Kotlin从一个类到另一个类获取变量/值

Question

我尝试使用okhttp进行api请求后，将变量从一个类传递到另一个类。

API请求（在我的MainActivity中）：

fun fetchJson() {
            val url = "https://......./api/.../....."

            val request = Request.Builder().url(url).build()

            val client = OkHttpClient()
            client.newCall(request).enqueue(object: Callback{

                override fun onResponse(call: Call, response: Response) {
                    val body = response?.body?.string()
                     println(body)
                    val gson = GsonBuilder().create()

                    val ApiStats = gson.fromJson(body, ApiStats::class.java)

                }

                override fun onFailure(call: Call, e: IOException) {
                    println("API execute failed")
                }
            })

        }

带有结果的类：

class ApiStats(val apple: String)

现在我想在MainActivity类中获取val，所以-> class MainActivity : AppCompatActivity()

我已经很有趣地看到了可能性，但是它似乎对我没有用...

我也尝试过：class MainActivity(val apiStats: ApiStaats : AppCompatActivity()

但是当我启动应用程序时，它使进程崩溃

2020-02-25 13:36:53.466 10543-10543/example.spectre.vision E/AndroidRuntime: FATAL EXCEPTION: main
    Process: example.spectre.vision, PID: 10543
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{example.spectre.vision/example.spectre.vision.MainActivity}: java.lang.InstantiationException: java.lang.Class<example.spectre.vision.MainActivity> has no zero argument constructor
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3194)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
     Caused by: java.lang.InstantiationException: java.lang.Class<example.spectre.vision.MainActivity> has no zero argument constructor
        at java.lang.Class.newInstance(Native Method)
        at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:95)
        at androidx.core.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:45)
        at android.app.Instrumentation.newActivity(Instrumentation.java:1243)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3182)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:214) 
        at android.app.ActivityThread.main(ActivityThread.java:7356) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
 ```

Answer 1

尝试这个==> class MainActivity : AppCompatActivity()

class MainActivity(val apiStats: ApiStaats : AppCompatActivity()

构造函数不会在类级别初始化，还会检查您的manifest