ViewConfiguration.java revision 54b6cfa9a9e5b861a9930af873580d6dc20f773c 
1/*
2 * Copyright (C) 2006 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.view;
18
19/**
20 * Contains methods to standard constants used in the UI for timeouts, sizes, and distances.
21 *
22 */
23public class ViewConfiguration {
24
25    /**
26     * Defines the width of the horizontal scrollbar and the height of the vertical scrollbar in
27     * pixels
28     */
29    private static final int SCROLL_BAR_SIZE = 6;
30
31    /**
32     * Defines the length of the fading edges in pixels
33     */
34    private static final int FADING_EDGE_LENGTH = 12;
35
36    /**
37     * Defines the duration in milliseconds of the pressed state in child
38     * components.
39     */
40    private static final int PRESSED_STATE_DURATION = 85;
41
42    /**
43     * Defines the duration in milliseconds before a press turns into
44     * a long press
45     */
46    private static final int LONG_PRESS_TIMEOUT = 500;
47
48    /**
49     * Defines the duration in milliseconds we will wait to see if a touch event
50     * is a top or a scroll. If the user does not move within this interval, it is
51     * considered to be a tap.
52     */
53    private static final int TAP_TIMEOUT = 100;
54
55    /**
56     * Defines the duration in milliseconds we will wait to see if a touch event
57     * is a jump tap. If the user does not complete the jump tap within this interval, it is
58     * considered to be a tap.
59     */
60    private static final int JUMP_TAP_TIMEOUT = 500;
61
62    /**
63     * Defines the duration in milliseconds we want to display zoom controls in response
64     * to a user panning within an application.
65     */
66    private static final int ZOOM_CONTROLS_TIMEOUT = 3000;
67
68    /**
69     * Defines the duration in milliseconds a user needs to hold down the
70     * appropriate button to bring up the global actions dialog (power off,
71     * lock screen, etc).
72     */
73    private static final int GLOBAL_ACTIONS_KEY_TIMEOUT = 1000;
74
75
76    /**
77     * Inset in pixels to look for touchable content when the user touches the edge of the screen
78     */
79    private static final int EDGE_SLOP = 12;
80
81    /**
82     * Distance a touch can wander before we think the user is scrolling in pixels
83     */
84    private static final int TOUCH_SLOP = 12;
85
86    /**
87     * Distance a touch needs to be outside of a window's bounds for it to
88     * count as outside for purposes of dismissing the window.
89     */
90    private static final int WINDOW_TOUCH_SLOP = 16;
91
92    /**
93     * Minimum velocity to initiate a fling, as measured in pixels per second
94     */
95    private static final int MINIMUM_FLING_VELOCITY = 50;
96
97    /**
98     * The maximum size of View's drawing cache, expressed in bytes. This size
99     * should be at least equal to the size of the screen in ARGB888 format.
100     */
101    private static final int MAXIMUM_DRAWING_CACHE_SIZE = 320 * 480 * 4; // One HVGA screen, ARGB8888
102
103    /**
104     * The coefficient of friction applied to flings/scrolls.
105     */
106    private static float SCROLL_FRICTION = 0.015f;
107
108    /**
109     * @return The width of the horizontal scrollbar and the height of the vertical
110     *         scrollbar in pixels
111     */
112    public static int getScrollBarSize() {
113        return SCROLL_BAR_SIZE;
114    }
115
116    /**
117     * @return Defines the length of the fading edges in pixels
118     */
119    public static int getFadingEdgeLength() {
120        return FADING_EDGE_LENGTH;
121    }
122
123    /**
124     * @return Defines the duration in milliseconds of the pressed state in child
125     * components.
126     */
127    public static int getPressedStateDuration() {
128        return PRESSED_STATE_DURATION;
129    }
130
131    /**
132     * @return Defines the duration in milliseconds before a press turns into
133     * a long press
134     */
135    public static int getLongPressTimeout() {
136        return LONG_PRESS_TIMEOUT;
137    }
138
139    /**
140     * @return Defines the duration in milliseconds we will wait to see if a touch event
141     * is a top or a scroll. If the user does not move within this interval, it is
142     * considered to be a tap.
143     */
144    public static int getTapTimeout() {
145        return TAP_TIMEOUT;
146    }
147
148    /**
149     * @return Defines the duration in milliseconds we will wait to see if a touch event
150     * is a jump tap. If the user does not move within this interval, it is
151     * considered to be a tap.
152     */
153    public static int getJumpTapTimeout() {
154        return JUMP_TAP_TIMEOUT;
155    }
156
157    /**
158     * @return Inset in pixels to look for touchable content when the user touches the edge of the
159     *         screen
160     */
161    public static int getEdgeSlop() {
162        return EDGE_SLOP;
163    }
164
165    /**
166     * @return Distance a touch can wander before we think the user is scrolling in pixels
167     */
168    public static int getTouchSlop() {
169        return TOUCH_SLOP;
170    }
171
172    /**
173     * @return Distance a touch must be outside the bounds of a window for it
174     * to be counted as outside the window for purposes of dismissing that
175     * window.
176     */
177    public static int getWindowTouchSlop() {
178        return WINDOW_TOUCH_SLOP;
179    }
180
181    /**
182     * Minimum velocity to initiate a fling, as measured in pixels per second
183     */
184    public static int getMinimumFlingVelocity() {
185     return MINIMUM_FLING_VELOCITY;
186    }
187
188    /**
189     * The maximum drawing cache size expressed in bytes.
190     *
191     * @return the maximum size of View's drawing cache expressed in bytes
192     */
193    public static int getMaximumDrawingCacheSize() {
194        return MAXIMUM_DRAWING_CACHE_SIZE;
195    }
196
197    /**
198     * The amount of time that the zoom controls should be
199     * displayed on the screen expressed in milliseconds.
200     *
201     * @return the time the zoom controls should be visible expressed
202     * in milliseconds.
203     */
204    public static long getZoomControlsTimeout() {
205        return ZOOM_CONTROLS_TIMEOUT;
206    }
207
208    /**
209     * The amount of time a user needs to press the relevant key to bring up
210     * the global actions dialog.
211     *
212     * @return how long a user needs to press the relevant key to bring up
213     *   the global actions dialog.
214     */
215    public static long getGlobalActionKeyTimeout() {
216        return GLOBAL_ACTIONS_KEY_TIMEOUT;
217    }
218
219    /**
220     * The amount of friction applied to scrolls and flings.
221     *
222     * @return A scalar dimensionless value representing the coefficient of
223     *         friction.
224     */
225    public static float getScrollFriction() {
226        return SCROLL_FRICTION;
227    }
228}
229