128 lines
5.1 KiB
Java
128 lines
5.1 KiB
Java
/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.view.accessibility;
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import android.annotation.IntDef;
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import android.annotation.Nullable;
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import android.content.Context;
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import android.os.Bundle;
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import android.os.Message;
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import android.view.View;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.ref.WeakReference;
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/**
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* Object responsible to ensuring that a {@link View} is prepared to meet a synchronous request for
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* accessibility data.
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* <p>
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* Because accessibility requests arrive to {@link View}s synchronously on the UI thread, a View
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* that requires information from other processes can struggle to meet those requests. Registering
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* an instance of this class with {@link AccessibilityManager} allows a View to be notified when
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* a request is about to be made, and to asynchronously inform the accessibility system when it is
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* ready to meet the request.
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* <p>
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* <strong>Note:</strong> This class should only be needed in exceptional situations where a
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* {@link View} cannot otherwise synchronously meet the request for accessibility data.
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*/
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public abstract class AccessibilityRequestPreparer {
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public static final int REQUEST_TYPE_EXTRA_DATA = 0x00000001;
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/** @hide */
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@IntDef(flag = true, prefix = { "REQUEST_TYPE_" }, value = {
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REQUEST_TYPE_EXTRA_DATA
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})
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@Retention(RetentionPolicy.SOURCE)
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public @interface RequestTypes {}
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private final WeakReference<View> mViewRef;
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private final int mAccessibilityViewId;
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private final int mRequestTypes;
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/**
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* @param view The view whose requests need preparation. It must be attached to a
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* window. This object will retain a weak reference to this view, and will unregister itself
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* from AccessibilityManager if the view is detached from a window. It will not re-register
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* itself.
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* @param requestTypes The types of requests that require preparation. Different types may
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* be ORed together.
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*
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* @throws IllegalStateException if the view is not attached to a window.
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*/
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public AccessibilityRequestPreparer(View view, @RequestTypes int requestTypes) {
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if (!view.isAttachedToWindow()) {
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throw new IllegalStateException("View must be attached to a window");
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}
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mViewRef = new WeakReference<>(view);
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mAccessibilityViewId = view.getAccessibilityViewId();
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mRequestTypes = requestTypes;
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view.addOnAttachStateChangeListener(new ViewAttachStateListener());
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}
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/**
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* Callback to allow preparation for filling extra data. Only called back if
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* REQUEST_TYPE_EXTRA_DATA is requested.
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*
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* @param virtualViewId The ID of a virtual child node, if the {@link View} for this preparer
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* supports virtual descendents, or {@link AccessibilityNodeProvider#HOST_VIEW_ID}
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* if the request is for the view itself.
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* @param extraDataKey The extra data key for the request
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* @param args The arguments for the request
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* @param preparationFinishedMessage A message that must be sent to its target when preparations
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* are complete.
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*
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* @see View#addExtraDataToAccessibilityNodeInfo(AccessibilityNodeInfo, String, Bundle)
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* @see View.AccessibilityDelegate#addExtraDataToAccessibilityNodeInfo(
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* View, AccessibilityNodeInfo, String, Bundle)
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* @see AccessibilityNodeProvider#addExtraDataToAccessibilityNodeInfo(
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* int, AccessibilityNodeInfo, String, Bundle)
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*/
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public abstract void onPrepareExtraData(int virtualViewId, String extraDataKey,
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Bundle args, Message preparationFinishedMessage);
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/**
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* Get the view this object was created with.
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*
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* @return The view this object was created with, or {@code null} if the weak reference held
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* to the view is no longer valid.
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*/
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public @Nullable View getView() {
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return mViewRef.get();
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}
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private class ViewAttachStateListener implements View.OnAttachStateChangeListener {
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@Override
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public void onViewAttachedToWindow(View v) {
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}
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@Override
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public void onViewDetachedFromWindow(View v) {
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Context context = v.getContext();
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if (context != null) {
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context.getSystemService(AccessibilityManager.class)
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.removeAccessibilityRequestPreparer(AccessibilityRequestPreparer.this);
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}
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v.removeOnAttachStateChangeListener(this);
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}
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}
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int getAccessibilityViewId() {
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return mAccessibilityViewId;
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}
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}
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