Android @IntDef的使用 - 代替枚举

谁践踏了优雅 2023-10-17 08:04 42阅读 0赞

## Android @IntDef的使用 - 代替枚举 ##

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。[\[ 参考 \]][Link 1]  
那么如果需要使用Enum应该怎么做呢？

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;
        }
    }

如果缺少依赖，在build.gradle中增加如下依赖

compile ‘com.android.support:support-annotations:22.0.0‘

#### String类型 ####

string类型和int类型类似，使用@StringDef即可

@StringDef({DepositStatus.PAID, DepositStatus.UNPAID, DepositStatus.FREE, DepositStatus.EXPIRE})
    @Retention(RetentionPolicy.SOURCE)
    public @interface DepositStatus {
        String PAID = "PAID"; 
        String UNPAID = "UNPAID";
        String FREE = "FREE"; 
        String EXPIRE = "EXPIRE"; 
    }

> 转载自[http://www.bubuko.com/infodetail-1070320.html][http_www.bubuko.com_infodetail-1070320.html]

[Link 1]: https://developer.android.com/training/articles/memory.html#Overhead
[http_www.bubuko.com_infodetail-1070320.html]: http://www.bubuko.com/infodetail-1070320.html