ViewGroupCompat.java revision 84eca98693cb666a5e003744987a75dc06542c01 
1/*
2 * Copyright (C) 2011 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.v4.view;
18
19import android.os.Build;
20import android.view.View;
21import android.view.ViewGroup;
22import android.view.accessibility.AccessibilityEvent;
23
24/**
25 * Helper for accessing features in {@link ViewGroup}
26 * introduced after API level 4 in a backwards compatible fashion.
27 */
28public class ViewGroupCompat {
29
30    /**
31     * This constant is a {@link #setLayoutMode(ViewGroup, int) layoutMode}.
32     * Clip bounds are the raw values of {@link android.view.View#getLeft() left},
33     * {@link android.view.View#getTop() top},
34     * {@link android.view.View#getRight() right} and {@link android.view.View#getBottom() bottom}.
35     */
36    public static final int LAYOUT_MODE_CLIP_BOUNDS = 0;
37
38    /**
39     * This constant is a {@link #setLayoutMode(ViewGroup, int) layoutMode}.
40     * Optical bounds describe where a widget appears to be. They sit inside the clip
41     * bounds which need to cover a larger area to allow other effects,
42     * such as shadows and glows, to be drawn.
43     */
44    public static final int LAYOUT_MODE_OPTICAL_BOUNDS = 1;
45
46    interface ViewGroupCompatImpl {
47        public boolean onRequestSendAccessibilityEvent(ViewGroup group, View child,
48                AccessibilityEvent event);
49
50        public void setMotionEventSplittingEnabled(ViewGroup group, boolean split);
51        public int getLayoutMode(ViewGroup group);
52        public void setLayoutMode(ViewGroup group, int mode);
53    }
54
55    static class ViewGroupCompatStubImpl implements ViewGroupCompatImpl {
56        public boolean onRequestSendAccessibilityEvent(
57                ViewGroup group, View child, AccessibilityEvent event) {
58            return true;
59        }
60
61        public void setMotionEventSplittingEnabled(ViewGroup group, boolean split) {
62            // no-op, didn't exist.
63        }
64
65        @Override
66        public int getLayoutMode(ViewGroup group) {
67            return LAYOUT_MODE_CLIP_BOUNDS;
68        }
69
70        @Override
71        public void setLayoutMode(ViewGroup group, int mode) {
72            // no-op, didn't exist. Views only support clip bounds.
73        }
74    }
75
76    static class ViewGroupCompatHCImpl extends ViewGroupCompatStubImpl {
77        @Override
78        public void setMotionEventSplittingEnabled(ViewGroup group, boolean split) {
79            ViewGroupCompatHC.setMotionEventSplittingEnabled(group, split);
80        }
81    }
82
83    static class ViewGroupCompatIcsImpl extends ViewGroupCompatHCImpl {
84        @Override
85        public boolean onRequestSendAccessibilityEvent(
86                ViewGroup group, View child, AccessibilityEvent event) {
87            return ViewGroupCompatIcs.onRequestSendAccessibilityEvent(group, child, event);
88        }
89    }
90
91    static class ViewGroupCompatJellybeanMR2Impl extends ViewGroupCompatIcsImpl {
92        @Override
93        public int getLayoutMode(ViewGroup group) {
94            return ViewGroupCompatJellybeanMR2.getLayoutMode(group);
95        }
96
97        @Override
98        public void setLayoutMode(ViewGroup group, int mode) {
99            ViewGroupCompatJellybeanMR2.setLayoutMode(group, mode);
100        }
101    }
102
103    static final ViewGroupCompatImpl IMPL;
104    static {
105        final int version = Build.VERSION.SDK_INT;
106        if (version >= 18) {
107            IMPL = new ViewGroupCompatJellybeanMR2Impl();
108        } else if (version >= 14) {
109            IMPL = new ViewGroupCompatIcsImpl();
110        } else if (version >= 11) {
111            IMPL = new ViewGroupCompatHCImpl();
112        } else {
113            IMPL = new ViewGroupCompatStubImpl();
114        }
115    }
116
117    /*
118     * Hide the constructor.
119     */
120    private ViewGroupCompat() {
121
122    }
123
124    /**
125     * Called when a child has requested sending an {@link AccessibilityEvent} and
126     * gives an opportunity to its parent to augment the event.
127     * <p>
128     * If an {@link AccessibilityDelegateCompat} has been specified via calling
129     * {@link ViewCompat#setAccessibilityDelegate(View, AccessibilityDelegateCompat)} its
130     * {@link AccessibilityDelegateCompat#onRequestSendAccessibilityEvent(ViewGroup, View,
131     * AccessibilityEvent)} is responsible for handling this call.
132     * </p>
133     *
134     * @param group The group whose method to invoke.
135     * @param child The child which requests sending the event.
136     * @param event The event to be sent.
137     * @return True if the event should be sent.
138     */
139    public static boolean onRequestSendAccessibilityEvent(ViewGroup group, View child,
140            AccessibilityEvent event) {
141        return IMPL.onRequestSendAccessibilityEvent(group, child, event);
142    }
143
144    /**
145     * Enable or disable the splitting of MotionEvents to multiple children during touch event
146     * dispatch. This behavior is enabled by default for applications that target an
147     * SDK version of 11 (Honeycomb) or newer. On earlier platform versions this feature
148     * was not supported and this method is a no-op.
149     *
150     * <p>When this option is enabled MotionEvents may be split and dispatched to different child
151     * views depending on where each pointer initially went down. This allows for user interactions
152     * such as scrolling two panes of content independently, chording of buttons, and performing
153     * independent gestures on different pieces of content.
154     *
155     * @param group ViewGroup to modify
156     * @param split <code>true</code> to allow MotionEvents to be split and dispatched to multiple
157     *              child views. <code>false</code> to only allow one child view to be the target of
158     *              any MotionEvent received by this ViewGroup.
159     */
160    public static void setMotionEventSplittingEnabled(ViewGroup group, boolean split) {
161        IMPL.setMotionEventSplittingEnabled(group, split);
162    }
163
164    /**
165     * Returns the basis of alignment during layout operations on this ViewGroup:
166     * either {@link #LAYOUT_MODE_CLIP_BOUNDS} or {@link #LAYOUT_MODE_OPTICAL_BOUNDS}.
167     * <p>
168     * If no layoutMode was explicitly set, either programmatically or in an XML resource,
169     * the method returns the layoutMode of the view's parent ViewGroup if such a parent exists,
170     * otherwise the method returns a default value of {@link #LAYOUT_MODE_CLIP_BOUNDS}.
171     *
172     * @return the layout mode to use during layout operations
173     *
174     * @see #setLayoutMode(ViewGroup, int)
175     */
176    public static int getLayoutMode(ViewGroup group) {
177        return IMPL.getLayoutMode(group);
178    }
179
180    /**
181     * Sets the basis of alignment during the layout of this ViewGroup.
182     * Valid values are either {@link #LAYOUT_MODE_CLIP_BOUNDS} or
183     * {@link #LAYOUT_MODE_OPTICAL_BOUNDS}.
184     *
185     * @param mode the layout mode to use during layout operations
186     *
187     * @see #getLayoutMode(ViewGroup)
188     */
189    public static void setLayoutMode(ViewGroup group, int mode) {
190        IMPL.setLayoutMode(group, mode);
191    }
192}
193