Kotlin Singleton应用类

Question

所以在android中我想让我的应用程序类成为单例。

像这样：

object MyApplication: Application(){}

没有工作。在运行时抛出以下错误：

java.lang.IllegalAccessException: private com....is not accessible from class android.app.Instrumentation.

这样做也是不可能的：

class MyApp: Application() {

    private val instance_: MyApp

    init{
        instance_ = this
    }

    override fun onCreate() {
        super.onCreate()
        if (BuildConfig.DEBUG) {
            Timber.plant(Timber.DebugTree());
        }
    }

    companion object{
        fun getInstance() = instance_         
    }
}

那么如何才能在我的应用中的任何地方获取应用类的实例，希望使用MyApp.instance()代替(applicationContext as MyApp)。

还解释了为什么我想要这个：我的应用程序中有类，例如，使用上下文初始化的SharedPreference Singleton，作为单例，不能有参数。

Answer 1

您可以执行与在Java中执行的操作相同的操作，即将> org.springframework.http.converter.HttpMessageNotWritableException: > Could not write content: not in non blocking mode. (through reference > chain: > org.apache.catalina.connector.RequestFacade["inputStream"]->org.apache.catalina.connector.CoyoteInputStream["ready"]); > nested exception is > com.fasterxml.jackson.databind.JsonMappingException: not in non > blocking mode. (through reference chain: > org.apache.catalina.connector.RequestFacade["inputStream"]->org.apache.catalina.connector.CoyoteInputStream["ready"]) > at > org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:238) > at > org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:208) > at > org.springframework.web.client.RestTemplate$HttpEntityRequestCallback.doWithRequest(RestTemplate.java:774) > at > org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:567) > at > org.springframework.web.client.RestTemplate.execute(RestTemplate.java:538) > at > org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:340) > at > com.xx.yy.zz.controller.MainController.webApiQueryByPost(MainController.java:78) > at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at > sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) > at > sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) > at java.lang.reflect.Method.invoke(Method.java:497) at > org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) > at > org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) > at > org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) > at > org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776) > at > org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705) > at > org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) > at > org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) > at > org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) > at > org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) > at > org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) at > org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > com.xx.xx.xx.filter.BlueBerryCORSFilter.doFilter(BlueBerryCORSFilter.java:54) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) > at > org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85) > at > org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) > at > org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) > at > org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) > at > org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) > at > org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) > at > org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) > at > org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) > at > org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) > at > org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668) > at > org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521) > at > org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478) > at > java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) > at > java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) > at > org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) > at java.lang.Thread.run(Thread.java:745) Caused by: > com.fasterxml.jackson.databind.JsonMappingException: not in non > blocking mode. (through reference chain: > org.apache.catalina.connector.RequestFacade["inputStream"]->org.apache.catalina.connector.CoyoteInputStream["ready"]) > at > com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:210) > at > com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:177) > at > com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:187) > at > com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:647) > at > com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152) > at > com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:505) > at > com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639) > at > com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152) > at > com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:128) > at > com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:1902) > at > org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:231) > ... 54 more Caused by: java.lang.IllegalStateException: not in non > blocking mode. at > org.apache.catalina.connector.InputBuffer.isReady(InputBuffer.java:285) > at > org.apache.catalina.connector.CoyoteInputStream.isReady(CoyoteInputStream.java:242) > at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at > sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) > at > sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) > at java.lang.reflect.Method.invoke(Method.java:497) at > com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:466) > at > com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639) > ... 61 more > org.springframework.http.converter.HttpMessageNotWritableException: > Could not write content: not in non blocking mode. (through reference > chain: > org.apache.catalina.connector.RequestFacade["inputStream"]->org.apache.catalina.connector.CoyoteInputStream["ready"]); > nested exception is > com.fasterxml.jackson.databind.JsonMappingException: not in non > blocking mode. (through reference chain: > org.apache.catalina.connector.RequestFacade["inputStream"]->org.apache.catalina.connector.CoyoteInputStream["ready"]) > at > org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:238) > at > org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:208) > at > org.springframework.web.client.RestTemplate$HttpEntityRequestCallback.doWithRequest(RestTemplate.java:774) > at > org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:567) > at > org.springframework.web.client.RestTemplate.execute(RestTemplate.java:538) > at > org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:340) > at > com.xx.yy.zz.controller.MainController.webApiQueryByPost(MainController.java:78) > at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at > sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) > at > sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) > at java.lang.reflect.Method.invoke(Method.java:497) at > org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) > at > org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) > at > org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) > at > org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776) > at > org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705) > at > org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) > at > org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) > at > org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) > at > org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) > at > org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) at > org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > com.xx.yy.zz.filter.BlueBerryCORSFilter.doFilter(BlueBerryCORSFilter.java:54) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) > at > org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85) > at > org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) > at > org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) > at > org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) > at > org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) > at > org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) > at > org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) > at > org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) > at > org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) > at > org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668) > at > org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521) > at > org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478) > at > java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) > at > java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) > at > org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) > at java.lang.Thread.run(Thread.java:745) Caused by: > com.fasterxml.jackson.databind.JsonMappingException: not in non > blocking mode. (through reference chain: > org.apache.catalina.connector.RequestFacade["inputStream"]->org.apache.catalina.connector.CoyoteInputStream["ready"]) > at > com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:210) > at > com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:177) > at > com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:187) > at > com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:647) > at > com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152) > at > com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:505) > at > com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639) > at > com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152) > at > com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:128) > at > com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:1902) > at > org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:231) > ... 54 more Caused by: java.lang.IllegalStateException: not in non > blocking mode. at > org.apache.catalina.connector.InputBuffer.isReady(InputBuffer.java:285) > at > org.apache.catalina.connector.CoyoteInputStream.isReady(CoyoteInputStream.java:242) > at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at > sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) > at > sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) > at java.lang.reflect.Method.invoke(Method.java:497) at > com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:466) > at > com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639) > ... 61 more > org.springframework.http.converter.HttpMessageNotWritableException: > Could not write content: not in non blocking mode. (through reference > chain: > org.apache.catalina.connector.RequestFacade["inputStream"]->org.apache.catalina.connector.CoyoteInputStream["ready"]); > nested exception is > com.fasterxml.jackson.databind.JsonMappingException: not in non > blocking mode. (through reference chain: > org.apache.catalina.connector.RequestFacade["inputStream"]->org.apache.catalina.connector.CoyoteInputStream["ready"]) > at > org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:238) > at > org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:208) > at > org.springframework.web.client.RestTemplate$HttpEntityRequestCallback.doWithRequest(RestTemplate.java:774) > at > org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:567) > at > org.springframework.web.client.RestTemplate.execute(RestTemplate.java:538) > at > org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:340) > at > com.xx.yy.zz.controller.MainController.webApiQueryByPost(MainController.java:78) > at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at > sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) > at > sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) > at java.lang.reflect.Method.invoke(Method.java:497) at > org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) > at > org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) > at > org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) > at > org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776) > at > org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705) > at > org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) > at > org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) > at > org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) > at > org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) > at > org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) at > org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > com.xx.yy.gateway.filter.BlueBerryCORSFilter.doFilter(BlueBerryCORSFilter.java:54) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) > at > org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85) > at > org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) > at > org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) > at > org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) > at > org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) > at > org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) > at > org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) > at > org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) > at > org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) > at > org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) > at > org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668) > at > org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521) > at > org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478) > at > java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) > at > java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) > at > org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) > at java.lang.Thread.run(Thread.java:745) Caused by: > com.fasterxml.jackson.databind.JsonMappingException: not in non > blocking mode. (through reference chain: > org.apache.catalina.connector.RequestFacade["inputStream"]->org.apache.catalina.connector.CoyoteInputStream["ready"]) > at > com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:210) > at > com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:177) > at > com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:187) > at > com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:647) > at > com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152) > at > com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:505) > at > com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639) > at > com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152) > at > com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:128) > at > com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:1902) > at > org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:231) > ... 54 more Caused by: java.lang.IllegalStateException: not in non > blocking mode. at > org.apache.catalina.connector.InputBuffer.isReady(InputBuffer.java:285) > at > org.apache.catalina.connector.CoyoteInputStream.isReady(CoyoteInputStream.java:242) > at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at > sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) > at > sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) > at java.lang.reflect.Method.invoke(Method.java:497) at > com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:466) > at > com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639) > ... 61 more 实例放在静态字段中。 Kotlin没有静态字段，但对象中的属性是静态可访问的。

Application

然后，您可以通过class MyApp: Application() { override fun onCreate() { super.onCreate() instance = this } companion object { lateinit var instance: MyApp private set } } 访问该媒体资源。

Answer 2

如果您想使用它来访问某些静态属性，那么您将拥有：您只有一个应用程序实例，因此只需使用您为该类提供的名称即可。不要担心它不是一个真正的单身人士，你可以用同样的方式使用它。

示例：

class MyApp : Application() {

    companion object {
        const val CONSTANT = 12
        lateinit var typeface: Typeface
    }

    override fun onCreate() {
        super.onCreate()
        typeface = Typeface.createFromAsset(assets, "fonts/myFont.ttf")
    }

}

然后，您可以在应用中的任何位置使用MyApp.CONSTANT和MyApp.typeface。

-

如果你想要的是将它用作应用程序上下文，你可以为Context创建一个扩展属性：

val Context.myApp: MyApp
        get() = applicationContext as MyApp

然后，您可以使用myApp在具有上下文的任何位置获取应用程序上下文。

Answer 3

fn main() {
    let name = String::from("World");
    let test = simple(&name);
    println!("Hello {}!", test())
}

fn simple<'a, T: 'a>(val: &'a T) -> impl Fn() -> &'a T {
    move || -> &'a T { val }
}

Answer 4

您不能这样做，因为Android使用其无参数构造函数创建Application实例。

您想要解决的问题可以通过DI轻松解决。只需使用注入器创建实例，以便Context可以作为依赖项注入对象。