Android 6.0错误?有权限，但在Android 6.0中getScanResults()仍返回空列表 [英] Android 6.0 bug ? Have permission but getScanResults() still return empty list in Android 6.0

问题描述

我已经在Android 6.0版-棉花糖中请求了权限，但是使用getScanResults()时它仍然返回空列表.

I have request the permission in android version 6.0 - Marshmallow,But it still return empty list when using getScanResults().

 private boolean checkPermission() {

    List<String> permissionsList = new ArrayList<String>();

    if (ContextCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        permissionsList.add(Manifest.permission.ACCESS_FINE_LOCATION);
    }
    if (ContextCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        permissionsList.add(Manifest.permission.ACCESS_COARSE_LOCATION);
    }

    if (permissionsList.size() > 0) {
        ActivityCompat.requestPermissions((Activity) mContext, permissionsList.toArray(new String[permissionsList.size()]),
                REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS);
        return false;
    }
    return true;
}

获得请求权限后，在onRequestPermissionsResult方法中，我获得了ACCESS_FINE_LOCATION和ACCESS_COARSE_LOCATION的许可，但是我仍然无法获得扫描结果

After request permission, then in the onRequestPermissionsResult method,I have get the permission of ACCESS_FINE_LOCATION and ACCESS_COARSE_LOCATION, But I still can not the scan result

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions,
                                       int[] grantResults) {
    switch (requestCode) {
        case REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS:
            if (permissions.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED ||
                    (permissions.length == 2 && grantResults[0] == PackageManager.PERMISSION_GRANTED &&
                            grantResults[1] == PackageManager.PERMISSION_GRANTED)){
                List<ScanResult> scanResults = mWifi.getScanResults();
                //list is still empty
            }
             else {
                // Permission Denied
                Toast.makeText(mContext, getString(R.string.permission_deny), Toast.LENGTH_LONG).show();
            }
            break;
    }
}

这是android M的错误吗?

Is this a bug of android M?

推荐答案

请求权限后，您仍然需要启用WIFI.简而言之，您必须按顺序执行此操作以扫描外围:

You still need to enable WIFI after you request the permission. So in short, you have to do this in sequence for scanning the perimeter:

1. 请求必要的权限( ACCESS_WIFI_STATE，CHANGE_WIFI_STATE，ACCESS_COARSE_LOCATION ).另外，如您所述，在MM上，您需要在运行时提出要求.
2. 使用WifiManager#setWifiEnabled(true)启用WIFI ；
3. 您不必必须以编程方式启用我知道的位置信息访问权限. 但是请阅读下面的注释 .
4. 您必须为 SCAN_RESULTS_AVAILABLE_ACTION 注册BrodcastReceiver.您可以在此处获得扫描已准备就绪的信号.不管您是通过AndroidManifest注册还是在运行时动态注册，只要在下一步之前完成注册即可.
5. 您必须使用WifiManager# startScan()才能请求精确到一个网络扫描更新.如果您想要更多，请设置计时器/计时器任务(推荐)或在收到上一个计时器(可能永远不会出现)时重新安排时间
6. 只有在BroadcastReceiver onReceive上，您才能调用WifiManager#getScanResults() 有可能的结果 .

1. Request the necessary permissions (ACCESS_WIFI_STATE, CHANGE_WIFI_STATE, ACCESS_COARSE_LOCATION). Additionally, on MM you need to request this at run-time, as you stated.
2. Enable WIFI with WifiManager#setWifiEnabled(true);
3. You don't have to enable location access programatically that I know off. But read the note below.
4. You have to register a BrodcastReceiver for SCAN_RESULTS_AVAILABLE_ACTION. This is where you get the signal that the scans are ready. Doesn't matter if you register through AndroidManifest or dynamically at run-time, as long as it's done before the next step.
5. You have to WifiManager#startScan() in order to request exactly ONE update for network scans. If you want more, set up a timer/timertask (recommended) or reschedule when you receive the previous one (which might never come)
6. Only on the BroadcastReceiver onReceive will you be able to call WifiManager#getScanResults() with plausible results.

注意:在某些手机(Moto X 2014)上，我注意到您需要启用基本位置才能获得任何结果，只有用户(系统用户界面)似乎能够在/离开.如果用户完全不在位置上，即使系统UI可以，我似乎也无法获得非空的结果列表.这可能是由于棉花糖需要在用户应用程序中进行蓝牙和WiFi扫描的位置，以及摩托罗拉的错误实施，或者是最新的棉花糖错误跟踪器中已修复的缺陷，而摩托罗拉的最新OTA中未修复该缺陷，因为这在以下情况中不会发生Nexus 5或Galaxy S6.

Note: On some phones (Moto X 2014), I noticed you need basic location enabled to get any results, which only the user (system UI) seems to be able to do trigger on/off. If the user has location completely off, I can't seem to get a non-empty result list, even though the system UI can. This is likely due to Marshmallow needs to have location for Bluetooth and WiFi scans in user apps, and a bad implementation by Motorola, or a defect already fixed in latest Marshmallow bug tracker but not in Motorola's latest OTA, because this doesn't happen in a Nexus 5 or a Galaxy S6.

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