Develop Reference

How to change textviews & imageviews of another activity in Android

I have an activity which can take a few seconds to load its content (mainly pictures) from the cloud. Let's say this content is pictures & description from a person. The user can go to pictures & description from another person by clicking on the next button. I'd like to avoid the loading time When this button is clicked.
To do this I have two activities : firstPersonActivity for the first person content, and secondPersonActivity for the second person content.
What I try to do is to load the content of the secondPersonActivity when the user is in the firstPersonActivity, so that the secondPersonActivity can be displayed "directly" (= without needing to load content from the cloud when the next button is clicked in the firstPersonActivity).
But I do not succeed in doing this, I don't know how to modify the views of the secondPersonActivity layout from the firstPersonActivity class.
I tested the following code in my firstPersonActivity but it doesn't work (there is no connexion to the cloud, it's just a test to better understand how it works). R.id.first_image_second_person is the id of my imageview in the secondPersonLayout (= the layout used in the secondPersonActivity).
ImageView firstImageSecondPerson = (ImageView) findViewById(R.id.first_image_second_person);
firstImageSecondPerson.setImageResource(R.drawable.mypicture);
When I click on the next button to go from the firstPersonActivity to the secondPersonActivity, my firstImageSecondPerson imageview is not filled.
Do you see what's wrong ?
Is there a better way to avoid the loading time when the user click on the next button ?

It is not possible to change activity if activity instance is not created. In my opinion to do what You need I would go to single activity with hidden content of second person ( VIEW.INVISIBLE ) and show/hide it when it is needed.
But if second activity must be there, then create some structure for saving bitmaps in memory. In Your code sample You get picture from drawable so we are not talking about some delays, but if images are downloaded from some server then You can create some class which will have those bitmaps created from url and instance of this class can be used on any activity.
So for example Your class for caching pictures would have some method for creating bitmaps like -How to load an ImageView by URL in Android?. And those bitmaps should be saved in some Array or HashMap to have access to it, for example ( pseudo code ):
//some structure for cashing pictures in app
class PictureCache {
static PictureCache instance;
final HashMap<Integer, Bitmap> bitmaps;
//singleton
static PictureCache getInstance(){
if (instance==null)
instance = new PictureCache();
return instance;
}
public PictureCache(){
bitmaps = new HashMap<>;
}
private Bitmap loadBitmap(String url);//#1
public addPicture(Integer personId, String href){
//add to hashMap
bitmaps.put(personId, loadBitmap(href));
}
public Bitmap getPicture(Integer personId){
return bitmaps.get(personId);
}
}
#1 - method from How to load an ImageView by URL in Android?
Using it in first activity:
PictureCache.getInstance().addPicture(12,"http://url.to.bitmap");
Using it in second activity:
Bitmap pic = PictureCache.getInstance().getPicture(12);
Important note - above code was written here and was not tested, it shows solution concept.
Important second note - using such approach with bitmaps in memory can cause to much memory usage

You cannot access the views of SecondActivity before its creation. If you called this activity once only then you are able to access its views by making them static.
One more Solution for this is..
Access the whole data at once and save it in static arraylist with the help of getter-setters. Then on SecondActivity set data from that arraylist.
Hope this will work.

I don't think you can access the view before creating the activity.
You can try to use Glide for caching your images and minimizing loading time.

Try this
Picasso.with(getContext()).load(R.drawable.generatedId).into(imageView);
or
imageView.setImageDrawable(ActivityCompat.getDrawable(getContext(),
R.drawable.generatedID));`

How to pass String from onClick Edit Text field to Background task - Android

How can i take user input from popup dialogue and pass it into a BackGround Async Task?
I have a "createGarden" button. When i click it i want to retrieve a string from user, and pass it to my Background AsyncTask.
In my onClick, i have tried calling String myGardenName = getGardenName(), which returns input from dialogue. Then passing this into my Background task.
new HomeBackgroundTask().execute("create_garden", UserID_String,myGardenName );
I also tried using a value container, and passing this instead of "myGardenName":
String myGN = gnVC.getVal();
HomeBackgroundTask mhomebackgroundtask1 = new HomeBackgroundTask();
mhomebackgroundtask1.execute("create_garden", UserID_String, myGN);
instantiated my 'gardenValueContainer' value container as final in my "getGardenName()" method (enclosing class?) as well as instantiating it in my onCreate()
- I then try SETTING that value from within my onClick (inner class?)
--Also tried calling my HomeBackgroundTask directly from the onClick
Problem
Seems that my create garden always tries to insert a BLANK as the garden name. resulting in "garden "" already exists". When debugging, the user input get's passed through as a paramater, there was an issue with moving from "onPreExectute" to "doInBackground" but now when i'm debugging i get stuck in looper where i can't step over/into/out and my app just says freezes on connecting. (debug halts on a comment line, which might be bad?)
My php scripts work just fine with the same logic for registering a user.
No errors in my console!
http://pastebin.com/2AzWmcM5
Any help greatly appreciated!

"debug halts on a comment line, which might be bad"
Have you tried removing all breakpoints, or putting breakpoints on method implementations rather than on the, say, first line of the method?

Application with different requests sent to a database (SQL) depending on buttons clicked

I still am a beginner in Android development and will try to make my question as clear as possible with a schema of what I have in my mind.
Purpose of this application:
- I want the user to have the choice between a few buttons and when clicking on any of them, it would open a list view with different content according to the button.
ex : if you click on "Category_1" button, only elements with a fitting id will appear in the listview.
So far, I have :
- defined my "handler" class (extends SQLiteOpenHelper) : name/path of DB, definition of CRUD, .getReadableDatabase, etc.
- define a class for my table, in my case "Restaurants.java" with getters/setters and constructor.
- defined my MainActivity with empty listeners for my button.
- defined my "DatabaseAdapter.java" in which I want to define the methods/sql requests which will communicate with the database and get the information I want from it.
- defined my ListViewActivity with nothing to display so far.
Here is a schema of what I want with the idea of how to make it to try to optimize my application :
To sum up:
- I want a listener for each button setting a variable to a certain value (for example: "if you click on 1 then set the value of A to 1") and opening the ListViewActivity.
- There would be a method defined in "...Adapter.java" sending a request to the database and having the variable A defined earlier as an input.
- And then, when clicking on the button, the ListViewActivity will open and call the method from "..Adapter.java", and finally display the results.
So, here are my questions :
- First of all, is the design optimized enough to allow my application to run fast? I think it should as all the button open only one activity and there is only one method defined for all buttons.
- I have a hard time defining the method in "...Adapter.java" which will be called from my ListViewAcitivity. The input should be the variable obtained when clicking on the button but I don't really know how to get a variable in one activity, open a second activity where to display results by using the variable in a third activity... :s
Is it fine to set a variable to a certain value when we click on a button and use this variable in another class as an input for a method?
public findNameInTable(int A){
string sql = " select NAME from MY_TABLE where CAT1 = " + A;
c = database.rawQuery(sql, null); }
Thanks in advance for any indications, suggestions or links which could help me to make my application come true, and sorry if some questions really sounds newbie, I am starting !
Have a good day !

Part 1: The best way I have found to pass variables to other activities is with a putExtra(String, variable);. Say you change the variable name on a button press, you can then call:
YourNewActivityClassName var = new YourNewActivityClassName();
Intent i = new Intent(context, YourNewActivityClassName.class);
i.putExtra("name", name);
startActivity(i);
Then in the activity you just created, you can call this in the onCreate method:
Intent i = getIntent();
final String name = i.getStringExtra("name");
Of course this is assuming the variable was defined as a String before the putExtra was called.
If you want to use other variable types, there are different get***Extra commands you can call like getIntExtra(int, defaultval) but the putExtra will still be used to send it.
Part 2: For calling a method with a variable assigned in a button click, I have found the best way to do this is with a "holder class" this holder can be defined as a final, and a button press assigns a value to one of it's slots. Here is my holder for Integers:
public class holder {
int to;
public void setTo(int to){
this.to = to;
}
public int getTo(){
return to;
}
}
I instantiate my class as final within my on create final holder hold = new holder();
then call my hold.setTo(int); within a list click listener. When I want to get the data, I simply call hold.getTo(); and I have my integer.
Heres a similar post: Pass value outside of public void onClick
Hope this helps!
Mike

Android: setImgVisibility() error

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)

Start (open) ListActivity without putExtra

I am trying to open a list activity in two ways, (both from different activity A)
In one method I use putExtra(String name, String value) to populate the listActivity with sqlite.
This works perfectly awesome.
But now with another button, I am trying to open this list activity without putExtras (just viewing it) but i get a Force Close with Null Pointer Exception for this,
Can any one provide me some solutions for this, thanks in advance...

In your List activity, you're doing something like this yeah?
String passedValue = getIntent().getStringExtra("key");
In the case when you don't putExtras() , passedValue is null, so trying to use this string will give a NPE. So if you want to use passedValue, you might want to do this:
if(passedValue != null)
doSomethingWith(passedValue);