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 final 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        boolean onRequestSendAccessibilityEvent(ViewGroup group, View child,
48                AccessibilityEvent event);
49        void setMotionEventSplittingEnabled(ViewGroup group, boolean split);
50        int getLayoutMode(ViewGroup group);
51        void setLayoutMode(ViewGroup group, int mode);
52        void setTransitionGroup(ViewGroup group, boolean isTransitionGroup);
53        boolean isTransitionGroup(ViewGroup group);
54        int getNestedScrollAxes(ViewGroup group);
55    }
56
57    static class ViewGroupCompatStubImpl implements ViewGroupCompatImpl {
58        public boolean onRequestSendAccessibilityEvent(
59                ViewGroup group, View child, AccessibilityEvent event) {
60            return true;
61        }
62
63        public void setMotionEventSplittingEnabled(ViewGroup group, boolean split) {
64            // no-op, didn't exist.
65        }
66
67        @Override
68        public int getLayoutMode(ViewGroup group) {
69            return LAYOUT_MODE_CLIP_BOUNDS;
70        }
71
72        @Override
73        public void setLayoutMode(ViewGroup group, int mode) {
74            // no-op, didn't exist. Views only support clip bounds.
75        }
76
77        @Override
78        public void setTransitionGroup(ViewGroup group, boolean isTransitionGroup) {
79        }
80
81        @Override
82        public boolean isTransitionGroup(ViewGroup group) {
83            return false;
84        }
85
86        @Override
87        public int getNestedScrollAxes(ViewGroup group) {
88            if (group instanceof NestedScrollingParent) {
89                return ((NestedScrollingParent) group).getNestedScrollAxes();
90            }
91            return ViewCompat.SCROLL_AXIS_NONE;
92        }
93    }
94
95    static class ViewGroupCompatHCImpl extends ViewGroupCompatStubImpl {
96        @Override
97        public void setMotionEventSplittingEnabled(ViewGroup group, boolean split) {
98            ViewGroupCompatHC.setMotionEventSplittingEnabled(group, split);
99        }
100    }
101
102    static class ViewGroupCompatIcsImpl extends ViewGroupCompatHCImpl {
103        @Override
104        public boolean onRequestSendAccessibilityEvent(
105                ViewGroup group, View child, AccessibilityEvent event) {
106            return ViewGroupCompatIcs.onRequestSendAccessibilityEvent(group, child, event);
107        }
108    }
109
110    static class ViewGroupCompatJellybeanMR2Impl extends ViewGroupCompatIcsImpl {
111        @Override
112        public int getLayoutMode(ViewGroup group) {
113            return ViewGroupCompatJellybeanMR2.getLayoutMode(group);
114        }
115
116        @Override
117        public void setLayoutMode(ViewGroup group, int mode) {
118            ViewGroupCompatJellybeanMR2.setLayoutMode(group, mode);
119        }
120    }
121
122    static class ViewGroupCompatLollipopImpl extends ViewGroupCompatJellybeanMR2Impl {
123        @Override
124        public void setTransitionGroup(ViewGroup group, boolean isTransitionGroup) {
125            ViewGroupCompatLollipop.setTransitionGroup(group, isTransitionGroup);
126        }
127
128        @Override
129        public boolean isTransitionGroup(ViewGroup group) {
130            return ViewGroupCompatLollipop.isTransitionGroup(group);
131        }
132
133        @Override
134        public int getNestedScrollAxes(ViewGroup group) {
135            return ViewGroupCompatLollipop.getNestedScrollAxes(group);
136        }
137    }
138
139    static final ViewGroupCompatImpl IMPL;
140    static {
141        final int version = Build.VERSION.SDK_INT;
142        if (version >= 21) {
143            IMPL = new ViewGroupCompatLollipopImpl();
144        } else if (version >= 18) {
145            IMPL = new ViewGroupCompatJellybeanMR2Impl();
146        } else if (version >= 14) {
147            IMPL = new ViewGroupCompatIcsImpl();
148        } else if (version >= 11) {
149            IMPL = new ViewGroupCompatHCImpl();
150        } else {
151            IMPL = new ViewGroupCompatStubImpl();
152        }
153    }
154
155    /*
156     * Hide the constructor.
157     */
158    private ViewGroupCompat() {}
159
160    /**
161     * Called when a child has requested sending an {@link AccessibilityEvent} and
162     * gives an opportunity to its parent to augment the event.
163     * <p>
164     * If an {@link AccessibilityDelegateCompat} has been specified via calling
165     * {@link ViewCompat#setAccessibilityDelegate(View, AccessibilityDelegateCompat)} its
166     * {@link AccessibilityDelegateCompat#onRequestSendAccessibilityEvent(ViewGroup, View,
167     * AccessibilityEvent)} is responsible for handling this call.
168     * </p>
169     *
170     * @param group The group whose method to invoke.
171     * @param child The child which requests sending the event.
172     * @param event The event to be sent.
173     * @return True if the event should be sent.
174     */
175    public static boolean onRequestSendAccessibilityEvent(ViewGroup group, View child,
176            AccessibilityEvent event) {
177        return IMPL.onRequestSendAccessibilityEvent(group, child, event);
178    }
179
180    /**
181     * Enable or disable the splitting of MotionEvents to multiple children during touch event
182     * dispatch. This behavior is enabled by default for applications that target an
183     * SDK version of 11 (Honeycomb) or newer. On earlier platform versions this feature
184     * was not supported and this method is a no-op.
185     *
186     * <p>When this option is enabled MotionEvents may be split and dispatched to different child
187     * views depending on where each pointer initially went down. This allows for user interactions
188     * such as scrolling two panes of content independently, chording of buttons, and performing
189     * independent gestures on different pieces of content.
190     *
191     * @param group ViewGroup to modify
192     * @param split <code>true</code> to allow MotionEvents to be split and dispatched to multiple
193     *              child views. <code>false</code> to only allow one child view to be the target of
194     *              any MotionEvent received by this ViewGroup.
195     */
196    public static void setMotionEventSplittingEnabled(ViewGroup group, boolean split) {
197        IMPL.setMotionEventSplittingEnabled(group, split);
198    }
199
200    /**
201     * Returns the basis of alignment during layout operations on this ViewGroup:
202     * either {@link #LAYOUT_MODE_CLIP_BOUNDS} or {@link #LAYOUT_MODE_OPTICAL_BOUNDS}.
203     * <p>
204     * If no layoutMode was explicitly set, either programmatically or in an XML resource,
205     * the method returns the layoutMode of the view's parent ViewGroup if such a parent exists,
206     * otherwise the method returns a default value of {@link #LAYOUT_MODE_CLIP_BOUNDS}.
207     *
208     * @return the layout mode to use during layout operations
209     *
210     * @see #setLayoutMode(ViewGroup, int)
211     */
212    public static int getLayoutMode(ViewGroup group) {
213        return IMPL.getLayoutMode(group);
214    }
215
216    /**
217     * Sets the basis of alignment during the layout of this ViewGroup.
218     * Valid values are either {@link #LAYOUT_MODE_CLIP_BOUNDS} or
219     * {@link #LAYOUT_MODE_OPTICAL_BOUNDS}.
220     *
221     * @param mode the layout mode to use during layout operations
222     *
223     * @see #getLayoutMode(ViewGroup)
224     */
225    public static void setLayoutMode(ViewGroup group, int mode) {
226        IMPL.setLayoutMode(group, mode);
227    }
228
229    /**
230     * Changes whether or not this ViewGroup should be treated as a single entity during
231     * Activity Transitions.
232     * @param isTransitionGroup Whether or not the ViewGroup should be treated as a unit
233     *                          in Activity transitions. If false, the ViewGroup won't transition,
234     *                          only its children. If true, the entire ViewGroup will transition
235     *                          together.
236     */
237    public static void setTransitionGroup(ViewGroup group, boolean isTransitionGroup) {
238        IMPL.setTransitionGroup(group, isTransitionGroup);
239    }
240
241    /**
242     * Returns true if this ViewGroup should be considered as a single entity for removal
243     * when executing an Activity transition. If this is false, child elements will move
244     * individually during the transition.
245     */
246    public static boolean isTransitionGroup(ViewGroup group) {
247        return IMPL.isTransitionGroup(group);
248    }
249
250    /**
251     * Return the current axes of nested scrolling for this ViewGroup.
252     *
253     * <p>A ViewGroup returning something other than {@link ViewCompat#SCROLL_AXIS_NONE} is
254     * currently acting as a nested scrolling parent for one or more descendant views in
255     * the hierarchy.</p>
256     *
257     * @return Flags indicating the current axes of nested scrolling
258     * @see ViewCompat#SCROLL_AXIS_HORIZONTAL
259     * @see ViewCompat#SCROLL_AXIS_VERTICAL
260     * @see ViewCompat#SCROLL_AXIS_NONE
261     */
262    public static int getNestedScrollAxes(ViewGroup group) {
263        return IMPL.getNestedScrollAxes(group);
264    }
265}
266