获取app 当前状态 在前台还是在后台

Application.kt

/**
 * @Author: hasiy
 * @Date: 2019/1/12 - 17 : 06
 * @LastEditors: hasiy
 * @LastEditTime: 2019/1/12 - 17 : 06
 * @Description: androoid
 * @Email: hasiy.jj@gmail.com
 * 程序主入口
 */
class MYApplication : Application() {

    private var isBackground = false

    companion object {
        lateinit var appContext: WeakReference<Context>
    }

    override fun onCreate() {
        super.onCreate()
        appContext = WeakReference(applicationContext)
        listenForForeground()
        listenForScreenTurningOff()
    }

    private fun listenForForeground() {
        registerActivityLifecycleCallbacks(object : ActivityLifecycleCallbacks {
            override fun onActivityPaused(activity: Activity) {}

            override fun onActivityStarted(activity: Activity) {}

            override fun onActivityDestroyed(activity: Activity) {}

            override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {}

            override fun onActivityStopped(activity: Activity) {}

            override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {}

            override fun onActivityResumed(activity: Activity?) {
                if (isBackground) {
                    isBackground = false
                    LogUtil.e("应用到前台了")
                }
            }
        })
    }

    private fun listenForScreenTurningOff() {
        registerReceiver(object : BroadcastReceiver() {
            override fun onReceive(context: Context, intent: Intent) {
                isBackground = true
                LogUtil.e("应用到后台了")
            }
        }, IntentFilter(Intent.ACTION_SCREEN_OFF))
    }

    override fun onTrimMemory(level: Int) {
        super.onTrimMemory(level)
        if (level == ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
            isBackground = true
            LogUtil.e("应用到后台了")
        }
    }
}