Android example source code file (DisplayMetrics.java)

This example Android source code file (DisplayMetrics.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, content, density_default, density_device, density_high, density_low, density_medium, displaymetrics, os, override, string

The DisplayMetrics.java Android example source code

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.util;

import android.content.res.CompatibilityInfo;
import android.content.res.Configuration;
import android.os.*;


/**
 * A structure describing general information about a display, such as its
 * size, density, and font scaling.
 * <p>To access the DisplayMetrics members, initialize an object like this:

 * <pre> DisplayMetrics metrics = new DisplayMetrics();
 * getWindowManager().getDefaultDisplay().getMetrics(metrics);</pre>
 */
public class DisplayMetrics {
    /**
     * Standard quantized DPI for low-density screens.
     */
    public static final int DENSITY_LOW = 120;

    /**
     * Standard quantized DPI for medium-density screens.
     */
    public static final int DENSITY_MEDIUM = 160;

    /**
     * Standard quantized DPI for high-density screens.
     */
    public static final int DENSITY_HIGH = 240;

    /**
     * The reference density used throughout the system.
     */
    public static final int DENSITY_DEFAULT = DENSITY_MEDIUM;

    /**
     * The device's density.
     * @hide becase eventually this should be able to change while
     * running, so shouldn't be a constant.
     */
    public static final int DENSITY_DEVICE = getDeviceDensity();

    /**
     * The absolute width of the display in pixels.
     */
    public int widthPixels;
    /**
     * The absolute height of the display in pixels.
     */
    public int heightPixels;
    /**
     * The logical density of the display.  This is a scaling factor for the
     * Density Independent Pixel unit, where one DIP is one pixel on an
     * approximately 160 dpi screen (for example a 240x320, 1.5"x2" screen), 
     * providing the baseline of the system's display. Thus on a 160dpi screen 
     * this density value will be 1; on a 120 dpi screen it would be .75; etc.
     *  
     * <p>This value does not exactly follow the real screen size (as given by 
     * {@link #xdpi} and {@link #ydpi}, but rather is used to scale the size of
     * the overall UI in steps based on gross changes in the display dpi.  For 
     * example, a 240x320 screen will have a density of 1 even if its width is 
     * 1.8", 1.3", etc. However, if the screen resolution is increased to 
     * 320x480 but the screen size remained 1.5"x2" then the density would be 
     * increased (probably to 1.5).
     *
     * @see #DENSITY_DEFAULT
     */
    public float density;
    /**
     * The screen density expressed as dots-per-inch.  May be either
     * {@link #DENSITY_LOW}, {@link #DENSITY_MEDIUM}, or {@link #DENSITY_HIGH}.
     */
    public int densityDpi;
    /**
     * A scaling factor for fonts displayed on the display.  This is the same
     * as {@link #density}, except that it may be adjusted in smaller
     * increments at runtime based on a user preference for the font size.
     */
    public float scaledDensity;
    /**
     * The exact physical pixels per inch of the screen in the X dimension.
     */
    public float xdpi;
    /**
     * The exact physical pixels per inch of the screen in the Y dimension.
     */
    public float ydpi;

    public DisplayMetrics() {
    }
    
    public void setTo(DisplayMetrics o) {
        widthPixels = o.widthPixels;
        heightPixels = o.heightPixels;
        density = o.density;
        densityDpi = o.densityDpi;
        scaledDensity = o.scaledDensity;
        xdpi = o.xdpi;
        ydpi = o.ydpi;
    }
    
    public void setToDefaults() {
        widthPixels = 0;
        heightPixels = 0;
        density = DENSITY_DEVICE / (float) DENSITY_DEFAULT;
        densityDpi = DENSITY_DEVICE;
        scaledDensity = density;
        xdpi = DENSITY_DEVICE;
        ydpi = DENSITY_DEVICE;
    }

    /**
     * Update the display metrics based on the compatibility info and orientation
     * NOTE: DO NOT EXPOSE THIS API!  It is introducing a circular dependency
     * with the higher-level android.res package.
     * {@hide}
     */
    public void updateMetrics(CompatibilityInfo compatibilityInfo, int orientation,
            int screenLayout) {
        boolean expandable = compatibilityInfo.isConfiguredExpandable();
        boolean largeScreens = compatibilityInfo.isConfiguredLargeScreens();
        
        // Note: this assume that configuration is updated before calling
        // updateMetrics method.
        if (!expandable) {
            if ((screenLayout&Configuration.SCREENLAYOUT_COMPAT_NEEDED) == 0) {
                expandable = true;
                // the current screen size is compatible with non-resizing apps.
                compatibilityInfo.setExpandable(true);
            } else {
                compatibilityInfo.setExpandable(false);
            }
        }
        if (!largeScreens) {
            if ((screenLayout&Configuration.SCREENLAYOUT_SIZE_MASK)
                    != Configuration.SCREENLAYOUT_SIZE_LARGE) {
                largeScreens = true;
                // the current screen size is not large.
                compatibilityInfo.setLargeScreens(true);
            } else {
                compatibilityInfo.setLargeScreens(false);
            }
        }
        
        if (!expandable || !largeScreens) {
            // This is a larger screen device and the app is not 
            // compatible with large screens, so diddle it.
            
            // Figure out the compatibility width and height of the screen.
            int defaultWidth;
            int defaultHeight;
            switch (orientation) {
                case Configuration.ORIENTATION_LANDSCAPE: {
                    defaultWidth = (int)(CompatibilityInfo.DEFAULT_PORTRAIT_HEIGHT * density +
                            0.5f);
                    defaultHeight = (int)(CompatibilityInfo.DEFAULT_PORTRAIT_WIDTH * density +
                            0.5f);
                    break;
                }
                case Configuration.ORIENTATION_PORTRAIT:
                case Configuration.ORIENTATION_SQUARE:
                default: {
                    defaultWidth = (int)(CompatibilityInfo.DEFAULT_PORTRAIT_WIDTH * density +
                            0.5f);
                    defaultHeight = (int)(CompatibilityInfo.DEFAULT_PORTRAIT_HEIGHT * density +
                            0.5f);
                    break;
                }
                case Configuration.ORIENTATION_UNDEFINED: {
                    // don't change
                    return;
                }
            }
            
            if (defaultWidth < widthPixels) {
                // content/window's x offset in original pixels
                widthPixels = defaultWidth;
            }
            if (defaultHeight < heightPixels) {
                heightPixels = defaultHeight;
            }
        }
        
        if (compatibilityInfo.isScalingRequired()) {
            float invertedRatio = compatibilityInfo.applicationInvertedScale;
            density *= invertedRatio;
            densityDpi = (int)((density*DisplayMetrics.DENSITY_DEFAULT)+.5f);
            scaledDensity *= invertedRatio;
            xdpi *= invertedRatio;
            ydpi *= invertedRatio;
            widthPixels = (int) (widthPixels * invertedRatio + 0.5f);
            heightPixels = (int) (heightPixels * invertedRatio + 0.5f);
        }
    }

    @Override
    public String toString() {
        return "DisplayMetrics{density=" + density + ", width=" + widthPixels +
            ", height=" + heightPixels + ", scaledDensity=" + scaledDensity +
            ", xdpi=" + xdpi + ", ydpi=" + ydpi + "}";
    }

    private static int getDeviceDensity() {
        // qemu.sf.lcd_density can be used to override ro.sf.lcd_density
        // when running in the emulator, allowing for dynamic configurations.
        // The reason for this is that ro.sf.lcd_density is write-once and is
        // set by the init process when it parses build.prop before anything else.
        return SystemProperties.getInt("qemu.sf.lcd_density",
                SystemProperties.getInt("ro.sf.lcd_density", DENSITY_DEFAULT));
    }
}