Java runOnUiThread gives error NetworkOnMainThreadException

Issue

I'm following a CRUD tutorial on https://www.androidhive.info/2012/05/how-to-connect-android-with-php-mysql/.

I changed settings to my own need, but the runOnUiThread like the tutorial gives me an forced close on the app.

If I replace the code by something else, the activity will run but the fields won't populate.

My code:

package nl.app.app.recipefinder;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.StrictMode;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;

public class EditIngredientActivity extends Activity {

// spinner text fields to select from
Spinner spinner;
String[] volume = {
        "Liter",
        "Mililiter",
        "Kilogram",
        "Gram",
        "Stuk(s)"
};

EditText txtName;
EditText txtQuantity;
EditText txtDesc;
EditText txtCreatedAt;
Button btnSave;
Button btnDelete;

String pid;

// Progress Dialog
private ProgressDialog pDialog;

// JSON parser class
JSONParser jsonParser = new JSONParser();

// single product url
private static final String url_ingredient_details = "http://www.linktosite";

// url to update product
private static final String url_update_ingredient = "http://www.linktosite";

// url to delete product
private static final String url_delete_ingredient = "http://www.linktosite";

// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_INGREDIENT = "ingredients";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
private static final String TAG_QUANTITY = "quantity";
private static final String TAG_DESCRIPTION = "description";
private static final String TAG_VOLUME = "volume";

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.edit_ingredient);

    // Get reference of SpinnerView from layout/current_layout.xml
    spinner = (Spinner)findViewById(R.id.DropDownVolume);

    ArrayAdapter<String> adapter= new ArrayAdapter<String>(this,android.
            R.layout.simple_spinner_dropdown_item ,volume);

    spinner.setAdapter(adapter);

    // save button
    btnSave = (Button) findViewById(R.id.btnSave);
    btnDelete = (Button) findViewById(R.id.btnDelete);

    // getting product details from intent
    Intent i = getIntent();

    // getting product id (pid) from intent
    pid = i.getStringExtra(TAG_PID);

    // Getting complete product details in background thread
    new GetProductDetails().execute();

    // save button click event
    btnSave.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // starting background task to update product
            new SaveProductDetails().execute();
            Log.d("good", "Created new ingredient");

        }
    });

    // Delete button click event
    btnDelete.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // deleting product in background thread
            new DeleteProduct().execute();
            Log.d("good", "Deleted ingredient");
        }
    });

}

/**
 * Background Async Task to Get complete product details
 * */
class GetProductDetails extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(EditIngredientActivity.this);
        pDialog.setMessage("Loading ingredient details. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    /**
     * Getting product details in background thread
     * */
    protected String doInBackground(String... params) {

        // updating UI from Background Thread
        runOnUiThread(new Runnable() {
            public void run() {
                // Check for success tag
                int success;
                try {
                    // Building Parameters
                    List<NameValuePair> params = new ArrayList<NameValuePair>();
                    params.add(new BasicNameValuePair("pid", pid));

                    // getting product details by making HTTP request
                    // Note that product details url will use GET request
                    JSONObject json = jsonParser.makeHttpRequest(
                            url_ingredient_details, "GET", params);

                    // check your log for json response
                    Log.d("Single Ingredient Det", json.toString());

                    // json success tag
                    success = json.getInt(TAG_SUCCESS);
                    if (success == 1) {
                        // successfully received product details
                        JSONArray productObj = json
                                .getJSONArray(TAG_INGREDIENT); // JSON Array

                        // get first product object from JSON Array
                        JSONObject product = productObj.getJSONObject(0);

                        // product with this pid found
                        // Edit Text
                        txtName = (EditText) findViewById(R.id.inputName);
                        txtQuantity = (EditText) findViewById(R.id.inputQuantity);
                        txtDesc = (EditText) findViewById(R.id.inputDesc);
                        spinner = (Spinner) findViewById(R.id.DropDownVolume);

                        // display product data in EditText
                        txtName.setText(product.getString(TAG_NAME));
                        txtQuantity.setText(product.getString(TAG_QUANTITY));
                        txtDesc.setText(product.getString(TAG_DESCRIPTION));

                        Log.d("good", "shows ingredient");
                    }else{
                        // product with pid not found
                        Log.d("bad", "ingredient not found");
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        });

        return null;

    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once got all details
        pDialog.dismiss();
    }
}

/**
 * Background Async Task to  Save product Details
 * */
class SaveProductDetails extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(EditIngredientActivity.this);
        pDialog.setMessage("Saving ingredient ...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    /**
     * Saving product
     * */
    protected String doInBackground(String... args) {

        // getting updated data from EditTexts
        String name = txtName.getText().toString();
        String price = txtQuantity.getText().toString();
        String description = txtDesc.getText().toString();
        String volume = spinner.getSelectedItem().toString();


        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair(TAG_PID, pid));
        params.add(new BasicNameValuePair(TAG_NAME, name));
        params.add(new BasicNameValuePair(TAG_QUANTITY, price));
        params.add(new BasicNameValuePair(TAG_DESCRIPTION, description));
        params.add(new BasicNameValuePair("TAG_VOLUME", volume));


        // sending modified data through http request
        // Notice that update product url accepts POST method
        JSONObject json = jsonParser.makeHttpRequest(url_update_ingredient,
                "POST", params);
        Log.d("good", "Posted ingredient");

        // check json success tag
        try {
            int success = json.getInt(TAG_SUCCESS);

            if (success == 1) {
                // successfully updated
                Intent i = getIntent();
                // send result code 100 to notify about product update
                setResult(100, i);
                finish();
                Log.d("good", "finished update");

            } else {
                // failed to update product
                Log.d("bad", "Update ingredient failed");

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

        return null;
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once product uupdated
        pDialog.dismiss();
    }
}

/*****************************************************************
 * Background Async Task to Delete Product
 * */
class DeleteProduct extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(EditIngredientActivity.this);
        pDialog.setMessage("Deleting ingredient...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    /**
     * Deleting product
     * */
    protected String doInBackground(String... args) {

        // Check for success tag
        int success;
        try {
            // Building Parameters
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            params.add(new BasicNameValuePair("pid", pid));

            // getting product details by making HTTP request
            JSONObject json = jsonParser.makeHttpRequest(
                    url_delete_ingredient, "POST", params);

            // check your log for json response
            Log.d("Delete Product", json.toString());

            // json success tag
            success = json.getInt(TAG_SUCCESS);
            if (success == 1) {
                // product successfully deleted
                // notify previous activity by sending code 100
                Intent i = getIntent();
                // send result code 100 to notify about product deletion
                setResult(100, i);
                finish();
                Log.d("good", "Deleted ingredient");
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once product deleted
        pDialog.dismiss();

    }

}
}

Solution

I am not sure what you are confused about. The exception is clear; You are performing a network operation on a UI thread. This is not permissible in Android. Move your HTTP request outside of your runonuithread block. Do all of your UI stuff in your post execute method. It seems to me that you do not quite understand what AsyncTask does. Here is a bit of info: https://developer.android.com/reference/android/os/AsyncTask

In short, the doInBackground() method runs on a non-UI thread and onPostExecute() method (which runs after doInBackground() method finishes) runs on the UI thread. That is why you should not put runonuithread block inside your doInBackground() method like you have done (where runonuithread is the only thing that you run in doInBackground() method). There is no point in using an AsyncTask if you do that.

Also I took a quick look at your tutorial link. The tutorial does not put runonUiThread block inside their asynctask's doInBackground() method. Is there a reason why you put it in?

Answered By - Steven