package hk.ust.cse.comp107x.ligthsensor; 
 
import android.content.Context; 
import android.hardware.Sensor; 
import android.hardware.SensorEvent; 
import android.hardware.SensorEventListener; 
import android.hardware.SensorManager; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.widget.TextView; 
 
public class MainActivity extends AppCompatActivity implements SensorEventListener{ 
  private SensorManager mSensorManager; 
  private Sensor mPressure; 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    // Get an instance of the sensor service, and use that to get an instance of 
    // a particular sensor. 
    mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE); 
    mPressure = mSensorManager.getDefaultSensor(Sensor.TYPE_LIGHT); 
  } 
  @Override 
  public final void onAccuracyChanged(Sensor sensor, int accuracy) { 
    // Do something here if sensor accuracy changes. 
  } 
  @Override 
  public final void onSensorChanged(SensorEvent event) { 
    float light = event.values[0]; 
    TextView v = (TextView)findViewById(R.id.textView); 
    v.setText(Float.toString(light)); 
    // Do something with this sensor data. 
  } 
  @Override 
  protected void onResume() { 
    // Register a listener for the sensor. 
    super.onResume(); 
    mSensorManager.registerListener(this, mPressure, SensorManager.SENSOR_DELAY_NORMAL); 
  } 
 
  @Override 
  protected void onPause() { 
    // Be sure to unregister the sensor when the activity pauses. 
    super.onPause(); 
    mSensorManager.unregisterListener(this); 
  } 
} 

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" 
  android:paddingBottom="@dimen/activity_vertical_margin" 
  android:paddingLeft="@dimen/activity_horizontal_margin" 
  android:paddingRight="@dimen/activity_horizontal_margin" 
  android:paddingTop="@dimen/activity_vertical_margin" 
  tools:context="hk.ust.cse.comp107x.ligthsensor.MainActivity"> 
 
  <TextView 
    android:id="@+id/textView" 
    android:textSize="50dp" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="Hello World!" 
    android:layout_alignParentTop="true" 
    android:layout_centerHorizontal="true" 
    android:layout_marginTop="177dp" /> 
</RelativeLayout> 

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
  package="hk.ust.cse.comp107x.ligthsensor"> 
 
  <application 
    android:allowBackup="true" 
    android:icon="@mipmap/ic_launcher" 
    android:label="@string/app_name" 
    android:supportsRtl="true" 
    android:theme="@style/AppTheme"> 
    <activity android:name=".MainActivity"> 
      <intent-filter> 
        <action android:name="android.intent.action.MAIN" /> 
 
        <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
    </activity> 
  </application> 
 
</manifest>