As a ratio of screen height, the total distance we want the parallax effect to span horizontally - Android User Interface

Android examples for User Interface:Screen Size

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Description

As a ratio of screen height, the total distance we want the parallax effect to span horizontally

Demo Code

/*//from w w w .ja va2s. co m
 * Copyright (C) 2015 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 com.java2s;

public class Main {
    /**
     * As a ratio of screen height, the total distance we want the parallax effect to span
     * horizontally
     */
    public static float wallpaperTravelToScreenWidthRatio(int width,
            int height) {
        float aspectRatio = width / (float) height;

        // At an aspect ratio of 16/10, the wallpaper parallax effect should span 1.5 * screen width
        // At an aspect ratio of 10/16, the wallpaper parallax effect should span 1.2 * screen width
        // We will use these two data points to extrapolate how much the wallpaper parallax effect
        // to span (ie travel) at any aspect ratio:

        final float ASPECT_RATIO_LANDSCAPE = 16 / 10f;
        final float ASPECT_RATIO_PORTRAIT = 10 / 16f;
        final float WALLPAPER_WIDTH_TO_SCREEN_RATIO_LANDSCAPE = 1.5f;
        final float WALLPAPER_WIDTH_TO_SCREEN_RATIO_PORTRAIT = 1.2f;

        // To find out the desired width at different aspect ratios, we use the following two
        // formulas, where the coefficient on x is the aspect ratio (width/height):
        //   (16/10)x + y = 1.5
        //   (10/16)x + y = 1.2
        // We solve for x and y and end up with a final formula:
        final float x = (WALLPAPER_WIDTH_TO_SCREEN_RATIO_LANDSCAPE - WALLPAPER_WIDTH_TO_SCREEN_RATIO_PORTRAIT)
                / (ASPECT_RATIO_LANDSCAPE - ASPECT_RATIO_PORTRAIT);
        final float y = WALLPAPER_WIDTH_TO_SCREEN_RATIO_PORTRAIT - x
                * ASPECT_RATIO_PORTRAIT;
        return x * aspectRatio + y;
    }
}

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