DisplayMetrics.java revision 2b31d53161789358de57fd396716a6503855c5da 
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.util;
18
19import android.os.SystemProperties;
20
21
22/**
23 * A structure describing general information about a display, such as its
24 * size, density, and font scaling.
25 * <p>To access the DisplayMetrics members, initialize an object like this:</p>
26 * <pre> DisplayMetrics metrics = new DisplayMetrics();
27 * getWindowManager().getDefaultDisplay().getMetrics(metrics);</pre>
28 */
29public class DisplayMetrics {
30    /**
31     * Standard quantized DPI for low-density screens.
32     */
33    public static final int DENSITY_LOW = 120;
34
35    /**
36     * Standard quantized DPI for medium-density screens.
37     */
38    public static final int DENSITY_MEDIUM = 160;
39
40    /**
41     * Standard quantized DPI for 720p TV screens.  Applications should
42     * generally not worry about this density, instead targeting
43     * {@link #DENSITY_XHIGH} for 1080p TV screens.  For situations where
44     * output is needed for a 720p screen, the UI elements can be scaled
45     * automatically by the platform.
46     */
47    public static final int DENSITY_TV = 213;
48
49    /**
50     * Standard quantized DPI for high-density screens.
51     */
52    public static final int DENSITY_HIGH = 240;
53
54    /**
55     * Standard quantized DPI for extra-high-density screens.
56     */
57    public static final int DENSITY_XHIGH = 320;
58
59    /**
60     * The reference density used throughout the system.
61     */
62    public static final int DENSITY_DEFAULT = DENSITY_MEDIUM;
63
64    /**
65     * The device's density.
66     * @hide becase eventually this should be able to change while
67     * running, so shouldn't be a constant.
68     */
69    public static final int DENSITY_DEVICE = getDeviceDensity();
70
71    /**
72     * The absolute width of the display in pixels.
73     */
74    public int widthPixels;
75    /**
76     * The absolute height of the display in pixels.
77     */
78    public int heightPixels;
79    /**
80     * The logical density of the display.  This is a scaling factor for the
81     * Density Independent Pixel unit, where one DIP is one pixel on an
82     * approximately 160 dpi screen (for example a 240x320, 1.5"x2" screen),
83     * providing the baseline of the system's display. Thus on a 160dpi screen
84     * this density value will be 1; on a 120 dpi screen it would be .75; etc.
85     *
86     * <p>This value does not exactly follow the real screen size (as given by
87     * {@link #xdpi} and {@link #ydpi}, but rather is used to scale the size of
88     * the overall UI in steps based on gross changes in the display dpi.  For
89     * example, a 240x320 screen will have a density of 1 even if its width is
90     * 1.8", 1.3", etc. However, if the screen resolution is increased to
91     * 320x480 but the screen size remained 1.5"x2" then the density would be
92     * increased (probably to 1.5).
93     *
94     * @see #DENSITY_DEFAULT
95     */
96    public float density;
97    /**
98     * The screen density expressed as dots-per-inch.  May be either
99     * {@link #DENSITY_LOW}, {@link #DENSITY_MEDIUM}, or {@link #DENSITY_HIGH}.
100     */
101    public int densityDpi;
102    /**
103     * A scaling factor for fonts displayed on the display.  This is the same
104     * as {@link #density}, except that it may be adjusted in smaller
105     * increments at runtime based on a user preference for the font size.
106     */
107    public float scaledDensity;
108    /**
109     * The exact physical pixels per inch of the screen in the X dimension.
110     */
111    public float xdpi;
112    /**
113     * The exact physical pixels per inch of the screen in the Y dimension.
114     */
115    public float ydpi;
116
117    /**
118     * The reported display width prior to any compatibility mode scaling
119     * being applied.
120     * @hide
121     */
122    public int noncompatWidthPixels;
123    /**
124     * The reported display height prior to any compatibility mode scaling
125     * being applied.
126     * @hide
127     */
128    public int noncompatHeightPixels;
129    /**
130     * The reported display density prior to any compatibility mode scaling
131     * being applied.
132     * @hide
133     */
134    public float noncompatDensity;
135    /**
136     * The reported scaled density prior to any compatibility mode scaling
137     * being applied.
138     * @hide
139     */
140    public float noncompatScaledDensity;
141    /**
142     * The reported display xdpi prior to any compatibility mode scaling
143     * being applied.
144     * @hide
145     */
146    public float noncompatXdpi;
147    /**
148     * The reported display ydpi prior to any compatibility mode scaling
149     * being applied.
150     * @hide
151     */
152    public float noncompatYdpi;
153
154    public DisplayMetrics() {
155    }
156
157    public void setTo(DisplayMetrics o) {
158        widthPixels = o.widthPixels;
159        heightPixels = o.heightPixels;
160        density = o.density;
161        densityDpi = o.densityDpi;
162        scaledDensity = o.scaledDensity;
163        xdpi = o.xdpi;
164        ydpi = o.ydpi;
165        noncompatWidthPixels = o.noncompatWidthPixels;
166        noncompatHeightPixels = o.noncompatHeightPixels;
167        noncompatDensity = o.noncompatDensity;
168        noncompatScaledDensity = o.noncompatScaledDensity;
169        noncompatXdpi = o.noncompatXdpi;
170        noncompatYdpi = o.noncompatYdpi;
171    }
172
173    public void setToDefaults() {
174        widthPixels = 0;
175        heightPixels = 0;
176        density = DENSITY_DEVICE / (float) DENSITY_DEFAULT;
177        densityDpi = DENSITY_DEVICE;
178        scaledDensity = density;
179        xdpi = DENSITY_DEVICE;
180        ydpi = DENSITY_DEVICE;
181        noncompatWidthPixels = 0;
182        noncompatHeightPixels = 0;
183    }
184
185    @Override
186    public String toString() {
187        return "DisplayMetrics{density=" + density + ", width=" + widthPixels +
188            ", height=" + heightPixels + ", scaledDensity=" + scaledDensity +
189            ", xdpi=" + xdpi + ", ydpi=" + ydpi + "}";
190    }
191
192    private static int getDeviceDensity() {
193        // qemu.sf.lcd_density can be used to override ro.sf.lcd_density
194        // when running in the emulator, allowing for dynamic configurations.
195        // The reason for this is that ro.sf.lcd_density is write-once and is
196        // set by the init process when it parses build.prop before anything else.
197        return SystemProperties.getInt("qemu.sf.lcd_density",
198                SystemProperties.getInt("ro.sf.lcd_density", DENSITY_DEFAULT));
199    }
200}
201