getSystemService(Context.LOCATION_SERVICE) 调用后出错
Error after getSystemService(Context.LOCATION_SERVICE) call
决定制作一个确定当前位置的应用程序。
为此，我创建了 class "GPSLocation"，它负责处理与 GPS 相关的所有内容。
应用程序启动并正常工作，直到我通过按下按钮（"onButtonGPS" 函数）从这个 class 调用一个函数。
在LogCat中可以看到错误发生在这一行：
val locationManager = getSystemService(Context.LOCATION_SERVICE) as LocationManager
据我了解，该错误表示系统服务在 "onCreate" 方法之前不可用。我尝试将此方法插入 class "GPSLocation" 并尝试了很多我在互联网上找到的其他方法，但问题无法解决。
MainActivity.kt
import android.os.AsyncTask
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*
import android.view.View
class MainActivity : AppCompatActivity() {
val myGPSLocation = GPSLocation(this)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
fun onButtonGPS(view: View){
myGPSLocation.setLocation()
}
}
GPSLocation.kt
import android.Manifest
import android.app.Activity
import android.content.Context
import android.content.pm.PackageManager
import android.location.Criteria
import android.location.Location
import android.location.LocationListener
import android.location.LocationManager
import android.os.Bundle
import android.support.v4.app.ActivityCompat
import android.support.v7.app.AppCompatActivity
import android.util.Log
import android.widget.Toast
class GPSLocation(val myContext: Context) : AppCompatActivity(), LocationListener {
val REQUEST_LOCATION = 2
fun setLocation() {
if (ActivityCompat.checkSelfPermission(myContext, Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED
&& ActivityCompat.checkSelfPermission(myContext, Manifest.permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions(myContext as Activity,
arrayOf(Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION),
REQUEST_LOCATION)
}else{
val locationManager = getSystemService(Context.LOCATION_SERVICE) as LocationManager
val criteria = Criteria()
val provider = locationManager.getBestProvider(criteria, false)
val location = locationManager.getLastKnownLocation(provider)
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 0f, this)
if (location != null){
Toast.makeText(myContext, convertLocationToString(location.latitude, location.longitude), Toast.LENGTH_SHORT).show()
}else{
Toast.makeText(myContext, "Location not available!", Toast.LENGTH_SHORT).show()
}
}
}
override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
if (requestCode == REQUEST_LOCATION) setLocation()
}
private fun convertLocationToString(latitude: Double, longitude: Double): String {
val builder = StringBuilder()
if (latitude < 0) builder.append("S ") else builder.append("N ")
val latitudeDegrees = Location.convert(Math.abs(latitude), Location.FORMAT_SECONDS)
val latitudeSplit = latitudeDegrees.split((":").toRegex()).dropLastWhile({it.isEmpty()}).toTypedArray()
builder.append(latitudeSplit[0])
builder.append("°")
builder.append(latitudeSplit[1])
builder.append("'")
builder.append(latitudeSplit[2])
builder.append("\"")
builder.append("\n")
if (longitude < 0) builder.append("W ") else builder.append("E ")
val longitudeDegrees = Location.convert(Math.abs(longitude), Location.FORMAT_SECONDS)
val longitudeSplit = longitudeDegrees.split((":").toRegex()).dropLastWhile({it.isEmpty()}).toTypedArray()
builder.append(longitudeSplit[0])
builder.append("°")
builder.append(longitudeSplit[1])
builder.append("'")
builder.append(longitudeSplit[2])
builder.append("\"")
return builder.toString()
}
override fun onLocationChanged(p0: Location?) {
setLocation()
}
override fun onStatusChanged(p0: String?, p1: Int, p2: Bundle?) {
}
override fun onProviderEnabled(p0: String?) {
}
override fun onProviderDisabled(p0: String?) {
}
}
LogCat
04-02 23:07:04.529 17809-17809/com.example.testtskwheather E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.testtskwheather, PID: 17809
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:389)
at android.view.View.performClick(View.java:4633)
at android.view.View$PerformClick.run(View.java:19330)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:157)
at android.app.ActivityThread.main(ActivityThread.java:5356)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:384)
at android.view.View.performClick(View.java:4633)*
at android.view.View$PerformClick.run(View.java:19330)*
at android.os.Handler.handleCallback(Handler.java:733)*
at android.os.Handler.dispatchMessage(Handler.java:95)*
at android.os.Looper.loop(Looper.java:157)*
at android.app.ActivityThread.main(ActivityThread.java:5356)*
at java.lang.reflect.Method.invokeNative(Native Method)*
at java.lang.reflect.Method.invoke(Method.java:515)*
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)*
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)*
at dalvik.system.NativeStart.main(Native Method)*
Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()
at android.app.Activity.getSystemService(Activity.java:4713)
at com.example.testtskwheather.GPSLocation.setLocation(GPSLocation.kt:41)
at com.example.testtskwheather.MainActivity.onButtonGPS(MainActivity.kt:84)
at java.lang.reflect.Method.invokeNative(Native Method)*
at java.lang.reflect.Method.invoke(Method.java:515)*
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:384)*
at android.view.View.performClick(View.java:4633)*
at android.view.View$PerformClick.run(View.java:19330)*
at android.os.Handler.handleCallback(Handler.java:733)*
at android.os.Handler.dispatchMessage(Handler.java:95)*
at android.os.Looper.loop(Looper.java:157)*
at android.app.ActivityThread.main(ActivityThread.java:5356)*
at java.lang.reflect.Method.invokeNative(Native Method)*
at java.lang.reflect.Method.invoke(Method.java:515)*
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)*
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)*
at dalvik.system.NativeStart.main(Native Method)*
04-02 23:07:06.691 17809-17809/com.example.testtskwheather I/Process: Sending signal. PID: 17809 SIG: 9
您正在尝试使用 Activity 个尚未创建的实例。
看，你有两个 Activity：MainActivity 和 GPSLocation。 MainActivity 已启动，但 GPSLocation 未启动。在 setLocation 方法中您使用了 GPSLocation activity 的实例，但是这个 activity 没有启动，这个 activity 的 onCreate 方法没有叫。要启动 GPSLocation 活动，您应该调用 startActivity 方法。行 GPSLocation(this) 是错误的，从不创建 activity 本身的实例，总是调用 startActivity 方法。另外，我认为 GPSLocation 不应该扩展 Activity.
如果您只需要摆脱崩溃，请使用此行：
val locationManager = myContext.getSystemService(Context.LOCATION_SERVICE) as LocationManager
决定制作一个确定当前位置的应用程序。 为此，我创建了 class "GPSLocation"，它负责处理与 GPS 相关的所有内容。
应用程序启动并正常工作，直到我通过按下按钮（"onButtonGPS" 函数）从这个 class 调用一个函数。
在LogCat中可以看到错误发生在这一行：
val locationManager = getSystemService(Context.LOCATION_SERVICE) as LocationManager
据我了解，该错误表示系统服务在 "onCreate" 方法之前不可用。我尝试将此方法插入 class "GPSLocation" 并尝试了很多我在互联网上找到的其他方法，但问题无法解决。
MainActivity.kt
import android.os.AsyncTask
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*
import android.view.View
class MainActivity : AppCompatActivity() {
val myGPSLocation = GPSLocation(this)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
fun onButtonGPS(view: View){
myGPSLocation.setLocation()
}
}
GPSLocation.kt
import android.Manifest
import android.app.Activity
import android.content.Context
import android.content.pm.PackageManager
import android.location.Criteria
import android.location.Location
import android.location.LocationListener
import android.location.LocationManager
import android.os.Bundle
import android.support.v4.app.ActivityCompat
import android.support.v7.app.AppCompatActivity
import android.util.Log
import android.widget.Toast
class GPSLocation(val myContext: Context) : AppCompatActivity(), LocationListener {
val REQUEST_LOCATION = 2
fun setLocation() {
if (ActivityCompat.checkSelfPermission(myContext, Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED
&& ActivityCompat.checkSelfPermission(myContext, Manifest.permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions(myContext as Activity,
arrayOf(Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION),
REQUEST_LOCATION)
}else{
val locationManager = getSystemService(Context.LOCATION_SERVICE) as LocationManager
val criteria = Criteria()
val provider = locationManager.getBestProvider(criteria, false)
val location = locationManager.getLastKnownLocation(provider)
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 0f, this)
if (location != null){
Toast.makeText(myContext, convertLocationToString(location.latitude, location.longitude), Toast.LENGTH_SHORT).show()
}else{
Toast.makeText(myContext, "Location not available!", Toast.LENGTH_SHORT).show()
}
}
}
override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
if (requestCode == REQUEST_LOCATION) setLocation()
}
private fun convertLocationToString(latitude: Double, longitude: Double): String {
val builder = StringBuilder()
if (latitude < 0) builder.append("S ") else builder.append("N ")
val latitudeDegrees = Location.convert(Math.abs(latitude), Location.FORMAT_SECONDS)
val latitudeSplit = latitudeDegrees.split((":").toRegex()).dropLastWhile({it.isEmpty()}).toTypedArray()
builder.append(latitudeSplit[0])
builder.append("°")
builder.append(latitudeSplit[1])
builder.append("'")
builder.append(latitudeSplit[2])
builder.append("\"")
builder.append("\n")
if (longitude < 0) builder.append("W ") else builder.append("E ")
val longitudeDegrees = Location.convert(Math.abs(longitude), Location.FORMAT_SECONDS)
val longitudeSplit = longitudeDegrees.split((":").toRegex()).dropLastWhile({it.isEmpty()}).toTypedArray()
builder.append(longitudeSplit[0])
builder.append("°")
builder.append(longitudeSplit[1])
builder.append("'")
builder.append(longitudeSplit[2])
builder.append("\"")
return builder.toString()
}
override fun onLocationChanged(p0: Location?) {
setLocation()
}
override fun onStatusChanged(p0: String?, p1: Int, p2: Bundle?) {
}
override fun onProviderEnabled(p0: String?) {
}
override fun onProviderDisabled(p0: String?) {
}
}
LogCat
04-02 23:07:04.529 17809-17809/com.example.testtskwheather E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.testtskwheather, PID: 17809
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:389)
at android.view.View.performClick(View.java:4633)
at android.view.View$PerformClick.run(View.java:19330)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:157)
at android.app.ActivityThread.main(ActivityThread.java:5356)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:384)
at android.view.View.performClick(View.java:4633)*
at android.view.View$PerformClick.run(View.java:19330)*
at android.os.Handler.handleCallback(Handler.java:733)*
at android.os.Handler.dispatchMessage(Handler.java:95)*
at android.os.Looper.loop(Looper.java:157)*
at android.app.ActivityThread.main(ActivityThread.java:5356)*
at java.lang.reflect.Method.invokeNative(Native Method)*
at java.lang.reflect.Method.invoke(Method.java:515)*
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)*
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)*
at dalvik.system.NativeStart.main(Native Method)*
Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()
at android.app.Activity.getSystemService(Activity.java:4713)
at com.example.testtskwheather.GPSLocation.setLocation(GPSLocation.kt:41)
at com.example.testtskwheather.MainActivity.onButtonGPS(MainActivity.kt:84)
at java.lang.reflect.Method.invokeNative(Native Method)*
at java.lang.reflect.Method.invoke(Method.java:515)*
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:384)*
at android.view.View.performClick(View.java:4633)*
at android.view.View$PerformClick.run(View.java:19330)*
at android.os.Handler.handleCallback(Handler.java:733)*
at android.os.Handler.dispatchMessage(Handler.java:95)*
at android.os.Looper.loop(Looper.java:157)*
at android.app.ActivityThread.main(ActivityThread.java:5356)*
at java.lang.reflect.Method.invokeNative(Native Method)*
at java.lang.reflect.Method.invoke(Method.java:515)*
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)*
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)*
at dalvik.system.NativeStart.main(Native Method)*
04-02 23:07:06.691 17809-17809/com.example.testtskwheather I/Process: Sending signal. PID: 17809 SIG: 9
您正在尝试使用 Activity 个尚未创建的实例。
看，你有两个 Activity：MainActivity 和 GPSLocation。 MainActivity 已启动，但 GPSLocation 未启动。在 setLocation 方法中您使用了 GPSLocation activity 的实例，但是这个 activity 没有启动，这个 activity 的 onCreate 方法没有叫。要启动 GPSLocation 活动，您应该调用 startActivity 方法。行 GPSLocation(this) 是错误的，从不创建 activity 本身的实例，总是调用 startActivity 方法。另外，我认为 GPSLocation 不应该扩展 Activity.
如果您只需要摆脱崩溃，请使用此行：
val locationManager = myContext.getSystemService(Context.LOCATION_SERVICE) as LocationManager