在 Android 中获取当前星期几的最简单方法是什么？

Java 日历类可以正常工作。

Calendar calendar = Calendar.getInstance();
int day = calendar.get(Calendar.DAY_OF_WEEK); 

switch (day) {
    case Calendar.SUNDAY:
        // Current day is Sunday
        break;
    case Calendar.MONDAY:
        // Current day is Monday
        break;
    case Calendar.TUESDAY:
        // etc.
        break;
}

为了更好地处理日期时间，请考虑使用Java 8时间API：

String day = LocalDate.now().getDayOfWeek().name()

要在 Android SDK 26 下面使用它，您需要在 build.gradle 中启用 Java 8 desugaring：

android {
  defaultConfig {
    // Required when setting minSdkVersion to 20 or lower
    multiDexEnabled true
  }

  compileOptions {
    // Flag to enable support for the new language APIs
    coreLibraryDesugaringEnabled true
    // Sets Java compatibility to Java 8
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }
}

dependencies {
  coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.0.9'
}

有关 Android 的 Java 8 支持的更多信息：https://developer.android.com/studio/write/java8-support

Calendar calendar = Calendar.getInstance();
Date date = calendar.getTime();
// 3 letter name form of the day
System.out.println(new SimpleDateFormat("EE", Locale.ENGLISH).format(date.getTime()));
// full name form of the day
System.out.println(new SimpleDateFormat("EEEE", Locale.ENGLISH).format(date.getTime()));

结果（今天）：

Sat
Saturday

更新： java8

LocalDate date = LocalDate.now();
DayOfWeek dow = date.getDayOfWeek();
System.out.println("Enum = " + dow);

String dayName = dow.getDisplayName(TextStyle.FULL, Locale.ENGLISH);
System.out.println("FULL = " + dayName);

dayName = dow.getDisplayName(TextStyle.FULL_STANDALONE, Locale.ENGLISH);
System.out.println("FULL_STANDALONE = " + dayName);

dayName = dow.getDisplayName(TextStyle.NARROW, Locale.ENGLISH);
System.out.println("NARROW = " + dayName);

dayName = dow.getDisplayName(TextStyle.NARROW_STANDALONE, Locale.ENGLISH);
System.out.println("NARROW_STANDALONE = " + dayName);

dayName = dow.getDisplayName(TextStyle.SHORT, Locale.ENGLISH);
System.out.println("SHORT = " + dayName);

dayName = dow.getDisplayName(TextStyle.SHORT_STANDALONE, Locale.ENGLISH);
System.out.println("SHORT_STANDALONE = " + dayName);

结果（今天）：

Enum = SATURDAY
FULL = Saturday
FULL_STANDALONE = Saturday
NARROW = S
NARROW_STANDALONE = 6
SHORT = Sat
SHORT_STANDALONE = Sat