Android市場上有一款叫Wifijumper的軟件,實現相同ssid的多個AP之間根據wifi信號的強弱與閥值進行判斷,實現自動切換AP的功能。目前在android4.2之前系統都沒有該功能,對於google來講,這是個相當簡單的問題,不明白爲什麼一直都不支持該功能。鄙人之前在某個方案公司就遇到過客戶需要該功能。以下是鄙人實現的具體過程,希望對大家有些許的幫助。
首先我們必須時刻監聽當前wifi的信號強度,那麼我們的手機連上wifi之後狀態蘭就會有wifi圖標出來,並且信號強度變化信號格也要跟隨變化,這部分工作是在SystemUI完成的。在目錄
framework/base/packages/SystemUI/src/com/android/systemui/statusbar/policy/NetworkController.java
這個類就是SystemUI監聽網絡連接狀態的Receiver。
在OnReceive方法中
if ( action.equals( WifiManager.RSSI_CHANGED_ACTION )
|| action.equals( WifiManager.WIFI_STATE_CHANGED_ACTION )
|| action.equals( WifiManager.NETWORK_STATE_CHANGED_ACTION ) )
{
updateWifiState( intent );
refreshViews();
}
調用了 updateWifiState(Intent intent)方法,那麼我們的切換功能就可以放到這個updateWifiState方法中:
mWifiRssi = intent.getIntExtra(WifiManager.EXTRA_NEW_RSSI, -200);
mWifiLevel = WifiManager.calculateSignalLevel(
mWifiRssi, WifiIcons.WIFI_LEVEL_COUNT);
添加一下代碼:
+import android.net.wifi.ScanResult; /* 導入包 */
boolean isWorking = false;
if ( mWifiConnected )
{
WifiInfo wifiInfo = ( (WifiManager) mContext.getSystemService( Context.WIFI_SERVICE ) ).getConnectionInfo();
/* ---- */
if ( (wifiInfo != null) && !isWorking )
{
String curentSSID = wifiInfo.getSSID();
String currentBssid = wifiInfo.getBSSID();
Log.e( TAG,
"updateWifiState curentSSID == " + curentSSID +
" currentBssid = " + currentBssid + " mWifiRssi = " +
mWifiRssi + " mWifiLevel = " + mWifiLevel );
List<ScanResult> sameSSIDList = new ArrayList<ScanResult>();
List<ScanResult> list = mWifiManager.getScanResults();
if ( list != null )
{
for ( ScanResult rt : list )
{
Log.e( TAG,
"list ---------- onReceive():ScanResult = " +
rt );
if ( curentSSID.equals( rt.SSID ) )
{
sameSSIDList.add( rt );
}
}
}
if ( sameSSIDList.size() >= 2 )
{
ScanResult strongestRssi = sameSSIDList.get( 0 );
for ( int i = 1; i <= (sameSSIDList.size() - 1); i++ )
{
if ( sameSSIDList.get( i ).level > strongestRssi.level )
{
strongestRssi = sameSSIDList.get( i );
}
}
/*
* int strongestLevel = WifiManager.calculateSignalLevel(
* strongestRssi.level, WifiIcons.WIFI_LEVEL_COUNT);
*/
Log.e( TAG,
"strongestRssi = " + strongestRssi +
" mWifiRssi = " + mWifiRssi );
/* if(!currentBssid.equals(strongestRssi.BSSID) && (strongestLevel - mWifiLevel) >= 1){ */
if ( (strongestRssi.level - mWifiRssi) >= 18 )
{
Log.e( TAG, "do reconnect now !!!!!!!!!!!!" );
mWifiManager.disconnect();
mWifiManager.reconnect();
isWorking = true;
}
}
}
}
邏輯其實很簡單,就是根據當前ssid去掃描的列表中找相同ssid的ap如果有,就找信號最強的,當最強的那個信號比當前的信號超過一定的值時,斷開重連。當然這種做法還是效率不是高的。原因就是當你在不停的移動中,傳過來的信號值其實和當前的實際值有一定的差異。