getScanResults在Android6.0上返回了一個空列表，範例程式碼：

 public List<ScanResult> getScanResults(String callingPackage) {

 enforceAccessPermission();

 int userId = UserHandle.getCallingUserId();

 int uid = Binder.getCallingUid();

 boolean canReadPeerMacAddresses = checkPeersMacAddress();

 boolean
 
 isActiveNetworkScorer =

 NetworkScorerAppManager.isCallerActiveScorer(mContext, uid);

 boolean hasInteractUsersFull = checkInteractAcrossUsersFull();

 long ident = Binder.clearCallingIdentity();

 try {

 if (!canReadPeerMacAddresses && !isActiveNetworkScorer

 && !isLocationEnabled()) {

 return
 
 new ArrayList<ScanResult>();

 }

 if (!canReadPeerMacAddresses && !isActiveNetworkScorer

 && !checkCallerCanAccessScanResults(callingPackage, uid)) {

 return new ArrayList<ScanResult>();

 }

 if (mAppOps.noteOp(AppOpsManager.OP_WIFI_SCAN, uid, callingPackage)

 != AppOpsManager.MODE_ALLOWED) {

 return
 
 new ArrayList<ScanResult>();

 }

 if (!isCurrentProfile(userId) && !hasInteractUsersFull) {

 return new ArrayList<ScanResult>();

 }

 return mWifiStateMachine.syncGetScanResultsList();

 } finally {

 Binder.restoreCallingIdentity(ident);

 }

 }

 private boolean isLocationEnabled() {

 return Settings.Secure.getInt(mContext.getContentResolver(), Settings.Secure.LOCATION_MODE,

 Settings.Secure.LOCATION_MODE_OFF) != Settings.Secure.LOCATION_MODE_OFF;

 }

重點在：

if (!canReadPeerMacAddresses && !isActiveNetworkScorer

 && !isLocationEnabled()) {

 return new ArrayList<ScanResult>();

 }

可以看到如果定位關閉，那麼將直接返回一個空的列表，當我去開啟定位時，果然就正常的返回了WiFi列表，於是解決方案就是在6.0以上系統中，幫使用者開啟GPS開關：

if (Build.VERSION.SDK_INT >= 23 && !AppUtil.isGpsOPen(this)) {    
Settings.Secure.putInt(getContentResolver(),Settings.Secure.LOCATION_MODE, 1);
}

當然，這裡還需要用到一些許可權：

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.WRITE_SECURE_SETTINGS"/>

如果App不是system app，那麼是獲取不到WRITE_SECURE_SETTINGS許可權的，此時就要引導使用者手動打啟GPS開關，上面的程式碼就會正常。也許有其他解法是不需要同時開啟 GPS。