如何在Android棉花糖上获取wifi扫描结果？

Question

I want get wifi scan result on my marshmallow device.
First, my area have many wifi ap.
If get wifi scan result on marshmallow device. add ACCESS_COARSE_LOCATION permission.

my source

@Override
public void onClick(View v) { 

        if (Build.VERSION.SDK_INT == Build.VERSION_CODES.M) {
            int permissionResult = checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION);

            if (permissionResult == PackageManager.PERMISSION_DENIED) {

                if (shouldShowRequestPermissionRationale(Manifest.permission.ACCESS_COARSE_LOCATION)) {
                    AlertDialog.Builder dialog = new AlertDialog.Builder(MainActivity.this);
                    dialog.setTitle("need permission")
                            .setMessage("permission grant?")
                            .setPositiveButton("yes", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                                        requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, 1000);
                                    }
                                }
                            }).setNegativeButton("no", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            Toast.makeText(MainActivity.this, "cancel", Toast.LENGTH_LONG).show();
                        }
                    }).create().show();

                } else {
                    requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, 1000);
                }
            } else {
                result = getScanWifiResult();
            }

    }
}


@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    if (requestCode == 1000) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                Log.d(TAG, "request permission");
                result = mUtils.getScanWifiResult();
            }
        } else {
            Toast.makeText(MainActivity.this, "permission denied", Toast.LENGTH_LONG).show();
        }
    }
}



public List<String> getScanWifiResult() {
    List<ScanResult> result;
    mWifiManager.startScan(); // service register
    result = mWifiManager.getScanResults();
    ArrayList<String> ssid = new ArrayList<String>();
    if (result != null) {
        for (ScanResult scan : result) {
             ssid.add(scan.SSID);
        }
    } 
    return ssid;
  }

With this source on marshmallow device or gradle targetSdkVersion above 23. wifi scan result null, but for gradle targetSdkVersion below 21 or kitkat device.
wifi scan result many wifi ap.

Why wifi scan result null on marshmallow device?

Answer 1

Because your calling it inside the else statement of the if(permission == denied)

Your result = getScanWifiResult() should be outside the permissions if-else statement.