取得 wifi scan ap result : ScanResult

在 android 手機中 -> 設定 -> Wi-Fi , 每隔一段時間會自動搜尋附近的wifi ap的訊息並顯示在列表上, 本篇介紹如何同步取得這些wifi ap的訊息
這些wifi ap的訊息是藉由ScanResult來顯示, ScanResult 類別相當簡單, 請參考官網
而每次搜尋wifi ap的動作都是以Broadcast的方式來達成, 所以我們只要建立一個專門來接收該動作的Broadcast Receiver 就能自動同步取得其搜尋結果(ScanResult)

package com.foxx.wifiapreceiver;
import java.util.List;
import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiManager;
import android.util.Log;
public class WifiApReceiver extends BroadcastReceiver
{
    private static final String TAG = "WifiApResult";
    private Activity mActivity;
    public WifiApReceiver(Activity activity) {
        mActivity = activity;
        mActivity.registerReceiver(this, new IntentFilter(
                WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
    }
    @Override
    public void onReceive(Context context, Intent intent)
    {
        getScanResults();
    }
    private void getScanResults()
    {
        List<ScanResult> scanResults = getWifiManager().getScanResults();
        Iterator<ScanResult> iter = scanResults.iterator();
        while (iter.hasNext()) {
            showAllFieldOfScanResult(iter.next());
        }
    }
    private WifiManager getWifiManager()
    {
        return (WifiManager) mActivity.getSystemService(Context.WIFI_SERVICE);
    }
    private void showAllFieldOfScanResult(ScanResult scanResult)
    {
        Log.d(TAG, "--------------------------------------");
        Log.d(TAG, "scanResult.SSID:" + scanResult.SSID);
        Log.d(TAG, "scanResult.BSSID:" + scanResult.BSSID);
        Log.d(TAG, "scanResult.capabilities:" + scanResult.capabilities);
        Log.d(TAG, "scanResult.frequency:" + scanResult.frequency);
        Log.d(TAG, "scanResult.level:" + scanResult.level);
        Log.d(TAG, "scanResult.BSSID:" + scanResult.describeContents());
    }
    public void unregisterReceiver()
    {
        try {
            mActivity.unregisterReceiver(this);
        } catch (Exception e) {
            Log.d(TAG, "execption in unregisterReceiver");
        }
    }
}

1. 在constructor註冊了receiver
2. OnReceiver 為 callback function , 只要有搜尋wifi ap的動作, OnReceiver就會被呼叫
 
在AndroidManifest.xml加入2個必要的permission

<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"></uses-permission>

 
使用的方式相當簡單

package com.foxx.wifiapreceiver;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity
{
    private WifiApReceiver mWifiReceiver;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initWifiReceiver();
    }
    private void initWifiReceiver(){
        mWifiReceiver = new WifiApReceiver(this);
    }
    @Override
    protected void onStop()
    {
        mWifiReceiver.unregisterReceiver();
        super.onStop();
    }
}

只要注意在onStop要unregister receiver即可