AndroidStudio 实例化了但是报unknown class错误

Question

package com.example.a54297.myapplication;

import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    TextView tvSensors = (TextView) findViewById(R.id.tv_sensors);
    //获取传感器SensorManager对象
    SensorManager mSensorManager;
    List<Sensor> sensorList;

    mSensorManager = (SensorManager)getsystemService(Context.SENSOR_SERVICE);

    sensorList = mSensorManager.getSensorList(Sensor.TYPE_ALL);
    List<String> sensorNameList = new ArrayList<String>();

}

我已经声明了mSensorManager和sensorList，但是在倒数第八行以及倒数第五行程序中报unknow class错误

Answer 1

你没有导入包吧
import android.hardware.SensorManager;
import android.hardware.Sensor;