Android锁屏状态获取音量按键事件

package com.hy2014.phonesafer.activity;

import android.app.Activity;
import android.content.Context;
import android.media.AudioManager;
import android.os.Bundle;

/**
 * 
 * @author Dawin Create 2015-01-19
 */
public class VolumeChangeActivity extends Activity
{

	/**
	 * 当前音量
	 */
	private int currentVolume;
	/**
	 * 控制音量的对象
	 */
	public AudioManager mAudioManager;
	/**
	 * 系统最大音量
	 */
	private int maxVolume;
	/**
	 * 确保关闭程序后，停止线程
	 */
	private boolean isDestroy;

	@Override
	protected void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		isDestroy = false;
		// 获得AudioManager对象
		mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);//音乐音量,如果要监听铃声音量变化，则改为AudioManager.STREAM_RING
		maxVolume = mAudioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
	}

	@Override
	protected void onDestroy()
	{
		super.onDestroy();
		isDestroy = true;
	}

	/**
	 * 监听音量按键的线程
	 */
	private Thread volumeChangeThread;

	/**
	 * 持续监听音量变化 说明： 当前音量改变时，将音量值重置为最大值减2
	 */
	public void onVolumeChangeListener()
	{

		currentVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
		volumeChangeThread = new Thread()
		{
			public void run()
			{
				while (!isDestroy)
					{
						int count = 0;
						boolean isDerease = false;
						// 监听的时间间隔
						try
							{
								Thread.sleep(20);
							} catch (InterruptedException e)
							{
								System.out.println("error in onVolumeChangeListener Thread.sleep(20) " + e.getMessage());
							}

						if (currentVolume < mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC))
							{
								count++;
								currentVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
								// 设置音量等于 maxVolume-2的原因是：当音量值是最大值和最小值时，按音量加或减没有改变，所以每次都设置为固定的值。
								mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, maxVolume - 2,
										AudioManager.FLAG_REMOVE_SOUND_AND_VIBRATE);
							}
						if (currentVolume > mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC))
							{
								count++;
								currentVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
								mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, maxVolume - 2,
										AudioManager.FLAG_REMOVE_SOUND_AND_VIBRATE);
								if (count == 1)
									{
										isDerease = true;
									}

							}

						if (count == 2)
							{
								System.out.println("按下了音量+");

							} else if (isDerease)
							{
								System.out.println("按下了音量-");
							}

					}
			};
		};
		volumeChangeThread.start();
	}

}