在 Fragment 中调用 getSystemServices 时未定义? [英] getSystemServices is undefined when called in a Fragment?

问题描述

我希望 TextViews 在 Fragment 中显示传感器读数.当尝试初始化 SensorManager 时，getSystemServices 在 Fragment 中未定义，eclipse 说.为什么以及如何修复它.

I want TextViews to display the sensors readings in a Fragment. When trying to initialize the SensorManager the getSystemServices is undefined in the Fragment, eclipse says.Why and how to fix it.

片段

public class FragSensors extends Fragment {

private TextView accXTv, accYTv, accZTv;
private SensorManager sensorManager;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    View v = inflater.inflate(R.layout.frag_sensors, container, false);
    accXTv = (TextView) v.findViewById(R.id.accXValue);
    accYTv = (TextView) v.findViewById(R.id.accYValue);
    accZTv = (TextView) v.findViewById(R.id.accZValue);
    return v;
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onActivityCreated(savedInstanceState);
    sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);

}

private final SensorEventListener mSensorListener = new SensorEventListener() {

    @Override
    public void onSensorChanged(SensorEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onAccuracyChanged(Sensor arg0, int arg1) {
        // TODO Auto-generated method stub

    }
};

}

推荐答案

再调用一个方法:

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

为什么要调用一个额外的方法?
提供对系统服务的访问的 getSystemService() 方法来自 Context.Activity 扩展了 Context，Fragment 没有.因此，您首先需要获得对包含 Fragment 的 Activity 的引用，然后神奇地检索您想要的系统服务.

Why that one extra method call?
the getSystemService() method that provides access to system services comes from Context. An Activity extends Context, a Fragment does not. Hence, you first need to get a reference to the Activity in which the Fragment is contained and then magically retrieve the system service you want.

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