Develop Reference

How to get a list of wi-fi networks

Good afternoon. For a very long time I have been trying to get a list of wi-fi networks using WifiManager. When I try to get through a virtual device, I get only one fictional network with an SSID: Android Wifi. However, I do not receive networks from my real environment. When using a real device, it is not possible to get any network.
What is the mistake?
Rights in AndroidManifest:
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
The code I use to work with Wifi:
WifiManager wifiManager = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);
wifiManager.startScan();
List<ScanResult> availNetworks = wifiManager.getScanResults();
Log.d("STRING",Integer.toString(availNetworks.size()));
if (availNetworks.size() > 0) {
for (int i=0; i< availNetworks.size();i++) {
String buf = availNetworks.get(i).toString();
String[] buflist = buf.split(",");
Log.d("STRING","In");
String elementWssid = buflist[0];
String elementWsec = buflist[2];
String elementWlevel = buflist[3];
String SSID = elementWssid.split(": ")[1];
String Sec = elementWsec.split(": ")[1];
String level = elementWlevel.split(": ")[1];
Log.d("STRING",SSID);
Log.d("STRING",Sec);
Log.d("STRING",level);
}
}
Permits have already been issued.

Solved a problem. In the application settings there is such a section as "other permissions". It contains permissions to work with wi-fi, which by default are in the "ask" status, after changing the status to "allow" the problem was solved. For some reason, android doesn't feel the need to ask for permissions like location.
P.s.
Xiaomi has a separate slider to access the location of ALL apps, it needs to be turned on to give permissions.
AndroidWifi on a virtual device is a test network for checking the performance of applications, since it does not know how to work with real networks.

Android Bluetooth Discovery BroadcasterReceiver not working

I just cannot get Android to scan for Bluetooth devices. I've tried several different approaches, but none of them work. Here is my latest code.
// Create a BroadcastReceiver for ACTION_FOUND.
devicesFoundReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// Discovery has found a device. Get the BluetoothDevice
// object and its info from the Intent.
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
String deviceName = device.getName();
String deviceHardwareAddress = device.getAddress(); // MAC address
devicesListArray.add(deviceName + "\n" + deviceHardwareAddress);
arrayAdapter.notifyDataSetChanged();
}
}
};
I register the receiver like this:
_thisContext.registerReceiver(devicesFoundReceiver, filter);
My manifest has these permissions:
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
I call
bluetoothAdapter.startDiscovery();
OnReceive on the broadcastreceiver NEVER fires.
I'm tired of looking at bajillion different websites, some with the same approach, other's don't. But NONE of them work. What am I doing wrong?
Here is the SDK version for reference:
minSdkVersion 26
targetSdkVersion 30

The Bluetooth related actions of mobile phones have nothing to do with net. Your problems are generally caused by the lack of authorized location permissions. When targetsdkversion 23 or above, you need to dynamically request mobile location permission“ android.permission.ACCESS_ FINE_ Location "can search for Bluetooth devices nearby. Of course, you can reduce the targetsdkversion version of the project to below 23. In this way, you do not need to apply for permission dynamically.
Here are some good dynamic permission application open source library, I hope to help you：
https://github.com/googlesamples/easypermissions
https://github.com/permissions-dispatcher/PermissionsDispatcher

Android NDK C++ camera2 API: ACameraManager_getCameraIdList return 0 cameras

I'm trying to create C++ Android native camera wrapper using the NDK camera2 API (from abi level 24). I created some snippet code using an example I found and compile it for target API level 24 and run it on Android 7.1 phone:
ACameraManager *cameraManager = ACameraManager_create();
VB(cameraManager!=nullptr, "Could not create CameraManager.");
camera_status = ACameraManager_getCameraIdList(cameraManager, &m_camera_id_list);
if (camera_status != ACAMERA_OK) {
LOGE("Failed to get camera id list (reason: %d)\n", camera_status);
return ERR_CAMERAAPI_UNKNOWN_ERROR;
}
if (m_camera_id_list->numCameras < 1) {
LOGE("No camera device detected.\n");
return ERR_CAMERAAPI_UNKNOWN_ERROR;
}
When I run this naive code on Xiaomi mi4c Android 7.1 phone I get an empty camera list.
I also tried to run on the same phone a snippet created with Java camera2 API that does the same thing:
import android.hardware.camera2.CameraDevice;
Activity activity = getActivity();
CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
String[] cameraIds = manager.getCameraIdList()
manager.openCamera(cameraIds[0], mStateCallback, mBackgroundHandler);
This time I see in the logical that it actually finds two cameras and print their resolutions.
My manifest of course contains these lines:
<uses-sdk android:minSdkVersion="24" />
<uses-feature android:name="android.hardware.camera2" android:required="true" />
<uses-feature android:name="android.hardware.sensor.gyroscope" android:required="false" />
<uses-permission android:name="android.permission.CAMERA"/>
And I approve the permissions requests.
Does anyone knows why it finds the phone cameras when using the Java camera2 API but does not find them when using the NDK camera2 API?

The NDK camera2 support does not work if
CameraCharacteristics.get(INFO_SUPPORTED_HARDWARE_LEVEL) == INFO_SUPPORTED_HARDWARE_LEVEL_LEGACY
This is probably the case of Xiaomi mi4c.

Mac address for android 6.0 and above shows null

I am using this code to get MAC ADDRESS and display it in my app. The code works fine for all devices except most latest devices and ANDROID BOX.
it shows null for ANDROID BOX and other latest device.
Here is code:
public static String getWifiMacAddress() {
try {
String interfaceName = "wlan0";
List<NetworkInterface> interfaces = Collections.list(NetworkInterface.getNetworkInterfaces());
for (NetworkInterface intf : interfaces) {
if (!intf.getName().equalsIgnoreCase(interfaceName)){
continue;
}
byte[] mac = intf.getHardwareAddress();
if (mac==null){
return "";
}
StringBuilder buf = new StringBuilder();
for (byte aMac : mac) {
buf.append(String.format("%02X:", aMac));
}
if (buf.length()>0) {
buf.deleteCharAt(buf.length() - 1);
}
return buf.toString();
}
} catch (Exception ex) { } // for now eat exceptions
return "";
}
I have written these permissions in manifest file
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

Firstly u will check the permission is granted or not?
WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
WifiInfo wInfo = wifiManager.getConnectionInfo();
String macAddress = wInfo.getMacAddress();
Also, add below permission in your manifest file
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
Please refer this link for 6.0 marshmalow

First you will need to add Internet user permission in AndroidManifest.xml.
<uses-permission android:name="android.permission.INTERNET" />
and then Refer this to get mac address: http://robinhenniges.com/en/android6-get-mac-address-programmatically
And if it doesn't works then refer this Android 6.0 changes
from this i have concluded that,
To provide users with greater data protection, starting in this
release, Android removes programmatic access to the device’s local
hardware identifier for apps using the Wi-Fi and Bluetooth APIs. The
WifiInfo.getMacAddress() and the BluetoothAdapter.getAddress() methods
now return a constant value of 02:00:00:00:00:00.
To access the hardware identifiers of nearby external devices via
Bluetooth and Wi-Fi scans, your app must now have the
ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION permissions.
Note That : you can't get your own MACs even having those permissions. Read carefully, It is said that you can get other devices MACs having those permissions, but not your own.

As in 6.0 and above adding permission in Manifest alone wont work. You should have runtime permission and grant it if not granted.
Check this link:
https://stackoverflow.com/a/30549756/3910281

How to access external usb camera on unrooted android devices

I want to access extern usb cameras via v4l on android.
I tried SimpleWebCam. After some slight modifications of the original source codes, i achieved to make it work on a rooted android device. However, on unrooted devices, it keeps complaining about "not have permission to access "/dev/video*". I checked the permission of /dev/video* with "ls -l /dev/video*", and got
crw-rw---- system camera 81, 0 2015-08-18 18:31 video0
I understand that it means /dev/video* are owned by system, and are readable/writable to users in group "camera". So I think if i add
<uses-permission android:name="android.permission.CAMERA" />
in the manifest of my app, the user id of my app will be added to the group "camera", then my app will be allowed to read data from /dev/video*.
But, it still complains about "not have permission to access /dev/video*" now.
i also tried
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
, but still not working.
Do i miss somthing or misunderstand somthing. Any help or discussion will be appreciated.
The codes i used to open device are
int opendevice(int i)
{
struct stat st;
sprintf(dev_name,"/dev/video%d",i);
if (-1 == stat (dev_name, &st)) {
LOGE("Cannot identify '%s': %d, %s", dev_name, errno, strerror (errno));
return ERROR_LOCAL;
}
if (!S_ISCHR (st.st_mode)) {
LOGE("%s is no device", dev_name);
return ERROR_LOCAL;
}
fd = open (dev_name, O_RDWR);// | O_NONBLOCK, 0);
if (-1 == fd) {
LOGE("Cannot open '%s': %d, %s", dev_name, errno, strerror (errno));
return ERROR_LOCAL;
}
return SUCCESS_LOCAL;
}
The return value of open is always -1, with logcat:
Cannot open '/dev/video3': 13, Permission denied

I finally achieve to read images from the external usb camera on unrooted android devices using an opensource project named uvccamera.
Here is the link, https://github.com/saki4510t/UVCCamera

Try to add also
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
in your manifest file:
http://developer.android.com/reference/android/hardware/Camera.html