我想让手机在锁屏状态下继续监听onSignalStrengthsChanged，用wakelock为什么不能实现？

Question

重要代码：
private class MyPhoneStateListener extends PhoneStateListener {
		/* 从得到的信号强度,每个tiome供应商有更新 */
		@Override
		public void onSignalStrengthsChanged(SignalStrength signalStrength) {
			acquire1();
			//acquire(true);
			super.onSignalStrengthsChanged(signalStrength);
			Toast.makeText(getApplicationContext(),
					"手机信号强度asu为 "
							+ String.valueOf(signalStrength.getGsmSignalStrength()),
					Toast.LENGTH_SHORT).show();
			 Log.i(DISPLAY_SERVICE, "operator name =周周周周周装置周周周周周 ");
		asu=signalStrength.getGsmSignalStrength();
		getSystemService(Context.POWER_SERVICE);
		PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);  
		boolean isScreen=pm.isScreenOn();
		if(dbm==1&&isScreen!=true&&asu<29)
		{	
		dbm=0;
		acquire(true);
		TextView2.setText("你liang");
		Intent it=new Intent("tw.android.MY_BROADCAST");//调用广播
		sendBroadcast(it);	
		}
		}
	};
	public void acquire1() { 
//release(); 
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE); 
int mode = PowerManager.PARTIAL_WAKE_LOCK;
if(mWakeLock==null)
{mode=mode|PowerManager.ON_AFTER_RELEASE;
mWakeLock = pm.newWakeLock(mode, ""); 
Log.i(DISPLAY_SERVICE, "重中之重重中之重");
mWakeLock.acquire(); }
} 
public void release() { 
if (mWakeLock != null) { 
    mWakeLock.release(); 
    mWakeLock = null; 
} 
}