2024 了， Insets 你不会还不懂吧？

本文主要聚焦于 App 端的 Insets（不是 WMS 端），从以下几个问题入手 Insets 相关的源码。

• 什么是 Insets ？
• Insets 来自哪里
• Insets 如何分发给 View

1. 什么是 Insets ？

Insets 在中文语境中，没有一个特别准确的对应词，Google 的文档以及博客将其翻译为边衬区。

Insets 描述的是显示屏幕上的一些矩形区域，这些区域是系统 UI 所在的区域，常见的有 StatusBar NavigationBar IME（输入法）等

既然是系统 UI，那为什么 App 端还需要去关注 Insets 呢？Activity 如果进行了显示方面的配置，Activity 的显示区域可能就会和 Insets 重叠。

比如我们配置了全屏的主题：

android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen"

或者配置了 window 的全屏 flag：

requestWindowFeature(Window.FEATURE_NO_TITLE);

getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);

那么 Activity 就会从 statusbar 下面开始布局和绘制：

要处理这种 App 界面与系统 UI 界面重叠的情况都需要了解 Insets。

最常见的场景就是沉浸式状态栏，沉浸式状态栏应该是每个 Android App 开发都处理过的恶心需求，不同的系统版本，不同的手机品牌（小米，魅族）都需要单独的适配！！!

我们可以通过 adb shell dumpsys activity 命令可以查看到 Insets 相关的信息：

图片来自 juejin.cn/post/703842…

那么源码中如何表示/描述一个 Insets，在 App 端使用 Insets 类：

public final class Insets implements Parcelable {
    public static final @NonNull Insets NONE = new Insets(0, 0, 0, 0);

    public final int left;
    public final int top;
    public final int right;
    public final int bottom;

    private Insets(int left, int top, int right, int bottom) {
        this.left = left;
        this.top = top;
        this.right = right;
        this.bottom = bottom;
    }

    
}

举个 Insets 对象的实际例子：

图片来自 juejin.cn/post/703842…

这里的 left top right bottom，描述的是一个偏移量，图片中有颜色的区域就是 insets 所在区域。

Insets 有很多类型，比如：

• StatusBar
• NavigationBar
• 系统手势区
• 刘海区
• 输入法
• …….

WindowInsets.Type 类中定义了多个常量来表示 Insets 的类型：

public final class WindowInsets {

    
    public static final class Type {
        static final int FIRST = 1;
        static final int STATUS_BARS = FIRST;

        static final int NAVIGATION_BARS = 1 << 1;
        static final int CAPTION_BAR = 1 << 2;

        static final int IME = 1 << 3;

        static final int SYSTEM_GESTURES = 1 << 4;
        static final int MANDATORY_SYSTEM_GESTURES = 1 << 5;
        static final int TAPPABLE_ELEMENT = 1 << 6;

        static final int DISPLAY_CUTOUT = 1 << 7;

        static final int LAST = 1 << 8;
        static final int SIZE = 9;
        static final int WINDOW_DECOR = LAST;

        private Type() {}

        
    }

    
}

具体每个类型的 Inset 的介绍可以查看官方博客处理视觉冲突 | 手势导航 (二)

2. Insets 来自哪里

2.1 App 中如何获取到 Insets

首先从 App 开发的角度，我们可以通过 View 的 setOnApplyWindowInsetsListener 方法设置一个回调对象来获取到 Insets:

        val main:View = findViewById(R.id.main)
        main.setOnApplyWindowInsetsListener { v, insets ->
            val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
            Log.d("zzh","top is ${systemBars.top}")
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
            insets
        }

如果是通用 App，推荐使用 AndroidX 提供的兼容库来实现：

        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets ->
            val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
            Log.d("zzh","top is ${systemBars.top}")
            insets
        }

setOnApplyWindowInsetsListener 中返回的数据的类型是 WindowInsets。

WindowInset 中有一个成员 private final Insets[] mTypeInsetsMap; 该成员保存了所有的 Insets。

public final class WindowInsets {

    

    private final Insets[] mTypeInsetsMap;

    

    public Insets getInsets(@InsetsType int typeMask) {
        return getInsets(mTypeInsetsMap, typeMask);
    }

    static Insets getInsets(Insets[] typeInsetsMap, @InsetsType int typeMask) {
        Insets result = null;
        for (int i = FIRST; i <= LAST; i = i << 1) {
            if ((typeMask & i) == 0) {
                continue;
            }
            Insets insets = typeInsetsMap[indexOf(i)];
            if (insets == null) {
                continue;
            }
            if (result == null) {
                result = insets;
            } else {
                result = Insets.max(result, insets);
            }
        }
        return result == null ? Insets.NONE : result;
    }

    

}

我们只需要传入一个 WindowInsets.Type 类型，就可以通过 WindowInsets::getInsets 方法获取到具体类型的 Insets 对象。

2.2 获取 InsetsState

那么这里的 Inset 是从哪里来的呢？

在 Activity/Window 的显示过程中，相关的调用链如下：

ViewRootImpl::setView
    ViewRootImpl::requestLayout
        ViewRootImpl::scheduleTraversals             
            ViewRootImpl.TraversalRunnable::run                 -- 异步操作 
                ViewRootImpl::doTraversal
                    ViewRootImpl::performTraversals
                        ViewRootImpl::dispatchApplyInsets       -- 第二步，计算并分发 Insets
                        ViewRootImpl::relayoutWindow
                            mWindowSession::relayout            -- 第三步，获取 InsetsSourceControl
                            InsetsController::onControlsChanged -- 分发 InsetsSourceControl
                        

    Session.addToDisplayAsUser                                  -- 第一步，获取 InsetsState
    InsetsController::onStateChanged                            -- 分发 InsetsState                         

在 addToDisplayAsUser 的时候，会从 wms 中获取到 private final InsetsState mTempInsets

private final InsetsState mTempInsets = new InsetsState();

res = mWindowSession.addToDisplayAsUser(mWindow, mWindowAttributes,
                            getHostVisibility(), mDisplay.getDisplayId(), userId,
                            mInsetsController.getRequestedVisibleTypes(), inputChannel, mTempInsets,
                            mTempControls, attachedFrame, compatScale);

InsetsState 又是什么？

InsetsState 保存了系统中所有的 Insets 的状态/信息

public class InsetsState implements Parcelable {
    
    private final SparseArray mSources;

    
    WindowInsets calculateInsets（...） {
        
    }

    
    
    
    

    
}

InsetsState 内部成员 private final SparseArray mSources; 对应了每一个 Insets。

从 adb shell dumpsys activity 打印的信息可以看出对应关系：

        InsetsSource id=f8ac0001 type=navigationBars frame=[0,2274][1080,2400] visible=true flags= insetsRoundedCornerFrame=false
        InsetsSource id=f8ac0004 type=systemGestures frame=[0,0][0,0] visible=true flags= insetsRoundedCornerFrame=false
        InsetsSource id=f8ac0005 type=mandatorySystemGestures frame=[0,2274][1080,2400] visible=true flags= insetsRoundedCornerFrame=false
        InsetsSource id=f8ac0006 type=tappableElement frame=[0,2274][1080,2400] visible=true flags= insetsRoundedCornerFrame=false
        InsetsSource id=f8ac0024 type=systemGestures frame=[0,0][0,0] visible=true flags= insetsRoundedCornerFrame=false
        InsetsSource id=3 type=ime frame=[0,0][0,0] visible=false flags= insetsRoundedCornerFrame=false
        InsetsSource id=27 type=displayCutout frame=[0,0][1080,128] visible=true flags= insetsRoundedCornerFrame=false
        InsetsSource id=13c0000 type=statusBars frame=[0,0][1080,128] visible=true flags= insetsRoundedCornerFrame=false
        InsetsSource id=13c0005 type=mandatorySystemGestures frame=[0,0][1080,160] visible=true flags= insetsRoundedCornerFrame=false
        InsetsSource id=13c0006 type=tappableElement frame=[0,0][1080,128] visible=true flags= insetsRoundedCornerFrame=false

InsetsSource 的实现如下：

public class InsetsSource implements Parcelable {
    
    private final @InternalInsetsType int mType;    
    private final Rect mFrame;    
    private boolean mVisible;     
    
}

InsetsState 中还有一个重要的方法 calculateInsets，该方法基于 mSources 计算出 windowInsets。这里没有具体的情景，源码我们先不分析。

2.3 获取 InsetsSourceControl

App 在 relayout 的时候，会从 wms 中获取到 InsetsSourceControl.Array mTempControls

 private final InsetsSourceControl.Array mTempControls = new InsetsSourceControl.Array();

            relayoutResult = mWindowSession.relayout(mWindow, params,
                    requestedWidth, requestedHeight, viewVisibility,
                    insetsPending ? WindowManagerGlobal.RELAYOUT_INSETS_PENDING : 0, mRelayoutSeq,
                    mLastSyncSeqId, mTmpFrames, mPendingMergedConfiguration, mSurfaceControl,
                    mTempInsets, mTempControls, mRelayoutBundle);

    public static class Array implements Parcelable {

        private @Nullable InsetsSourceControl[] mControls;

        
    
    }

可以看出 InsetsSourceControl.Array 实际就是 InsetsSourceControl 的数组。

InsetsSourceControl 对象与一个具体的 Insets 对应，主要用于控制 Insets 的显示与隐藏，输入法会涉及的场景会比较多一些。

public class InsetsSourceControl implements Parcelable {

    private final int mId;
    private final @InsetsType int mType;
    private final Point mSurfacePosition;
    private Insets mInsetsHint;    

    
}

通过 adb shell dumpsys activity 命令可以查看到 InsetsSourceControl 相关的信息：

        InsetsSourceControl: {13c0000 mType=statusBars initiallyVisible mSurfacePosition=Point(0, 0) mInsetsHint=Insets{left=0, top=128, right=0, bottom=0}}
        InsetsSourceControl: {f8ac0001 mType=navigationBars initiallyVisible mSurfacePosition=Point(0, 2274) mInsetsHint=Insets{left=0, top=0, right=0, bottom=126}}
        InsetsSourceControl: {3 mType=ime mSurfacePosition=Point(0, 128) mInsetsHint=Insets{left=0, top=0, right=0, bottom=0}}

3. Insets 相关数据的分发

3.1 InsetsState 的分发

在调用 Session.addToDisplayAsUser 获取到 InsetsState 后，会调用到 InsetsController::onStateChanged 方法。

这里使用到了 InsetsController，它又是干什么的？

每个 窗口/ViewRootImpl 对应一个 InsetController，用于控制 insets 的显示，隐藏，状态更新以及动画的调度。

InsetsController 在 ViewRootImpl 初始化时构建并初始化。

    private final InsetsController mInsetsController;

    public ViewRootImpl(@UiContext Context context, Display display, IWindowSession session,
            WindowLayout windowLayout) {
        

        
        mInsetsController = new InsetsController(new ViewRootInsetsControllerHost(this));
        
    }

InsetsController 的实现如下：

public class InsetsController implements WindowInsetsController, InsetsAnimationControlCallbacks {
    
    
    private final Host mHost;

    private final InsetsState mState = new InsetsState();

    private final SparseArray mTmpControlArray = new SparseArray<>();

    private final TriFunction mConsumerCreator;
    
    private final SparseArray mSourceConsumers = new SparseArray<>();
    private final InsetsSourceConsumer mImeSourceConsumer;

    

    public InsetsController(Host host) {

        this(host, (controller, id, type) -> {
            if (type == ime()) {
                return new ImeInsetsSourceConsumer(id, controller.mState,
                        Transaction::new, controller);
            } else {
                return new InsetsSourceConsumer(id, type, controller.mState,
                        Transaction::new, controller);
            }
        }, host.getHandler());
    }

    @VisibleForTesting
    public InsetsController(Host host,
            TriFunction consumerCreator,
            Handler handler) {
        mHost = host;
        mConsumerCreator = consumerCreator;
        mHandler = handler;
        mAnimCallback = () -> {
            
        };

        
        mImeSourceConsumer = getSourceConsumer(ID_IME, ime());
    }
    

    @VisibleForTesting
    public @NonNull InsetsSourceConsumer getSourceConsumer(int id, int type) {
        InsetsSourceConsumer consumer = mSourceConsumers.get(id);
        if (consumer != null) {
            return consumer;
        }
        if (type == ime() && mImeSourceConsumer != null) {
            
            mSourceConsumers.remove(mImeSourceConsumer.getId());
            consumer = mImeSourceConsumer;
            consumer.setId(id);
        } else {
            consumer = mConsumerCreator.apply(this, id, type);
        }
        mSourceConsumers.put(id, consumer);
        return consumer;
    }

    
}

InsetsController 有一个重要成员 SparseArray mSourceConsumers，是 InsetsSource 的消费者。

InsetsController 的另一个成员 InsetsSourceConsumer mImeSourceConsumer;（InsetsSourceConsumer 的子类） 是 Ime InsetSource 的消费者。

InsetsSourceConsumer 中有几个重要的方法：

public void updateSource(InsetsSource newSource, @AnimationType int animationType)   
public int requestShow(boolean fromController, @Nullable ImeTracker.Token statsToken) 
void requestHide(boolean fromController, @Nullable ImeTracker.Token statsToken)  

这里消费的意思是什么？ 应该是指执行 Insets 的 show or hide 操作。

InsetsController 的另外一个成员 mConsumerCreator 用于生成 InsetsSourceConsumer。mConsumerCreator 在构造函数中初始化。

接下来就来看 onStateChanged 方法的实现：

    @VisibleForTesting
    public boolean onStateChanged(InsetsState state) {
        boolean stateChanged = false;
        if (!CAPTION_ON_SHELL) {
            stateChanged = !mState.equals(state, true ,
                    false )
                    || captionInsetsUnchanged();
        } else {
            stateChanged = !mState.equals(state, false ,
                    false );
        }
        if (!stateChanged && mLastDispatchedState.equals(state)) {
            return false;
        }
        if (DEBUG) Log.d(TAG, "onStateChanged: " + state);
        mLastDispatchedState.set(state, true );

        final InsetsState lastState = new InsetsState(mState, true );

        
        
        updateState(state);

        applyLocalVisibilityOverride();
        
        updateCompatSysUiVisibility();

        if (!mState.equals(lastState, false ,
                true )) {
            if (DEBUG) Log.d(TAG, "onStateChanged, notifyInsetsChanged");
            mHost.notifyInsetsChanged();
            if (lastState.getDisplayFrame().equals(mState.getDisplayFrame())) {
                InsetsState.traverse(lastState, mState, mStartResizingAnimationIfNeeded);
            }
        }
        return true;
    }

这里我们主要关心 updateState 方法，该方法会把从 WMS 中获取到的 InsetState 保存到 InsetsController 的成员 private final InsetsState mState 中。

3.2 dispatchApplyInsets 计算和分发 Insets

接下来会调用到 dispatchApplyInsets 方法，从名字就可以看出来，该方法用于分发 Insets：

    public void dispatchApplyInsets(View host) {
        Trace.traceBegin(Trace.TRACE_TAG_VIEW, "dispatchApplyInsets");
        mApplyInsetsRequested = false;
        
        WindowInsets insets = getWindowInsets(true );
        if (!shouldDispatchCutout()) {
            
            
            insets = insets.consumeDisplayCutout();
        }
        
        host.dispatchApplyWindowInsets(insets);
        mAttachInfo.delayNotifyContentCaptureInsetsEvent(insets.getInsets(Type.all()));
        Trace.traceEnd(Trace.TRACE_TAG_VIEW);
    }

这里主要两个关键点：

• getWindowInsets，计算 Insets，实际就是将从 WMS 获取到的 InsetsState 转换为 App 需要的 InsetState
• dispatchApplyWindowInsets，将 WindowInsets 分发给 View

3.2.1 getWindowInsets 计算 Insets

getWindowInsets 的实现如下：

    private WindowInsets mLastWindowInsets;

    WindowInsets getWindowInsets(boolean forceConstruct) {
        if (mLastWindowInsets == null || forceConstruct) {
            final Configuration config = getConfiguration();
            
            mLastWindowInsets = mInsetsController.calculateInsets(
                    config.isScreenRound(), mAttachInfo.mAlwaysConsumeSystemBars,
                    mWindowAttributes.type, config.windowConfiguration.getWindowingMode(),
                    mWindowAttributes.softInputMode, mWindowAttributes.flags,
                    (mWindowAttributes.systemUiVisibility
                            | mWindowAttributes.subtreeSystemUiVisibility));

            mAttachInfo.mContentInsets.set(mLastWindowInsets.getSystemWindowInsets().toRect());
            mAttachInfo.mStableInsets.set(mLastWindowInsets.getStableInsets().toRect());
            mAttachInfo.mVisibleInsets.set(mInsetsController.calculateVisibleInsets(
                    mWindowAttributes.type, config.windowConfiguration.getWindowingMode(),
                    mWindowAttributes.softInputMode, mWindowAttributes.flags).toRect());
        }

        return mLastWindowInsets;
    }

接着调用 InsetsController::calculateInsets 计算 Insets：

    private WindowInsets mLastInsets;
    private final InsetsState mState = new InsetsState();

    @VisibleForTesting
    public WindowInsets calculateInsets(boolean isScreenRound, boolean alwaysConsumeSystemBars,
            int windowType, int windowingMode, int legacySoftInputMode, int legacyWindowFlags,
            int legacySystemUiFlags) {
        mWindowType = windowType;
        mLastWindowingMode = windowingMode;
        mLastLegacySoftInputMode = legacySoftInputMode;
        mLastLegacyWindowFlags = legacyWindowFlags;
        mLastLegacySystemUiFlags = legacySystemUiFlags;
        
        mLastInsets = mState.calculateInsets(mFrame, null ,
                isScreenRound, alwaysConsumeSystemBars, legacySoftInputMode, legacyWindowFlags,
                legacySystemUiFlags, windowType, windowingMode, null );
        return mLastInsets;
    }

接着调用 InsetsState::calculateInsets：

    private final SparseArray mSources;

    public WindowInsets calculateInsets(Rect frame, @Nullable InsetsState ignoringVisibilityState,
            boolean isScreenRound, boolean alwaysConsumeSystemBars,
            int legacySoftInputMode, int legacyWindowFlags, int legacySystemUiFlags,
            int windowType, @WindowConfiguration.WindowingMode int windowingMode,
            @Nullable @InternalInsetsSide SparseIntArray idSideMap) {

        Insets[] typeInsetsMap = new Insets[Type.SIZE];
        Insets[] typeMaxInsetsMap = new Insets[Type.SIZE];
        boolean[] typeVisibilityMap = new boolean[Type.SIZE];
        final Rect relativeFrame = new Rect(frame);
        final Rect relativeFrameMax = new Rect(frame);
        @InsetsType int suppressScrimTypes = 0;

        for (int i = mSources.size() - 1; i >= 0; i--) {

            final InsetsSource source = mSources.valueAt(i);

            if ((source.getFlags() & InsetsSource.FLAG_SUPPRESS_SCRIM) != 0) {
                suppressScrimTypes |= source.getType();
            }

            
            processSource(source, relativeFrame, false , typeInsetsMap,
                    idSideMap, typeVisibilityMap);


            
            
            
            if (source.getType() != WindowInsets.Type.ime()) {
                InsetsSource ignoringVisibilitySource = ignoringVisibilityState != null
                        ? ignoringVisibilityState.peekSource(source.getId())
                        : source;
                if (ignoringVisibilitySource == null) {
                    continue;
                }
                processSource(ignoringVisibilitySource, relativeFrameMax,
                        true , typeMaxInsetsMap, null ,
                        null );
            }
        }

        final int softInputAdjustMode = legacySoftInputMode & SOFT_INPUT_MASK_ADJUST;

        @InsetsType int compatInsetsTypes = systemBars() | displayCutout();
        if (softInputAdjustMode == SOFT_INPUT_ADJUST_RESIZE) {
            compatInsetsTypes |= ime();
        }
        if ((legacyWindowFlags & FLAG_FULLSCREEN) != 0) {
            compatInsetsTypes &= ~statusBars();
        }
        if (clearsCompatInsets(windowType, legacyWindowFlags, windowingMode)
                && !alwaysConsumeSystemBars) {
            compatInsetsTypes = 0;
        }

        
        return new WindowInsets(typeInsetsMap, typeMaxInsetsMap, typeVisibilityMap, isScreenRound,
                alwaysConsumeSystemBars, suppressScrimTypes, calculateRelativeCutout(frame),
                calculateRelativeRoundedCorners(frame),
                calculateRelativePrivacyIndicatorBounds(frame),
                calculateRelativeDisplayShape(frame),
                compatInsetsTypes, (legacySystemUiFlags & SYSTEM_UI_FLAG_LAYOUT_STABLE) != 0);
    }

接着看

    private void processSource(InsetsSource source, Rect relativeFrame, boolean ignoreVisibility,
            Insets[] typeInsetsMap, @Nullable @InternalInsetsSide SparseIntArray idSideMap,
            @Nullable boolean[] typeVisibilityMap) {
        Insets insets = source.calculateInsets(relativeFrame, ignoreVisibility);

        final int type = source.getType();

        processSourceAsPublicType(source, typeInsetsMap, idSideMap, typeVisibilityMap,
                insets, type);

        if (type == Type.MANDATORY_SYSTEM_GESTURES) {
            
            
            
            
            
            processSourceAsPublicType(source, typeInsetsMap, idSideMap, typeVisibilityMap,
                    insets, Type.SYSTEM_GESTURES);
        }
        if (type == Type.CAPTION_BAR) {
            
            
            
            processSourceAsPublicType(source, typeInsetsMap, idSideMap, typeVisibilityMap,
                    insets, Type.SYSTEM_GESTURES);
            processSourceAsPublicType(source, typeInsetsMap, idSideMap, typeVisibilityMap,
                    insets, Type.MANDATORY_SYSTEM_GESTURES);
            processSourceAsPublicType(source, typeInsetsMap, idSideMap, typeVisibilityMap,
                    insets, Type.TAPPABLE_ELEMENT);
        }
    }

接着调用 calculateInsets 方法

    private Insets calculateInsets(Rect relativeFrame, Rect frame, boolean ignoreVisibility) {
        if (!ignoreVisibility && !mVisible) {
            return Insets.NONE;
        }
        
        
        
        if (getType() == WindowInsets.Type.captionBar()) {
            return Insets.of(0, frame.height(), 0, 0);
        }
        
        final boolean hasIntersection = relativeFrame.isEmpty()
                ? getIntersection(frame, relativeFrame, mTmpFrame)
                : mTmpFrame.setIntersect(frame, relativeFrame);
        if (!hasIntersection) {
            return Insets.NONE;
        }

        
        
        if (getType() == WindowInsets.Type.ime()) {
            return Insets.of(0, 0, 0, mTmpFrame.height());
        }

        
        if (mTmpFrame.width() == relativeFrame.width()) {
            if (mTmpFrame.top == relativeFrame.top) {
                return Insets.of(0, mTmpFrame.height(), 0, 0);
            } else if (mTmpFrame.bottom == relativeFrame.bottom) {
                return Insets.of(0, 0, 0, mTmpFrame.height());
            }
            
            
            
            if (mTmpFrame.top == 0) {
                return Insets.of(0, mTmpFrame.height(), 0, 0);
            }
        }
        
        else if (mTmpFrame.height() == relativeFrame.height()) {
            if (mTmpFrame.left == relativeFrame.left) {
                return Insets.of(mTmpFrame.width(), 0, 0, 0);
            } else if (mTmpFrame.right == relativeFrame.right) {
                return Insets.of(0, 0, mTmpFrame.width(), 0);
            }
        }
        return Insets.NONE;
    }

不同的条件生成不同的 Insets 返回。

processSourceAsPublicType 将生成的 Insets 插入会数组中。

    private void processSourceAsPublicType(InsetsSource source, Insets[] typeInsetsMap,
            @InternalInsetsSide @Nullable SparseIntArray idSideMap,
            @Nullable boolean[] typeVisibilityMap, Insets insets, int type) {
        int index = indexOf(type);
        Insets existing = typeInsetsMap[index];
        if (existing == null) {
            typeInsetsMap[index] = insets;
        } else {
            typeInsetsMap[index] = Insets.max(existing, insets);
        }

        if (typeVisibilityMap != null) {
            typeVisibilityMap[index] = source.isVisible();
        }

        if (idSideMap != null) {
            @InternalInsetsSide int insetSide = getInsetSide(insets);
            if (insetSide != ISIDE_UNKNOWN) {
                idSideMap.put(source.getId(), insetSide);
            }
        }
    }

3.2.2 dispatchApplyWindowInsets 分发 Insets

我们接着看 dispatchApplyWindowInsets 分发 Insets 的过程：

    @Override
    public WindowInsets dispatchApplyWindowInsets(WindowInsets insets) {
        insets = super.dispatchApplyWindowInsets(insets);
        if (insets.isConsumed()) {
            return insets;
        }
        if (View.sBrokenInsetsDispatch) {
            return brokenDispatchApplyWindowInsets(insets);
        } else {
            return newDispatchApplyWindowInsets(insets);
        }
    }

无论那种情况都会去调用 View::dispatchApplyWindowInsets

    private WindowInsets brokenDispatchApplyWindowInsets(WindowInsets insets) {
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            insets = getChildAt(i).dispatchApplyWindowInsets(insets);
            if (insets.isConsumed()) {
                break;
            }
        }
        return insets;
    }

    private WindowInsets newDispatchApplyWindowInsets(WindowInsets insets) {
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            getChildAt(i).dispatchApplyWindowInsets(insets);
        }
        return insets;
    }

View::dispatchApplyWindowInsets 的实现如下：

    public WindowInsets dispatchApplyWindowInsets(WindowInsets insets) {
        try {
            mPrivateFlags3 |= PFLAG3_APPLYING_INSETS;
            if (mListenerInfo != null && mListenerInfo.mOnApplyWindowInsetsListener != null) {
                return mListenerInfo.mOnApplyWindowInsetsListener.onApplyWindowInsets(this, insets);
            } else {
                return onApplyWindowInsets(insets);
            }
        } finally {
            mPrivateFlags3 &= ~PFLAG3_APPLYING_INSETS;
        }
    }

优先调用 Listener，其次调用覆写方法，二选一，不会被同时调用。

3.3 InsetsSourceControl 的分发

我们接着看 onControlsChanged 分发 InsetsSourceControl 的过程：

    
    private final SparseArray mTmpControlArray = new SparseArray<>();
    private final SparseArray mSourceConsumers = new SparseArray<>();

    public void onControlsChanged(InsetsSourceControl[] activeControls) {

        if (activeControls != null) {
            for (InsetsSourceControl activeControl : activeControls) {
                if (activeControl != null) {
                    
                    mTmpControlArray.put(activeControl.getId(), activeControl);
                }
            }
        }

        @InsetsType int controllableTypes = 0;
        int consumedControlCount = 0;
        final @InsetsType int[] showTypes = new int[1];
        final @InsetsType int[] hideTypes = new int[1];

        
        for (int i = mSourceConsumers.size() - 1; i >= 0; i--) {

            final InsetsSourceConsumer consumer = mSourceConsumers.valueAt(i);
            final InsetsSourceControl control = mTmpControlArray.get(consumer.getId());

            if (control != null) {
                controllableTypes |= control.getType();
                consumedControlCount++;
            }

            
            
            consumer.setControl(control, showTypes, hideTypes);
        }

        
        if (consumedControlCount != mTmpControlArray.size()) {
            for (int i = mTmpControlArray.size() - 1; i >= 0; i--) {
                final InsetsSourceControl control = mTmpControlArray.valueAt(i);
                
                getSourceConsumer(control.getId(), control.getType())
                        .setControl(control, showTypes, hideTypes);
            }
        }

        if (mTmpControlArray.size() > 0) {
            
            for (int i = mRunningAnimations.size() - 1; i >= 0; i--) {
                mRunningAnimations.get(i).runner.updateSurfacePosition(mTmpControlArray);
            }
        }
        mTmpControlArray.clear();

        
        
        int animatingTypes = invokeControllableInsetsChangedListeners();
        showTypes[0] &= ~animatingTypes;
        hideTypes[0] &= ~animatingTypes;

        if (showTypes[0] != 0) {
            applyAnimation(showTypes[0], true , false ,
                    null );
        }
        if (hideTypes[0] != 0) {
            applyAnimation(hideTypes[0], false , false ,
                    null );
        }

        if (mControllableTypes != controllableTypes) {
            if (WindowInsets.Type.hasCompatSystemBars(mControllableTypes ^ controllableTypes)) {
                mCompatSysUiVisibilityStaled = true;
            }
            mControllableTypes = controllableTypes;
        }

        
        reportRequestedVisibleTypes();
    }

    
        
}

核心两点：

• 把 Control 保存到 mTmpControlArray 中
• 把 consumer 和 control 关联起来，他两一起负责 Insets 的显示与隐藏

最后给出一个相关类的类图：

参考资料