【Android代码片段之八】监听Android屏幕是否锁屏

原文网址：http://blog.csdn.net/m_changgong/article/details/7608911 作者：张燕广

实现方法：1）通过BroadcastReceiver接收广播Intent.ACTION_SCREEN_ON和Intent.ACTION_SCREEN_OFF可以判断屏幕状态是否锁屏，但是只有屏幕状态发生改变时才会发出广播；

2）如果要在屏幕状态发生改变之前就想获取屏幕状态，可以通过反射机制调用PowerManager的isScreenOn方法 。

具体实现，见代码：

实现Screen状态监听的类ScreenObserver，实现如下：

<pre name="code" class="java">public class ScreenObserver {
	private static String TAG = "ScreenObserver";  
    private Context mContext;  
    private ScreenBroadcastReceiver mScreenReceiver;  
    private ScreenStateListener mScreenStateListener;  
    private static Method mReflectScreenState;  
      
    public ScreenObserver(Context context){  
        mContext = context;  
        mScreenReceiver = new ScreenBroadcastReceiver();  
        try {  
            mReflectScreenState = PowerManager.class.getMethod("isScreenOn",  
                    new Class[] {});  
        } catch (NoSuchMethodException nsme) {  
            Log.d(TAG, "API < 7," + nsme);  
        }  
    }  
      
    /** 
     * screen状态广播接收者 
     * @author zhangyg 
     * 
     */  
    private class ScreenBroadcastReceiver extends BroadcastReceiver{  
        private String action = null;  
        @Override  
        public void onReceive(Context context, Intent intent) {  
            action = intent.getAction();  
            if(Intent.ACTION_SCREEN_ON.equals(action)){  
                mScreenStateListener.onScreenOn();  
            }else if(Intent.ACTION_SCREEN_OFF.equals(action)){  
                mScreenStateListener.onScreenOff();  
            }  
        }  
    }  
      
      
    /** 
     * 请求screen状态更新 
     * @param listener 
     */  
    public void requestScreenStateUpdate(ScreenStateListener listener) {  
        mScreenStateListener = listener;  
        startScreenBroadcastReceiver();  
          
        firstGetScreenState();  
    }  
      
    /** 
     * 第一次请求screen状态 
     */  
    private void firstGetScreenState(){  
        PowerManager manager = (PowerManager) mContext  
                .getSystemService(Activity.POWER_SERVICE);  
        if (isScreenOn(manager)) {  
            if (mScreenStateListener != null) {  
                mScreenStateListener.onScreenOn();  
            }  
        } else {  
            if (mScreenStateListener != null) {  
                mScreenStateListener.onScreenOff();  
            }  
        }  
    }  
      
    /** 
     * 停止screen状态更新 
     */  
    public void stopScreenStateUpdate(){  
        mContext.unregisterReceiver(mScreenReceiver);  
    }  
      
    /** 
     * 启动screen状态广播接收器 
     */  
    private void startScreenBroadcastReceiver(){  
        IntentFilter filter = new IntentFilter();  
        filter.addAction(Intent.ACTION_SCREEN_ON);  
        filter.addAction(Intent.ACTION_SCREEN_OFF);  
        mContext.registerReceiver(mScreenReceiver, filter);  
    }  
      
    /** 
     * screen是否打开状态 
     * @param pm 
     * @return 
     */  
    private static boolean isScreenOn(PowerManager pm) {  
        boolean screenState;  
        try {  
            screenState = (Boolean) mReflectScreenState.invoke(pm);  
        } catch (Exception e) {  
            screenState = false;  
        }  
        return screenState;  
    }  
      
    public interface ScreenStateListener {  
        public void onScreenOn();  
        public void onScreenOff();  
    }  
}

测试ScreenObserver功能的示例类ScreenObserverActivity，实现如下：

public class ScreenObserverActivity extends Activity {

	 private String TAG = "ScreenObserverActivity";  
	    private ScreenObserver mScreenObserver;  
	      
	    @Override  
	    public void onCreate(Bundle savedInstanceState) {  
	        super.onCreate(savedInstanceState);  
	        setContentView(R.layout.main);  
	  
	        mScreenObserver = new ScreenObserver(this);  
	        mScreenObserver.requestScreenStateUpdate(new ScreenStateListener() {  
	            @Override  
	            public void onScreenOn() {  
	                doSomethingOnScreenOn();  
	            }  
	  
	            @Override  
	            public void onScreenOff() {  
	                doSomethingOnScreenOff();  
	            }  
	        });  
	    }  
	  
	    private void doSomethingOnScreenOn() {  
	        Log.i(TAG, "Screen is on");  
	    }  
	  
	    private void doSomethingOnScreenOff() {  
	        Log.i(TAG, "Screen is off");  
	    }  
	      
	    @Override  
	    protected void onDestroy() {  
	        super.onDestroy();  
	        //停止监听screen状态  
	        mScreenObserver.stopScreenStateUpdate();  
	    }  
}