Android5.1应用中WebView出现内存泄漏如何解决

private final CopyOnWriteArrayList
    mAccessibilityStateChangeListeners = new CopyOnWriteArrayList<>();

/**
 * Registers an {@link AccessibilityStateChangeListener} for changes in
 * the global accessibility state of the system.
 *
 * @param listener The listener.
 * @return True if successfully registered.
 */
public boolean addAccessibilityStateChangeListener(
    @NonNull AccessibilityStateChangeListener listener) {
  // Final CopyOnWriteArrayList - no lock needed.
  return mAccessibilityStateChangeListeners.add(listener);
}

/**
 * Unregisters an {@link AccessibilityStateChangeListener}.
 *
 * @param listener The listener.
 * @return True if successfully unregistered.
 */
public boolean removeAccessibilityStateChangeListener(
    @NonNull AccessibilityStateChangeListener listener) {
  // Final CopyOnWriteArrayList - no lock needed.
  return mAccessibilityStateChangeListeners.remove(listener);
}

public void registerComponentCallbacks(ComponentCallbacks callback) {
  synchronized (mComponentCallbacks) {
    mComponentCallbacks.add(callback);
  }
}

public void unregisterComponentCallbacks(ComponentCallbacks callback) {
  synchronized (mComponentCallbacks) {
    mComponentCallbacks.remove(callback);
  }
}

/**
 * Add a new {@link ComponentCallbacks} to the base application of the
 * Context, which will be called at the same times as the ComponentCallbacks
 * methods of activities and other components are called. Note that you
 * must be sure to use {@link #unregisterComponentCallbacks} when
 * appropriate in the future; this will not be removed for you.
 *
 * @param callback The interface to call. This can be either a
 * {@link ComponentCallbacks} or {@link ComponentCallbacks2} interface.
 */
public void registerComponentCallbacks(ComponentCallbacks callback) {
  getApplicationContext().registerComponentCallbacks(callback);
}

/**
 * Remove a {@link ComponentCallbacks} object that was previously registered
 * with {@link #registerComponentCallbacks(ComponentCallbacks)}.
 */
public void unregisterComponentCallbacks(ComponentCallbacks callback) {
  getApplicationContext().unregisterComponentCallbacks(callback);
}

@Override
    public void onAttachedToWindow() {
      if (isDestroyed()) return;
      if (mIsAttachedToWindow) {
        Log.w(TAG, "onAttachedToWindow called when already attached. Ignoring");
        return;
      }
      mIsAttachedToWindow = true;
      mContentViewCore.onAttachedToWindow();
      nativeOnAttachedToWindow(mNativeAwContents, mContainerView.getWidth(),
          mContainerView.getHeight());
      updateHardwareAcceleratedFeaturesToggle();
      if (mComponentCallbacks != null) return;
      mComponentCallbacks = new AwComponentCallbacks();
      mContext.registerComponentCallbacks(mComponentCallbacks);
    }
    @Override
    public void onDetachedFromWindow() {
      if (isDestroyed()) return;
      if (!mIsAttachedToWindow) {
        Log.w(TAG, "onDetachedFromWindow called when already detached. Ignoring");
        return;
      }
      mIsAttachedToWindow = false;
      hideAutofillPopup();
      nativeOnDetachedFromWindow(mNativeAwContents);
      mContentViewCore.onDetachedFromWindow();
      updateHardwareAcceleratedFeaturesToggle();
      if (mComponentCallbacks != null) {
        mContext.unregisterComponentCallbacks(mComponentCallbacks);
        mComponentCallbacks = null;
      }
      mScrollAccessibilityHelper.removePostedCallbacks();
      mNativeGLDelegate.detachGLFunctor();
    }

/**

   * Destroys this object and deletes its native counterpart.

   */

  public void destroy() {

    mIsDestroyed = true;

    destroyNatives();

  }

@Override
protected void onDestroy() {
  super.onDestroy();
  if (mWebView != null) {
   ViewParent parent = mWebView.getParent();
   if (parent != null) {
     ((ViewGroup) parent).removeView(mWebView);
   }
   mWebView.removeAllViews();
   mWebView.destroy();
   mWebView = null;
  }
}

/**
 * @see android.view.View#onAttachedToWindow()
 *
 * Note that this is also called from receivePopupContents.
 */
public void onAttachedToWindow() {
  if (mNativeAwContents == 0) return;

  mIsAttachedToWindow = true;

  mContentViewCore.onAttachedToWindow();

  nativeOnAttachedToWindow(mNativeAwContents, mContainerView.getWidth(),

      mContainerView.getHeight());

  updateHardwareAcceleratedFeaturesToggle();

  if (mComponentCallbacks != null) return;
  mComponentCallbacks = new AwComponentCallbacks();
  mContainerView.getContext().registerComponentCallbacks(mComponentCallbacks);
}

/**
 * @see android.view.View#onDetachedFromWindow()
 */

public void onDetachedFromWindow() {
  mIsAttachedToWindow = false;

  hideAutofillPopup();

  if (mNativeAwContents != 0) {
    nativeOnDetachedFromWindow(mNativeAwContents);
  }
  mContentViewCore.onDetachedFromWindow();
  updateHardwareAcceleratedFeaturesToggle();

  if (mComponentCallbacks != null) {
    mContainerView.getContext().unregisterComponentCallbacks(mComponentCallbacks);
    mComponentCallbacks = null;
  }
  mScrollAccessibilityHelper.removePostedCallbacks();

  if (mPendingDetachCleanupReferences != null) {
    for (int i = 0; i < mPendingDetachCleanupReferences.size(); ++i) {
      mPendingDetachCleanupReferences.get(i).cleanupNow();
    }
    mPendingDetachCleanupReferences = null;
  }
}