java - Gmail 导航抽屉效果

Question

我想知道如何在 Gmail 应用程序中实现淡化效果。当您在导航抽屉上拖动手指并打开或关闭它时，导航抽屉下方的视图会变亮或变暗（如果将其向左移动，它将变得更亮，反之亦然）。

我试着像下面的代码那样做，但它崩溃了，而且它的视觉效果不如 Gmail 应用程序好。

    String colorString = "0x00000000";

    int max = MAX_SIZE_X;
    int auxMax = (int) (MAX_SIZE_X * 0.9); // 90
    int betMax = (int) (MAX_SIZE_X * 0.8); // 80
    int auxMaM = (int) (MAX_SIZE_X * 0.7); // 70
    int betMaM = (int) (MAX_SIZE_X * 0.6); // 60
    int auxMid = (int) (MAX_SIZE_X * 0.5); // 50
    int betMid = (int) (MAX_SIZE_X * 0.4); // 40
    int auxMiM = (int) (MAX_SIZE_X * 0.3); // 30
    int betMiM = (int) (MAX_SIZE_X * 0.2); // 20
    int betMin = (int) (MAX_SIZE_X * 0.1); // 10

    if (touch < max && touch >= auxMax) {
        colorString = "#88000000";

    } 
    if (touch < auxMax && touch >= betMax) {
        colorString = "#84000000";

    } 
    if (touch < betMax && touch >= auxMaM) {
        colorString = "#80000000";

    } 
    if (touch < auxMaM && touch >= betMaM) {
        colorString = "#76000000";

    } 
    if (touch < betMaM && touch >= auxMid) {
        colorString = "#72000000";

    } 
    if (touch < auxMid && touch >= betMid) {
        colorString = "#68000000";

    } 
    if (touch < betMid && touch >= auxMiM) {
        colorString = "#64000000";

    } 
    if (touch < auxMiM && touch >= betMiM) {
        colorString = "#60000000";

    } 
    if (touch < betMiM && touch >= betMin) {
        colorString = "#00000000";

    }
    colorInt = Color.parseColor(colorString);

    return colorInt;