注解代替枚举案例 2019-01-25

title: 注解代替枚举案例 20180312

参考：
@IntDef的使用（替代枚举）

使用情形：比如 对 acitivity、 view、 fragment 中错误状态、重试状态、无网络状态等的处理 可以考虑该方式

前提：需依赖 annotations 库，如果有 'com.android.support:appcompat ..' 则不需要单独依赖（其已包含 annotations 库）

添加android注解依赖：
[java] view plain copy
compile 'com.android.support:support-annotations:25.1.0'  

//一种使用方式：

public class WeeksDays {
    @WeekDays int currentDay = SUNDAY;/*默认为 周日*/

    //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{

    }

    public void setCurrentDay(@WeekDays int currentDay) {
        this.currentDay = currentDay;
    }

    @WeekDays
    public int getCurrentDay() {
        return currentDay;
    }

}
//activity 中使用
public class Main2Activity extends AppCompatActivity {
    static final String TAG = "Main2Activity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        WeeksDays weeksDays = new WeeksDays();
        weeksDays.setCurrentDay(SATURDAY);
        @WeeksDays.WeekDays int today = weeksDays.getCurrentDay();
        switch (today) {
            case SUNDAY:
                Log.d(TAG,"SUNDAY");
                break;
            case MONDAY:
                Log.d(TAG,"MONDAY");
                break;
            case TUESDAY:
                Log.d(TAG,"TUESDAY");
                break;
            case WEDNESDAY:
                Log.d(TAG,"WEDNESDAY");
                break;
            case THURSDAY:
                Log.d(TAG,"THURSDAY");
                break;
            case FRIDAY:
                Log.d(TAG,"FRIDAY");
                break;
            case SATURDAY:
                Log.d(TAG,"SATURDAY");
                break;
            default:
                break;


        }

    }
}