I keep trying to set an imageview through my main activity and it keeps returning a null pointer exception in LogCat. My code is fairly self explanatory.
I'm pulling data from a JSON url and pulling data out of objects.
for (int i=0; i<forecastday_arr.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
JSONObject e = forecastday_arr.getJSONObject(i);
JSONObject date_obj = e.getJSONObject("date");
String curDate = date_obj.getString("weekday");
String conditions = e.getString("conditions");
String icon_to_use = e.getString("icon");
map.put("weekday", curDate);
map.put("conditions", conditions);
map.put("icon", icon_to_use);
if (icon_to_use=="rain") {
ImageView imgView = (ImageView) findViewById(R.id.imageViewDayOne);
imgView.setImageBitmap(BitmapFactory.decodeResource(this.getResources(), R.drawable.rain));
}
mylist.add(map);
}
From my code I'm checking to see if the value in "icon" is equal to rain, which it is (today), and if so, return the rain icon that's stored in my drawable folder. Even without the if statement I get the same null pointer exception. I'm quite new to Android so debugging isn't the easiest thing right now.
I presume I'm setting the image correctly. I've attached a picture of my LogCat below.
Sorry to be so vague but I thought it would be really simple to set an image. I'm sorry if I've missed anything as well - if I have I will quickly correct.
Pastebin of my MainActivity.java: http://pastebin.com/uNfYDGAw and a pastebin of my activity_main.xml: http://pastebin.com/M1xy1buB
So it appears your NullPointerException is coming from this line:
imgView.setImageBitmap(BitmapFactory.decodeResource(this.getResources(), R.drawable.rain));
I suspect that either this.getResources() or more likely BitmapFactory.decodeResource is returning null.
Luckily for you, there is an easier way to set an image on an ImageView. You can use setImageResource to set the drawable resource at runtime, like this:
imgView.setImageResource(R.drawable.rain);
--EDIT--
You also need to make sure you call setContentView with the layout that contains the ImageView you are attempting to use in onCreate of you MainActivity, before trying to reference any Views using findViewById.
setContentView(R.layout.layoutContainingImageViewDayOne);
Lastly, if you are attempting to do any network requests, they should be done in a background thread (off the UI thread) or the application with get an "Application Not Responding" crash. AsyncTasks are useful for this (however there are other methods). See http://developer.android.com/training/basics/network-ops/connecting.html for more info.
--EDIT 2--
So now that you posted all of the code, I see there are some major flaws here. Your R.layout.activity_main should actually be renamed to R.layout.list_row since it contains your row elements. Right now you are trying to use the same layout (R.layout.activity_main) for your Activity and its ListAdapter, which is impossible. R.layout.activity_main needs to have a ListView in it, that you attach your ListAdapter to. You are also trying to set your ImageView in your Activity code for your list rows, which the ListAdapter will already do for you.
So I'm going to suggest you take a look at some examples and refactor your app, Vogella has some great tutorials - http://www.vogella.com/articles/AndroidListView/article.html.
First use equals method to compare the Strings. Instead of ==
if (icon_to_use != null && icon_to_use.equals("rain")) {
....
}
Cause of NullPointerException
It might be because of you did not call setContentView to the layout or did not set right layout. means imageViewDayOne is not define in that layout.
Related
Hi I'm implementing click listeners in the following way but after some time the methods and variables inside the listener's closure get the wrong values or something. Let me explain the implementation of the listener a little better a for loop creates the listener for a set of image views then later in the program the for loop is called a second time and it resets the listener methods and variables to different values. Everything works great for about 30 minutes but then for some reason, the listener's methods and variables start having the wrong values. Has anybody ever heard of this behavior or can tell me where I've gone wrong with the code? Keep in mind that the listener I'm about to paste here is just a small piece of a 1014 line class. I'm hoping somebody can spot How I'm implementing the listener wrongly and can give me some advice on how to "reset" the listener so that it's variables and values stay over time. Hopefully you can read the code without putting it in an editor but feel free to copy it for readability's sake Here is the code for the image view listener with comments.
//image views are held in an array
//set an image view in its imageview container
imgArr0[slotId1].invalidate()
imgArr0[slotId1].setImageDrawable(null)
//drw is not defined in this example
imgArr0[slotId1].setImageDrawable(drw)
/*if video or image id is set to image then set a listener for the image
*/
/*slotId1 is not defined in this example but it is simply a counter to iterate over the ImageView array
*/
if (videoOrImageId0[slotId1] == "image") {
//null any listeners that might be attached to the image view
imgArr0[slotId1].setOnClickListener(null)
//set or reset the listener
imgArr0[slotId1].setOnClickListener() {
`enter code here`//if the current config is portrait then set a new image image
if (currentConfig0 == "portrait0") {
act0.lrgImage0.invalidate()
act0.lrgImage0.setImageDrawable(null)
/*drw is not defined in this example but works fine in the production script
*/
act0.lrgImage0.setImageDrawable(drw)
}
--calmchess
ccc tv application with problem.
(https://i.stack.imgur.com/PjdbN.jpg)]
I want to create a list of these elements and iterate through them, count them, get their attributes.
In the documentation, I found two similar methods:
findElement(locator, value)
and
findMultipleElements(locator, value)
Though it's totally unclear to me how to use it. I tried to find examples on it but with no success.
Could someone help me with this?
Here is the solution that I have found.
#kaqqao is right that findMultipleItems call returns Atom<List<ElementReference>> that is not usable with onWebView() because there you have only withElement() that accepts either Atom<ElementReference> or just ElementReference
What you can do though is perform your action that find multiple items and just get results from your Atom. This is how it works internally if you check the source of doEval method inside Web.java for espresso.
val elements = with(AtomAction(findMultipleElements(
Locator.XPATH,
"YOUR_COMPLEX_XPATH"
), null, null)) {
onView(ViewMatchers.isAssignableFrom(WebView::class.java)).perform(this)
this.get()
}
This code will give you List<ElementMatcher>.
Then just run it as
elements.forEach {
onWebView().forceJavascriptEnabled().withElement(it).perform(webClick())
}
Can you try something like that? Since what you should care about is really the ElementReference and you can iterate the lsit returned from findMultipleElements with simple for/foreach statement:
yourList = findMultipleElements(locator, value);
yourList.size(); //this will get you the count of found elements with that locator
for(Atom<ElementReference> item : yourList ){
item.getAttribute...
//and whatever you want
}
In my app I have a header with icon hidden, I have a adapter with a listview when I click the listview I go to a login screen using listener, when the login is successful is should come back to listview(adapter) and icon should get visible on header.
In the login activity I have the following code:
public void onClick(View v) {
String password = etPassword.getText().toString();
if(password.equals("guest")){
SearchAdapter.setImgVisibility();
} else {
//-----
}
finish();
}
In my adapter I am calling the setImgVisibility() as follows, but it is not working
public static void setImgVisibility() {
img.setVisibility(View.VISIBLE);
}
I am getting a Nullpointerexception near the line img.setVisibility(View.VISIBLE);
I am stuck here and don't know what I am doing wrong. Any suggestions or help is appreciated
I would imagine that img is null. You need to look at where this value is set and make sure happens before you call the method setImgVisibility.
Show more of your complete code for people to help further.
Additionally, i've just noticed you've used a static reference to your search adapter, you should be really careful using statics, especially where any referencing of images is concerned as images can be bound to the context, as such unless you nullify the static you will end up with a memory leak. (this used to be an old problem, not sure its still valid, but i would still avoid using a static reference).
Without more code we're not likely to be able to properly help you. For example are you switching activities when logging in? If you are, this won't work at all.
[given the comment below] If you switch activities then your activity containing the list view is going to be destroyed and then rebuilt then you navigate back to it. or it will at least go through the activity lifecycle. This means you can set the icon during the instantiation of the header img.
You could store your logged in state as a property of the Application or a preference. Grab this value when you set the header image and set the image accordingly.
your img object is null. Is your img object is same as View v then you can pass v in setImgVisibility() and then set v.setVisibility(View.VISIBLE)
In my application I have a list of questions stored in an ArrayList, and I want to display a dialog that shows one question, and then continues to the next one after the question is answered. The way that I'm currently doing it (iterating through a loop) hasn't been working because it just layers all of the dialogs on top of one another all at once which causes a host of other issues. What I'm looking for is a way to still iterate through the questions, but just change the layout of the dialog each time until it has finished each question in the list. Can anyone give me a good pointer for how to get this going?
You can make a function that takes title and message as parameters and shows a dialog.
showDialog(String title, String message){ // Show dialog code here}
Within that dialog's answer button's listener call another function (showQuestion(currentQuestion)) that iterates the arrayList till it is over
int currentQuestion=0;
ArrayList<QuestionObject> questionList;
showQuestion(int i){
if(i<questionList.size()){
showDialog(questionList.get(i).getTitle,questionList.get(i).getMessage);
currentQuestion++;
}else{
//quiz is over
}
}
I assume you mean that you just want to change 1 single layout(created within XML i.e main.xml). In order to do this, make sure that the class your working on is pointing to that layout. From there (assuming your using an Event listener for when the user submits an answer) you can change do as you want by the following:
TextView txt = (TextView) findViewById(R.id.textView); // references the txt XML element
and in your Event listener, if the answer is correct then change(Have i be a global variable thats initially set to 0).
if(i<arrayList.size()){
txt.setText(arrayList.get(++i));
}else{
txt.setText("You Finished");
}
From there, in the else statement, you can change arrayLists and reset i to 0;
If you are trying to use the positive, neutral, and negative buttons; then you may have problems with multiple dialogs. Try defining a customized layout with your own TextViews, ListViews, and Buttons. You can implement listeners and everything else like a regular layout. Then just pass your customized layout to the dialog through AlertDialog.Builder.setView().
PS If you include code examples of what you are currently doing we can provided answers that are less vague.
i have a row of buttins created like this
i want to change the background colour at runtime in code.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
LinearLayout track1 = (LinearLayout)findViewById(R.id.my_toggle_container);
for (int i = 0; i<32; i++) {
ToggleButton tgl = new ToggleButton(this);
tgl.setId(i);
...
track1.addView(tgl);
this names the id of the togglebuttons 1, 2, 3... (i presume?)
i have an int variable called 'xBtn' that changes 1, 2,..
this is how i get a reference to the button using xBtn
String buttonID = ""+xBtn;
int resID = getResources().getIdentifier(buttonID, "id", "com.thing");
//find the button
ToggleButton tb = (ToggleButton) findViewById(resID);
//change its colour
tb.setBackgroundColor(Color.BLUE);
it crashes on the setBackgroundColor line.
it may be obvious to someone whats wrong and thats what im hoping
any help would be totaly ace ta
thanks
main.xml
<LinearLayout android:layout_width="wrap_content" android:layout_height="match_parent" android:id="#+id/my_toggle_container" android:orientation="vertical">
The id of your togglebuttons is gonna be a number from 1 to 32... However, trying to find the toggle button by id will return null because simply instantiating a new toggle button and giving an id wont help you. findViewById looks in the parent view for a child view with the specified id. If you havent added that toggle button with that id to the view, then findViewById will return null. I am 99.99% sure even without looking at the log, that it crashes because you are calling setBackgroundColor on a null object.
In other words, the id that you set a view to is only relevant once the view is actually added to a parent view. In your case you are probably trying to add these toggle buttons to your main content view, in which case you need grab hold of that view that you used for setContentView and call addView on that view and pass in each new toggle button. Note that this will probably not look right unless you also specify layoutparams for the togglebuttons.
EDIT
If thats your entire main.xml, then you've got other issues. Post the full xml file. In any event, you still are going to have to do what I've said, which is to grab hold of the view or a child view of that view and then add the toggle buttons to it via addView (after giving the togglebuttons their proper ids). Once the button has been added, then you can find it. Note though that if you're gonna add the toggle buttons to a child view of your main view, then you'll likely have to grab hold of that child view and call findViewById on THAT.
For example, you can do a nested call like this. findViewById(1) <--- gets you the LinearLayout or whatever inside of your main content view, then once you have that you can call addView on it. So LinearLayout ll = (LinearLayout)findViewById(someNumber); ll.addView(tb);
Try to use the method setTag() , and then you can get all your ToggleButton by using : findViewByTag();
Perhaps tb is null? Could you check that out?
To expand on what LuxuryMode said... What gets an ID INTO your java is inflating it via setContentView and setting it as content. That's why it's ok to have overlapping (duplicate) IDs in different layouts. You can have #+id/submit_button in layout1.xml and in layout2.xml and the Activity will get you the object via findViewById(R.id.submit_button) based on which one you have loaded into setContentView() at any given moment.
So, we're all guessing that you're probably not setting the content view and hoping that the code will find your object in your non inflated XML, which it won't. Which would lead (as everyone has guessed) to you now dealing with a null object, which you obviously can't set a background color on.
I know it gets confusing cause you have the XML RIGHT THERE!!! But the reality is that the xml isn't "alive". It's just stuff for you to look at until you have tasked the Application with inflating it and converting all of it into Android objects of some kind. A lot of the time this is done mostly transparently to you, so, it's easy to forget that none of these things really exist.
It's very likely that tb is null, because findViewById() didn't go as you expected.
You can verify this by surrounding the erroneous line with try.. catch block:
try {
tb.setBackgroundColor(Color.BLUE);
} catch (Exception e){
}
and watch for the message of e. It's likely to be null pointer exception.
In fact, I think you should not use getResources().getIdentifier(buttonID, "id", "com.thing") in the first place. It seems to me that all these resources are continuously numbered in R file, thus you should simply get the first id (as an integer), and then increment on that.
That is, you should do things like:
// The following code is not tested; I just wrote it here on SO.
for (int resID = R.id.button1; resID <= 32; resID++) {
ToggleButton tb = (ToggleButton) findViewById(resID);
tb.setBackgroundColor(Color.BLUE);
}
this should make all 32 buttons blue.