使用Kotlin的Android CoordinatorLayout

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 it

      scroll ：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 pattern

      enterAlways ：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 exiting

      exitUntilCollapsed ：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 view

      snap ：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.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android: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.FloatingActionButton
        android: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" />


    <Button
        android: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：

<Button
        android: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。

Set layout_insetEdges to bottom on the Button and you’ll see that the FloatingActionButton is no longer visible in the same position. This is because the Button locks the bottom part of the layout. 将layout_insetEdges设置为Button的底部，您将看到FloatingActionButton在相同位置不再可见。 这是因为Button锁定了布局的底部。

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.FloatingActionButton
        android: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.FloatingActionButton
        android: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.FloatingActionButton
        android: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.FloatingActionButton
        android: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：

AndroidlyCoordinatorLayout AndroidlyCoordinatorLayout

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