android

Android开发之Enum （枚举）— @IntDef的使用

官方文档说明，安卓开发应避免使用Enum（枚举类），因为相比于静态常量Enum会花费两倍以上的内存。参 http://developer.android.com/training/articles/memory.html#Overhead

那么如果需要使用Enum应该怎么做呢？

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public class MainActivity extends Activity {
  
    //先定义 常量
    public static final int SUNDAY = 0;
    public static final int MONDAY = 1;
    public static final int TUESDAY = 2;
    public static final int WEDNESDAY = 3;
    public static final int THURSDAY = 4;
    public static final int FRIDAY = 5;
    public static final int SATURDAY = 6;
  
    //用 @IntDef "包住" 常量；
    // @Retention 定义策略
    // 声明构造器
    @IntDef({SUNDAY, MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY})
    @Retention(RetentionPolicy.SOURCE)
    public @interface WeekDays {}
  
    @WeekDays int currentDay = SUNDAY;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setCurrentDay(WEDNESDAY);
  
        //声明变量
        @WeekDays int today = getCurrentDay();
  
        switch (today){
            case SUNDAY:
                break;
            case MONDAY:
                break;
            case TUESDAY:
                break;
            case WEDNESDAY:
                break;
            case THURSDAY:
                break;
            case FRIDAY:
                break;
            case SATURDAY:
                break;
            default:
                break;
        }
  
    }
  
    public void setCurrentDay(@WeekDays int currentDay) {
        this.currentDay = currentDay;
    }
  
    @WeekDays
    public int getCurrentDay() {
        return currentDay;
    }
}

build.gradle中：
compile 'com.android.support:support-annotations:22.0.0'