FATAL EXCEPTION: AsyncTask #1 while working with JSON

Question

I am new to android programming, and I want to create a very simple app that takes a String in EditText and when I click a button, it takes the String and sends it to my localhost to save it in my database.

But it is giving a run time error for the doInBackground(), and I don't understand why. Please, help me.

Here is my Log :

07-28 12:27:21.591: E/AndroidRuntime(2267): FATAL EXCEPTION: AsyncTask #1
07-28 12:27:21.591: E/AndroidRuntime(2267): Process: com.appeight.jsontest, PID: 2267
07-28 12:27:21.591: E/AndroidRuntime(2267): java.lang.RuntimeException: An error occured while  executing doInBackground()
07-28 12:27:21.591: E/AndroidRuntime(2267):     at android.os.AsyncTask$3.done(AsyncTask.java:300)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.util.concurrent.FutureTask.run(FutureTask.java:242)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.lang.Thread.run(Thread.java:841)
07-28 12:27:21.591: E/AndroidRuntime(2267): Caused by: java.lang.StringIndexOutOfBoundsException: length=0; index=3
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.lang.String.indexAndLength(String.java:584)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.lang.String.substring(String.java:1449)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at com.appeight.jsontest.JSONParser.makeHttpRequest(JSONParser.java:79)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at com.appeight.jsontest.AddScreen$CreateNewProduct.doInBackground(AddScreen.java:50)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at com.appeight.jsontest.AddScreen$CreateNewProduct.doInBackground(AddScreen.java:1)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at android.os.AsyncTask$2.call(AsyncTask.java:288)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
07-28 12:27:21.591: E/AndroidRuntime(2267):     ... 4 more

My code is this :

package com.appeight.jsontest;

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

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

import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class AddScreen extends ActionBarActivity {
EditText tv;
JSONParser jsonParser = new JSONParser();
String name;

private static String add_name = "http://10.0.2.2/android_test/add.php";

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

    tv = (EditText) findViewById(R.id.editText1);
}

public void addToDb(View vvv)
{
    new CreateNewProduct().execute();
}

class CreateNewProduct extends AsyncTask<String, String, String>
{
    protected String doInBackground(String... args)
    {
        name = tv.getText().toString();
        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair("name", name));

        // getting JSON Object
        // Note that add name URL accepts POST method
        JSONObject json = jsonParser.makeHttpRequest(add_name,
        "POST", params);

        return null;
    }

    protected void onPostExecute(String result)
    {
        Toast.makeText(getBaseContext(), "Successful", Toast.LENGTH_SHORT).show();
    }
}
}

Someone, please help, I am really stuck bad here, and I am a newbie, so please pardon me for any silly mistakes.

Answer 1

You have few mistakes here:

• in doInBackground you are not supposed to access the UI
• You return null doInBackground when postExecute expect a String result.

---

here is a clean way to do the same thing

public void addToDb(View vvv)
{
    //Get the value from the textView
    name = tv.getText().toString();
    //build Params
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("name", name));

    CreateNewProduct productTask = new CreateNewProduct(params);
    productTask.execute();
}

class CreateNewProduct extends AsyncTask<String, String, JSONObject>
{
    List<NameValuePair> params;

    public CreateNewProduct(List<NameValuePair> params){
      this.params = params;
    }

    protected JSONObject doInBackground(String... args)
    {

        JSONObject json = jsonParser.makeHttpRequest(add_name,"POST", this.params);

        return json;
    }

    protected void onPostExecute(JSONObject result)
    {
        //this assumes that the response looks like this:
        //{"success" : true }
        boolean success = result.getBoolean("success");
        Toast.makeText(getBaseContext(), success ? "Successful" : "Failure", Toast.LENGTH_SHORT).show();     
    }
}

Answer 2

A string of length 0 is accessed by your com.appeight.jsontest.JSONParser object, but it is trying to access index 3. Is this a class you wrote or a library? If a class you wrote, try to find out why (check line code in it).

07-28 12:27:21.591: E/AndroidRuntime(2267): Caused by: java.lang.StringIndexOutOfBoundsException: length=0; index=3
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.lang.String.indexAndLength(String.java:584)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at java.lang.String.substring(String.java:1449)
07-28 12:27:21.591: E/AndroidRuntime(2267):     at com.appeight.jsontest.JSONParser.makeHttpRequest(JSONParser.java:79)

Answer 3

Surround the contents of doInBackground with try and catch the exception, and also do not forget to dismiss the dialog using the command: pDialog.dismiss(); in onPostExecute()