sensorManager对象的未定义getSystemService()函数

Question

我的源码是：

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函数定义不足。我试着用这样的方式来写这行：

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，因此在创建SensorEventListener时需要对上下文对象(如Activity)的引用。然后你就可以调用context.getSystemService()了。

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);

Answer 2

您需要将上下文对象传递给此类并调用getSystemService(..)在它上面

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