java 什么是 WindowInsets？

What are WindowInsets?

提问by Samvid Mistry

I am trying to learn about the Android OS and while I was reading the Google I/O 2014 app, I came across the WindowInsets. If anyone can explain what they are then it would be a great help. Thank you.

我正在尝试了解 Android 操作系统，在阅读 Google I/O 2014 应用程序时，我遇到了WindowInsets. 如果有人可以解释它们是什么，那么这将是一个很大的帮助。谢谢你。

采纳答案by Henry

You can learn all about WindowInsets here.WindowInsetsprovides you with the area on the window that is usable by the application. By itself it's of not much use. It's true purpose comes when you either override View.onApplyWindowInsetsor implement View.OnApplyWindowInsetsListener. You can read about them here: View.onApplyWindowInsetsand View.OnApplyWindowInsetsListener

您可以在此处了解有关WindowInsets 的所有信息。WindowInsets为您提供应用程序可用的窗口区域。它本身并没有多大用处。当您覆盖View.onApplyWindowInsets或实施时，真正的目的就来了View.OnApplyWindowInsetsListener。你可以在这里阅读它们：View.onApplyWindowInsets和View.OnApplyWindowInsetsListener

Listener for applying window insets on a view in a custom way.

Apps may choose to implement this interface if they want to apply custom policy to the way that window insets are treated for a view. If an OnApplyWindowInsetsListener is set, its onApplyWindowInsets method will be called instead of the View's own onApplyWindowInsets method. The listener may optionally call the parameter View's onApplyWindowInsets method to apply the View's normal behavior as part of its own.

以自定义方式在视图上应用窗口插图的侦听器。

如果应用程序想要将自定义策略应用于处理视图的窗口插图的方式，则它们可以选择实现此接口。如果设置了 OnApplyWindowInsetsListener，则将调用其 onApplyWindowInsets 方法而不是 View 自己的 onApplyWindowInsets 方法。侦听器可以选择调用参数 View 的 onApplyWindowInsets 方法来应用 View 的正常行为作为其自身的一部分。

In short, overriding this will let you control area of the window available for your View.

简而言之，覆盖它将使您可以控制可用于您的视图的窗口区域。

回答by azizbekian

WindowInsetsare insets (or sizes) of system views (e.g. status bar, navigation bar), that are applied to the window.

WindowInsets是应用于窗口的系统视图（例如状态栏、导航栏）的插入（或大小）。

It would be easy to understand on concrete example. Image this scenario:

通过具体的例子很容易理解。想象一下这个场景：

Now, you don't want WindowInsetsto be applied to the background ImageView, because in that case the ImageViewwould be padded by status bar height.

现在，您不想WindowInsets被应用到 background ImageView，因为在这种情况下，ImageView它将被状态栏高度填充。

But you do want insets to be applied to Toolbar, because otherwise Toolbarwould be drawn somewhere mid status bar.

但是您确实希望将插图应用于Toolbar，否则Toolbar会被绘制在状态栏中间的某处。

The view declares a desire to apply WindowInsetsin xml by saying:

该视图通过以下语句声明了WindowInsets在 xml 中应用的愿望：

android:fitsSystemWindows="true"

In this example you cannot apply the WindowInsetsto the root layout, because the root layout would consume WindowInsets, and the ImageViewwould be padded.

在此示例中，您不能将 应用于WindowInsets根布局，因为根布局会消耗WindowInsets，并且ImageView将被填充。

Instead you may use ViewCompat.setOnApplyWindowInsetsListenerto apply insets to toolbar:

相反，您可以使用ViewCompat.setOnApplyWindowInsetsListener将插图应用于工具栏：

ViewCompat.setOnApplyWindowInsetsListener(toolbar, (v, insets) -> {
            ((ViewGroup.MarginLayoutParams) v.getLayoutParams()).topMargin =
                    insets.getSystemWindowInsetTop();
            return insets.consumeSystemWindowInsets();
        });

Note, this callback would be called, when Toolbar's root layout passes WindowsInsetsto its children. Layouts like FrameLayout, LinearLayoutdo not, DrawerLayout, CoordinatorLayoutdo.

请注意，当Toolbar的根布局传递WindowsInsets给其子项时，将调用此回调。布局，如FrameLayout，LinearLayout不DrawerLayout，，CoordinatorLayout做。

You can subclass your layout, e.g. FrameLayoutand override onApplyWindowInsets:

您可以子类化您的布局，例如FrameLayout并覆盖onApplyWindowInsets：

@TargetApi(Build.VERSION_CODES.KITKAT_WATCH)
@Override
public WindowInsets onApplyWindowInsets(WindowInsets insets) {
    int childCount = getChildCount();
    for (int index = 0; index < childCount; index++)
        getChildAt(index).dispatchApplyWindowInsets(insets); // let children know about WindowInsets

    return insets;
}

There's a nice blog post at mediumby Ian Lake concerning this stuff, also "Becoming a master window fitter"presentation by Chris Banes.

Ian Lake在 medium上有一篇关于这些东西的不错的博客文章，还有Chris Banes 的“成为窗户装配大师”的演讲。

I've also created a detailed article at Mediumconcerning WindowInsets.

我还在Medium 上创建了一篇关于WindowInsets的详细文章。

More resources:

更多资源：

• Windows Insets + Fragment Transitions by Chris Banes
• WindowInsets - Listeners to layouts by Chris Banes

• Windows Insets + Fragment Transitions by Chris Banes
• WindowInsets - Chris Banes 的布局监听器