Question

我想在光传感器上进行活动，但恢复方法显示错误。

package com.example.user.projectandroid;

import android.app.Activity;
import android.app.Service;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.util.Log;
import android.widget.EditText;


public class pushup extends Activity implements SensorEventListener{
SensorManager sensorManager;
Sensor sensor;
EditText ed;
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Log.d("myn", "onCreate: ");
    setContentView(R.layout.ushup);

     ed=(EditText)findViewById(R.id.editText8);
    SensorManager sensorManager=
(SensorManager)getSystemService(Service.SENSOR_SERVICE);
    sensor=sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
}

protected void onPause(){
    super.onPause();
    Log.d("myn", "onpause: ");
    sensorManager.unregisterListener(this);
}
protected void onResume(){
    super.onResume();                                                       
sensorManager.registerListener(this,sensor, 
                         SensorManager.SENSOR_DELAY_NORMAL);//error                      
  }
@Override
public void onSensorChanged(SensorEvent sensorEvent) {
    Log.d("myn", "onSensorChanged: ");
if(sensorEvent.sensor.getType()==Sensor.TYPE_LIGHT)
ed.setText(""+sensorEvent.values[0]);
}

@Override
public void onAccuracyChanged(Sensor sensor, int i) {

}
}

错误是

java.lang.NullPointerException：尝试在空对象引用上调用虚方法'boolean android.hardware.SensorManager.registerListener（android.hardware.SensorEventListener，android.hardware.Sensor，int）'

Answer 1

好的，我可以看到问题是你已经两次声明了SensorManager's个对象，因此导致NullPointerException。尝试从下面描述的行中删除SensorManager并将其更正为：

sensorManager = (SensorManager)getSystemService(Service.SENSOR_SERVICE);

希望它有所帮助...

SensorEventListener上的活动

1 个答案: