In this tutorial, we’ll be discussing CoordinatorLayout in our Android Application using Kotlin.

在本教程中，我们将使用Kotlin在Android应用程序中讨论CoordinatorLayout。

CooridinatorLayout (CooridinatorLayout)

We have discussed FrameLayouts in the past.
CoordinatorLayout is super-powered FrameLayouts with more properties.
Properties such as:

过去我们讨论过FrameLayouts 。
CoordinatorLayout是具有更多属性的超级功能FrameLayouts。
属性例如：

• Setting certain behaviors on the layout based on actions performed on the views.根据对视图执行的操作在布局上设置某些行为。
• Setting views dependent on one another based on certain actions. One view acts as the layout_anchor of the other. This way we can define how one view changes when another is changed.根据某些操作设置相互依赖的视图。 一个视图充当另一个视图的layout_anchor。 这样，我们可以定义一个视图在另一个视图改变时如何改变。

• • Create a fresh new android studio project and choose Basic Activity Type. Do not forget to enable Kotlin Support!

    创建一个全新的android studio项目，然后选择基本活动类型。 不要忘记启用Kotlin支持！

    In your layout folder, you’ll have two files activity_main.xml and content_main.xml.
    content_main.xml is a part of the activity_main.xml layout and is included using the <include> tag

    在布局文件夹中，将有两个文件activity_main.xml和content_main.xml 。
    content_main.xml是activity_main.xml布局的一部分，并包含在<include>标签中

    Following is how each of these XML layouts look like:

    以下是每个XML布局的外观：

    activity_main.xml

    

    activity_main.xml

    The CoordinatorLayout by default consists of an AppBarLayout and a FloatingActionButton.
    These are a part of the material design support library.

    默认情况下，CoordinatorLayout由AppBarLayout和FloatingActionButton组成。
    这些是材料设计支持库的一部分。

    AppBarLayout (AppBarLayout)

    The AppBarLayout is used to hold the Toolbar. Those the Toolbar would animate the way the AppBarLayout would want it to.
    AppBarLayout in itself is a vertical LinearLayout.
    To provide it’s child views the desired scrolling behaviour, we need to set the app:layout_scrollFlags on the child view.

    AppBarLayout用于保存工具栏。 那些工具栏将使AppBarLayout想要的方式具有动画效果。
    AppBarLayout本身是垂直的LinearLayout。
    为了向子视图提供所需的滚动行为，我们需要在子视图上设置app：layout_scrollFlags。

    app:layout_scrollFlags can be set on the Toolbar. It can have the following properties,

    app：layout_scrollFlags可以在工具栏上设置。 它可以具有以下属性，

    • scroll: This flag is generally set for all views that need to scroll off-screen. Views that don’t use this flag remain static allowing the other scrollable views to slide behind itscroll ：通常为需要在屏幕外滚动的所有视图设置此标志。 不使用此标志的视图保持静态，从而允许其他可滚动视图在其后滑动
    • enterAlways: This flag ensures that any downward scroll will cause the view to become visible, enabling the quick return patternenterAlways ：此标志确保任何向下滚动都将导致视图变为可见，从而启用快速返回模式
    • enterAlwaysCollapsed: An additional flag for ‘enterAlways’ which modifies the returning view to only initially scroll back to it’s collapsed height.enterAlwaysCollapsed ：'enterAlways'的附加标志，用于修改返回的视图，使其仅最初滚动回到其折叠高度。
    • exitUntilCollapsed: This flag causes the view to be scrolled until it is collapsed (its minHeight is reached) before exitingexitUntilCollapsed ：此标志导致视图在退出之前一直滚动到其合拢（达到其minHeight）为止
    • snap: Upon a scroll ending, if the view is only partially visible then it will be snapped and scrolled to it’s the closest edge. Hence this avoids mid-animation states of a viewsnap ：滚动结束后，如果视图仅部分可见，则将对其进行捕捉并滚动到最接近的边缘。 因此，这避免了视图的中期动画状态

    content_main.xml

    content_main.xml

    Ignore the ConstraintLayout for now. We’ll discuss it in a later tutorial.
    Notice the app:layout_behavior="@string/appbar_scrolling_view_behavior".
    Its the standard scrolling behaviour that scrolls the content underneath the AppBarLayout.

    现在忽略ConstraintLayout。 我们将在以后的教程中进行讨论。
    注意app:layout_behavior="@string/appbar_scrolling_view_behavior" 。
    它是在AppBarLayout下面滚动内容的标准滚动行为。

    Back to the activity_main.xml let’s look at some of the important XML Attributes

    回到activity_main.xml，让我们看一些重要的XML属性

    重要的XML属性 (Important XML Attributes)

    android:layout_gravity : Specifies the gravity of the child view relative to the parent.
    If app_layoutAnchorGravity is used then the layout_gravity attribute would set the gravity relative to the anchor view.
    app:layout_anchor is used to set the anchor view on the current child. The view would be positioned relatively.

    android:layout_gravity ：指定子视图相对于父视图的重力。
    如果使用app_layoutAnchorGravity ，则layout_gravity属性将设置相对于锚视图的重力。
    app:layout_anchor用于设置当前子项的锚点视图。 该视图将相对放置。

    app:layout_insetEdge is used to set insets on the view. That locks the certain space for the view.
    app:layout_dodgeInsetEdges is used to set whether the view is willing to move away from it’s one side when needed. We can pass start, end, top or bottom.

    app:layout_insetEdge用于设置视图上的插图。 这样就为视图锁定了一定的空间。
    app:layout_dodgeInsetEdges用于设置视图在需要时是否愿意从一侧移开。 我们可以传递开始，结束，顶部或底部。

    FloatingActionButton has a default layout behaviour where it shifts up to give space to the SnackBar when pressed.
    FloatingActionButton具有默认的布局行为，该行为会在按下时向上移动以为SnackBar留出空间。

    layout_insetEdge和layout_dodgeInsetEdges (layout_insetEdge and layout_dodgeInsetEdges)

    Let’s add another button in our activity_main.xml CoordinatorLayout.

    让我们在activity_main.xml CoordinatorLayout中添加另一个按钮。

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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"><android.support.design.widget.AppBarLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:theme="@style/AppTheme.AppBarOverlay"><android.support.v7.widget.Toolbarandroid:id="@+id/toolbar"android:layout_width="match_parent"android:layout_height="?attr/actionBarSize"android:background="?attr/colorPrimary"app:popupTheme="@style/AppTheme.PopupOverlay" /></android.support.design.widget.AppBarLayout><include layout="@layout/content_main" /><android.support.design.widget.FloatingActionButtonandroid:id="@+id/fab"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="bottom|end"android:layout_margin="@dimen/fab_margin"app:srcCompat="@android:drawable/ic_dialog_email" /><Buttonandroid:layout_width="wrap_content"android:text="WATCH ME"android:layout_gravity="bottom|start"android:layout_height="wrap_content" /></android.support.design.widget.CoordinatorLayout>

As you see the Button is hidden and the SnackBar is displayed over it.
To overcome this issue change the button to:

如您所见，按钮是隐藏的，并且SnackBar显示在其上方。
要解决此问题，请将按钮更改为：

<Buttonandroid:layout_width="wrap_content"android:text="WATCH ME"android:layout_gravity="bottom|start"app:layout_dodgeInsetEdges="bottom"android:layout_height="wrap_content" />

So app:layout_dodgeInsetEdges is set to bottom which displaces the bottom side of the button from its position when the Snackbar is displayed.

因此，将app:layout_dodgeInsetEdges设置为bottom，这将在显示Snackbar时将按钮的底部从其位置移开。

layout_anchor和layout_anchor重力 (layout_anchor and layout_anchorGravity)

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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"><android.support.design.widget.FloatingActionButtonandroid:id="@+id/fab"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="center"android:layout_margin="@dimen/fab_margin" /><android.support.design.widget.FloatingActionButtonandroid:id="@+id/fab1"android:layout_width="wrap_content"android:layout_height="wrap_content"app:layout_anchor="@id/fab"app:layout_anchorGravity="left|top"android:layout_margin="@dimen/fab_margin" /><android.support.design.widget.FloatingActionButtonandroid:id="@+id/fab2"android:layout_width="wrap_content"android:layout_height="wrap_content"app:layout_anchor="@id/fab1"app:layout_anchorGravity="end|top"android:layout_margin="@dimen/fab_margin" /><android.support.design.widget.FloatingActionButtonandroid:id="@+id/fab3"android:layout_width="wrap_content"android:layout_height="wrap_content"app:layout_anchor="@id/fab2"android:layout_gravity="top"app:layout_anchorGravity="end|top"android:layout_margin="@dimen/fab_margin" /></android.support.design.widget.CoordinatorLayout>

With this, we’ve covered all the major XML Attributes present in a CoordinatorLayout.

至此，我们涵盖了CoordinatorLayout中存在的所有主要XML属性。

The MainActivity.kt is unchanged and looks like the following:

MainActivity.kt保持不变，如下所示：

This brings an end to this tutorial. You can download the project from the link below:

本教程到此结束。 您可以从下面的链接下载项目：

翻译自: https://www.journaldev.com/37765/android-coordinatorlayout-using-kotlin