我可以在Android中使用POST方法从URL获取数据吗？

Question

I want to fetch data from a URL using the POST method. I already fetched data using the GET method. Now I want to do it with the POST method. When I click on the button I don't get any response even though I have provided internet permission. I think there's some other problem.

I have tried searching many sites and watching tutorials, but all I get is how to send data to the server using the POST method.

MainActivity.java

package com.example.apipostmethod;

import android.os.StrictMode;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    public String data="";
    public TextView response;
    public Button btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (android.os.Build.VERSION.SDK_INT > 15) {
            StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
            StrictMode.setThreadPolicy(policy);
        }
        response = findViewById(R.id.textView);
        btn = findViewById(R.id.button);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Async().execute();
            }
        });
        data = Async.data();
        Toast.makeText(getApplicationContext(),data,Toast.LENGTH_LONG).show();
        response.setText(data);
    }
}

Async.java

package com.example.apipostmethod;

import android.os.AsyncTask;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Scanner;

public class Async extends AsyncTask {

    public String URLine = "https://api.myjson.com/bins/uizi7";
    public static String result="";
    @Override
    protected Object doInBackground(Object[] objects) {
        try {
            URL url = new URL(URLine);
            HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.connect();

            Scanner sc = new Scanner(url.openStream());
            while(sc.hasNext())
            {
                result+=sc.nextLine();
            }

        }

        catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static String data(){

        return result;
        }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"

    android:orientation="vertical"
    tools:context="com.example.apipostmethod.MainActivity">


    <Button
        android:id="@+id/button"
        android:layout_width="236dp"
        android:layout_height="57dp"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginBottom="8dp"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.496"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.898" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="347dp"
        android:layout_height="531dp"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginBottom="8dp"
        android:text="Response::"
        app:layout_constraintBottom_toTopOf="@+id/button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</LinearLayout>

I am getting this error continuously in logcat for like unlimited times.

2019-06-06 16:03:48.315 1930-2875/? I/GnssLocationProvider: WakeLock acquired by sendMessage(REPORT_SV_STATUS, 0, com.android.server.location.GnssLocationProvider$SvStatusInfo@494d84f)
2019-06-06 16:03:48.316 1930-1944/? I/GnssLocationProvider: WakeLock released by handleMessage(REPORT_SV_STATUS, 0, com.android.server.location.GnssLocationProvider$SvStatusInfo@494d84f)

I want the fetched data in the textview but I am not able to see even the text written in textview.

Answer 1

Use this for POST request using HttpURLConnection, you can add or remove properties based on your requirement:

URL url = new URL("http://yoururl.com");
HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
conn.setReadTimeout(7000);
conn.setConnectTimeout(10000);
conn.setRequestMethod("POST");
conn.setDoInput(true);
conn.setDoOutput(true);

List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("param1", paramValue1));
params.add(new BasicNameValuePair("param2", paramValue2));

OutputStream outputStream = conn.getOutputStream();
BufferedWriter writer = new BufferedWriter(
        new OutputStreamWriter(outputStream, "UTF-8"));
writer.write(getQuery(params));
writer.flush();
writer.close();
outputStream.close();

conn.connect();

Here is getQuery() method :

private String getQuery(List<NameValuePair> params) throws UnsupportedEncodingException
{
    StringBuilder result = new StringBuilder();
    boolean first = true;

    for (NameValuePair pair : params)
    {
        if (first)
            first = false;
        else
            result.append("&");

        result.append(URLEncoder.encode(pair.getName(), "UTF-8"));
        result.append("=");
        result.append(URLEncoder.encode(pair.getValue(), "UTF-8"));
    }

    return result.toString();
}