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.PrintServiceInfo;
25import com.android.internal.util.Preconditions;
26
27import java.util.List;
28
29/**
30 * Loader for the list of print services. Can be parametrized to select a subset.
31 *
32 * @hide
33 */
34public class PrintServicesLoader extends Loader<List<PrintServiceInfo>> {
35    /** What type of services to load. */
36    private final int mSelectionFlags;
37
38    /** The print manager to be used by this object */
39    private final @NonNull PrintManager mPrintManager;
40
41    /** Handler to sequentialize the delivery of the results to the main thread */
42    private final @NonNull Handler mHandler;
43
44    /** Listens for updates to the data from the platform */
45    private PrintManager.PrintServicesChangeListener mListener;
46
47    /**
48     * Create a new PrintServicesLoader.
49     *
50     * @param printManager   The print manager supplying the data
51     * @param context        Context of the using object
52     * @param selectionFlags What type of services to load.
53     */
54    public PrintServicesLoader(@NonNull PrintManager printManager, @NonNull Context context,
55            int selectionFlags) {
56        super(Preconditions.checkNotNull(context));
57        mHandler = new MyHandler();
58        mPrintManager = Preconditions.checkNotNull(printManager);
59        mSelectionFlags = Preconditions.checkFlagsArgument(selectionFlags,
60                PrintManager.ALL_SERVICES);
61    }
62
63    @Override
64    protected void onForceLoad() {
65        queueNewResult();
66    }
67
68    /**
69     * Read the print services and queue it to be delivered on the main thread.
70     */
71    private void queueNewResult() {
72        Message m = mHandler.obtainMessage(0);
73        m.obj = mPrintManager.getPrintServices(mSelectionFlags);
74        mHandler.sendMessage(m);
75    }
76
77    @Override
78    protected void onStartLoading() {
79        mListener = new PrintManager.PrintServicesChangeListener() {
80            @Override public void onPrintServicesChanged() {
81                queueNewResult();
82            }
83        };
84
85        mPrintManager.addPrintServicesChangeListener(mListener);
86
87        // Immediately deliver a result
88        deliverResult(mPrintManager.getPrintServices(mSelectionFlags));
89    }
90
91    @Override
92    protected void onStopLoading() {
93        if (mListener != null) {
94            mPrintManager.removePrintServicesChangeListener(mListener);
95            mListener = null;
96        }
97
98        mHandler.removeMessages(0);
99    }
100
101    @Override
102    protected void onReset() {
103        onStopLoading();
104    }
105
106    /**
107     * Handler to sequentialize all the updates to the main thread.
108     */
109    private class MyHandler extends Handler {
110        /**
111         * Create a new handler on the main thread.
112         */
113        public MyHandler() {
114            super(getContext().getMainLooper());
115        }
116
117        @Override
118        public void handleMessage(Message msg) {
119            if (isStarted()) {
120                deliverResult((List<PrintServiceInfo>) msg.obj);
121            }
122        }
123    }
124}
125