Java tutorial
/** * Copyright (c) 2017-present, Facebook, Inc. * All rights reserved. * * This source code is licensed under the BSD-style license found in the * LICENSE file in the root directory of this source tree. An additional grant * of patent rights can be found in the PATENTS file in the same directory. */ package com.facebook.litho; import java.util.List; import android.graphics.Rect; import android.graphics.drawable.Drawable; import android.os.Bundle; import android.support.v4.view.AccessibilityDelegateCompat; import android.support.v4.view.accessibility.AccessibilityNodeInfoCompat; import android.support.v4.view.accessibility.AccessibilityNodeProviderCompat; import android.support.v4.widget.ExploreByTouchHelper; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.view.ViewGroup; import android.view.accessibility.AccessibilityEvent; /** * Class that is used to set up accessibility for {@link ComponentHost}s. * Virtual nodes are only exposed if the component implements support for * extra accessibility nodes. */ class ComponentAccessibilityDelegate extends ExploreByTouchHelper { private static final String TAG = "ComponentAccessibility"; private final View mView; private NodeInfo mNodeInfo; private final AccessibilityDelegateCompat mSuperDelegate; private static Rect sDefaultBounds; ComponentAccessibilityDelegate(View view, NodeInfo nodeInfo) { super(view); mView = view; mNodeInfo = nodeInfo; mSuperDelegate = new SuperDelegate(); } ComponentAccessibilityDelegate(View view) { this(view, null); } /** * {@link ComponentHost} contains the logic for setting the {@link NodeInfo} containing the * {@link EventHandler}s for its delegate instance whenever it is set/unset * * @see ComponentHost#setTag(int, Object) */ void setNodeInfo(NodeInfo nodeInfo) { mNodeInfo = nodeInfo; } @Override public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfoCompat node) { final MountItem mountItem = getAccessibleMountItem(mView); if (mNodeInfo != null && mNodeInfo.getOnInitializeAccessibilityNodeInfoHandler() != null) { EventDispatcherUtils.dispatchOnInitializeAccessibilityNodeInfoEvent( mNodeInfo.getOnInitializeAccessibilityNodeInfoHandler(), host, node, mSuperDelegate); } else if (mountItem != null) { super.onInitializeAccessibilityNodeInfo(host, node); // Coalesce the accessible mount item's information with the // the root host view's as they are meant to behave as a single // node in the accessibility framework. final Component<?> component = mountItem.getComponent(); component.getLifecycle().onPopulateAccessibilityNode(node, component); } else { super.onInitializeAccessibilityNodeInfo(host, node); } } @Override protected void getVisibleVirtualViews(List<Integer> virtualViewIds) { final MountItem mountItem = getAccessibleMountItem(mView); if (mountItem == null) { return; } final Component<?> component = mountItem.getComponent(); final int extraAccessibilityNodesCount = component.getLifecycle() .getExtraAccessibilityNodesCount(component); // Expose extra accessibility nodes declared by the component to the // accessibility framework. The actual nodes will be populated in // {@link #onPopulateNodeForVirtualView}. for (int i = 0; i < extraAccessibilityNodesCount; i++) { virtualViewIds.add(i); } } @Override protected void onPopulateNodeForVirtualView(int virtualViewId, AccessibilityNodeInfoCompat node) { final MountItem mountItem = getAccessibleMountItem(mView); if (mountItem == null) { Log.e(TAG, "No accessible mount item found for view: " + mView); // ExploreByTouchHelper insists that we set something. node.setContentDescription(""); node.setBoundsInParent(getDefaultBounds()); return; } final Drawable drawable = (Drawable) mountItem.getContent(); final Rect bounds = drawable.getBounds(); final Component<?> component = mountItem.getComponent(); final ComponentLifecycle lifecycle = component.getLifecycle(); node.setClassName(lifecycle.getClass().getName()); if (virtualViewId >= lifecycle.getExtraAccessibilityNodesCount(component)) { Log.e(TAG, "Received unrecognized virtual view id: " + virtualViewId); // ExploreByTouchHelper insists that we set something. node.setContentDescription(""); node.setBoundsInParent(getDefaultBounds()); return; } lifecycle.onPopulateExtraAccessibilityNode(node, virtualViewId, bounds.left, bounds.top, component); } /** * Finds extra accessibility nodes under the given event coordinates. * Returns {@link #INVALID_ID} otherwise. */ @Override protected int getVirtualViewAt(float x, float y) { final MountItem mountItem = getAccessibleMountItem(mView); if (mountItem == null) { return INVALID_ID; } final Component<?> component = mountItem.getComponent(); final ComponentLifecycle lifecycle = component.getLifecycle(); if (lifecycle.getExtraAccessibilityNodesCount(component) == 0) { return INVALID_ID; } final Drawable drawable = (Drawable) mountItem.getContent(); final Rect bounds = drawable.getBounds(); // Try to find an extra accessibility node that intersects with // the given coordinates. final int virtualViewId = lifecycle.getExtraAccessibilityNodeAt((int) x - bounds.left, (int) y - bounds.top, component); return (virtualViewId >= 0 ? virtualViewId : INVALID_ID); } @Override protected void onPopulateEventForVirtualView(int virtualViewId, AccessibilityEvent event) { // TODO (T10543861): ExploreByTouchHelper enforces subclasses to set a content description // or text on new events but components don't provide APIs to do so yet. event.setContentDescription(""); } @Override protected boolean onPerformActionForVirtualView(int virtualViewId, int action, Bundle arguments) { return false; } /** * Returns a {AccessibilityNodeProviderCompat} if the host contains a component * that implements custom accessibility logic. Returns {@code NULL} otherwise. * Components with accessibility content are automatically wrapped in hosts by * {@link LayoutState}. */ @Override public AccessibilityNodeProviderCompat getAccessibilityNodeProvider(View host) { final MountItem mountItem = getAccessibleMountItem(mView); if (mountItem != null && mountItem.getComponent().getLifecycle().implementsExtraAccessibilityNodes()) { return super.getAccessibilityNodeProvider(host); } return null; } private static MountItem getAccessibleMountItem(View view) { if (!(view instanceof ComponentHost)) { return null; } return ((ComponentHost) view).getAccessibleMountItem(); } @Override public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event) { if (mNodeInfo != null && mNodeInfo.getOnInitializeAccessibilityEventHandler() != null) { EventDispatcherUtils.dispatchOnInitializeAccessibilityEvent( mNodeInfo.getOnInitializeAccessibilityEventHandler(), host, event, mSuperDelegate); } else { super.onInitializeAccessibilityEvent(host, event); } } @Override public void sendAccessibilityEvent(View host, int eventType) { if (mNodeInfo != null && mNodeInfo.getSendAccessibilityEventHandler() != null) { EventDispatcherUtils.dispatchSendAccessibilityEvent(mNodeInfo.getSendAccessibilityEventHandler(), host, eventType, mSuperDelegate); } else { super.sendAccessibilityEvent(host, eventType); } } @Override public void sendAccessibilityEventUnchecked(View host, AccessibilityEvent event) { if (mNodeInfo != null && mNodeInfo.getSendAccessibilityEventUncheckedHandler() != null) { EventDispatcherUtils.dispatchSendAccessibilityEventUnchecked( mNodeInfo.getSendAccessibilityEventUncheckedHandler(), host, event, mSuperDelegate); } else { super.sendAccessibilityEventUnchecked(host, event); } } @Override public boolean dispatchPopulateAccessibilityEvent(View host, AccessibilityEvent event) { if (mNodeInfo != null && mNodeInfo.getDispatchPopulateAccessibilityEventHandler() != null) { return EventDispatcherUtils.dispatchDispatchPopulateAccessibilityEvent( mNodeInfo.getDispatchPopulateAccessibilityEventHandler(), host, event, mSuperDelegate); } return super.dispatchPopulateAccessibilityEvent(host, event); } @Override public void onPopulateAccessibilityEvent(View host, AccessibilityEvent event) { if (mNodeInfo != null && mNodeInfo.getOnPopulateAccessibilityEventHandler() != null) { EventDispatcherUtils.dispatchOnPopulateAccessibilityEvent( mNodeInfo.getOnPopulateAccessibilityEventHandler(), host, event, mSuperDelegate); } else { super.onPopulateAccessibilityEvent(host, event); } } @Override public boolean onRequestSendAccessibilityEvent(ViewGroup host, View child, AccessibilityEvent event) { if (mNodeInfo != null && mNodeInfo.getOnRequestSendAccessibilityEventHandler() != null) { return EventDispatcherUtils.dispatchOnRequestSendAccessibilityEvent( mNodeInfo.getOnRequestSendAccessibilityEventHandler(), host, child, event, mSuperDelegate); } return super.onRequestSendAccessibilityEvent(host, child, event); } @Override public boolean performAccessibilityAction(View host, int action, Bundle args) { if (mNodeInfo != null && mNodeInfo.getPerformAccessibilityActionHandler() != null) { return EventDispatcherUtils.dispatchPerformAccessibilityActionEvent( mNodeInfo.getPerformAccessibilityActionHandler(), host, action, args, mSuperDelegate); } return super.performAccessibilityAction(host, action, args); } private static Rect getDefaultBounds() { synchronized (sDefaultBounds) { if (sDefaultBounds == null) { sDefaultBounds = new Rect(0, 0, 1, 1); } } return sDefaultBounds; } private class SuperDelegate extends AccessibilityDelegateCompat { @Override public boolean dispatchPopulateAccessibilityEvent(View host, AccessibilityEvent event) { return ComponentAccessibilityDelegate.super.dispatchPopulateAccessibilityEvent(host, event); } @Override public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event) { ComponentAccessibilityDelegate.super.onInitializeAccessibilityEvent(host, event); } @Override public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfoCompat node) { ComponentAccessibilityDelegate.super.onInitializeAccessibilityNodeInfo(host, node); } @Override public void onPopulateAccessibilityEvent(View host, AccessibilityEvent event) { ComponentAccessibilityDelegate.super.onPopulateAccessibilityEvent(host, event); } @Override public boolean onRequestSendAccessibilityEvent(ViewGroup host, View child, AccessibilityEvent event) { return ComponentAccessibilityDelegate.super.onRequestSendAccessibilityEvent(host, child, event); } @Override public boolean performAccessibilityAction(View host, int action, Bundle args) { return ComponentAccessibilityDelegate.super.performAccessibilityAction(host, action, args); } @Override public void sendAccessibilityEvent(View host, int eventType) { ComponentAccessibilityDelegate.super.sendAccessibilityEvent(host, eventType); } @Override public void sendAccessibilityEventUnchecked(View host, AccessibilityEvent event) { ComponentAccessibilityDelegate.super.sendAccessibilityEventUnchecked(host, event); } } }