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How to get the context inside a mouse click listener

In Android Studio, developing in Java, I have the following (a somewhat minimized version of what I'm trying to do).
package com.example.japanesequiz;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import java.util.Random;
public class MainActivity extends AppCompatActivity {
String[] hiragana = {"あ", "か"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button generate = findViewById(R.id.generate);
TextView questionText = findViewById(R.id.question_text);
RadioGroup radioGroup = new RadioGroup(this);
MainActivity ma_inst = this;
generate.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Random rand = new Random();
int hir_index = rand.nextInt(2);
questionText.setText(hiragana[hir_index]);
RadioButton rb1 = new RadioButton(ma_inst);
rb1.setId(View.generateViewId());
rb1.setText("Ah");
radioGroup.addView(rb1);
RadioButton rb2 = new RadioButton(ma_inst);
rb2.setId(View.generateViewId());
rb2.setText("Ka");
radioGroup.addView(rb2);
}
});
}
}
The basic idea is that I want to have the main screen initially mostly blank, but with a button at the bottom. When tapped, it eventually show some text and a radio button group. (I haven't yet fully built out the rest, of course.)
But at this stage what I expect when I launch the app is to see the mostly blank screen, and maybe if I tap the button it will generate some text and options (that then do nothing, further implementation to come).
But the app never launches. Instead, Graddle finishes building, I get a terminal saying that it's launching the app, but it hangs and times out.
If I had to guess -- and this is a guess because I'm very new to Android development -- there is some issue with grabbing the this instance and then using it in the OnClickListener. I'm not certain what the issue is, but it's the only thing I see here that looks fishy. Also, I'm not sure how else one is supposed to add objects to the current activity from inside of the anonymous class passed into the OnClickListener since, there, a reference to this then refers to the anonymous inner class.
I know that it is possible to use a lambda instead, and that probably resolves the issue, but I want to really understand what's going on here, since it seems like it might be conceptually important for later development.
My question: If I have correctly understood this much, then how does a lambda get around this issue? If I've not correctly understood then I'd appreciate any insight, thanks!

There are many questions in one question. First, let me try to answer your title question: "How to get context inside a mouse click listener":
There are many ways, but you can consider this one (your click lisener's onClick has the signature void onClick(View view), hence you have access to view.
view.getContext()
Next, nothing wrong with these though you better migrate to view binding https://developer.android.com/topic/libraries/view-binding as butterknife is deprecated officially
Button generate = findViewById(R.id.generate);
TextView questionText = findViewById(R.id.question_text);
Next, you don't really need this trick in order to get activity in your lambda:
MainActivity ma_inst = this;
Instead and if really needed, you can always do Context context = MainActivity.this;
Lastly, I think the issue the app never launches roots into something else not related with title question you posted, unfortunately.

Passing string literals to stored procedure in android studio with EditText?

Second post here, the first one was extremely helpful so thank you for those that contributed. I will try to be concise with the issue I'm having. I am using android studio in intellij to develop an application. Part of the functionality of the app is a fragment that accepts a new username input from the end user, and then stores that username into my database (a preexisting database that has been linked to intellij). I am new to java and only in the last couple days started to change from creating UI with swing and awt, to xml files. My understanding is that xml files are data descriptors and useful for creating static objects/widgets while the .java files use java to create behaviors for the objects by referencing their IDs created in the xml file. Now comes the confusing part for me, and forgive me if this seems like a no brainer, as I'm pretty new to all this- I have "piggybacked" off a base shell for a android app, and as best as I can tell, setOnClickListener is essentially the android java version of action listeners. I added to the method that essentially took a button and navigated from one fragment to the next, with code that connects to the database, and then executes the stored procedure presumably when the "next"/"submit" button is clicked. Now here's the catch: obviously when a submit button is clicked, there is no user defined username that gets passed into the stored procedure, so obviously it won't work. The problem is, the TextEdit text field that I created is created in an xml file with no way to reference it or manipulate it in the java code, yet it accepts "text" parameters and works fine in the emulator. Obviously I want the stored procedure to take the user inputs in that text field and store it as a new username in the database, but since xml just describes data, and there isn't any defined text field in the java code, I'm at a loss for how to accomplish this task. I can't just write up an action listener and attach it to the xml id of the TextEdit because there isn't anything in the xml file that explains where the actual typed characters are! I know, higher level programming issues. Can anyone help explain how to do what I'm trying to do? Preferably as much as possible in laymans terms. Here is the code:
package com.example.callit;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import java.sql.*;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.navigation.fragment.NavHostFragment;
public class FirstFragment extends Fragment {
#Override
public View onCreateView(
LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState
) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_first, container, false);
}
public void onViewCreated(#NonNull View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
view.findViewById(R.id.button_first).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
NavHostFragment.findNavController(FirstFragment.this)
.navigate(R.id.action_FirstFragment_to_SecondFragment);
String sqldatabase = "//database connection url";
try {
Connection con = DriverManager.getConnection(sqldatabase);
CallableStatement cs = con.prepareCall("{EXEC [dbo].[CreateUser] #UserName = N'Dog', #UserID = #UserID OUTPUT}");
cs.execute();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
});
}
}
I included it in case there was something inherently wrong with the connection to the database code (I also am aware that I should disconnect from the database as well). I would like to note that the code runs without errors, it just doesn't do what it should (for the reasons I explained above). Any help would be greatly appreciated!

How do I change the main xml file from another activity?

I am very new to Java. I am doing a school project at the moment and I have my main activity, then I have a settings activity. I am trying to modify the xml from the main activity with the settings activity. I am able to modify the settings xml file with the settings.java, but I would like to modify the main activity xml with settings.java
public class Settings extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings);
// Get the Intent that started this activity and extract the string
Switch switchButton;
final RelativeLayout mRelativeLayout = (RelativeLayout) findViewById(R.id.activity_settings);
final RelativeLayout mRelativeLayoutMain = (RelativeLayout) findViewById(R.id.activity_main);
switchButton = (Switch) findViewById(R.id.switch1);
switchButton.setChecked(true);
switchButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton compoundButton, boolean bChecked) {
if (bChecked) {
mRelativeLayoutMain.setBackgroundColor(Color.GRAY);
mRelativeLayout.setBackgroundColor(Color.GRAY);
} else {
mRelativeLayoutMain.setBackgroundColor(Color.WHITE);
mRelativeLayout.setBackgroundColor(Color.WHITE);
}
}
});
if (switchButton.isChecked()) {
mRelativeLayoutMain.setBackgroundColor(Color.GRAY);
mRelativeLayout.setBackgroundColor(Color.GRAY);
} else {
mRelativeLayoutMain.setBackgroundColor(Color.WHITE);
mRelativeLayout.setBackgroundColor(Color.WHITE);
}}
public void toast1(View view) {
android.widget.Toast.makeText(this, "Created by Cody Walls and Tommy Serfas", android.widget.Toast.LENGTH_LONG).show();
}
/*public void switch1(View view) {
ScrollView mScrollView = (ScrollView) findViewById(R.id.scrollView);
mScrollView.setBackgroundColor(Color.GRAY);
}*/
}
In the Code I am trying to change the background of the main activity xml with :
mRelativeLayoutMain.setBackgroundColor(Color.GRAY);
and when I run the app and click the intent it will crash with the error:
"java.lang.NullPointerException: Attempt to invoke virtual method
'void android.widget.RelativeLayout.setBackgroundColor(int)' on a null
object reference"

I think the easiest way is to create an PreferenceManager.SharedPreferences, in which I recommend you to store current app data. This will help you not to loose any changes in app after you exit the it. Here is short instructions:
Create button in settings activity which will change something in main activity.
Create onClickListener for your button.
Use .SharedPreferences to store was you button clicked or not. (I recommend storing boolean variables, this way you can store was button clicked or not.)
I both of your activities in onCreate method call .getSharedPreferences to read saved app values. (I mean to read was the button clicked or not.)
Use app values you got from 4. to change any element in activity. (For example if you stored that button was clicked, then change some TextView text or etc.)
I hope you understood the idea.
Link to the Android developer tutorial about App key values storing & saving
Link to the StackOverflow much easier explanation & examples

There are a couple of ways of doing this (Some of which depends on how you are switching back and forth from each activity). It also depends on what things you are changing.
From your settings page, as you are changing different settings, you'll save this content within Preferences. (You can see more how to use Preferences here: https://examples.javacodegeeks.com/android/core/ui/settings/android-settings-example/ or by just Googling it).
On you main activity, depending on how you come back to it (onStart most likely), you can setup the things you need to programmatically.
So, you may need to do a little research on the Android lifecycle and how each cycle works (https://developer.android.com/guide/components/activities/activity-lifecycle.html), how to program the UI programmatically through Java (http://startandroid.ru/en/lessons/220-lesson-16-creating-layout-programmatically-layoutparams.html), and the Preferences Android library to save certain settings.
The xml isn't meant to be "altered". You can change the UI programmatically. It's possible to build an Android app without any xml. When Android was first built, it didn't use the xml to create the UI. It was all done through Java. It was then added to use xml to create your activities or fragments or any UI component. This made things easier for more static activities or activities with very little dynamic content.

Android: Basic Dialog Implementation

I have searched and found a lot of different answers for this question, but nothing quite settles it for me. Total android n00b, and I ask for your patience in advance.
I'm having trouble dealing with a FileChooser problem with Android KitKat. As per [here][1], and according to [Steve N][2] i get the impression that this file chooser problem is caused by my android version (4.4.2)
Given that filechooser isn't working, I want to implement a basic dialog. I'm going to check the android version number for the device, and then display a message, citing the current lack of support, if the version number comes back with a 4.4 in front.
At present, i'm just using toast
public boolean checkVersionSupport(){
if (Build.VERSION.RELEASE.equals("4.4.2") {
Toast toast = Toast.makeText(context, androidOS, duration);
toast.show();
}
}
Instead of toast, I'd like a simple, one button dialog box to open, with an OK button, which I will use to redirect the user out of the native app and off to chrome, where the whole file chooser thing seems to be working.
Couple of things that I have found difficult after reading through the android developer materials.
Do I need a layout XML file for the dialog box?
Where do I put the class file for the MyAlertDialogFragment class I am creating? Can it be anywhere in the java folder or does it have to be in a sub folder java/com.myproject... And what impact does that have for importing the class into my java activity file?
Can someone please explain where FragmentAlertDialog comes from in the Android Developer Materials.
public static class MyAlertDialogFragment extends DialogFragment {
public static MyAlertDialogFragment newInstance(int title) {
MyAlertDialogFragment frag = new MyAlertDialogFragment();
Bundle args = new Bundle();
args.putInt("title", title);
frag.setArguments(args);
return frag;
}
#Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
int title = getArguments().getInt("title");
return new AlertDialog.Builder(getActivity())
.setIcon(R.drawable.alert_dialog_icon)
.setTitle(title)
.setPositiveButton(R.string.alert_dialog_ok,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
((**FragmentAlertDialog**)getActivity()).doPositiveClick();
}
}
)
.setNegativeButton(R.string.alert_dialog_cancel,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
((**FragmentAlertDialog**)getActivity()).doNegativeClick();
}
}
)
.create();
}
}
What's best practice for icons? I see a debate going on about this, but for the simple purpose of having an icon at the top of a dialog, for one single basic usage, what would be the quickest way of getting it done? I'm just copying files into the res folder and referencing them... 48dp? This might be a whole different question.

Do I need a layout XML file for the dialog box?
That honestly depends on which type of Dialog you use.
The AlertDialog does not require a specified layout, all you need is to use AlertDialog.Builder() and set the positive/negative buttons, and how it handles that.
The DialogFragment onCreateDialog() method is the preferred way of using an AlertDialog. It also doesn't require an XML layout, but as such, its layout is still restricted to essentially a Yes/No option: look here for complete example
The DialogFragment onCreateView() method allows you to create a dialog from a specified layout XML. So if you wish to customize the view of the dialog beyond "title, description, yes/no", then yes, you need to specify the XML file for the dialog fragment, look here for an example, although the advice says you should look into ButterKnife and Otto libraries to make it even better.
Where do I put the class file for the MyAlertDialogFragment class I am creating? Can it be anywhere in the java folder or does it have to be in a sub folder java/com.myproject... And what impact does that have for importing the class into my java activity file?
Anywhere inside the project. Although I prefer to put it in something like <projectroot>/presentation/fragments/dialog, package-wise.
Can someone please explain where FragmentAlertDialog comes from in the Android Developer Materials.
FragmentAlertDialog is an assumed Activity from which the MyAlertDialogFragment dialog fragment is shown, and is assumed to have the methods doPositiveClick() and doNegativeClick(). The title int that is provided is most likely a string resource defined in /res/values/strings.xml which is used for localization. For example, R.string.fancy_title_name.
So it's something like this
public class FragmentAlertDialog extends AppCompatActivity {
#Override
public void onCreate(Bundle saveInstanceState) {
super.onCreate(saveInstanceState);
setContentView(R.layout.activity_fragment_alert_dialog);
//stuff
}
#Override
public void onPostResume() {
MyAlertDialogFragment madf = MyAlertDialogFragment.newInstance(R.string.something);
madf.show(getSupportFragmentManager(), "alert-dialog-fragment");
}
}
Otherwise, MyAlertDialogFragment just extends from DialogFragment and overrides onCreateDialog to create an AlertDialog inside this DialogFragment.
In case you'd ask, the newInstance() method is so that you would NOT use a parametrized constructor. Fragments should not have parametrized constructors, they ought to receive their data in the setArguments(Bundle) method.
What is the best practice for icons?
Refer to the material design guidelines.

Android programming and using HTML parsers to pull category data from a Wikia.com page for use in a ListView

first off I was wondering if there are even HTML parsers that work with Android app programming or not, or if all I have access to is the html commands listed on the Android developers web site. The reason is I am making an app that allows you to access the Zelda Wikia and instead of hard coding everything such as the titles of the video games I wanted to go ahead and pull the names using the MediaWiki API, the command I found was this:
http://zelda.wikia.com/api.php?action=query&list=categorymembers&cmtitle=Category:Games&cmlimit=500
This returns all of the titles in HTML formatting and the only way that I can think to pull what I need from what this returns is using an HTML parser, but I am not sure that there is one that works with Android programming and if so how I would even go about pulling what I need from this. After I get the data from this I want to display it in a ListView and when the title is clicked it will take the user to the Wikia for that specific title in a WebView. Is this the way I should be going about this or are there any other recommendations that anyone has, please I really need help. The rest of the code is as follows just incase anyone wants to see what I have:
package com.lvlup.kikurself.zeldatest;
import android.app.ListActivity;
import android.content.Intent;
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 zeldaGames extends ListActivity {
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
String[] values = new String[] { "The Legend of Zelda", "Zelda II: The
Adventure of Link", "The Legend of Zelda: Ocarina of Time",};
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, values);
setListAdapter(adapter);
final ListView zeldaList = getListView();
zeldaList.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v, int position, long thisID)
{
Object o = (zeldaList.getItemAtPosition(position));
String gameName_temp = (o.toString());
Intent newIntent = new Intent(v.getContext(), gameDisp.class);
newIntent.putExtra("tempG", gameName_temp);
startActivity(newIntent);
}
});
Thank you for taking the time to read this.

I wouldn't use a parser on the phone. Before you know, the owner of the page could come up with a new layout, ruining your app.
Instead, I would build a webservice (PHP with DomXML is an exelent choice) which parses the given site, and returns file in XML, JSON or other format. And then I would write an app to use the parser webservice as a datasource.
In this way, you will have a lot more computer power. You only have to maintain one instance of the parser, an you know it works on any device, that has downloaded your app.
Maybe sounds like a lot of work, but trust me on this - you'll be better of.
Personal and profesional experience

Append &format=xml to your URL to get machine-readable data. See MW help on API formats at https://www.mediawiki.org/wiki/API:Data_formats and general API help at https://www.mediawiki.org/wiki/API