Annotations(注解)支持库

compile 'com.android.support:support-annotations:24.2.0'

1	compile 'com.android.support:support-annotations:24.2.0'

Nullness注解

使用@NonNull注解修饰的字段,方法参数,返回值, 都不可已为null。
@Nullable 表示可以为空

    @Nullable  public String notNull(@NonNull Fragment fragment){
        return null;
    }

@Nullable public String notNull(@NonNull Fragment fragment){

return null;

}

资源类型注解

符合 @XXXRes 格式的注解, 限制传入的int值参数为对应类型的资源id;

    //传入参数为 String.xml 对应的id
    public void getStringSrc(@StringRes int id){
        //...
    }

//传入参数为 String.xml 对应的id

public void getStringSrc(@StringRes int id){

//...

}

例:

@AnimRes 动画文件夹里的资源的id
@LayoutRes 布局资源的id
@StringRes 字符串

IntDef和StringDef注解

限制int或string从特定的几个值内取值;

public class IntDefDemo {

    public int status;

    public static final int Open = 0;
    public static final int Close = 1;

    //可能的值放在{}内, 使用IntDef注解
    @IntDef({Open, Close})
    public @interface StatusW {
        //接口内无其他值
    }

    // 使用接口名限制传入参数
    public void setSattus(@StatusW int newStatus){
        status=newStatus;
    }

    @StatusW
    public int getStatus(){
        return status;
    }

}

// 使用
IntDefDemo intDefDemo=new IntDefDemo();
intDefDemo.setSattus(IntDefDemo.Close);

public class IntDefDemo {

public int status;

public static final int Open = 0;

public static final int Close = 1;

//可能的值放在{}内, 使用IntDef注解

@IntDef({Open, Close})

public @interface StatusW {

//接口内无其他值

}

// 使用接口名限制传入参数

public void setSattus(@StatusW int newStatus){

status=newStatus;

}

@StatusW

public int getStatus(){

return status;

}

// 使用

IntDefDemo intDefDemo=new IntDefDemo();

intDefDemo.setSattus(IntDefDemo.Close);

@Keep

keep修饰的元素在编译时不会因为没有被调用过而被删除;

    @Keep String k;
    
    @Keep
    public void tKeep(){

    }

@Keep String k;

@Keep

public void tKeep(){

}

限制范围 @IntRange @@FloatRange

限制修饰的元素的取值范围;

    @IntRange(from = 10,to = 100) int s;

    @IntRange(from = 10,to = 100)
    public int getIndex(){
        return 10;
    }

@IntRange(from = 10,to = 100) int s;

@IntRange(from = 10,to = 100)

public int getIndex(){

return 10;

}

限制线程

修饰函数方法时限制该方法运行的线程, 修饰类时限制该类中所有的方法的运行线程

@BinderThread 限制在Binder Thread
AnyThread 任意线程
MainThread 主线程
UiThread ui线程
WorkerThread 工作线程

Size

限制大小

public void getLocationInWindow(@Size(2) int[] location) {
      ...
  }

public void getLocationInWindow(@Size(2) int[] location) {

...

}

指定权限 RequiresPermission

该内容的执行需要权限

//指定一个
   @RequiresPermission(Manifest.permission.SET_WALLPAPER)
   public abstract void setWallpaper(Bitmap bitmap) throws IOException;

   @RequiresPermission(ACCESS_COARSE_LOCATION)
   public abstract Location getLastKnownLocation(String provider);

// 多个权限, 有一个就满足
   @RequiresPermission(anyOf = {ACCESS_COARSE_LOCATION, ACCESS_FINE_LOCATION})
   public abstract Location getLastKnownLocation(String provider);

// 需要列表中的全部权限
   @RequiresPermission(allOf = {ACCESS_COARSE_LOCATION, ACCESS_FINE_LOCATION})
   public abstract Location getLastKnownLocation(String provider);

// 一些特殊权限
   @RequiresPermission.Read(@RequiresPermission(READ_HISTORY_BOOKMARKS))
   @RequiresPermission.Write(@RequiresPermission(WRITE_HISTORY_BOOKMARKS))
   public static final Uri BOOKMARKS_URI = Uri.parse("content://browser/bookmarks");

// 修饰参数, 表示需要这个参数顺利执行的权限
    public void startActivity(@RequiresPermission Intent intent) { ... }

// 修饰字段
    @RequiresPermission(Manifest.permission.CALL_PHONE)
   public static final String ACTION_CALL = "android.intent.action.CALL";

//指定一个

@RequiresPermission(Manifest.permission.SET_WALLPAPER)

public abstract void setWallpaper(Bitmap bitmap) throws IOException;

@RequiresPermission(ACCESS_COARSE_LOCATION)

public abstract Location getLastKnownLocation(String provider);

// 多个权限, 有一个就满足

@RequiresPermission(anyOf = {ACCESS_COARSE_LOCATION, ACCESS_FINE_LOCATION})

public abstract Location getLastKnownLocation(String provider);

// 需要列表中的全部权限

@RequiresPermission(allOf = {ACCESS_COARSE_LOCATION, ACCESS_FINE_LOCATION})

public abstract Location getLastKnownLocation(String provider);

// 一些特殊权限

@RequiresPermission.Read(@RequiresPermission(READ_HISTORY_BOOKMARKS))

@RequiresPermission.Write(@RequiresPermission(WRITE_HISTORY_BOOKMARKS))

public static final Uri BOOKMARKS_URI = Uri.parse("content://browser/bookmarks");

// 修饰参数, 表示需要这个参数顺利执行的权限

public void startActivity(@RequiresPermission Intent intent) { ... }

// 修饰字段

@RequiresPermission(Manifest.permission.CALL_PHONE)

public static final String ACTION_CALL = "android.intent.action.CALL";

RequiresApi

指定需要指定或更高的 API 级别

    @RequiresApi(19)
    public  void tag(){

    }

@RequiresApi(19)

public void tag(){

}

CallSuper

子类重写 CallSuper 修饰的方法时, 必须调用父类的方法(super.);

public class A {
    @CallSuper
    public void cs(){

    }
}


public class B extends A {
    
    @Override
    public void cs() {
        super.cs();//必须调用父类的方法
    }
}

public class A {

@CallSuper

public void cs(){

}

public class B extends A {

@Override

public void cs() {

super.cs();//必须调用父类的方法

}

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