android APN切换cmwap实现

有的中国移动的业务需要走CMWAP接入点才能够连接网络的，在做这类应用的时候，不可避免地需要判断当前APN, 切换APN，以及成功连接到网络后连接到服务器。
首先，获取当前的APN有两种方式，一种是从当前系统的网络连接服务获取，即通过
ConnectivityManager conManager= (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo info = conManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
String currentAPN = info.getExtraInfo();
CurrentAPN为‘cmnet’或者’cmwap’。。。
还有一种是通过查询数据库的方式，因为我们设置的APN是存放在本地的xml中的
首先申明APN_URI:
public static final Uri CURRENT_APN_URI = Uri.parse("content://telephony/carriers/preferapn");
public static final Uri APN_LIST_URI = Uri.parse("content://telephony/carriers");
当前选中的APN记录在CURRENT_APN_URI中，而APN_LIST_URI里面是所以的APN列表。通过以下方法获取到选中的apn名字,
public static String getCurrentAPNFromSetting(ContentResolver resolver) {
        Cursor cursor = null;
        try {
            cursor = resolver.query(CURRENT_APN_URI, null, null, null, null);
            String curApnId = null;
            if (cursor != null && cursor.moveToFirst()) {
                curApnId = cursor.getString(cursor.getColumnIndex("apn_id"));
                String apnName1 = cursor.getString(cursor.getColumnIndex("apn"));
            }
            cursor.close();
            //find apn name from apn list
            if (curApnId != null) {
                cursor = resolver.query(APN_LIST_URI, null, " _id = ?", new String[]{curApnId}, null);
                if (cursor != null && cursor.moveToFirst()) {
                    String apnName = cursor.getString(cursor.getColumnIndex("apn"));
                    return apnName;
                }
            }
           
        } catch (SQLException e) {
            Debug.error(e.getMessage());
        } finally {
            if (cursor != null) {
                cursor.close();
            }
        }
       
        return null;
}
获取到APN之后，需要判断是否是cmwap, 如果不是需要更改当前APN为cmwap. 可以通过改数据库的方式：
public static int updateCurrentAPN(ContentResolver resolver, String newAPN) {
        Cursor cursor = null;
        try {
            //get new apn id from list
            cursor = resolver.query(APN_LIST_URI, null, " apn = ? and current = 1", new String[]{newAPN.toLowerCase()}, null);
            String apnId = null;
            if (cursor != null && cursor.moveToFirst()) {
                apnId = cursor.getString(cursor.getColumnIndex("_id"));
            }
            cursor.close();
           
            //set new apn id as chosen one
            if (apnId != null) {
                ContentValues values = new ContentValues();
                values.put("apn_id", apnId);
                resolver.update(CURRENT_APN_URI, values, null, null);
            } else {
                //apn id not found, return 0.
                return 0;
            }
        } catch (SQLException e) {
            Debug.error(e.getMessage());
        } finally {
            if (cursor != null) {
                cursor.close();
            }
        }
       
        //update success
        return 1;
}
在更改数据库之后，网络并不是立刻就能连接上的，我们需要加一个网络连接的消息监听器，发现切换成cmwap之后才开始连接服务器。NetworkChangeReceiver如下：
/*
     * receiver for observing network connection change
     */
    public class NetworkChangeReceiver extends BroadcastReceiver {
        public void onReceive(Context context, Intent intent) {
            if (ConnectivityManager.CONNECTIVITY_ACTION.equals(intent.getAction())) {
                NetworkInfo info = conManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
                String apn = info.getExtraInfo();
                if ("cmwap".equals(apn)) {
                    /*
                     * apn change message is sent out more than once during a second, but it
                     * only happens once practically.
                     */
                    if (mNChangeReceiver != null) {
                        updateDcdContent(mManRequest);
                        HwDcdCmService.this.unregisterReceiver(mNChangeReceiver);
                        mNChangeReceiver = null;
                    }
                }
            }
        }
    }
切换apn总入口如下，包括了检测当前apn, 切换，注册网络监听器：
/*
     * change current network connection to cmwap if it's not.
     */
    public int forceCMWapConnection() {
       
        NetworkInfo info = conManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
        oldAPN = info.getExtraInfo();
       
        //if current apn is not cmwap, we have to switch to cmwap.
        if (!"cmwap".equals(oldAPN)) {
            mNChangeReceiver = new NetworkChangeReceiver();
            //register receiver for wap network connection.
            IntentFilter upIntentFilter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
            registerReceiver(mNChangeReceiver, upIntentFilter); 
            MyUtil.updateCurrentAPN(getContentResolver(), "cmwap");
            return 1;
        }
        return 0;
    }
顺便值得一提的是，使用cmwap来连接网络的时候，仅仅切换接入点还不够，需要在请求头上加上http-route.default-proxy: 10.0.172:80. 代码如下：
HttpParams baseParams = new BasicHttpParams();
        baseParams.setParameter("http.route.default-proxy",
                new HttpHost(“10.0.0.172”, 80));
        HttpConnectionParams.setConnectionTimeout(baseParams, 30 * 1000);
        HttpConnectionParams.setSoTimeout(baseParams, 45 * 1000);
        // establish HttpClient
        DefaultHttpClient client = new DefaultHttpClient(baseParams);
备注：笔者发现ConnectionManager提供了一个conManager.startUsingNetworkFeature(type, value)，第一个设置为ConnectivityManager.TYPE_MOBILE， 第二个为”mms”的时候，也可以进行网络的切换，不涉及到setting里面的APN值的改变。第二个参数为APN接入点中的APN类型。但是这需要framework层的支持。中移动的Ophone sdk中可以使用这种方式来切换到cmwap或internet. 但是原版的android sdk中貌似不行。