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如何在Kotlin中定义应用程序类和静态变量

kotlin android

-1

Devrath · 技术社区 · 6 年前

如何在Kotlin中编写等效代码,我需要使用定义的静态变量

public class ThisForThatApplication extends Application {

    static ThisForThatApplication appInstance;

    public static ThisForThatApplication getAppInstance() {
        if (appInstance == null) {
            appInstance = new ThisForThatApplication();
        }
        return appInstance;
    }
}

3 回复 | 直到 6 年前

Goku Farhana Naaz Ansari 6 年前

试试这个方法

class ThisForThatApplication : Application() {

    companion object {

        @JvmField
        var appInstance: ThisForThatApplication? = null



        @JvmStatic fun getAppInstance(): ThisForThatApplication {
            return appInstance as ThisForThatApplication
        }
    }

    override fun onCreate() {
        super.onCreate()
        appInstance=this;
    }

}

欲了解更多信息,请阅读 Static Fields 和; Static Methods

Sharan 6 年前

Kotlin中的应用程序类和静态变量

class App : Application() {

init {
    instance = this
}

companion object {
    private var instance: App? = null

    fun applicationContext(): Context {
        return instance!!.applicationContext
    }
}

override fun onCreate() {
    super.onCreate()
}
}

yyunikov 6 年前

没有 static 科特林的概念。但是,您可以实现相同的用途 companion objects . 查看Kotlin object expression and declaration 更多解释。

因为在您的示例中,您只想创建一个单例,所以可以执行以下操作:

class ThisForThatApplication: Application() {
    companion object {
        val instance = ThisForThatApplication()
    }
}

然而,当你创建Android时 Application 类,在Android中初始化实例会更好 onCreate() 方法:

class ThisForThatApplication : Application() {

    companion object {
        lateinit var instance: ThisForThatApplication
            private set
    }

    override fun onCreate() {
        super.onCreate()
        ThisForThatApplication.instance = this
    }
}

private set 在伴生对象的底部,只允许thisforthattapplication类设置该值。