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。我试着用这样的方式写这一行：

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

但后来我收到错误消息，指出ShakeEvent对象未定义getContext（）函数。我该怎么写呢？感谢。

Answer 1

您的类似乎没有引用任何Context对象。 getSystemService()是Context方法，因此在创建Activity时需要引用上下文对象（如SensorEventListener）。然后，您就可以致电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);

Answer 2

您需要将Context对象传递给此类并在其上调用getSystemService（..）

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)
         ...
    }
}

sensorManager对象的未定义getSystemService（）函数

2 个答案: