Android dynamic listview

Question

I want to make a ListView that gets its elements(strings) from user input. I have a button that directs the user to another activity and while in it, the user enters a name and presses another button to come back to the original activity. The same button gets and adds a string to the ArrayAdapter that the ListView uses and displays it as an element in the ListView. It doesn't seem to work and I know it's a stupid mistake, but I'm fresh to android development and this in particular I haven't done before.

Here's all the code:

the MainActivity

import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;

import java.util.ArrayList;


public class MainActivity extends ActionBarActivity {

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

    ArrayList<String> simpleArray =new ArrayList<String>();

    ListAdapter simpleAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,
            simpleArray);

    ListView lv = (ListView) findViewById(R.id.lv);
    lv.setAdapter(simpleAdapter);
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

public void enterActivity(View view) {
    Intent toEnterSecond = new Intent(this, SecondActivity.class);
    startActivity(toEnterSecond);
}
}

The second acitivity

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;

import java.util.ArrayList;

public class SecondActivity extends Activity{

private EditText projectName;
ArrayList simpleArray;
ArrayAdapter simpleAdapter;

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

    projectName = (EditText) findViewById(R.id.eTxt);

}

public void getBack(View view) {
    String projectCalling = String.valueOf(projectName.getText());
    simpleArray.add(projectCalling);
    simpleAdapter.notifyDataSetChanged();

    Intent comeBack = new Intent(this, MainActivity.class);
    startActivity(comeBack);
}
}

And the layouts

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<Button
    android:layout_width="match_parent"
    android:layout_height="80dp"
    android:id="@+id/simpleButton"
    android:text="click me plox"
    android:onClick="enterActivity"/>

<ListView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/simpleButton"
    android:id="@+id/lv">
</ListView>

</RelativeLayout>

//

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

<TextView
    android:layout_width="wrap_content"
    android:layout_height="20dp"
    android:text="Enter the name of your project:"
    android:id="@+id/txt"/>
<EditText
    android:layout_width="200dp"
    android:layout_height="40dp"
    android:layout_below="@+id/txt"
    android:id="@+id/eTxt"/>
<Button
    android:layout_width="100dp"
    android:layout_height="60dp"
    android:layout_below="@+id/eTxt"
    android:text="click"
    android:onClick="getBack"/>

</RelativeLayout>

Answer 1

Explanation: You can start SecondActivity with startActivityForResult() instead of startActivity as answered here and in onResultActivity method you can call simpleAdapter.notifyDataSetChanged();. Don't call simpleAdapter.notifyDataSetChanged(); in SecondActivity.

To learn how to use startActivityForResult check this.

Also use finish() instead of

Intent comeBack = new Intent(this, MainActivity.class);
startActivity(comeBack);

in SecondActivity to go back to MainActivity.

Solution: Change MainActivity enterActivity method to this:

...
public void enterActivity(View view) {
    Intent toEnterSecond = new Intent(this, SecondActivity.class);
    startActivityForResult(toEnterSecond,1);
}

Add this to end of SecondActivity getBack method:

MainActivity.simpleArray.add(projectCalling);
Intent returnIntent = new Intent();    
setResult(RESULT_OK,returnIntent);
finish();

Finally add this new method to MainActivity:

protected void onActivityResult(int requestCode, int resultCode, Intent data{
    if (requestCode == 1) {
        if(resultCode == RESULT_OK){
             ((ArrayAdapter) simpleAdapter).notifyDataSetChanged();
        }

    }
}

To be able to access simpleAdapter, you need to define it outside of onCreate:

public class MainActivity extends ActionBarActivity {
private ListAdapter simpleAdapter;
public static ArrayList<String> simpleArray;
@Override
protected void onCreate(Bundle savedInstanceState) {
    ...
    simpleArray =new ArrayList<String>();
    simpleAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,
            simpleArray);
    ...
}