Android kotlin - 应用程序在检查GPS是否启用时停止

Question

这是代码：

        val gps_enabled = locationManager!!.isProviderEnabled(LocationManager.GPS_PROVIDER)

        if(!gps_enabled) {
            Log.d("letsSee", "GPS IS OFF")
        }else{
            Log.d("letsSee", "GPS IS ON")
        }

当我尝试检查GPS是打开还是关闭时，应用程序崩溃了。一切都工作正常没有检查，但我仍然需要检查它！有任何想法吗？

09-16 03:59:12.533 32454-32454/com.amoflirt.amoflirt E/dalvikvm: Could not find class 'android.graphics.drawable.RippleDrawable', referenced from method android.support.v7.widget.AppCompatImageHelper.hasOverlappingRendering
09-16 03:59:13.713 32454-32454/com.amoflirt.amoflirt E/AndroidRuntime: FATAL EXCEPTION: main
    kotlin.KotlinNullPointerException
        at com.amoflirt.amoflirt.MainActivity.getLocation(MainActivity.kt:95)
        at com.amoflirt.amoflirt.MainActivity$onCreate$3.onClick(MainActivity.kt:67)
        at android.view.View.performClick(View.java:4475)
        at android.view.View$PerformClick.run(View.java:18786)
        at android.os.Handler.handleCallback(Handler.java:730)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:176)
        at android.app.ActivityThread.main(ActivityThread.java:5419)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:525)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

确保在访问locationManager之前已经定义了val locationManager by lazy { //however you define it normally } 。

作为旁注，您可以使用Kotlin lazy init：

qazxswpoi

只有在第一次访问它时才会初始化它，然后在该类的生命周期内保留该实例。