Why do I get a Fatal Exception when I click on the button in my app that tells me if I should bring an umbrella today?

Question

I am making an Android app using Java and I get a Fatal Exception when I click on the button. The idea of the code is (using the jsoup library) to look up the chance to rain today and if the percentage is greater than 50% then it says yes and if it less than that it says no.
Here is the code

enterpackage com.example.doineedanumbrellatoday;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;

import android.view.View;
import android.widget.*;
import java.io.IOException;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
TextView txtview;
Button button;

    public MainActivity() throws IOException {
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        txtview = (TextView)findViewById(R.id.text);
        button = (Button)findViewById(R.id.button);
        button.setOnClickListener(this);
    }


    @Override
    public void onClick(View view) {
        if(view.getId()==R.id.button){
            Document doc= null;
            try {
                doc = Jsoup.connect("https://dalivali.bg/?location=222").timeout(6000).get();

            } catch (IOException e) {
                e.printStackTrace();
            }
        org.jsoup.select.Elements rain = doc.select("span.rain-num");
        //System.out.println(rain);
        char[] chars2 = rain.toString().toCharArray();
        StringBuilder chance = new StringBuilder();

        for(char c : chars2){
            if(Character.isDigit(c)){
                chance.append(c);
            }
        }
        if(Integer.parseInt(chance.toString())>=50) {
            txtview.setText("Yes");
        } else {
            txtview.setText("No");
        }
    }
}



} 

Could someone tell me why I get an exception?

Answer 1

As Gabe Sechan suggested, you have to run the connection of JSoup code in a background thread so your UI doesn't freeze and then you have to start a UI thread inside a background thread because you can't access views like TextView inside a background thread. So, you can start a background thread for the connection and UI thread for setting of texts like this:

        Thread thread = new Thread() {
            @Override
            public void run() {

                Document document = null;

                try {
                    document = Jsoup.connect("https://dalivali.bg/?location=222").timeout(6000).get();
                } catch (IOException e) {
                    e.printStackTrace();
                }

                assert document != null;
                org.jsoup.select.Elements rain = document.select("span.rain-num");

                char[] chars2 = rain.toString().toCharArray();
                StringBuilder chance = new StringBuilder();

                for (char c : chars2) {
                    if (Character.isDigit(c)) {
                        chance.append(c);
                    }
                }

                runOnUiThread(() -> {
                    if (Integer.parseInt(chance.toString()) >= 50)
                        txtview.setText("Yes");
                    else
                        txtview.setText("No");
                });
            }
        };

        thread.start();