Question

我正在尝试创建一个返回可用Wi-Fi网络的代码。但我遇到了一个问题。 getScanResults返回为空，但我已经给出了所有可能的网络权限。

public class MainActivity extends Activity {

    private static final String  TAG = "My Activity";
    private StringBuilder sb = new StringBuilder();
    private TextView tv;
    List<ScanResult> scanList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        final String CoarseLocation = Manifest.permission.ACCESS_COARSE_LOCATION;
        final String AccessWifi = Manifest.permission.ACCESS_WIFI_STATE;
        final String ChangeWifi = Manifest.permission.CHANGE_WIFI_STATE;

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.textView2);
        Button btn = (Button) findViewById(R. id. button);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v)
            {
                if (checkSelfPermission(CoarseLocation) != PackageManager.PERMISSION_GRANTED)
                {
                    requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION}, 123);
                }

                if (checkSelfPermission(AccessWifi) != PackageManager.PERMISSION_GRANTED)
                {
                    requestPermissions(new String[]{Manifest.permission.ACCESS_WIFI_STATE, Manifest.permission.ACCESS_WIFI_STATE}, 123);
                }

                if (checkSelfPermission(ChangeWifi) != PackageManager.PERMISSION_GRANTED)
                {
                    requestPermissions(new String[]{Manifest.permission.CHANGE_WIFI_STATE, Manifest.permission.CHANGE_WIFI_STATE}, 123);
                }

                LocationManager lman = (LocationManager) getApplicationContext().getSystemService(Context.LOCATION_SERVICE);
                boolean network_enabled = false;

                try
                {
                    network_enabled = lman.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
                } catch (Exception ex) {}

                if (!network_enabled)
                {
                    startActivityForResult(new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS), 0);
                }

                final WifiManager mWifiManager = (WifiManager) getSystemService(WIFI_SERVICE);
                mWifiManager.setWifiEnabled(true);

                IntentFilter filter = new IntentFilter();
                filter.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);

                registerReceiver(new BroadcastReceiver() {
                    @Override
                    public void onReceive(Context context, Intent intent) {

                        List<ScanResult> results = mWifiManager.getScanResults();
                        final int Amount = results.size();

                        Log.v(TAG, "Wifi Scan Results Count: " + Amount);

                        int num = 1;

                        while (num <= Amount)
                        {
                            Log.v(TAG, "SSID  =  " + results.get(num).SSID);

                            num = num+1;
                        }
                    }
                }, filter);

                mWifiManager.startScan();
            }
        });
    }
}

更新

以下是我在启用位置服务时尝试扫描Wi-Fi时出现的错误。我只进行了一个月的android编程，所以有人可以解释这个错误意味着什么吗？

10-15 21:55:21.843 21441-21441/com.example.gytis.imlost E/AndroidRuntime: FATAL EXCEPTION: main
      Process: com.example.gytis.imlost, PID: 21441
      java.lang.RuntimeException: Error receiving broadcast Intent { act=android.net.wifi.SCAN_RESULTS flg=0x4000010 (has extras) } in com.example.gytis.imlost.MainActivity$1$1@a300383
          at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:935)
          at android.os.Handler.handleCallback(Handler.java:739)
          at android.os.Handler.dispatchMessage(Handler.java:95)
          at android.os.Looper.loop(Looper.java:148)
          at android.app.ActivityThread.main(ActivityThread.java:5527)
          at java.lang.reflect.Method.invoke(Native Method)
          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
       Caused by: java.lang.IndexOutOfBoundsException: Invalid index 2, size is 2
          at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
          at java.util.ArrayList.get(ArrayList.java:308)
          at com.example.gytis.imlost.MainActivity$1$1.onReceive(MainActivity.java:110)
          at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:925)
          at android.os.Handler.handleCallback(Handler.java:739) 
          at android.os.Handler.dispatchMessage(Handler.java:95) 
          at android.os.Looper.loop(Looper.java:148) 
          at android.app.ActivityThread.main(ActivityThread.java:5527) 
          at java.lang.reflect.Method.invoke(Native Method) 
          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) 
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)

请帮忙。谢谢！

Answer 1

如果您在使用Android 6或更高版本的设备上使用它，则必须启用位置服务才能获得扫描结果，即使您拥有正确的权限。

有关详细信息，请参阅此处：https://stackoverflow.com/a/32151901/6951450

Answer 2

从Android 6开始，您必须启用位置服务才能获得所需的结果。授予权限只是完成的一半工作。

您还可以触发将用户重定向到此设置的意图：

Intent myIntent = new Intent( Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(myIntent);

位置服务是必要的，因为当您访问扫描结果时，您可以访问BSSID（接入点的地址）等信息。此信息还可用于检测设备的位置。通过要求定位服务，操作系统可确保用户在使用您的应用时了解他们的位置信息。

Answer 3

我也遇到了同样的问题，有一天应用程序运行良好，第二天早上没有运行，getScanResults() 返回 0，尽管所有权限都在清单中设置，我似乎正在检查 Activity。事实证明，您现在必须检查 ACCESS_FINE_LOCATION。

因此将onclick中的代码更改为如下

@Override
        public void onClick(View v)
        { if ( Build.VERSION.SDK_INT >= 23){
        if (ActivityCompat.checkSelfPermission(context, Manifest.
                permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
                && ActivityCompat.checkSelfPermission(context,
                Manifest.permission.ACCESS_COARSE_LOCATION) !=
                PackageManager.PERMISSION_GRANTED ){
            
            requestPermissions(new String[]{
                            Manifest.permission.ACCESS_FINE_LOCATION},
                    REQUEST_CODE_ASK_PERMISSIONS);
            Log.i(TAG, "User location NOT ENABLED, waiting for permission");

        }else{
            //Start scanning for wifi
        }
    }}

我的清单权限是：

<uses-permission android:name = "android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name = "android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_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.INTERNET" />

希望这对您或将来的某人有所帮助:)

Android Studio：getScanResults返回空，但是给出了权限

3 个答案: