如何從Android中的Java實現Kotlin類？

Question

我是Java / Kotlin新手，正在開發Android應用程序。 我試圖將以下內容實現到YourApplication.kt中，在這里找到： https ://stackoverflow.com/a/42679191/4666306

package com.tijaname.fortysix

import android.app.Activity
import android.app.Application
import android.os.Bundle
import android.util.Log.println

class YourApplication : Application() {

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

}


class AppLifecycleTracker : Application.ActivityLifecycleCallbacks  {
    private var numStarted = 0

    override fun onActivityStarted(activity: Activity?) {
        if (numStarted == 0) {
            println("Activity has started");
        }
        numStarted++
    }

    override fun onActivityStopped(activity: Activity?) {
        numStarted--
        if (numStarted == 0) {
            println("Activity  has stopped");
        }
    }

}

我加了

 ext.kotlin_version = '1.1.51'
 classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

到我的gradle腳本。 我還將此添加到清單中：

         <activity android:name=".YourApplication"></activity>

我試圖這樣調用kotlin腳本（從我在Java中的MainActivity）：

 Intent intent = new Intent(getBaseContext(), YourApplication.class);
    startActivity(intent);

但是我收到以下錯誤：

類'YourApplication'不是抽象的，並且沒有實現抽象成員公共抽象樂趣onActivityResumed（p0：Activity！）...

我遵循Android-Studio的建議使其抽象，但這導致了更多錯誤。

我還嘗試按照AS的建議“實施成員”，但這會使我的應用在模擬器中崩潰。

謝謝！

Answer 1

您的內部類（即AppLifecycleTracker類）需要重寫一些其他方法。

  import android.app.Activity
  android.app.Application
  import android.os.Bundle


/**
 * Created by saritha high 13/2/18.
 */
class AirventApplication : Application() {


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

  class AppLifecycleTracker : Application.ActivityLifecycleCallbacks {

      private var numStarted = 0

      override fun onActivityStarted(activity: Activity?) {
          if (numStarted == 0) {
              println("Activity has started");
          }
          numStarted++
      }

      override fun onActivityStopped(activity: Activity?) {
          numStarted--
          if (numStarted == 0) {
              println("Activity  has stopped");
          }
      }

      override fun onActivityPaused(p0: Activity?) {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
       }

      override fun onActivityResumed(p0: Activity?) {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
      }

      override fun onActivityDestroyed(p0: Activity?) {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
      }

      override fun onActivitySaveInstanceState(p0: Activity?, p1: Bundle?)  {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
      }

      override fun onActivityCreated(p0: Activity?, p1: Bundle?) {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
      }
 }
}

並在清單中聲明您的應用程序類，例如：

  <application
    android:name=".YourApplication"
    android:icon="@mipmap/app_icon"
    android:label="@string/app_name"
    android:theme="@style/AppTheme">
    <activity
        android:name=".YourActivity"
        android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
   </application>