传感器取值如何保持不变？

[Dylumi]

package com.example.n_on;

import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;


public class MainActivity extends AppCompatActivity implements SensorEventListener {
    private SensorManager sm_L;
    private Boolean doWrite;
    float lux;
    static float array=9999999;
    static  int i = 0;
    private TextView mTextView,mTextView2;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mTextView = (TextView)findViewById(R.id.textView);
        mTextView2= (TextView)findViewById(R.id.textView2);
        sm_L = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
    }

    @Override
    protected void onResume() {
        super.onResume();
        sm_L.registerListener( this,sm_L.getDefaultSensor(Sensor.TYPE_LIGHT),SensorManager.SENSOR_DELAY_GAME);
    }

    public void onSensorChanged(SensorEvent event) {
        lux = event.values[0];//获取当前 光感值
        mTextView.setText("数值" + lux);
//-------------------------------------------------------------------
        for (; i < 10; i++) {
                new Thread() {
                    public void run() {
                        try {
                            Thread.sleep(10000);
                            doWrite = true;
                            if (doWrite) {
                                array = lux;//锁定当前光感值
                                doWrite = false;
                            }
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }
                }.start();
//---------------------------------------------------------------------------------------------
        }
        //当光线强度大于10s前的值时 播放声音。
        if (lux>array){
            playMusic();
        }
    }
    public void onAccuracyChanged(Sensor sensor, int accuracy) {

    }
    private void playMusic() {
        // 播放音乐
        MediaPlayer mPlayer = MediaPlayer.create(MainActivity.this, R.raw.alarm);
        mPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        try {
            mPlayer.prepare();
        } catch (Exception e) {
            e.printStackTrace();
        }
        //理论上应该异步准备，在准备完成的回调函数中启动播放器
        mPlayer.start();
    }
}

如源代码，我想取 现在时刻的光感值 的值，再n秒之后再与前面取到的值比较。虚线之间的代码， 自己乱写的，不知道大神们有没有更好的方法。
还有个问题，就是音乐会重叠播放。不懂如何解决。