PrintServiceRecommendationsLoader.java revision 00c3659eca6f9ab9235e7746b6d74702ab90555b 
1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.print;
18
19import android.annotation.NonNull;
20import android.content.Context;
21import android.content.Loader;
22import android.os.Handler;
23import android.os.Message;
24import android.printservice.recommendation.RecommendationInfo;
25import com.android.internal.util.Preconditions;
26
27import java.util.List;
28
29/**
30 * Loader for the list of print service recommendations.
31 *
32 * @hide
33 */
34public class PrintServiceRecommendationsLoader extends Loader<List<RecommendationInfo>> {
35    /** The print manager to be used by this object */
36    private final @NonNull PrintManager mPrintManager;
37
38    /** Handler to sequentialize the delivery of the results to the main thread */
39    private final @NonNull Handler mHandler;
40
41    /** Listens for updates to the data from the platform */
42    private PrintManager.PrintServiceRecommendationsChangeListener mListener;
43
44    /**
45     * Create a new PrintServicesLoader.
46     *
47     * @param printManager The print manager supplying the data
48     * @param context      Context of the using object
49     */
50    public PrintServiceRecommendationsLoader(@NonNull PrintManager printManager,
51            @NonNull Context context) {
52        super(Preconditions.checkNotNull(context));
53        mHandler = new MyHandler();
54        mPrintManager = Preconditions.checkNotNull(printManager);
55    }
56
57    @Override
58    protected void onForceLoad() {
59        queueNewResult();
60    }
61
62    /**
63     * Read the print service recommendations and queue it to be delivered on the main thread.
64     */
65    private void queueNewResult() {
66        Message m = mHandler.obtainMessage(0);
67        m.obj = mPrintManager.getPrintServiceRecommendations();
68        mHandler.sendMessage(m);
69    }
70
71    @Override
72    protected void onStartLoading() {
73        mListener = new PrintManager.PrintServiceRecommendationsChangeListener() {
74            @Override
75            public void onPrintServiceRecommendationsChanged() {
76                queueNewResult();
77            }
78        };
79
80        mPrintManager.addPrintServiceRecommendationsChangeListener(mListener);
81
82        // Immediately deliver a result
83        deliverResult(mPrintManager.getPrintServiceRecommendations());
84    }
85
86    @Override
87    protected void onStopLoading() {
88        if (mListener != null) {
89            mPrintManager.removePrintServiceRecommendationsChangeListener(mListener);
90            mListener = null;
91        }
92
93        mHandler.removeMessages(0);
94    }
95
96    @Override
97    protected void onReset() {
98        onStopLoading();
99    }
100
101    /**
102     * Handler to sequentialize all the updates to the main thread.
103     */
104    private class MyHandler extends Handler {
105        /**
106         * Create a new handler on the main thread.
107         */
108        public MyHandler() {
109            super(getContext().getMainLooper());
110        }
111
112        @Override
113        public void handleMessage(Message msg) {
114            if (isStarted()) {
115                deliverResult((List<RecommendationInfo>) msg.obj);
116            }
117        }
118    }
119}
120