【Android】IntDef用法示例\API说明：比int更安全，比enum更轻量

转载署源 by-KyleCe：http://blog.youkuaiyun.com/KyleCeshen/article/details/50214845

今天在研究Toast中无意看到Toast的如下源码：

发现它在用IntDef，遂把它的用法记录一下：

public class Toast {
    static final String TAG = "Toast";
    static final boolean localLOGV = false;

    /** @hide */
    /*定义部分*/
    @IntDef({LENGTH_SHORT, LENGTH_LONG})
    @Retention(RetentionPolicy.SOURCE)
    public @interface Duration {}

    public static final int LENGTH_SHORT = 0;
    public static final int LENGTH_LONG = 1;

    ...

    /*作为类型使用时*/
     /**
     * Set how long to show the view for.
     * @see #LENGTH_SHORT
     * @see #LENGTH_LONG
     */
    public void setDuration(@Duration int duration) {
        mDuration = duration;
    }

    /*做为返回值时*/
    /**
     * Return the duration.
     * @see #setDuration
     */
    @Duration
    public int getDuration() {
        return mDuration;
    }

}

这里是IntDef的API说明啦：

/*IntDef
implements Annotation
android.support.annotation.IntDef
Class Overview
Denotes that the annotated element of integer type, represents a logical type and that its value should be one of the explicitly named constants. If the IntDef#flag() attribute is set to true, multiple constants can be combined.
*/

//Example:

@Retention(SOURCE)
@IntDef({NAVIGATION_MODE_STANDARD, NAVIGATION_MODE_LIST, NAVIGATION_MODE_TABS})
  public @interface NavigationMode {}
  public static final int NAVIGATION_MODE_STANDARD = 0;
  public static final int NAVIGATION_MODE_LIST = 1;
  public static final int NAVIGATION_MODE_TABS = 2;
  ...
  public abstract void setNavigationMode(@NavigationMode int mode);
  @NavigationMode
  public abstract int getNavigationMode();

//For a flag, set the flag attribute:
@IntDef(
      flag = true
      value = {NAVIGATION_MODE_STANDARD, NAVIGATION_MODE_LIST, NAVIGATION_MODE_TABS})

转载署源 by-KyleCe：http://blog.youkuaiyun.com/KyleCeshen/article/details/50214845