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Trying to add to an arraylist on a different activity each time a button is pressed

So just to practice I've created a Pythagorean theorem calculator app. I want each answer that I obtain to be stored in another activity(a "history" page). I'm trying to use intents to send/receive the arraylist and items. I get the most recent one, but it is overwritten after each press of the button.
package com.example.hypnotenusecalculatorrebuild;
import androidx.appcompat.app.AppCompatActivity;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
//ToDo history button is broken. doesn't display listview when pressed.
public void toHistory(View view) {
// Intent intent = new Intent(getApplicationContext(), HistoryActivity.class);
//
// startActivity(intent);
}
public void findHypno(View view) {
Log.i("Info", "button pressed");
EditText editTextNumberA = (EditText) findViewById(R.id.editTextNumberA);
EditText editTextNumberB = (EditText) findViewById(R.id.editTextNumberB);
TextView textViewAnswer = (TextView) findViewById(R.id.textViewAnswer);
String message;
String cSquared;
if (editTextNumberA.getText().toString().isEmpty() || editTextNumberB.getText().toString().isEmpty()) {
message = "Please enter a number for each dimension";
Toast.makeText(this, message, Toast.LENGTH_LONG).show();
} else {
Number numberA = new Number();
Number numberB = new Number();
Number numberC = new Number();
numberA.number = Double.parseDouble(editTextNumberA.getText().toString());
numberB.number = Double.parseDouble(editTextNumberB.getText().toString());
numberA.squareNumber();
numberB.squareNumber();
numberC.number = numberA.number + numberB.number;
numberC.squareRoot();
Log.i("test numberA", String.valueOf(numberA.number));
Log.i("test numberB", String.valueOf(numberB.number));
Log.i("test numberC", String.valueOf(numberC.number));
cSquared = Double.toString(numberC.number);
textViewAnswer.setText(cSquared);
ArrayList<String> historyList = new ArrayList<String>();
historyList.add("test");
Intent intent = new Intent(getApplicationContext(), HistoryActivity.class);
intent.putExtra("answer", cSquared);
intent.putStringArrayListExtra("arrayList", historyList);
startActivity(intent);
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
package com.example.hypnotenusecalculatorrebuild;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.List;
import java.util.function.ToDoubleBiFunction;
public class HistoryActivity extends AppCompatActivity {
public void back(View view) {
finish();
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
Intent getList = getIntent();
ArrayList<String> historyList = getList.getStringArrayListExtra("arrayList");
historyList.add(getList.getStringExtra("answer"));
ListView listViewHistory = (ListView) findViewById(R.id.listViewHistory);
ArrayAdapter historyListArrayAdapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, historyList);
listViewHistory.setAdapter(historyListArrayAdapter);
// ToDo - intent isn't working as attended, only saves one item and gets overwritten each time
//Intent historyIntent = getIntent();
// get extra needs a name from put extra
// String testGetIntent = historyIntent.getStringExtra("answer");
// Log.i("testIntentString", testGetIntent);
// historyList.add(historyIntent.getStringExtra("answer"));
}
}

here is a different approach. make a public interface in a separate file named "extensions" or whatever and initialize your arraylist there like so:
public interface ext {
ArrayList<String> myArray = new ArrayList<String>();
}
this interface is created when the app runs and lives for as long as the app lives meaning you can always access and manipulate it anywhere in your app without worrying whether the activity is being killed or not. so you can add or remove elements to or from it wherever you want.
Access the array this way:
ext.myArray.add("new item")

Save markers to csv file

I am wondering how to when the user closes the app, save the markers to a file then load them back in when the app is opened again
Here is my code:
package com.example.mapapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.provider.Settings;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.content.Intent;
import android.view.View;
import android.widget.Button;
import org.osmdroid.config.Configuration;
import org.osmdroid.tileprovider.tilesource.TileSourceFactory;
import org.osmdroid.util.GeoPoint;
import org.osmdroid.views.MapView;
import org.osmdroid.views.overlay.ItemizedIconOverlay;
import org.osmdroid.views.overlay.OverlayItem;
import java.io.File;
import java.util.ArrayList;
public class MainActivity extends Activity
{
MapView mv;
StringBuffer filePath;
File file;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// This line sets the user agent, a requirement to download OSM maps
Configuration.getInstance().load(this, PreferenceManager.getDefaultSharedPreferences(this));
setContentView(R.layout.activity_main);
mv = (MapView)findViewById(R.id.map1);
ItemizedIconOverlay<OverlayItem> items;
mv.setBuiltInZoomControls(true);
mv.getController().setZoom(11);
mv.getController().setCenter(new GeoPoint(53.3710,-1.4502));
}
public boolean onOptionsItemSelected(MenuItem item)
{
if(item.getItemId() == R.id.addpoi)
{
// react to the menu item being selected...
Intent intent = new Intent(this,AddPoi.class);
startActivityForResult(intent,0);
return true;
}
Intent intent = new Intent(this,AddPoi.class);
startActivityForResult(intent,0);
return false;
}
public boolean onCreateOptionsMenu(Menu menu)
{
MenuInflater inflater=getMenuInflater();
inflater.inflate(R.menu.menu_mad_assignment, menu);
return true;
}
protected void onActivityResult(int requestCode,int resultCode,Intent intent)
{
if(requestCode==0)
{
if (resultCode==RESULT_OK)
{
Bundle extras=intent.getExtras();
String poiName= extras.getString("poiName");
String poiType= extras.getString("poiType");
String poiDesc= extras.getString("poiDesc");
ItemizedIconOverlay<OverlayItem> items = new ItemizedIconOverlay<>(this, new ArrayList<OverlayItem>(), null);
OverlayItem marker = new OverlayItem(poiName, poiType,poiDesc, new GeoPoint(53.3710,-1.4502));
items.addItem(marker);
mv.getOverlays().add(items);
Log.d("NAME",poiName);
Log.d("NAME",poiType);
Log.d("NAME",poiDesc);
}
}
}
}
Add marker code:
package com.example.mapapp;
import android.app.Activity;
import android.os.Bundle;
import android.content.Intent;
import android.widget.Button;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.EditText;
import com.example.luke.madassignment.R;
public class AddPoi extends Activity implements OnClickListener {
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.add_poi);
Button addPoiButton = (Button)findViewById(R.id.addPoi);
Button cancelButton = (Button)findViewById(R.id.cancel);
addPoiButton.setOnClickListener(this);
cancelButton.setOnClickListener(this);
}
#Override
public void onClick(View v) {
Intent intent = new Intent();
Bundle bundle=new Bundle();
EditText poiName = (EditText)findViewById(R.id.editTextPoiName);
EditText poiType = (EditText)findViewById(R.id.editTextPoiType);
EditText poiDesc = (EditText)findViewById(R.id.editTextPoiDesc);
String poiNameString = poiName.toString();
String poiTypeString = poiName.toString();
String poiDescString = poiName.toString();
bundle.putString("poiName",poiNameString);
bundle.putString("poiType",poiTypeString);
bundle.putString("poiDesc",poiDescString);
intent.putExtras(bundle);
setResult(RESULT_OK,intent);
finish();
}
}
The problem is i cant figure out a way to save the users marker to a file if the app is closed and then load back in the markers when the app is opened again

Use built in sharedPref, simple key value storage, to save data in persistence mode. Check doc here
The SharedPreferences class provides a general framework that allows
you to save and retrieve persistent key-value pairs of primitive data
types. You can use SharedPreferences to save any primitive data:
booleans, floats, ints, longs, and strings. This data will persist
across user sessions (even if your application is killed).
https://developer.android.com/guide/topics/data/data-storage.html#pref

Using OSMBonusPack, you can grab your markers in a KML structure, then save the KML file locally (in onStop).
And load back this KML file when the app is opened (in onCreate).

I can't get my scan results to display in android

When I run my app on a rooted device the ListView is blank and I am not sure why?
import android.content.IntentFilter;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.content.Context;
import android.content.BroadcastReceiver;
import android.content.Intent;
import java.util.List;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiManager;
import android.widget.Toast;
This is my main class:
public class Network_List extends AppCompatActivity {
WifiManager wifiM;
WifiScanReciever wifiR;
ListView networklist;
String wifis[];
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_network__list);
Search box for searching networks (not yet implemented so don't worry about it)
EditText searchNet = (EditText) findViewById(R.id.networkEditText);
This is the main list to display the network information
networklist = (ListView) findViewById(R.id.networkList);
Search button for the EditText (This is for future development)
Button networkButton = (Button) findViewById(R.id.searchButton);
scanButton is a button that starts the scan
Button scanButton = (Button) findViewById(R.id.buttonScan);
Declares wifiM as wifi manager and gets service
wifiM = (WifiManager) getSystemService(Context.WIFI_SERVICE);
Declares wifiR as WifiScanReciever
wifiR = new WifiScanReciever();
Button for starting the scan
scanButton.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v) {
wifiM.startScan();
}
});
}
protected void onPause(){
unregisterReceiver(wifiR);
super.onPause();
}
protected void onResume(){
registerReceiver(wifiR, new IntentFilter(wifiM.SCAN_RESULTS_AVAILABLE_ACTION));
super.onResume();
}
This receives the scan results and puts it an array called wifis. onReceive captures scan results and sets the size of the array wifis.
private class WifiScanReciever extends BroadcastReceiver{
public void onReceive(Context c, Intent intent){
List<ScanResult> wifiSList = wifiM.getScanResults();
wifis = new String[wifiSList.size()];
for (int x = 0; x<wifiSList.size(); x++){
wifis[x] = ((wifiSList.get(x)).toString());
}
networklist.setAdapter(new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_list_item_1,wifis));
}
}
}

Unable to get list items correct code using Java

I am trying to create a list view in Java that allows each list item to open a web url address but I can not seem to get the code right. Please can some one show me where IO going wrong.
package com.sasquatchapps.hydraquip10.bestofmonsterquest;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
public class Season1Activity extends Activity{
private String episodes[] = {"America's Loch Ness Monster","Sasquatch Attack",
"Giant Squid Found","Birdzilla","Bigfoot","“Mutant K9","Lions in the Backyard","Gigantic Killer Fish","Swamp Beast","Russia's Killer Apemen","Unidentified Flying Creatures","The Real Hobbit",
"Giganto: The Real King Kong","American Werewolf"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ArrayAdapter<String> adapter = new
ArrayAdapter<>(this,
android.R.layout.simple_list_item_1, episodes);
setListAdapter(adapter);
}
#Override
protected void onListItemClick(ListView l, View v, int position, long id) {
Toast.makeText(this, "Item clicked;" + episodes[position], Toast.LENGTH_SHORT).show();
if (position == 0) {
Intent intent = new Intent(android.content.Intent.ACTION_VIEW, Uri.parse("https://www.youtube.com/watch?v=o7-RdxrCFAg"));
startActivity(intent);
}
}
}

You have some errors - Where is your listview? Modify your code
1) create listview -
ListView myList;
2) In your onCreate assign this list:
myList = (ListView) findViewById(R.id.my_list);
3) Set adapter to your list:
myList.setAdapter(adapter);

Getting the position of a list item in Android

So I have this class here:
package phil.droid.game;
import android.content.Intent;
import android.content.res.Resources;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.AdapterView.OnItemClickListener;
public class GameList extends GamesTrialActivity
{
private ListView lv1;
protected String Game_names[]={"God of War","FOS RO DAH", "dhwaud"};
private String Game_pics[]={"God of War","God of War II"};
private int pos;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.gamelist);
lv1=(ListView)findViewById(R.id.thegamelist);
lv1.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1 , Game_names));
lv1.setOnItemClickListener(new OnItemClickListener()
{
public void onItemClick(AdapterView<?> parent, View view, int position, long id)
{
pos = position;
Intent i = new Intent(GameList.this, game_viewer.class);
startActivity(i);
}
});
}
}
And then this VclassV extends the one ^above^
package phil.droid.game;
import android.os.Bundle;
import android.widget.TextView;
public class game_viewer extends GameList
{
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.game_template);
TextView game_title = (TextView)findViewById(R.id.GameTitle);
game_title.setText("" + pos);
}
}
The problem is at the moment that the last bit recognizes "pos" as "0" no matter what option I click on. Can someone suggest a way to make it so pos is recognized as the number element that's clicked on in the previous class?

Make pos protected, not private.

What you're trying to do can't work: The newly launched activity will not share the same storage as the parent, even if they inherit. The only way it would be possible is if the value was static, but that's not a good idea either.
What you should do instead is to send the data as part of the intent before starting the activity, e.g.:
intent.putExtra("pos", position);
and then you can pull it out in the new activity with
getIntent().getIntExtra("pos", -1); // -1 is used as default value
Also, game_viewer should most likely be a separate activity, rather than inherit from GameList.