Develop Reference

Want the EditText to display in all Activitys

First of, I'm a noob in Android development....
So, my problem is - I have a Activity with a EditText view, so someone can put his name in it.
And what I want to do with that input - I want it to be displayed in all activities in TextViews where it needs to be.
Example - Like in a book -> Input name: What are you doing kid? Kir: "I don't know..." Input name: "Just don't do it anymore..."ect.
And then in the next Activity by clicking a Button, the same, I want that same input name to display in ALL ACTIVITES , TextViews where it needs to be, but I don't know how to declare it, where to declare it, what code ect.
I hope you all will understand what i mean.
And thank you for your support.

One way is by passing data into intents before starting the activity.
Intent intent = new Intent(context, MyActivity.class);
intent.putExtra("key_name", "John Cena");
context.startActivity(intent);
Then retrieve the data in MyActivity by:
Bundle extras = getIntent().getExtras();
String name = extras.getString("key_name"); // name should be John Cena
Simillar functionality also exists for Fragments.

Basically you wants to Preserve the Value\Data. For such scenarios, it is best to use [Preferences] where you can save your data on disk in a private file and read it anytime and anywhere.
Android Preferences

getStringExtra - Public Static Final - The Busy Coder's Guide to Android

I am on page 301 of this book and it is an example of an Activity getting "extras" from the intent that started it. I am fairly new to Java so maybe am missing something pretty obvious but...
I thought that when you declare a variable as "final" it meant that it doesn't change.
There is a line of code initialising a final variable:
public static final String EXTRA_MESSAGE="msg";
and then later in onCreate method:
tv.setText(getIntent().getStringExtra(EXTRA_MESSAGE));
The text displayed in the activity is not "msg" but is the string passed from the intent "I am the other activity". Why do you have to have the variable declaration above for the code to work? I don't understand what its doing.
Thanks

You are getting the extra received from another Activity indexed by the key 'msg'.
Like when you do this with the Intent used to start your Activity:
intent.putExtra("msg", "text going in the TextView");
The key is 'msg', but the value you get for the TextView is 'text going in the TextView'

Yes, final means EXTRA_MESSAGE value won't change, but you're not displaying EXTRA_MESSAGE value, but
getIntent().getStringExtra(EXTRA_MESSAGE)
which actually contains the value put in the previous activity. Regarding your question
Why do you have to have the variable declaration above for the code to work?
You don't actually need that variable for the code to work, but it's a good practice to use constant values instead of just hardcoding string values such in.-
getIntent().getStringExtra("msg")

The parameter you pass to getStringExtra is the key to which the String is mapped. All the extras you put in an Intent are mapped as key-value, so if you want to get a value you have to know the key, which must be the same key you used in the previous activity to save the value (with putStringExtra).
http://developer.android.com/reference/android/content/Intent.html#getStringExtra(java.lang.String)

Why this type casting?

I am using an intent to start another activity, and making my intent carry some data as an extra to the newly created activity. I am following a tutorial to do that.
This data is actually read from a text field in the first activity in the hierarchy, and carried to the other activity as an extra. so my code will be like:
//Make the intent
Intent intent = new Intent(this, SecondActivity.class);
/* Find the text field (view) which contains the data, and save it into a newly created text field (view of the same type)*/
EditText editText = (EditText) findViewById(R.id.iden1); //******************************
//Read that view's string data into a string called message
String message= editmessage.getText().toString();
//copy this message into the extra named extra_name, of intent.
intent.putExtra(extra_name, message);
My question is from this statement:
EditText editText = (EditText) findViewById(R.id.iden1);
My question is explicit casting i.e. (EditText). Why are we casting the EditText view (which was defined in layout.xml and was identified by android:id="#+id/iden1") returned by findViewById()to an EditText view again. The type of the view editText here and the one created in layout.xml is the same. So what is the point of this type-casting?

The point is that findViewById(int id) returns a generic View object. This method doesn't parse your xml in order to understand what kind of type is your view. It just makes a new View object from the relationship put in place by your R.java file, built up by your IDE (Eclipse, I suppose).
You need to cast the result of findViewById(int id) because you're not casting an EditText object, your casting a View, of which EditText is only a specification.

findViewById returns a View. If you need to use methods of a derived class you need to cast. If you need to use only the methods of the base class you can avoid the cast

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

How do you get a view reference from a class that doesn't extend Activity?

I want to have a class "Utils", that will have several methods used all over my code. For example, I have a top bar with a textview and two ImageButtons that must display different texts and icons on different activities.
I find myself writing stuff like this on every activity:
(TextView) topBarText = (TextView) findViewById(R.id.topBarText);
topBarText.setText(R.id.mytextForThisView);
I'd like to findViewById once in my whole app, and call a method setupTopBar(String text, R.id.iconForImageButton1, R.id.iconForImageButton2), or even pass the current Activity's id and let the method figure out what to show in the text and images.
I created the class Util, but it doesn't extend Activity. The problem is that if it doesn't, findViewById isn't accessible, so I can't use it.
What's the pattern to do something like this in Android?

Your helper methods should look like
public static void setTopBarText(Activity act, int textId){
(TextView) topBarText = (TextView)act.findViewById(R.id.topBarText);
topBarText.setText(textId);
}
Then you can do a static import from Activity and call
setTopBarText(this, R.id.mytextForThisView);

The Answer is not good for some situation.
This is my method:
In your Activity:
YouCustomClassObject.passView((View)findViewById(R.id.aview));
Using parameter passing can solve this kind of problem.