在Android中如何使用注解取代Enum

Android中定义了许多的注解，如@IdRes,@LayoutRes…可以帮助我们在传递参数时，避免参数传递出错。当然我们也可以通过枚举定义参数，也可以达到相同效果。在Android中，系统为我们定义好了2个注解，@IntDef和@StringDef,具体代码如下所示：

Test类定义好注解

public class Test {    public static final int A = 0;    public static final int B = 1;    public static final int C = 2;    public static final int D = 3;    public static final String E = "E";    public static final String F = "F";    public static final String G = "G";    public static final String H = "H";    @IntDef({A, B, C, D})    @Retention(RetentionPolicy.SOURCE)    public @interface FormatInt {    }    @StringDef({E, F, G, H})    @Retention(RetentionPolicy.SOURCE)     public @interface FormatString {    }}

public class MainActivity extends AppCompatActivity {   public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        int format = getInt(Test.A);        String f = getString(Test.E);    }    //在方法参数上使用注解    public int getInt(@Test.FormatInt int format) {        return format;    }    public String getString(@Test.FormatString String format) {        return format;    }}

@IntDef注解的代码

@Retention(SOURCE)@Target({ANNOTATION_TYPE})public @interface IntDef {    /** Defines the allowed constants for this element */    long[] value() default {};    /** Defines whether the constants can be used as a flag, or just as an enum (the default) */    boolean flag() default false;}

@StringDef的注解代码

@Retention(SOURCE)@Target({ANNOTATION_TYPE})public @interface StringDef {    /** Defines the allowed constants for this element */    String[] value() default {};}