NullPointerException setting onClickEvent for dynamic button [duplicate] - java

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 6 years ago.
I have a function which creates a button, which has an onClick event to bring up a custom dialog which just shows some information from the functions parameters. The dialog has two buttons on it as well, one to close the dialog, and one to add information to a file.
When I try to set onClick events for those buttons, the app crashes, and the error I get is a NullPointerException which says that I am trying to invoke a virtual method on a null object reference.
If I comment out the part where I set the onClickEventListener code for both buttons, then the dialog appears as normal, with the buttons on it.
Note: context is a variable declared in the class. It is simply Context context = this
Code is below:
public void addButton(String text, int id, String areas, String details, String notes) {
Button button = new Button(this);
final String title = "Add "+text;
final String dName = text;
final String dAreas = areas;
final String dDetails = details;
final String dNotes = notes;
button.setText(text);
button.setTextColor(ContextCompat.getColor(context, R.color.buttonText));
button.setTextSize(32);
button.setId(id);
if (isEven(id+1)) {
button.setBackgroundResource(R.drawable.buttonshapeother);
} else {
button.setBackgroundResource(R.drawable.buttonshape);
}
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// Make custom dialog
final Dialog dialog = new Dialog(context);
Button add = (Button) dialog.findViewById(R.id.btnAddExer);
Button cancel = (Button) dialog.findViewById(R.id.btnCancel);
dialog.setContentView(R.layout.popup_exercise);
dialog.setTitle(title);
// Set the custom components now
TextView tName = (TextView) dialog.findViewById(R.id.lblNameData);
TextView tAreas = (TextView) dialog.findViewById(R.id.lblAreaData);
TextView tDetails = (TextView) dialog.findViewById(R.id.lblDetailsData);
TextView tNotes = (TextView) dialog.findViewById(R.id.lblNotesData);
tName.setText(dName);
tAreas.setText(dAreas);
tDetails.setText(dDetails);
tNotes.setText(dNotes);
// Add functions to buttons
add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (addExercise(dName, dAreas, dDetails, dNotes)) { // Add exercise to user's workout
Toast.makeText(context, "Exercise was added to your workout", Toast.LENGTH_LONG).show();
dialog.dismiss(); // Close dialog
} else {
Toast.makeText(context, "There was an error adding your exercise", Toast.LENGTH_LONG).show();
}
}
});
cancel.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
dialog.dismiss(); // Close dialog
}
});
dialog.show(); // Actually show the dialog
}
});
LinearLayout lay = (LinearLayout) findViewById(R.id.innerLay);
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
lay.addView(button, params);
}
public boolean isEven(int num) {
if ((num&1) == 0) {
return true;
} else {
return false;
}
}

Because you are trying to find button view before setting the layout to it. So try like this:
final Dialog dialog = new Dialog(context);
dialog.setContentView(R.layout.popup_exercise);
dialog.setTitle(title);
Button add = (Button) dialog.findViewById(R.id.btnAddExer);
Button cancel = (Button) dialog.findViewById(R.id.btnCancel);

Related

Reset Button to default background

I know that was already asked but it is outdated:
I have 2 buttons that represent 2 choices and if one is selected the background color gets changed to yellow. But if i want to change the choice i need to somehow reset the button:
I already try to set it back but some old design comes out. Can you provide me the id of the modern button style? And show me how to implement it?
int myChoice;
if (view == findViewById(R.id.choice1)){
myChoice = 1;
choice1.setBackgroundColor(getResources().getColor(R.color.highlightButton));
choice2.setBackgroundResource(android.R.drawable.btn_default);
}
else if (view == findViewById(R.id.choice2)){
myChoice = 2;
choice2.setBackgroundColor(getResources().getColor(R.color.highlightButton));
choice1.setBackgroundResource(android.R.drawable.btn_default);
}
}
Use Tags with getBackground(). This will assure you are always setting back to original.
Add following in beginning of function
if (v.getTag() == null)
v.setTag(v.getBackground());
Then instead of setBackgroundResource, use
v.setBackground(v.getTag());
Starting from here, you can store the default color of the button into a Drawable and grab the selection color (Yellow in your case) into anther Drawable, then toggle background colors of buttons with these Drawable variables
please check below demo
public class MainActivity extends AppCompatActivity {
private Drawable mDefaultButtonColor;
private Drawable mSelectedButtonColor;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final Button btn1 = findViewById(R.id.btn1);
final Button btn2 = findViewById(R.id.btn2);
mDefaultButtonColor = (btn1.getBackground());
mSelectedButtonColor = ContextCompat.getDrawable(this, R.color.buttonSelected);
btn1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
toggleButton(btn1, true);
toggleButton(btn2, false);
}
});
btn2.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
toggleButton(btn1, false);
toggleButton(btn2, true);
}
});
}
private void toggleButton(Button button, boolean isSelected) {
button.setBackground(isSelected ? mSelectedButtonColor : mDefaultButtonColor);
}
}

Android Studio - Create an EditText with a click of a button

Can't seem to find a post/video on the net that explains adding new EditText fields with a button. I need to use the edittexts later. Can someone please explain to me how to create this system? Or link a video/post that explains this. I've been searching for a long time but I still haven't found a good explanation. Thanks.
Button mButton = (Button) findViewById(R.id.my_button);
mButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
EditText t = new EditText(myContext);
t.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
root.addView(t);
}
});
root: is the root layout where you want to add the EditText.
use below code
Add this Java File..
LinearLayout linearLayout = findViewById(R.id.editTextContainer);
Button btnShow = findViewById(R.id.btnShow);
if (btnShow != null) {
btnShow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// Create EditText
final EditText editText = new EditText(this);
editText.setHint(R.string.enter_something);
editText.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT));
editText.setPadding(20, 20, 20, 20);
// Add EditText to LinearLayout
if (linearLayout != null) {
linearLayout.addView(editText);
}
}
});
}

How should I return to a previous dialog from another one?

I've got an inputDialog, which allows for some text inputs. On clicking save, the inputDialog checks if the entered text is already available (to prevent double entries). If this is the case, a new AlertDialog is created, simply stating "The value you entered already exists", with just an "Ok" button to dismiss this AlertDialog. This all works.
I would like to have the inputDialog pop back up again, after dismissing the AlertDialog, with the values that were entered by the user before still in the editText fields.
I'm not expecting any problems on getting those values back in the editText fields (Store them in a variable on clicking save, if the double entry error occurs, set those variables on the editText's. If I'm doing this in a stupid way, please let me know).
I am however having trouble with getting the first (inputDialog) dialog to come back. The code you see below is the code for my inputDialog fragment (The code is simplified, so if something seems to be missing, it probably is. Let me know, so I can add it back in.)
So, to repeat myself: How can I return to the previous dialog after dismissing the second one?
StuffManagerInputDialogFragment.java:
public class StuffManagerInputDialogFragment extends DialogFragment {
EditText nameInputField;
EditText tagInputField;
DBHandler dbHandler;
StuffManagerFragment f = new StuffManagerFragment();
#Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
LayoutInflater inflater = getActivity().getLayoutInflater();
final View v_iew = inflater.inflate(R.layout.fragment_inputdialog, null);
nameInputField = (EditText) v_iew.findViewById(R.id.inputdialogname);
tagInputField = (EditText) v_iew.findViewById(R.id.inputdialogtag);
dbHandler = new DBHandler(getActivity(), null, null, 1);
final MainActivity ma = (MainActivity) getActivity();
final AlertDialog.Builder newLinkDialog = new AlertDialog.Builder(getActivity());
newLinkDialog.setView(v_iew)
.setTitle("New Link")
.setPositiveButton("Save", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
String nameInputFieldText = nameInputField.getText().toString();
String tagInputFieldText = tagInputField.getText().toString();
ArrayList<String> nameArray = dbHandler.nameArrayMethod();
ArrayList<String> tagArray = dbHandler.tagArrayMethod();
NavigationView navigationView = (NavigationView) getActivity().findViewById(R.id.nav_view);
Menu menu = navigationView.getMenu();
if (nameArray.contains(nameInputFieldText) || tagArray.contains(tagInputFieldText)) {
if (nameArray.contains(nameInputFieldText) && tagArray.contains(tagInputFieldText)) {
AlertDialog.Builder errorBoth = new AlertDialog.Builder(getActivity())
.setTitle("Error")
.setMessage("The name and tag you entered are already in use.")
.setIcon(R.drawable.ic_error_black)
.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
//Return to previous dialog here
}
});
errorBoth.show();
}
} else {
dbHandler.addLink(nameInputFieldText, tagInputFieldText);
nameArray = dbHandler.nameArrayMethod();
int nameArraySize = (nameArray.size() - 1);
MenuItem item = menu.add(R.id.group1, nameArraySize, 1, nameArray.get(nameArraySize));
Toast.makeText(getContext(), "'" + nameInputFieldText + " - " + tagInputFieldText + "' link saved.", Toast.LENGTH_SHORT).show();
ma.addSMVFFragments();
f.hideDeleteAllButton = false;
getActivity().invalidateOptionsMenu();
}
}
})
.setNegativeButton("Cancel", null);
return newLinkDialog.create();
}
}
A better solution is to have a dialog fragment for your input layout, and that dialog fragment would display an AlertDialog on OK if the text validation fails. The input dialog fragment would not dismiss in this case, it will remain in the background so when you dismiss the alert dialog to tell the user the input is invalid, you return to the input dialog as it was.
To prevent the dialog fragment from dismissing on OK you would override onStart and get a reference to the OK button and set the listener there, like this:
#Override
public void onStart() {
super.onStart();
AlertDialog alertDialog = (AlertDialog) getDialog();
if (alertDialog != null) {
mOKButton = alertDialog.getButton(AlertDialog.BUTTON_POSITIVE);
mOkButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (field OK) {
// save data
dismiss();
} else {
// show error dialog
}
}
});
}
}

Removing TextViews when i clicked backbutton

My problem is I have a button and that button is doing create new textview but that textviews removing when i click back button. How I saved textviews in activity?
My java sourcecodes here
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.notlar);
Button btnNotEkle = (Button) findViewById(R.id.btnNotEkle);
final EditText etNot = new EditText(NotEkle.this);
final LinearLayout layoutNotlar = (LinearLayout) findViewById(R.id.layoutNotlar);
final TextView tv1 = (TextView) findViewById(R.id.tvnotOrtalama);
etNot.setInputType(InputType.TYPE_CLASS_NUMBER);
AlertDialog.Builder notEkle = new AlertDialog.Builder(NotEkle.this);
notEkle.setTitle("Notunuz");
notEkle.setView(etNot);
//Positive button
notEkle.setPositiveButton("Tamam", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
tvNot = new TextView(NotEkle.this);//girelen not burdaki textview e yazdırılacak.
girilenNot = etNot.getText().toString();//Girilen notu alıyoruz
tvNot.setText(girilenNot);//girilen notu textviewa veriyoruz
notTopla += Integer.parseInt(girilenNot);//Notları topluyoruz
layoutNotlar.addView(tvNot);
count = layoutNotlar.getChildCount();
dersOrtalamaYazdir=String.valueOf(dersOrtalama());
tv1.setText("Ders Ortalamanız : "+dersOrtalamaYazdir);
dialog.cancel();
}
});
final AlertDialog notEkleCreate = notEkle.create();
btnNotEkle.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
notEkleCreate.show();
}
});
}
}
Try giving your TextView objects ids.
You need to know that when you click back button - by default your activity is destroyed so all views are removed.
When you are adding new TextView you should add information about this TextView (like the text itself) to some list declared as field in your activity.
Then you can save this list when activity is recreated see: onSaveInstanceState/nRestoreInstanceState
You can also pass this list back or to new activity so that they can take actions based on this list.
Following my understanding your TextView had been created inside Dialog and after you press back button the dialog dismisses and all views you created inside will be removed and you can't access it from your Activity.
You may try to create TextView in onCreate, pass and in Dialog just call setText. I hope this is the answer you're looking for.
Cheers.

Text view if statement not working

Can anyone help me work out where I'm going wrong here. On the button click the media player plays one of the mfiles at random and I'm trying to set a textview depending on which file was played. Currently the setText if statements only match the audio playing half the time. Really not sure where I'm going wrong here.
private final int SOUND_CLIPS = 3;
private int mfile[] = new int[SOUND_CLIPS];
private Random rnd = new Random();
MediaPlayer mpButtonOne;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mfile[0] = R.raw.one;
mfile[1] = R.raw.two;
mfile[2] = R.raw.three;
//Button setup
Button bOne = (Button) findViewById(R.id.button1);
bOne.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
final TextView textOne = (TextView)findViewById(R.id.textView1);
mpButtonOne = MediaPlayer.create(MainActivity.this, mfile[rnd.nextInt(SOUND_CLIPS)]);
if (mpButtonOne==null){
//display a Toast message here
return;
}
mpButtonOne.start();
if (mfile[rnd.nextInt(SOUND_CLIPS)] == mfile[0]){
textOne.setText("one");
}
if (mfile[rnd.nextInt(SOUND_CLIPS)] == mfile[1]){
textOne.setText("two");
}
if (mfile[rnd.nextInt(SOUND_CLIPS)] == mfile[2]){
textOne.setText("three");
}
mpButtonOne.setOnCompletionListener(new soundListener1());
{
}
So just to clarify the problem I am having is that the setText only matches the audio occasionally, not on every click. The rest of the time it displays the wrong text for the wrong audio.
You are choosing another random file
mfile[rnd.nextInt(SOUND_CLIPS)]
set that to a variable in onClick() then check against that variable in your if statement
public void onClick(View v) {
int song = mfile[rnd.nextInt(SOUND_CLIPS)];
final TextView textOne = (TextView)findViewById(R.id.textView1);
mpButtonOne = MediaPlayer.create(MainActivity.this, song);
if (song == mfile[0]){
textOne.setText("one");
}
Edit
To make it a member variable so you can use it anywhere in the class, just declare it outside of a method. Usually do this before onCreate() just so all member variables are in the same place and it makes your code more readable/manageable.
public class SomeClass extends Activity
{
int song;
public void onCreate()
{
// your code
}
then you can just initialize it in your onClick()
public void onClick(View v) {
song = mfile[rnd.nextInt(SOUND_CLIPS)];
final TextView textOne = (TextView)findViewById(R.id.textView1);
mpButtonOne = MediaPlayer.create(MainActivity.this, song);

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