kotlin在线转java_Kotlin转Java记录

昨天写了一篇PermissionsDispatcher初探，文章最后说要用java重写processor模块，今天花了半天时间完成，现在把代码放在github上：https://github.com/ileelay/PermissionsDispatcher/tree/2.2.0j，欢迎大家纠正！同时感慨到Kotlin太强大，Java太繁琐；

虽然Kotlin语法很简练，终究还是基于JVM，同时这篇文章不是循序渐进的Kotlin语法讲解，只是为了记录在转PermissionsDispatcher时的粗略见解；

普通class

kotlin是这样子写的

class NoParametersAllowedException(e: ExecutableElement) : RuntimeException(“Method ‘${e.simpleString()}()’ must not have any parameters”)

为了保持参数一致，我用java是这样写的：

public class NoParametersAllowedException extends RuntimeException {

public static RuntimeException getInstance(ExecutableElement e) {

return new NoParametersAllowedException(“Method “+e.getSimpleName().toString()+” must not have any parameters”);

}

private NoParametersAllowedException(String s) {

super(s);

}

}

常量的定义

kotlin这样

//Constants.kt

val FILE_COMMENT = “This file was generated by PermissionsDispatcher. Do not modify!”

val GEN_CLASS_SUFFIX = “PermissionsDispatcher”

val GEN_REQUESTCODE_PREFIX = “REQUEST_”

val GEN_PERMISSION_PREFIX = “PERMISSION_”

val GEN_PENDING_PREFIX = “PENDING_”

val GEN_WITHCHECK_SUFFIX = “WithCheck”

val GEN_PERMISSIONREQUEST_SUFFIX = “PermissionRequest”

说实话，kotlin这样写好变态，连class关键字都不用声明，我用java也尽量保持简洁，可还是比不过它；

public interface Constants {

String FILE_COMMENT = “This file was generated by PermissionsDispatcher. Do not modify!”;

String GEN_CLASS_SUFFIX = “PermissionsDispatcher”;

String GEN_REQUESTCODE_PREFIX = “REQUEST_”;

String GEN_PERMISSION_PREFIX = “PERMISSION_”;

String GEN_PENDING_PREFIX = “PENDING_”;

String GEN_WITHCHECK_SUFFIX = “WithCheck”;

String GEN_PERMISSIONREQUEST_SUFFIX = “PermissionRequest”;

}

Extensions

//Extensions.kt

fun TypeMirror.simpleString(): String {

val toString: String = this.toString()

val indexOfDot: Int = toString.lastIndexOf(‘.’)

return if (indexOfDot == -1) toString else toString.substring(indexOfDot + 1)

}

//调用

typeMirror.simpleString()

这个用java写就比较尴尬了，我是用工具类，功能可以实现，但还是没法保持统一的调用方式；

//Extensions.java

public static String TypeMirrorSimpleString(TypeMirror typeMirror) {

String toString = typeMirror.toString();

int indexOfDot = toString.lastIndexOf(‘.’);

if (indexOfDot == -1)

return toString;

else

return toString.substring(indexOfDot + 1);

}

//调用

Extensions.TypeMirrorSimpleString(typeMirror);

初始化一个List

processorUnits = listOf(ActivityProcessorUnit(),SupportFragmentProcessorUnit(),NativeFragmentProcessorUnit())

用java咋写，尴尬了

processorUnits = new ArrayList();

processorUnits.add(new ActivityProcessorUnit());

processorUnits.add(new SupportFragmentProcessorUnit());

processorUnits.add(new NativeFragmentProcessorUnit());

Safe Call (?. ?:)

先看这一段懵逼的代码

//ADD_WITH_CHECK_BODY_MAP是一个HashMap

ADD_WITH_CHECK_BODY_MAP[needsPermissionParameter]?.addHasSelfPermissionsCondition(builder, activityVar, permissionField) ?: builder.beginControlFlow(“if (\$T.hasSelfPermissions(\$N, \$N))”, PERMISSION_UTILS, activityVar, permissionField)

用Java理解是啥样子

SensitivePermissionInterface anInterface = ADD_WITH_CHECK_BODY_MAP.get(needsPermissionParameter);

if (anInterface != null) {

anInterface.addHasSelfPermissionsCondition(builder, activityVar, permissionField);

} else {

builder.beginControlFlow(“if ($T.hasSelfPermissions($N, $N))”, PERMISSION_UTILS, activityVar, permissionField);

}

未完待续