android studio项目中没有dimens.xml

Question

I have installed Android Studio 2.2.2 on my laptop. Then I updated it recently. But when I create an empty project, there is no dimens.xml on the project. Whereas when I used Android Studio 2.2.2 there is a dimens directory (with 2 dimens.xml). What happen to my Android Studio?

Answer 1

Your Android Studio is fine. From 2.3, the default Activity layout templates have a ConstraintLayout as their root element with no margins applied to it. In the old templates, this used to be a RelativeLayout with its margins set as resource values in dimens.xml . Since these values are no longer in the default layout file, an empty dimens.xml is not created in the project by default.

If you need a dimens.xml , you can just create one under the res/values folder with New -> Values resource file .

---

For reference, the old default layout that used dimens resources:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.package.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

</LinearLayout>

And the new default that doesn't:

<?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="com.example.package.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>