Android判断是否有可用网络的代码

private boolean CheckNetwork() {
        boolean flag = false;
        ConnectivityManager cwjManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        if (cwjManager.getActiveNetworkInfo() != null)
            flag = cwjManager.getActiveNetworkInfo().isAvailable();
        if (!flag) {
            Builder b = new AlertDialog.Builder(this).setTitle("没有可用的网络").setMessage(getResources().getString("请开启GPRS或WIFI网络连接"));
            b.setPositiveButton("确定", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int whichButton) {
                    Intent mIntent = new Intent("/");
                    ComponentName comp = new ComponentName("com.android.settings", "com.android.settings.WirelessSettings");
                    mIntent.setComponent(<span class="hilite2">com</span>p);
                    mIntent.setAction("android.intent.action.VIEW");
                    startActivity(mIntent);
                }
            }).setNeutralButton("取消", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int whichButton) {
                    dialog.cancel();
                }
            }).create();
            b.show();
        }
 
        return flag;
    }