Develop Reference

Remove items from array with auto generated onclick

I create a vertical list of textviews with an arraylist and attach on onclicklistener to each one. In the onclick I set code to remove that item. When I click in sequence from the last generated to the first this works fine. But if I remove the first one and then the last one it gives me a null pointer exception. I know this is happening because it is attempting to remove an index that is no longer present, or at least that is what I think is happening. But I cannot figure out how to solve that.
private void generateViews(){
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
final TextView[] textView = new TextView[questionArray.size()];
for(int i = 0; i < questionArray.size(); i++){
final int Index = i;
textView[Index] = new TextView(getActivity());
textView[Index].setText(questionArray.get(i));
textView[Index].setId(Index);
textView[Index].setGravity(Gravity.CENTER);
textView[Index].setPadding(15,15,15,15);
textView[Index].setLayoutParams(params);
textView[i].setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (textView[Index].getId() == (v).getId()) {
questionArray.remove(Index);
answerArray.remove(Index);
saveVariables();
updateViews();
((ViewGroup) textView[Index].getParent()).removeView(textView[Index]);
Toast.makeText(getActivity(), "Question and Answer removed!", Toast.LENGTH_SHORT).show();
}
}
});
mainLayout.addView(textView[Index]);
}
EDIT:
I figured out a small fix but it has it's problems. Instead of removing the items from the arrays with the index I can remove them by searching for the text within the textview.
The problem with this solve is that if my array contains 2 items that are identical then it may remove the wrong index.
questionText = textView[Index].getText().toString();
answerText = textView[Index].getText().toString();
if(questionArray.contains(questionText) && questionArray.size() > 0){
questionArray.remove(questionText);
answerArray.remove(answerText);
}
Solved:
I solved it by first searching for the index of the question text and removing that index from both arrays. The arrays are user generated and I plan on preventing the user from entering the same question twice.
questionText = textView[Index].getText().toString();
int questionIndex = questionArray.indexOf(questionText);
questionArray.remove(questionIndex);
answerArray.remove(questionIndex);
Also, I did it this way because I am still an amateur and was not aware of the Recyclerview. I plan on educating myself on that function and hopefully implementing it.

I really have no idea about why you want do this? if you just want remove textview in a list , why don't you use listview or recyclerview instead ?

You should consider using RecyclerView.

Wrong variable value in onClickListener

I am duplicating my linear layout dynamically and I have to set onClickListeners for buttons inside the linear layout.
for(int i = 0; i <10 ; i++){
// other code here
Button approve_btn = (Button) findViewById(R.id.rent_number_up_btn);
approve_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
approve_btn.setText(String.valueOf(i));
}
});
}
Everything works fine except that my button's text is always set to 9. I think that's because when the listener is called the value of i is 9 at that time. What I want the value of i at the time the button's listener is set and I am not sure how to do that.
How can I solve this problem? Any help is appreciated.

The issue is that you are setting click listener to the same button (by calling findViewById()) 10 times in a row. You get the value 9 because thats the last click listener which you added to the button.

for(int i = 0; i <10 ; i++){
// other code here
Button button = new Button(<Activity Instance>);
button.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
approve_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
approve_btn.setText(String.valueOf(i));
}
});
}
In above code you need to add those buttons in your linearlayout.
Hope this will help you,
Thanks

I am not sure what you want to do but:
Like #Shaishav said your are using same button (R.id.rent_number_up_btn) and your are replacing the click listeners on top of each other. The last value (of the your counter "i") before your loop finish is 9 , that's why it show 9 all the time. If you want to add 10 buttons inside your Linear layout just create new Button(context) every time when your loop starts and add this button to your layout via
yourLinearlayout.addView(yourNewButton);
Then if you set click listener to your new button maybe it will show different values :)

Android Development - Create a menu with 3 imageButtons

First of all english is not my first language but i will try my best.
Also... i am pretty sure my title choice was not the best so sorry for that.
Basically what i wanted to do is a menu with three ImageButtons but there is a tricky part (tricky for me at least) since every time i press one button that same button changes image (to a colored version instead of a grayed out image) and the other two change as well from colored version of their respective images to grayed out ones, actually only one of the other two will change since the purpose of this is to be able to activate only one at a time so it would not be possible to have the other two active at the same time.
Notice that this is not a menu on the top right corner but just a set of three ImageButtons on a activity or Fragment.
I already tried a lot of stuff to make that happen but so far no luck but i think i know why though i can't find a workaround for this since i am actually new in android dev.
what i tried was inside the setOnClickListener of any of those buttons such as:
eventsButton.setOnClickListener(
new View.OnClickListener() {
public void onClick(View view) {
ImageButton eventsButton = (ImageButton) view.findViewById(R.id.eventsButton);
eventsButton.setBackgroundResource(R.drawable.events_icon_active);
eventsButton.setClickable(false);
}
}
);
i tried to add the functions to change the other imageButtons as well like:
eventsButton.setOnClickListener(
new View.OnClickListener() {
public void onClick(View view) {
ImageButton eventsButton = (ImageButton) view.findViewById(R.id.eventsButton);
eventsButton.setBackgroundResource(R.drawable.events_icon_inactive);
eventsButton.setClickable(false);
ImageButton contactsButton = (ImageButton) view.findViewById(R.id.contactsButton);
contactsButton.setBackgroundResource(R.drawable.contacts_icon_inactive);
contactsButton.setClickable(true);
ImageButton interestsButton = (ImageButton) view.findViewById(R.id.interestsButton);
interestsButton.setBackgroundResource(R.drawable.interests_icon_inactive);
interestsButton.setClickable(true);
}
}
);
and i repeated that three time, always setting the other buttons clickable and setting their images to the inactive one (the grayed out one), also setting the button i click as no longer clickable.
But from what i gather i cant do any references to any other buttons inside the eventsButton.setOnClickListener like the buttons interestsButton or contactsButton, it will crash the app as soon as i touch any of those three buttons with the following error message:
Attempt to invoke virtual method 'void android.widget.ImageButton.setBackgroundResource(int)' on a null object reference
And it always point to the first line where i make a reference to another button other then the one used to start the setOnClickListener.
If you can just point me in the right direction i would be tremendously grateful.
All the best

You can declare your ImageViews as final outside the scope of the listener and when the onClickListener(View v) is called you can then just call setBackground because they are final and you can reference them from inside the listener.
Something like this:
final ImageView view1 = (ImageView) findViewById(R.id.view1id);
final ImageView view2 = (ImageView) findViewById(R.id.view2id);
view1.setOnClickListener(
new View.OnClickListener() {
public void onClick(View view) {
// do whatever you want to the ImageViews
// view1.setBackground...
}
}
);

eventsButton.setOnClickListener(
new View.OnClickListener() {
public void onClick(View view) {
ImageButton contactsButton = (ImageButton) view.findViewById(R.id.contactsButton);
contactsButton.setBackgroundResource(R.drawable.contacts_icon_inactive);
contactsButton.setClickable(true);
}
}
);
Your problem is in view.findViewById(R.id.contactsButton): view here is the button being clicked (the events one), and by calling view.findViewById(contactsButton) you are implicitly saying that the contact button is a child of view, which is not.
Just use findViewById() (from Activity), getActivity().findViewById() (from Fragments), or better container.findViewById() (if you have a reference to the layout containing the three buttons).
I'm not saying that yours is the most efficient way to deal with a menu, just pointing out your error.

You can first make things simple; I suggest:
you add 3 array (Arraylist might be better) fields in your activity class, one for the buttons, one for the active resources and one for the inactive resources
initialize those arrays in the onCreate method;
define a single onClickListener object and use it for all the buttons; Use a loop in the onClick method, see bellow.
In terms of code, it looks like this:
ImageButton[] buttons;
int[] activeResources;
int[] inactiveResources;
protected void onCreate2(Bundle savedInstanceState) {
View.OnClickListener onClickListener = new View.OnClickListener(){
public void onClick(View view) {
ImageButton clickedButton = (ImageButton) view;
for(int i = 0; i<buttons.length; i++){
ImageButton bt = buttons[i];
if(clickedButton==bt){
bt.setBackgroundResource(inactiveResources[i]);
bt.setClickable(false);
}else{
bt.setBackgroundResource(activeResources[i]);
bt.setClickable(true);
}
}
}
};
buttons = new ImageButton[3];
activeResources = new int[3];
inactiveResources = new int[3];
int idx = 0;
buttons[idx] = (ImageButton) findViewById(R.id.eventsButton);
inactiveResources[idx] = R.drawable.events_icon_inactive;
activeResources[idx] = R.drawable.events_icon_active;
idx = 1;
buttons[idx] = (ImageButton) findViewById(R.id.contactsButton);
inactiveResources[idx] = R.drawable.contacts_icon_inactive;
activeResources[idx] = R.drawable.contacts_icon_active;
idx = 3;
buttons[idx] = (ImageButton) findViewById(R.id.interestsButton);
inactiveResources[idx] = R.drawable.interests_icon_inactive;
activeResources[idx] = R.drawable.interests_icon_active;
for(int i =0; i<buttons.length; i++){
buttons[i].setBackgroundResource(activeResources[i]);
buttons[i].setOnClickListener(onClickListener);
}
}
Do not expect it to run right the way, I am giving only ideas, you have to look and see if it fit for you are looking for.

Different On-clicks for programmatically added buttons

I was looking through some topics but couldn't find exact answer or at least couldn't get it right. What happens in the code is that i create one button for each row in my database and each button is supposed to have an OnClick that sends us to another activity along with some values(each button is supposed to have different value) but in the end it seems like i get the same value for all of my buttons which makes me think that it only creates 1 view for all of the buttons.
Cursor przepis = bazaUzytkownikow.rawQuery("SELECT * FROM przepisy", null);
int liczba_wierszy = przepis.getCount();
przepis.moveToPosition(0);
for (int i = 0; i < (liczba_wierszy/4)+1; i++) {
LinearLayout row = new LinearLayout(this);
row.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
for (int j = 0; j < 4; j++) {
if((przepis.moveToPosition((i*4)+j)!=false))
{
nrPrzepisu=(i*4)+j;
Button btnTag = new Button(this);
btnTag.setLayoutParams(new LayoutParams(115, 60));
btnTag.setText(przepis.getString(przepis.getColumnIndex("nazwa")));
btnTag.setTextSize(10);
btnTag.setId(j + 1 + (i * 4));
btnTag.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View t) {
// TODO Auto-generated method stub
Intent IdzPrzepis = new Intent(getApplicationContext(), DodajPrzepis.class);
IdzPrzepis.putExtra("ID_uzytkownika", ID_uzytkownika);
IdzPrzepis.putExtra("nr_Przepisu", nrPrzepisu);
startActivity(IdzPrzepis);
}
});
row.addView(btnTag);
}
}
layout.addView(row);
}
To make the code more clear for you - bazaUzytkownikow is my database, liczba_wierszy is the number of the rows that i got. I move the cursor to the beginning since it's where i want to start and i proceed to "cut" my data using 2 loops. I am aiming for 4 buttons in 1 row.
The part that i think doesn't work is the OnClick method where i want my button to switch activity and send nrPrzepisu which is basically adding a connection between my button and proper row in the database (In the other activity i want to set text, reading rows from database depends on which button you click).
I checked the other activity and it seems to be reading same nrPrzepisu everytime which usually equals the last value of nrPrzepisu=(i*4)+j when loops finish and it made me think that i somehow need to make different views for each button.

you are passing the same object to each onClick then changing that object with the next iteration. In the end all the onClicks have the same nrPzepisu object and it is returning the value which is whatever is last in this example.
int nrPrzepisu = (i*4) + j;
This way you aren't passing the same object into all the onClicks.

Some alternative to hundreds of buttons

Im going to write some android app, which will basically consists of two activities. So first should have a lot of buttons (100+) and on click on any of them I will just get some special id and move to second activity. But is there any alternative to declare that hundreds of buttons and copy/paste one piece of code to every of them setting almost same onClickLister? Is there any special construction? Thanks
Edit: every of buttons are actually indexed from 1 to n. And on the click second activity will be launched and get that index to show it. I cant basically use any spinner or smth else, because there will be 3 rows of clickable things and each of them carring different images
Edit 2: so, to give you an idea, im going to do some table of buttons like in Angry Birds menu when you actually choosing the level you want to play. So, on click you will get id of button and start second activity

Call the method to add buttons
private void addButton(){
LinearLayout view = (LinearLayout) findViewById(R.id.linear_layout_id_here);
Button btn = null;
int w = 50;
int h = 25;
for(int i=1; i<100; i++) {
btn = new Button(this);
btn.setLayoutParams(new LayoutParams(w,h));
btn.setText("button " +i);
btn.setTag(""+i);
btn.setOnClickListener(onClickBtn);
view.addView(btn);
btn = null;
}
}
Call this method for handling onclick on button
private View.OnClickListener onClickBtn = new View.OnClickListener() {
public void onClick(View view) {
final int tag = Integer.parseInt(view.getTag().toString());
switch (tag) {
case 1:
// Do stuff
break;
case 2:
// Do stuff
break;
default:
break;
}
}
};

You should use a ListView.
ListViews are great for handling a lot of items at the same time. They are also natural for the user. Additionally, you use only one click listener - OnItemClickListener.
There's a useful example on how to work with ListViews in the Android Referenence.

You may add buttons in code, something like this:
#Override
public void onCreate(Bundle savedInstanceState) {
/*your code here*/
GroupView gw =findViewById(R.id.pnlButtonscontainer); //find the panel to add the buttons
for(int i=0; i<100; i++) {
Button b = new Button(this);
b.setLayoutParameters(new LayoutParameters(w,h));
b.settext = i+"";
b.setOnClickListener(new OnClickListener(){
});
}
}
I coded directly into browser, so some syntax error may appear in my code, but this is the point, a way, not the only one, to add 100 buttons.