content: /*
   * 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 mAccessibilityViewId;
      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);
          mAccessibilityViewId = view.getAccessibilityViewId();
          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 View.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);
          }
      }
  
      int getAccessibilityViewId() {
          return mAccessibilityViewId;
      }
  }
  