问题
Friends, I want to find all available WiFi networks and display them in a list I have tried as below. But it\'s not working. I have edited my code, and now I got the result but with all the result that I don\'t need. I only need names of wifi network in my list.
public class MainActivity extends Activity {
TextView mainText;
WifiManager mainWifi;
WifiReceiver receiverWifi;
List<ScanResult> wifiList;
StringBuilder sb = new StringBuilder();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mainText = (TextView) findViewById(R.id.tv1);
mainWifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
if (mainWifi.isWifiEnabled() == false)
{
// If wifi disabled then enable it
Toast.makeText(getApplicationContext(), \"wifi is disabled..making it enabled\",
Toast.LENGTH_LONG).show();
mainWifi.setWifiEnabled(true);
}
receiverWifi = new WifiReceiver();
registerReceiver(receiverWifi, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
mainWifi.startScan();
mainText.setText(\"Starting Scan...\");
}
public boolean onCreateOptionsMenu(Menu menu) {
menu.add(0, 0, 0, \"Refresh\");
return super.onCreateOptionsMenu(menu);
}
public boolean onMenuItemSelected(int featureId, MenuItem item) {
mainWifi.startScan();
mainText.setText(\"Starting Scan\");
return super.onMenuItemSelected(featureId, item);
}
protected void onPause() {
unregisterReceiver(receiverWifi);
super.onPause();
}
protected void onResume() {
registerReceiver(receiverWifi, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
super.onResume();
}
// Broadcast receiver class called its receive method
// when number of wifi connections changed
class WifiReceiver extends BroadcastReceiver {
// This method call when number of wifi connections changed
public void onReceive(Context c, Intent intent) {
sb = new StringBuilder();
wifiList = mainWifi.getScanResults();
sb.append(\"\\n Number Of Wifi connections :\"+wifiList.size()+\"\\n\\n\");
for(int i = 0; i < wifiList.size(); i++){
sb.append(new Integer(i+1).toString() + \". \");
sb.append((wifiList.get(i)).toString());
sb.append(\"\\n\\n\");
}
mainText.setText(sb);
}
}
}
回答1:
You need to create a BroadcastReceiver to listen for Wifi scan results:
private final BroadcastReceiver mWifiScanReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context c, Intent intent) {
if (intent.getAction().equals(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION)) {
List<ScanResult> mScanResults = mWifiManager.getScanResults();
// add your logic here
}
}
}
In onCreate() you would assign mWifiManager and initiate a scan:
mWifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
registerReceiver(mWifiScanReceiver,
new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
mWifiManager.startScan();
getScanResults() will return data only if you have appropriate permissions. For this, add one of the following two lines to your AndroidManifest.xml:
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
Also note that in API 23+, permissions must be requested at runtime. (For a lab environment, you can also grant permissions manually in Settings instead—less coding required, but not recommended for an end-user app.)
Note that the code which handles your scan results would run every time a new scan result is available, updating the result.
回答2:
After Android 6.0
If your Android OS version is 6.0 or above then your application must ask for the following permission at runtime(Either of the following).
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
How to ask the permission at runtime
Just add this code in the onResume method of your activity
@Override
public void onResume()
{
super.onResume();
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
{
if(checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
{
requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, 87);
}
}
}
What will happen if you don't have the above permission at Runtime?
Wifi.getScanResults() will return 0 results.
Many people including me have faced this problem in Nexus 5 phones and referred to it as a "bug".
How to scan and read wifi networks? (Deeper Understanding)
Scanning can be requested by
wifiManager.startScan();
boolean startScan() returns true or false immediately based on the fact whether the scan has started successfully or not.
However it starts an asynchronous event which sends an intent (WifiManager.SCAN_RESULTS_AVAILABLE_ACTION) when the scan completes. Since the scan results (asynchronous event result) will not be available immediately, you will have to register your activity with a BroadcastReceiver.
Here is the code snippet to read those results(asynchronously) using BroadcastReceiver.
public class WifiScanReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
if(intent.getAction().equals(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION))
{
List<ScanResult> scanResults = wifimanager.getScanResults();
// Write your logic to show in the list
}
}
}
You can see this demo on BroadcastReceiver
Relevant links
Scan result returns an empty list in Android 6.0
回答3:
class WifiReceiver extends BroadcastReceiver {
public void onReceive(Context c, Intent intent) {
sb = new StringBuilder();
wifiList = mainWifi.getScanResults();
for (int i = 0; i < wifiList.size(); i++){
sb.append(new Integer(i+1).toString() + ".");
sb.append((wifiList.get(i)).SSID);
sb.append("\n");
}
mainText.setText(sb);
}
}
来源：https://stackoverflow.com/questions/18741034/how-to-get-available-wifi-networks-and-display-them-in-a-list-in-android