当在Android Studio中同时连接WiFi和蜂窝数据时，如何分别以编程方式执行网络操作？

Question

这是用于连接到地址为192.168.22.1的wifi屏幕的代码。当关闭移动数据连接时，它可以正常工作，但如果打开了移动数据，则无法正常工作：

public void onConnectClicked(View view){
        Y2Screen screen = new Y2Screen("http://192.168.22.1");
        final TextView message=findViewById(R.id.mess);
        try {
            message.setText("Connecting....");
            if (!screen.login("guest", "guest")) {
                message.setText("Connection Failed");
            } else {
                message.setText("Done Loging.");
                //VideoArea va = new VideoArea(0, 0, screen.getWidth(), screen.getHeight());
                PicArea pa=new PicArea(0, 0, screen.getWidth(), screen.getHeight());


                File dir = Environment.getExternalStorageDirectory();
                String path = dir.getAbsolutePath();


                //va.addVideo(path+"/glomo/image.jpeg", 100);
                pa.addPage(path+"/glomo/test3.png","PNG");
                ProgramPlayFile prog = new ProgramPlayFile(1);
                prog.getAreas().add(pa);
                String listId = screen.writePlaylist(new ProgramPlayFile[]{prog});
                screen.play(listId);

            }
        } catch (Y2Exception e) {
            e.printStackTrace();
        }
    }

Answer 1

可能是因为192.168.22.1是本地地址，所以只能从本地网络（wifi，...）访问。如果您使用的是移动连接数据，则位于公共Internet上，因此您需要将该本地地址NAT到公共地址端口。

您可以使用以下方法检测连接类型：

ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo info = cm.getActiveNetworkInfo();

Detect network connection type on Android以及有关NAT问题的更多信息：Get the NAT translated IP and port of some local port和How to expose my localhost to the WWW? (port forwarding?)

如果两个连接都处于活动状态，请从ConnectivityManager.getAllNetworks（）循环所有网络，并通过ConnectivityManager.bindProcessToNetwork（network）选择一个网络；

for (Network network : connectivityManager.getAllNetworks()) {
  NetworkInfo networkInfo = connectivityManager.getNetworkInfo(network);
  if (networkInfo.getType() == ConnectivityManager.TYPE_ETHERNET || networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {
    connectivityManager.bindProcessToNetwork(network);
    break;
  }
}

请参见Use multiple network interfaces in an app

Answer 2

我找到了解决方案及其工作原理，我们只需要更改网络通道即可通过wifi而不是移动互联网进行传输。

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
            final ConnectivityManager manager = (ConnectivityManager) MainActivity.this
                    .getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkRequest.Builder builder;
            builder = new NetworkRequest.Builder();
            //set the transport type do WIFI
            builder.addTransportType(NetworkCapabilities.TRANSPORT_WIFI);
            manager.requestNetwork(builder.build(), new ConnectivityManager.NetworkCallback() {
                @Override
                public void onAvailable(Network network) {
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                        manager.bindProcessToNetwork(network);
                    } else {
                        //This method was deprecated in API level 23

                        ConnectivityManager.setProcessDefaultNetwork(network);
                    }
                    try {

                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    manager.unregisterNetworkCallback(this);
                }
            });
        }