PreferenceScreen.java revision 6904f67c96a28a0e5966b4fb6d37a0ad5f136858 
1/*
2 * Copyright (C) 2015 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.support.v7.preference;
18
19import android.content.Context;
20import android.support.v7.widget.RecyclerView;
21import android.util.AttributeSet;
22
23/**
24 * Represents a top-level {@link Preference} that
25 * is the root of a Preference hierarchy. A {@link PreferenceFragmentCompat}
26 * points to an instance of this class to show the preferences. To instantiate
27 * this class, use {@link PreferenceManager#createPreferenceScreen(android.content.Context)}.
28 * <ul>
29 * This class can appear in two places:
30 * <li> When a {@link PreferenceFragmentCompat} points to this, it is used as the root
31 * and is not shown (only the contained preferences are shown).
32 * <li> When it appears inside another preference hierarchy, it is shown and
33 * serves as the gateway to another screen of preferences (either by showing
34 * another screen of preferences as a {@link android.app.Dialog} or via a
35 * {@link android.content.Context#startActivity(android.content.Intent)} from the
36 * {@link Preference#getIntent()}). The children of this {@link PreferenceScreen}
37 * are NOT shown in the screen that this {@link PreferenceScreen} is shown in.
38 * Instead, a separate screen will be shown when this preference is clicked.
39 * </ul>
40 * <p>Here's an example XML layout of a PreferenceScreen:</p>
41 * <pre>
42 &lt;PreferenceScreen
43 xmlns:android="http://schemas.android.com/apk/res/android"
44 android:key="first_preferencescreen"&gt;
45 &lt;CheckBoxPreference
46 android:key="wifi enabled"
47 android:title="WiFi" /&gt;
48 &lt;PreferenceScreen
49 android:key="second_preferencescreen"
50 android:title="WiFi settings"&gt;
51 &lt;CheckBoxPreference
52 android:key="prefer wifi"
53 android:title="Prefer WiFi" /&gt;
54 ... other preferences here ...
55 &lt;/PreferenceScreen&gt;
56 &lt;/PreferenceScreen&gt; </pre>
57 * <p>
58 * In this example, the "first_preferencescreen" will be used as the root of the
59 * hierarchy and given to a {@link PreferenceFragment} or {@link PreferenceFragmentCompat}.
60 * The first screen will
61 * show preferences "WiFi" (which can be used to quickly enable/disable WiFi)
62 * and "WiFi settings". The "WiFi settings" is the "second_preferencescreen" and when
63 * clicked will show another screen of preferences such as "Prefer WiFi" (and
64 * the other preferences that are children of the "second_preferencescreen" tag).
65 *
66 * <div class="special reference">
67 * <h3>Developer Guides</h3>
68 * <p>For information about building a settings UI with Preferences,
69 * read the <a href="{@docRoot}guide/topics/ui/settings.html">Settings</a>
70 * guide.</p>
71 * </div>
72 *
73 * @see PreferenceCategory
74 */
75public final class PreferenceScreen extends PreferenceGroup  {
76
77    private RecyclerView.Adapter mRootAdapter;
78
79    /**
80     * Do NOT use this constructor, use {@link PreferenceManager#createPreferenceScreen(Context)}.
81     * @hide-
82     */
83    public PreferenceScreen(Context context, AttributeSet attrs) {
84        super(context, attrs, R.attr.preferenceScreenStyle);
85    }
86
87    /**
88     * Returns an adapter that can be attached to a {@link PreferenceFragment}
89     * or {@link PreferenceFragmentCompat} to show the preferences contained in this
90     * {@link PreferenceScreen}.
91     * <p>
92     * This {@link PreferenceScreen} will NOT appear in the returned adapter, instead
93     * it appears in the hierarchy above this {@link PreferenceScreen}.
94     *
95     * @return An adapter that manages the {@link Preference} contained in this
96     *         {@link PreferenceScreen}.
97     */
98    public final RecyclerView.Adapter getAdapter() {
99        if (mRootAdapter == null) {
100            mRootAdapter = onCreateAdapter();
101        }
102
103        return mRootAdapter;
104    }
105
106    /**
107     * Creates the root adapter.
108     *
109     * @return An adapter that contains the preferences contained in this {@link PreferenceScreen}.
110     * @see #getAdapter()
111     */
112    protected RecyclerView.Adapter onCreateAdapter() {
113        return new PreferenceGroupAdapter(this);
114    }
115
116    @Override
117    protected void onClick() {
118        if (getIntent() != null || getFragment() != null || getPreferenceCount() == 0) {
119            return;
120        }
121        final PreferenceManager.OnNavigateToScreenListener listener =
122                getPreferenceManager().getOnNavigateToScreenListener();
123        if (listener != null) {
124            listener.onNavigateToScreen(this);
125        }
126    }
127
128    @Override
129    protected boolean isOnSameScreenAsChildren() {
130        return false;
131    }
132
133}
134