content: /*
   * Copyright (C) 2016 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.print;
  
  import android.annotation.NonNull;
  import android.content.Context;
  import android.content.Loader;
  import android.os.Handler;
  import android.os.Message;
  import android.printservice.PrintServiceInfo;
  
  import com.android.internal.util.Preconditions;
  
  import java.util.List;
  
  /**
   * Loader for the list of print services. Can be parametrized to select a subset.
   *
   * @hide
   */
  public class PrintServicesLoader extends Loader<List<PrintServiceInfo>> {
      /** What type of services to load. */
      private final int mSelectionFlags;
  
      /** The print manager to be used by this object */
      private final @NonNull PrintManager mPrintManager;
  
      /** Handler to sequentialize the delivery of the results to the main thread */
      private final @NonNull Handler mHandler;
  
      /** Listens for updates to the data from the platform */
      private PrintManager.PrintServicesChangeListener mListener;
  
      /**
       * Create a new PrintServicesLoader.
       *
       * @param printManager   The print manager supplying the data
       * @param context        Context of the using object
       * @param selectionFlags What type of services to load.
       */
      public PrintServicesLoader(@NonNull PrintManager printManager, @NonNull Context context,
              int selectionFlags) {
          super(Preconditions.checkNotNull(context));
          mHandler = new MyHandler();
          mPrintManager = Preconditions.checkNotNull(printManager);
          mSelectionFlags = Preconditions.checkFlagsArgument(selectionFlags,
                  PrintManager.ALL_SERVICES);
      }
  
      @Override
      protected void onForceLoad() {
          queueNewResult();
      }
  
      /**
       * Read the print services and queue it to be delivered on the main thread.
       */
      private void queueNewResult() {
          Message m = mHandler.obtainMessage(0);
          m.obj = mPrintManager.getPrintServices(mSelectionFlags);
          mHandler.sendMessage(m);
      }
  
      @Override
      protected void onStartLoading() {
          mListener = new PrintManager.PrintServicesChangeListener() {
              @Override public void onPrintServicesChanged() {
                  queueNewResult();
              }
          };
  
          mPrintManager.addPrintServicesChangeListener(mListener, null);
  
          // Immediately deliver a result
          deliverResult(mPrintManager.getPrintServices(mSelectionFlags));
      }
  
      @Override
      protected void onStopLoading() {
          if (mListener != null) {
              mPrintManager.removePrintServicesChangeListener(mListener);
              mListener = null;
          }
  
          mHandler.removeMessages(0);
      }
  
      @Override
      protected void onReset() {
          onStopLoading();
      }
  
      /**
       * Handler to sequentialize all the updates to the main thread.
       */
      private class MyHandler extends Handler {
          /**
           * Create a new handler on the main thread.
           */
          public MyHandler() {
              super(getContext().getMainLooper());
          }
  
          @Override
          public void handleMessage(Message msg) {
              if (isStarted()) {
                  deliverResult((List<PrintServiceInfo>) msg.obj);
              }
          }
      }
  }
  