ConnectivityManager判断是否有网络

/** 判断是否有网络 */
  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("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(comp);
          mIntent.setAction("<span class=\"hilite\">android</span>.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;
  }

Android编程获取网络连接状态(3G/Wifi)及调用网络配置界面

/**
     * 检测是否开启wify或gprs
     * @param context
     * @return
     */
    public boolean checkNetwork(final Context context){
        ConnectivityManager manager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

        //mobile 3G Data Network
        State mobile = manager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState();
        //wifi
        State wifi = manager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState();
        
        //如果3G网络和wifi网络都未连接，且不是处于正在连接状态 则进入Network Setting界面 由用户配置网络连接
        if(mobile==State.CONNECTED||mobile==State.CONNECTING)
            return true;
        if(wifi==State.CONNECTED||wifi==State.CONNECTING)
            return true;
        
        
        Builder b = new android.app.AlertDialog.Builder(context).setTitle("没有可用的网络").setMessage("请开启GPRS或WIFI网络连接");
        b.setPositiveButton("设置网络", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int whichButton) {
                context.startActivity(new Intent(Settings.ACTION_WIRELESS_SETTINGS));//进入无线网络配置界面
//              context.startActivity(new Intent(Settings.ACTION_WIFI_SETTINGS)); //进入手机中的wifi网络设置界面
            }
        }).setNeutralButton("取消", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int whichButton) {
                dialog.cancel();
            }
        }).create();
        b.show();
        return false;
        
    }