Develop Reference

how to pass data using intent in xamarin

i'm new in developing android in xamarin i just want to ask in how to pass data through other activity using intent ? This thing work (https://developer.xamarin.com/recipes/android/fundamentals/activity/pass_data_between_activity/) but i want to collect first all the data in 2 activity before they show the summary in my 3rd activity.(by the way i'm creating a registration app thanks for the future answers :) )

On the first activity you create the second activity by an intent and use the method PutExtra to pass the data you want with a relevant key name that you will need after starting the new activity to retrieve the data.
var secondActivity = new Intent (this, typeof(SecondActivity));
secondActivity.PutExtra ("Data", "Sample Data");
StartActivity(secondActivity);
On second activity OnCreate retrieve the data using the key name it was stored with and the correct method relevant to the data type passed. In this example as is a string by calling Intent.GetStringExtra.
string text = Intent.GetStringExtra ("Data") ?? "Data not available";
You can repeat 1 & 2 for the summary activity.

you can pass whole object and desterilize that in another activity like this
//To pass:
intent.putExtra("yourKey", item);
// To retrieve object in second Activity
getIntent().getSerializableExtra("yourKey");
For only single value you can use
//Method 1
string code = Intent.GetStringExtra("id") ?? string.Empty;
string name = Intent.GetStringExtra("Name") ?? string.Empty;
//OR
//Method 2
string Id = Intent.GetStringExtra("id") ?? string.Empty;
Item item = new Item();
item = itemRepo.Find(Convert.ToInt32(id));

SharedPreferences - Android (different data types)

I have a problem with with sharing data between two different activities. I have data like :
int number
String name
int number_2
int time
int total
I'm trying to make something like order list with this set of data . So it will take one set of data , then back to previous activity , move forward and again add data to it .
I have an idea of making it in array of object - but data inside was cleared after changing activity.
How can I make it ?
I don't know if and how to add Array of object to SharedPreferences , and get value of one element from there.

You should have a look at the documentation of the Intent(s) if you want to do that on the fly associating a key to the value(s) that you want to pass to your second activity.
Anyway, you can think any(sharedpref, database,...) way to pass your parameters but for those kind of things it's a convention and a good practice to follow that.

Don't used share preferences for this...Use the singleton pattern, extend Application, or just make a class with static variables and update them...
You can use .putExtra but since you are communicating with more than one activity the above suggestions are probably the best.
public class ShareData {
private String s;
private int s;
private static ShareData shareData = new ShareData();
private ShareData(){}
public static ShareData getInstance(){ return shareData}
//create getters and setters;
}

Why not to use Intents
Intent intent = new Intent(FirstActivity.this, (destination activity)SecondActivity.class);
intent.putExtra("some_key", value);
intent.putExtra("some_other_key", "a value");
startActivity(intent);
in the second activity
Bundle bundle = getIntent().getExtras();
int value = bundle.getInt("some_key");
String value2 = bundle.getString("some_other_key");
EDIT if you want to read more about adding array to shared preferences check this
Is it possible to add an array or object to SharedPreferences on Android
also this
http://www.sherif.mobi/2012/05/string-arrays-and-object-arrays-in.html

How to pass object to an activity?

I have two activities, NewTransferMyOwn.java and FromAccount.java
When I go from NewTransferMyOwn.java to FromAccount.java, I do write code as following
Intent i = new Intent(NewTransferMyOwn.this, FromAccount.class);
startActivityForResult(i, FROM_ACCOUNT);
When I do come back from FromAccount.java to NewTransferMyOwn.java, then I want to pass a complete object of class Statement
I do write code as
Statement st = ItemArray.get(arg2);//ItemArray is ArrayList<Statement>, arg2 is int
Intent intent = new Intent(FromAccount.this,NewTransferMyOwn.class).putExtra("myCustomerObj",st);
I do get error as following on putExtra,
Change to 'getIntExtra'
as I do, there is again casting st to int, what is issue over here, how can I pass Statement object towards back to acitivity?

You can also implement your custom class by Serializable and pass the custom Object,
public class MyCustomClass implements Serializable
{
// getter and setters
}
And then pass the Custom Object with the Intent.
intent.putExtra("myobj",customObj);
To retrieve your Object
Custom custom = (Custom) data.getSerializableExtra("myobj");
UPDATE:
To pass your custom Object to the previous Activity while you are using startActivityForResult
Intent data = new Intent();
Custom value = new Custom();
value.setName("StackOverflow");
data.putExtra("myobj", value);
setResult(Activity.RESULT_OK, data);
finish();
To retrieve the custom Object on the Previous Activity
if(requestCode == MyRequestCode){
if(resultCode == Activity.RESULT_OK){
Custom custom = (Custom) data.getSerializableExtra("myobj");
Log.d("My data", custom.getName()) ;
finish();
}
}

You can't pass arbitrary objects between activities. The only data you can pass as extras/in a bundle are either fundamental types or Parcelable objects.
And Parcelables are basically objects that can be serialized/deserialized to/from a string.
You can also consider passing only the URI refering to the content and re-fetching it in the other activity.

Passing data using Intents

I have two activities, Activity A and Activity B. I pass objects from Activity A to Activity B using intents. When i make changes to the Object in Activity B the data changes does not get reflected in Activity A. Have i missed out on something?

You are missing the fact that when you pass Object O from Activity A to Activity B via intents, activity B receives a COPY of object O. The way things work is that The object O gets serialized (converted to a sequence of bytes) and that sequence of bytes is then passed to Activity B. Then activity B recreates a copy of object O at the moment it was serialized. Any changes to the original object after it was serialized are not reflected in it's copy.
If both activities are part of the same application then just use a static field (or singleton) to communicate between them.

If you are passing a String, then it will not change since they are immutable.
Edit: See below for an alternative to Intent extras.

If you wish to use the architecture of passing immutable objects in messages you can create an immutable serializable data class. Pass an immutable instance of the data class in the intent using startActivityForResult. When the second activity is completed, send a different instance of the same immutable data class back to the first activity where it is trapped in onActivityResult. So in code, given an immutable class PasswordState.java with public final fields.
public final class PasswordState implements Serializable {
Create an instance of this immutable class and send it to the second activity as in:
private void launchManagePassword() {
Intent i= new Intent(this, ManagePassword.class); // no param constructor
PasswordState outState= new PasswordState(lengthKey,
timeExpire,
isValidKey,
timeoutType,
password,
model.getIsHashPassword(),
model.getMinimumPasswordLength()); // NOT minimumHashedPasswordLength
Bundle b= new Bundle();
b.putSerializable("jalcomputing.confusetext.PasswordState", outState);
i.putExtras(b);
startActivityForResult(i,REQUEST_MANAGE_PASSWORD); // used for callback
}
The second activity returns a new object when it is done.
PasswordState outPasswordState= new PasswordState(lengthKey,
timeExpire,
isValidKey,
timeoutType,
password,
isHashPassword,
minimumPasswordLength);
Bundle b= new Bundle();
b.putSerializable("jalcomputing.confusetext.PasswordState", outPasswordState);
getIntent().putExtras(b);
setResult(RESULT_OK,getIntent()); // call home with data on success only
finish(); // go back <=== EXITS Here
Where it is trapped in Activity one.
// ON_ACTIVITY_RESULT used for callback from ManageKeys.java
protected void onActivityResult(int request, int result, Intent data)
{
switch (request){
case REQUEST_MANAGE_PASSWORD:
if (result == RESULT_OK) { // Success. New password.
try {
PasswordState inMessage= (PasswordState)data.getSerializableExtra("jalcomputing.confusetext.PasswordState");
password= inMessage.password;
timeExpire= inMessage.timeExpire;
isValidKey= true;
writeToPrefs(); // support first launch and incoming tagged sms, save pw
}
catch(Exception e){ // data == null, extras == null
password= "";
isValidKey= false;
timeExpire= PasswordState.LONG_YEAR_MILLIS;
Log.d(Utilities.TAG,"FailedToGetResult",e); // will be stripped at runtime
}
...
break;
}
}
When you are done prototyping and the data objects are stable, you can refactor the code to use parcels instead of serializing objects. Since a copy is being sent between activities using serialization, it could be argued that the use of an immutable object is overkill. Using a mutable object and serializing a mutable object to and from the second activity would simplify the implementation.
Hope that helps.
JAL

Saving data from activity(A) and reading in another Activity(history)

I have an activity that contain a list of data (TextView), i need to save this data that have been choose (onClick) in the list and been able to get and read it in another activity(history)
I understand that is exist a possibility with the "serializable" but i did not success to understand how it could help me.
i will be happy if someone can clarify this subject for me,example?.
Thank you for helping!!

If you're trying to pass a String to another activity, you can do this with putExtra and getStringExtra:
Intent intent = new Intent(this, OtherActivity.class);
intent.putExtra("parameter", myStringParameter);
startActivity(intent);
and then read it in OtherActivity's onCreate method:
String parameter = getIntent().getStringExtra("parameter");
The Serializable interface is useful for marshalling more complicated objects; you don't need this if you're just dealing with String.
Edit - if you need to store small amounts of data persistently you could use SharedPreferences:
final String TAG = "MyApplication";
SharedPreferences prefs = getSharedPreferences(TAG, MODE_PRIVATE);
prefs.edit().putString("parameter", myStringParameter).commit();
and then to read the preferences:
final String TAG = "MyApplication";
SharedPreferences prefs = getSharedPreferences(TAG, MODE_PRIVATE);
String parameter = prefs.getString("parameter", null);
This data will be available even after your application closes.

Yes, use classes that implement Serializable. See my answer on this question: How to pass several variables of different types from one function to another on android?
Create some model classes which will hold data:
public class Page implements Serializable {
private String name;
private String description;
//and so on...
public Page(String name, String description) {
this.name = name;
this.description = description;
}
public String getName() {
return name;
}
public String getDescription() {
return description;
}
}
Now you can create a Page object and fill it with data(name, description) via the constructor. Optionally make some setters.
Page p = new Page("James", "Hello World");
startActivity(new Intent(context, MyActivity.class).putExtra("Page", p));
Retrieve your Page in MyActivity in its onCreate method:
Page p = (Page)getIntent().getExtras().getSerializable("Page");
Toast.makeText(this, "Name: " + p.getName() + ", Description:" + p.getDescription(), Toast.LENGTH_LONG).show();

I am aware about the methods mentioned above. But just for alternative thoughts, since you are mentioning the history word, how about using SQLite for this purpose?
In first activity, you can save the data, and in second activity, retrieve the data.

You can share data between your activities in various ways depending on how much data you need to save and how long the data needs to be saved.
Intents : Useful when transferring small bits of data between 2-3 screens
Singleton / Static data store classes : useful when sharing lot of data between various activities
SQLite DB : Large amount of data to be shared , also useful to save the same between app launches
Shared Preferences : Small amount of data , between app launches.
For your use-case its best to use intents unless the data is shared between more than 2-3 activities where option 2 would be a better solution

Sending immutable stateful objects between activities (messaging) is commendable, IMHO. It can be argued that OOP is about messaging, not objects. Two suggestions. 1) use the fully qualified name for the name:value pair so do:
private void launchManagePassword() {
Intent i= new Intent(this, ManagePassword.class); // no param constructor
PasswordState outState= new PasswordState(lengthKey,timeExpire,isValidKey,timeoutType,"",model.getIsHashPassword());
Bundle b= new Bundle();
b.putSerializable("jalcomputing.confusetext.PasswordState", outState);
i.putExtras(b);
startActivityForResult(i,REQUEST_MANAGE_PASSWORD); // used for callback
}
This will minimize runtime casting errors.
2) When you have the app working well and the object interface is stabilized consider refactoring the code to a Parcel for speed.
JAL
EDIT: AS REQUESTED Code