Develop Reference

How to create a util that can be referenced multiple times in different activities

I have successfully implemented a custom Dialog box that appears when the user tries to leave an activity via a back button or by using onBackPressed(). They can simply cancel the dialog box or continue, and leave the activity. This function has been implemented in multiple activities, however its making my code a lot longer than it needs to be. I wanted to know how to create a util that can be referenced in different activities, without the need for the chunk of code to copy pasted multiple times. Please note that I am retrieving the dialog title and description from string.xml
This is my code:
Dialog customDialog;
Button button_one, button_two;
TextView dialog_title, dialog_description;
customDialog = new Dialog(this);
//Back button will close app
#Override
public void onBackPressed() {
customDialog.setContentView(R.layout.custom_dialog_box);
dialog_title = customDialog.findViewById(R.id.dialog_title);
dialog_title.setText(getString(R.string.leaving_activity_warning_title));
dialog_description = customDialog.findViewById(R.id.dialog_description); dialog_description.setText(getString(R.string.leaving_activity_warning_description));
button_one = customDialog.findViewById(R.id.button_one);
button_one.setText(getString(R.string.cancel));
button_two = customDialog.findViewById(R.id.button_two);
button_two.setText(getString(R.string.leave_anyway));
button_one.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.dismiss();
}
});
button_two.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.dismiss();
finish();
overridePendingTransition(R.anim.slide_in_left, R.anim.slide_out_right);
}
});
Objects.requireNonNull(customDialog.getWindow()).setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
customDialog.show();
}
UPDATE
Created a Java file called "DialogBoxMessage"
DialogBoxMessage Code:
class DialogBoxMessage {
private Dialog customDialog;
private TextView dialog_title, dialog_description;
private Button button_one, button_two;
//Custom Dialog Box Initialization
DialogBoxMessage(Button myButtonOne, TextView myDialogTitle, TextView myDialogDescription, Dialog myCustomDialog) {
customDialog = myCustomDialog;
button_one = myButtonOne;
button_two = myButtonOne;
dialog_title = myDialogTitle;
dialog_description = myDialogDescription;
}
void leaveActivity() {
customDialog.setContentView(R.layout.custom_dialog_box);
dialog_title = customDialog.findViewById(R.id.dialog_title);
dialog_title.setText(Resources.getSystem().getString(R.string.leaving_activity_warning_title));
dialog_description = customDialog.findViewById(R.id.dialog_description);
dialog_description.setText(Resources.getSystem().getString(R.string.leaving_activity_warning_description));
button_one = customDialog.findViewById(R.id.button_one);
button_one.setText(Resources.getSystem().getString(R.string.cancel));
button_two = customDialog.findViewById(R.id.button_two);
button_two.setText(Resources.getSystem().getString(R.string.leave_anyway));
button_one.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.dismiss();
}
});
button_two.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.dismiss();
}
});
Objects.requireNonNull(customDialog.getWindow()).setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
customDialog.show();
}
}
I input the following code in another activity
Other activity code:
//Reusable exit dialog message
DialogBoxMessage dialogBoxMessage;
//Back button will close app
#Override
public void onBackPressed() {
dialogBoxMessage.leaveActivity();
finish();
}
But it doesn't seem to work, I think there are a lot of issues... please help :(

I assume customDialog is a seperate class you wrote - therefore i would suggest you put main information like contentview, title, message or type in the constructor when you initialize ur Dialog.
For your onClick Method I suggest you create an Interface to handle Button Clicks in your
customDialog class.

This could be implemented as a static method in a utilities class. The method would require 'this' as a parameter, which contains the activity context. The method should return the result of the button press. The activity can use this response to determine if finish() should be called or not.
UPDATE
I had suggested a simple static method, but you've gone down the object-oriented route. That's fine.
However, your constructor requires passing in several views, which wouldn't appear to achieve the code efficiency you are after.
Your constructor should just require the Activity context; everything else is encapsulated in your new class.
In each Activity's onBackPressed method you will need to create the object with
dialogBoxMessage = new DialogBoxMessage(this);
before you can call any of that object's methods.

Saving Activity State when switching activities

I'm currently trying to create an activity, which should be creating a new TextView on my main activity, everytime a Button is clicked on the first activity. However, instead of creating a new TextView everytime the button is clicked, it just changes the values of the first created TextView, so that there is always only one TextView. Is there a way to make it so that my first activity will not only create one single textview?
Here's the code from my "NewSubjectActivity":
**public class NewSubjectActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_new_subject);
Button SaveBtn = findViewById(R.id.SaveBtn);
nsaSaveBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Click();
}
});
}
protected void Click(){
Intent intent = new Intent(NewSubjectActivity.this, MainActivity.class);
Boolean createnewTextView = true;
intent.putExtra("createnewTextView",createnewTextView);
startActivity(intent);
}
}
And here's the (relevant) code from my MainActivity:
protected void ReceiveValue (){
//getting Extras
Intent nsareceivedvalues = getIntent();
boolean createTextView = false;
createTextView = nsareceivedvalues.getExtras().getBoolean("createnewTextView");
//declaring fixed Views
final LinearLayout mainLinearLayout = (LinearLayout)findViewById(R.id.mainLinearLayout);
//Params for TextView
RelativeLayout.LayoutParams Params = new RelativeLayout.LayoutParams(1000, 200);
Params.setMargins(0, 10, 0, 10);
while(createTextView) {
//creating a TextView
TextView newsubject = new TextView(MainActivity.this);
//applying values to the TextView
newsubject.setLayoutParams(Params);
newsubject.setGravity(CENTER);
newsubject.setBackgroundColor(Color.GRAY);
mainLinearLayout.addView(newsubject);
createTextView = false;
}
}
As I said, this only create one text view, everytime I press the button on my "NewSubjectActivity" I think this might be, because the previous text view is not saved and the MainActivity is reset everytime I switch between the activities.
Every help and advise is much appreciated <3

Maybe when you are going back to your main activity you should call to onBackPressed() function, so it will reset nothing at all. Here's the example in kotlin
val back_button:Button = findViewById(R.id.button2)
back_button.setOnClickListener { v -> run {
//Change activity
onBackPressed()
} }
in Java should be:
Button back_button = findViewById(R.id.button2);
back_button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Change activity
onBackPressed()
}
});
Let's hope it works!

image view not being visible based on number of clicks

In my MainActiviy class I want to display image views of smiley faces based on the number of clicks that occur on the buttons jokes, poems and funnystories combined. However my switch statement does not seem to working as no images appear. Also if any of those image views become visible, then they should remain visible even after the user closing the app and reopening it.
I also notice a click count increasing by one when the user opens the app which is not correct. It should increase based on the buttons mentioned previously being clicked.
public class MainActivity extends AppCompatActivity {
SharedPreferencesManager prefManager = SharedPreferencesManager.getInstance(this);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button jokesButton = findViewById(R.id.button_jokes);
Button poemsButton = findViewById(R.id.button_poems);
Button funnyStoriesButton = findViewById(R.id.button_funny_stories);
ImageView yellowSmileyFace = findViewById(R.id.yellow_happy);
ImageView greenSmileyFace = findViewById(R.id.green_happy);
ImageView redSmileyFace = findViewById(R.id.red_happy);
jokesButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
prefManager.increaseClickCount();
openContentPage("jokes");
}
});
poemsButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
prefManager.increaseClickCount();
openContentPage("poems");
}
});
funnyStoriesButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
prefManager.increaseClickCount();
openContentPage("funnystories");
}
});
TextView clickCountText = findViewById(R.id.click_count);
clickCountText.setText(Integer.toString(prefManager.increaseClickCount()));
switch (prefManager.increaseClickCount()){
case 4 :
yellowSmileyFace.setVisibility(View.VISIBLE);
break;
case 8 :
greenSmileyFace.setVisibility(View.VISIBLE);
break;
case 12 :
redSmileyFace.setVisibility(View.VISIBLE);
break;
default :
yellowSmileyFace.setVisibility(View.INVISIBLE);
greenSmileyFace.setVisibility(View.INVISIBLE);
redsmileyFace.setVisibility(View.INVISIBLE);
}
}
private void openContentPage(String v) {
Intent intentContentPage = new Intent(MainActivity.this, Content.class);
intentContentPage.putExtra("keyPage", v);
startActivity(intentContentPage);
}
}
below is the Shared preferences class
public class SharedPreferencesManager {
private static final String APP_PREFS = "AppPrefsFile";
private static final String NUMBER_OF_CLICKS = "numberOfClicks";
private SharedPreferences sharedPrefs;
private static SharedPreferencesManager instance;
private SharedPreferencesManager(Context context) {
sharedPrefs = context.getApplicationContext().getSharedPreferences(APP_PREFS, MODE_PRIVATE);
}
public static synchronized SharedPreferencesManager getInstance(Context context){
if(instance == null)
instance = new SharedPreferencesManager(context);
return instance;
}
public int increaseClickCount() {
int clickCount = sharedPrefs.getInt(NUMBER_OF_CLICKS, 0);
clickCount++;
SharedPreferences.Editor editor = sharedPrefs.edit();
editor.putInt(NUMBER_OF_CLICKS, clickCount);
editor.apply();
return clickCount;
}
}

You need to add a getter for your clicks
public int getClicks(){
return sharedPrefs.getInt(NUMBER_OF_CLICKS, 0);
}
Whenever you want to get your clicks currently you are calling increaseClickCount() which causes your clicks to increment before returning them. That is why it gains clicks every time you open the stage and why your switch isn't working correctly
so add the above getter to your SharedPrefrenceManager and change these two lines
switch (prefManager.increaseClickCount()){
to
switch (prefManager.getClicks()){
clickCountText.setText(Integer.toString(prefManager.increaseClickCount()));
to
clickCountText.setText(Integer.toString(prefManager.getClicks()));
Tell me if that fixes your problem

The reason for counts' increase is you use increaseClickCount() to receive click count.You have to create another method to receive current clickCount. Your switch statement works only when they equal to 4,8 or 12. Maybe you should use if instead.

I also notice a click count increasing by one when the user opens the app which is not correct
It looks to me like this line of code, in MainActivity.onCreate() method will pass a text String of count 1 to clickCountText.
clickCountText.setText(Integer.toString(prefManager.increaseClickCount()));
Also, every time you call SharedPreferencesManager.increaseClickCount, you are assigning a value to clickCount, and whatever was there gets overwritten.
int clickCount = sharedPrefs.getInt(NUMBER_OF_CLICKS, 0);
What is that value?
System.out.println is your friend.
I use this pattern
System.out.println("MyClass, MyMethod, MyVariable:" + myVariable);
I always include the class and method because it can be annoying trying to figure out where println are coming from if you leave several in for debugging purposes and want to get rid of them later.

Buttons outside the onCreate

Always in my apps I added buttons in void onCreate, but now I'm trying to do app with more buttons (about 10). I would like to all buttons active on start app.
In my opinion it is too much buttons to add in this onCreate and app will be starting to long.
I tried to put this:
myButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
myMethod();
}
})
out of onCreate
but AndroidStudio underlines setOnClickListener and view
I don't have ideas, how and where can i add button out of onCreate.

If you don't want to overcrowd your oncreate method, then create a clicklistener outside onCreate anywhere in activity and in onCreate just set it.
onCreate :
edit_a_member = (Button) findViewById(R.id.edit_member);
delete_a_member = (Button) findViewById(R.id.delete_member);
edit_a_member.setOnClickListener(handleClick);
delete_a_member.setOnClickListener(handleClick);
clickListener:
private View.OnClickListener handleClick = new View.OnClickListener() {
#Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.edit_member:
member_selected = EDIT_MEMBER_SELECTED;
callDialog();
break;
case R.id.delete_member:
callDeleteAlert();
break;
}
}
};

You can simply add a separate method for your buttons in the same class, e.g.:
public void onCreate(...){
//Standard setup of views or whatever you want to do here
this.addButtons();
}
private void addButtons(){
Button b1 = new Button("Hi");
b1.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
myMethod();
}
});
Button b2 = new Button("Hi to you too");
b2.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
myMethod();
}
});
}
This is an example. You can do this in soooo many ways. I feel like you should thoroughly learn Java's fundamental Object Oriented programming, because that's really what your question suggests you don't understand. Go follow a youtube tutorial. I always like "The New Boston"'s Java tutorial series on youtube.
PS: You can make code like this beautiful under the 'Words of wisdom': Don't repeat yourself

If you have to do a lot of work in your onCreate but you are worried that the UI will take too long to load you can always post a delayed runnable to a handler so in the onCreate method put :
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//add your code here
}
},10);
what this will do is your UI will load then the code in your Runnable will be executed 10 milliseconds after your UI loads thus your app will not take too long to load the UI, even though in your case I doubt it would be necessary.

If you are declaring the buttons in xml file :
Add these properties in each button Declaration in your Xml :
android:clickable="true"
android:onClick="onClick"
And now in Activity Class create a method like this :
public void onClick(View v){
switch(v.getId){
case R.id.{buttons_id_in_xml}
(Your Code)
break;
(Like for others)
}
}
If you want to add buttons dynamically :
Create a method to add the button like this:
void addButton(String buttonName, int button id){
Button button = new Button(this);
button.setText("Push Me");
(add it to parent Layout of xml)
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
switch(id){
case id1:
(handle )
break;
(like for others)
}
}
});
}

The best way to do this is:
add implements View.OnClickListener to
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
// declare variables
private Button mBtn1;
private Button mBtn2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
// make an instance to the btns
mBtn1 = findViewById(R.id.btn1);
mBtn2 = findViewById(R.id.btn2);
// set onClickListener
mBtn1.setOnClickListener(this); // with "this" you are passing the view
mBtn2.setOnClickListener(this);
}
// implement onClick
#Override
public void onClick(View view) {
// check which btn was clicked by id
switch (view.getId()) {
case R.id.btn1:
btn1Clicked();
break;
case R.id.btn2:
btn2Clicked();
break;
}
}
private void btn1Clicked() {
// your code btn1 clicked
}
private void btn2Clicked() {
// your code btn2 clicked
}
Hope this helped. Cheers!

How to make a button permanently unclickable

I am making a log-in system on Android. And I want the register Button to be unclickable when it has been clicked. I am using this code:
final Button register = (Button) findViewById(R.id.register);
register.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
register.setEnabled(false);
Intent register = new Intent(getApplicationContext(), register.class);
startActivity(register);
}
});
This is working great, but I want the Button to remain unclickable even when the application or phone has been restarted. Does anyone know a way to make the Button unclickable permanently even when the application has been shut down?

As I already said in the comments section something like this may work:
public class MyActivity extends Activity {
private static final String KEY_IS_BUTTON_CLICKABLE = "key_clickable";
#Override
public void onCreate(Bundle savedInstanceState) {
...
final Button register = (Button) findViewById(R.id.register);
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
boolean isClickable = sharedPreferences.getBoolean(KEY_IS_BUTTON_CLICKABLE, true);
register.setEnabled(isClickable);
if(isClickable) {
register.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
register.setEnabled(false);
PreferenceManager.getDefaultSharedPreferences(getApplicationContext()).edit()
.putBoolean(KEY_IS_BUTTON_CLICKABLE, false);
Intent register = new Intent(getApplicationContext(), register.class);
startActivity(register);
}
});
}
}
...
}

In this case you could take a pessimistic approach and disable the button in the layout (by default) with android:clickable="false" and enable it in the condition where registration is required.