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