从我的android studio java应用程序上的node.js服务器获取txt文件

Question

我正在使用java制作android studio上的应用程序，我想制作一个网站，您可以编辑txt文件。我希望安卓应用程序连接到web服务器和检索这些文件。我只是不明白如何把这两者联系起来。就像我如何从我的node.js服务器到我的安卓应用程序的txt文件。我最初的想法想是一个HTTP请求服务器，但我不知道如何甚至开始编码。任何帮助都将非常感激提前谢谢你

JAVA

public class MainActivity extends AppCompatActivity {
private static final String SERVER = "http://10.0.2.2:3000/";
private TextView tvServerResponse;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvServerResponse = findViewById(R.id.textView);
Button contactServerButton = findViewById(R.id.button);
contactServerButton.setOnClickListener(onButtonClickListener);
}
View.OnClickListener onButtonClickListener = new View.OnClickListener() {
@Override
public void onClick(View v) {
HttpGetRequest request = new HttpGetRequest();
request.execute();
}
};
public class HttpGetRequest extends AsyncTask<Void, Void, String> {
static final String REQUEST_METHOD = "GET";
static final int READ_TIMEOUT = 15000;
static final int CONNECTION_TIMEOUT = 15000;
@Override
protected String doInBackground(Void... params){
String result;
String inputLine;
try {
// connect to the server
URL myUrl = new URL(SERVER);
HttpURLConnection connection =(HttpURLConnection) myUrl.openConnection();
connection.setRequestMethod(REQUEST_METHOD);
connection.setReadTimeout(READ_TIMEOUT);
connection.setConnectTimeout(CONNECTION_TIMEOUT);
connection.connect();
// get the string from the input stream
InputStreamReader streamReader = new InputStreamReader(connection.getInputStream());
BufferedReader reader = new BufferedReader(streamReader);
StringBuilder stringBuilder = new StringBuilder();
while((inputLine = reader.readLine()) != null){
stringBuilder.append(inputLine);
}
reader.close();
streamReader.close();
result = stringBuilder.toString();
} catch(IOException e) {
e.printStackTrace();
result = "error";
}
return result;
}
protected void onPostExecute(String result){
super.onPostExecute(result);
tvServerResponse.setText(result);
}
}

}

JS:

const http = require('http');
const hostname = '127.0.0.1';
const port = 3000;
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('Hello World');
});
server.listen(port, hostname, () => {
console.log(`Server running at http://${hostname}:${port}/`);
});`

我得到了这段代码，但是它在java代码中抛出了connection.connect()

我假设它不能连接到服务器，但我不明白为什么

Answer 1

您可以使用一个非常流行的HTTP库OkHttp (https://github.com/square/okhttp)

我写了这段代码，这样你就可以在你的应用程序中使用它了:

Java:

public void downloadTxt(String url) {
Request request = new Request.Builder()
.url(url)
.build();
OkHttpClient client = new OkHttpClient();
client
.newCall(request)
.enqueue(new Callback() {
@Override
public void onFailure(@NotNull Call call, @NotNull IOException e) {
//error reaching your site
e.printStackTrace();
}
@Override
public void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {
if(response.isSuccessful()) {
System.out.println(response.body().string());
} else {
System.out.println("Error with code: "+response.code());
}
}
});
}

芬兰湾的科特林:

fun downloadTxt(url: String) {
val request: Request = Request.Builder()
.url(url)
.build()
val client = OkHttpClient()
client
.newCall(request)
.enqueue(object : Callback() {
fun onFailure(call: Call, e: IOException) {
e.printStackTrace()
}
fun onResponse(call: Call, response: Response) {
if (response.isSuccessful()) {
println(response.body().string())
} else {
println("Error with code: ${response.code()}")
}
}
})
}