通过注册一个BroadcastReceiver监听屏幕状态变化，即可获取手机的锁屏状态。代码示例如下：

public class ScreenReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equals(Intent.ACTION_SCREEN_OFF)) {
            // 手机锁屏了
        } else if (intent.getAction().equals(Intent.ACTION_SCREEN_ON)) {
            // 手机解锁了
        }
    }

}

注册监听器代码如下：

ScreenReceiver mReceiver = new ScreenReceiver();
IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_SCREEN_OFF);
filter.addAction(Intent.ACTION_SCREEN_ON);
registerReceiver(mReceiver, filter);

需要注意的是，为了避免内存泄漏，一定要在合适的时机取消注册该接收器，代码如下：

unregisterReceiver(mReceiver);