have already tried using them both but I just don't understand which is the difference.

Answer 1

Actually 0dp takes full width/height in it constrained areas whereas wrap_content takes whatever it's required to hold it's content.

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    android:padding="16dp">


    <Button
        android:id="@+id/button_wrap"
        android:text="Wrap Button"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>


    <Button
        android:id="@+id/button_0dp"
        android:text="0dp Button"
        app:layout_constraintTop_toBottomOf="@+id/button_wrap"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_width="0dp"
        android:layout_height="wrap_content"/>

</androidx.constraintlayout.widget.ConstraintLayout>

Output:

In the above example

• Button with wrap_content takes only the space that required to hold Wrap Button whereas
• Button with 0dp takes all the space in it's constrained areas

Answer 2

The main difference is that the wrap_content will take only into account its size, and it won't use the constraints attached to it.

With the 0dp the constraints will be used.

Answer 3

Wrap content mainly take exact space which it need and 0dp width means that in width side it less than 0dp size. Better understand just change width size i mean 0 to upper value