SensorManager 对象未定义 getSystemService() 函数

Question

我的源代码是：

import android.content.Context;
import android.hardware.SensorManager;

public class ShakeEvent implements SensorEventListener  {
     private static SensorManager sensorManager;
     ...
     ...
     public static boolean isSupported (){
          sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);

我收到错误消息，指出 getSystemService 函数未定义。我也尝试以这种方式写这一行：

sensorManager = (SensorManager) getContext().getSystemService(Context.SENSOR_SERVICE);

但随后我收到错误消息，指出 ShakeEvent 对象的 getContext() 函数未定义。我该怎么写呢？谢谢。

Answer 1

您的类似乎没有引用任何Context对象。getSystemService()是一种Context方法，因此Activity在创建SensorEventListener. 然后你就可以打电话了context.getSystemService()。

import android.content.Context;
import android.hardware.SensorManager;

public class ShakeEvent implements SensorEventListener  {
     private static SensorManager sensorManager;
     private final Context context;

     public ShakeEvent(Context context) {
         this.context = context;
     }

     ...
     ...
     public static boolean isSupported (){
          sensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);