Android编程巧用注解

1. keep
   在编写混淆规则的时候，直接带keep注解的可以在混淆规则脚本中，可以直接如此来keep

   //比如keep主该cass
   
   @keep
   class Bean{
       ...
   }
   
   
   #保留注解，如果不添加此行会导致我们的@Keep注解失效
   -keepattributes *Annotation*
   -keep @android.support.annotation.Keep class **
   

2. IntDef
   用来代替Enum枚举，与枚举相比，省内存，省空间。

   private static final int RESTART = 1;
   private static final int REVERSE = 2;
   
   @IntDef({RESTART, REVERSE})
   @Retention(RetentionPolicy.SOURCE)
   public @interface RepeatMode {}
   
   

3. StringDef

   public static final String DEV = "dev";
   public static final String OFFICIAL = "official";
   
   @StringDef({DEV, OFFICIAL})
   @Retention(RetentionPolicy.SOURCE)
   private @interface LogType {
   
   }
   

4. Nullable
   用来声明方法返回不能为空，参数不能为空，在IDE编码中可以尽量避免空指针问题。

private void init(@Nullable AttributeSet attrs)

@Nullable
  public LottieComposition getComposition() {
    return composition;
  }

5. NonNull
   用来声明方法返回不为空，参数不能为空。也可以避免多余的判空问题。

    @NonNull
    @Override
    public LayoutInflater getLayoutInflater()
    
    public LauncherView(@NonNull Context context) 

6. intRange

public void setAlpha(@IntRange(from = 0, to = 255) int alpha) {
    this.alpha = alpha;
  }

7. MainThread
   声明必须在主线程调用

@MainThread
    public void requestPermissionIfNeed(Activity activity, int storagePermissionType)

8. WorkerThread
   声明必须在子线程调用

@WorkThread
    public void requestPermissionIfNeed(Activity activity, int storagePermissionType)