Passing my object to one to other activity

[vina parmar]

Hi all

I want to pass my object to one activity to other.
eg. I have class myClass which holds sting array, integer, Vector, Hash.
Now I have activity A which set the myClass which stored through json parsing and that object pass to Activity B then B to C.
So how can I pass the object of myClass from activity A to B?
putExtra() working for String, integer only.
I dont have only the myClass object to pass , I may have to pass other object also with it.

Please help.

Thanks,
vina

[Monu Tripathi]

you can use putExtra(Serializable..) and getSerializableExtra() methods to pass and retrieve objects of your class type; you will have to mark your class Serializable and make sure that all your member variables are serializable too...

[vina parmar]

Thanks Monu.
First it was giving me error then after restarting it's working fine.
You are really helping a lot.

[vina parmar]

How can I serialize the Hashtable to pass it?
I can pass myClass but not able to pass Hashtable which is in other class.

[Monu Tripathi]

I can pass myClass but not able to pass Hashtable which is in other class

I am not sure I understand what you are saying.

Hashtable IS Serializable.

[vina parmar]

I am also cofused.
My code is

  	
// In Activity A               
Hashtable hashtable = new Hashtable();
/* adding element in hashtable */

Intent intent = new Intent(A.this, B.class);  
		intent.putExtra("hashtable", hashtable);
                intent.putExtra("MyClass", obj);
		startActivity(intent); 

//in Activity B
		Bundle bundel = getIntent().getExtras();
			try{
			ads = (myClass) bundel.get("MyClass");
			hashtable = (Hashtable) bundel.get("hashtable");
                }catch(Exception e){Log.i(" Error at bundle " , e.toString());}

  

It will get the object of myClass but giving error at hashtable

[PrasannaKumar Sathiyanantham]

i am not sure whether i can understand your question

i will give this however

Not all types are serializable.....

check with the api specification whether the java class you have used can be serializable....

If your class uses the file object ,then even though the user defined class is serialized and passed the file object will not pass .....

so make sure the hashtable is serializable

i hope this answer is okay

[vina parmar]

Ok
Let me clarify

I have to pass Hashtable, and other one is myClass which contains Vectors (myClass is Serializable no file class simple vector in myClass).

Now when I passing the object of hashtable and myClass obj Activity A to B, then it will show me the value of myClass and its vectors but giving me error for hashtable.

And How can I know Hashtable is Serializable?

Thanks

[PrasannaKumar Sathiyanantham]

First to know whether a particular java class is serialized(predefined java class like collections,swing and others) type the class name + api in google.It will take you to the java api page where it will have a name called All implemented Interfaces :see whether it has serializable in it .

Example
For hashtable use this link:http://java.sun.com/j2se/1.4.2/docs/api/java/util/Hashtable.html

are you passing the intent object from one system to another..if yes it must also be serialized....

Actually what is activity A and activity B

For my college project i spent nearly three months on the serialization problem alone

If your myclass is working then the hashtable must also work

I have the following questions
1)what is activity A and B
2) check whether you have overloaded get methods in bundle......
3)you have not given any information about the bundle class and intent class

[vina parmar]

Thanks for the reply

OK even I am not able to understand your que.
Let me explain again.
Activity Class A contains EditText, Spinner and Button. On Click event of Button it parse json and put the values into the Vectors this will done in myClass which is serialized.
After that as per records I am putting values in the Hashtable which is related to Vectors.
So i have to pass both to the Activity Class B which will display them.

I am not overloading get method.
I am not using Bundle and Intent class more then the given code.

[Monu Tripathi]

I tried sending Hashtable using put(Serializable) and getSerializableExtra(..); I am getting ClassCastExceptions..

[vina parmar]

Hi

It is giving me error as : Error in B(304): java.lang.ClassCastException: java.util.HashMap

// In A
Hashtable hs = new Hashtable();
hs.put("1","Data");.....

try{
	Bundle bundle = new Bundle();  
	bundle.putSerializable("table", hs);  
	  
	Intent intent = new Intent(this,B.class);  
        intent.putExtras(bundle);
        startActivity(intent);
	
	}catch(Exception e){Log.i("Error in A " , e.toString());}

//In B
Bundle bundel = getIntent().getExtras();

			try{
				Hashtable hash = (Hashtable) bundel.get("table");
			}catch(Exception e){Log.i(" Error in B" , e.toString());}
		
    

Anything I am missing.

[vina parmar]

So how do i do this.

[Monu Tripathi]

Okay, I am not sure of why this is happening but it seems that if you cast your object to a HashMap instead of HashTable and then retrieve the value using a key, the code actually works!

//create a Hashtable
Hashtable<String, String> table = new Hashtable<String,String>();

//load dummy data
table.put("one", "neo");

// create intent and set Extra
Intent intent = new Intent(this,SecondActivity.class);
intent.putExtra("table", table);

/////RETRIEVAL
// get Serializable extra and cast it to HashMap and NOT Hashtable
HashMap table = (HashMap) getIntent().getSerializableExtra("table");

//get the values
Log.i(TAG,table.get("one"));

[vina parmar]

Thanks Monu,

I have tried HashMap and it works fine.
But in next Activity I have to use Vector then it will again create problem.

If you can find the solution please reply.

[Tim Holloway]

Reminder: just because a container class is serializable doesn't mean that the container object is serializable. If you store a non-serializable object in a HashMap or Vector, the entire HashMap or Vector becomes effectively non-serializable.

This won't result in compile-time errors. The compiler cannot usually deduce such things.

[vina parmar]

Thanks Tim

It will help me a lot.

[Monu Tripathi]

Tim Holloway wrote:Reminder: just because a container class is serializable doesn't mean that the container object is serializable. If you store a non-serializable object in a HashMap or Vector, the entire HashMap or Vector becomes effectively non-serializable.

This won't result in compile-time errors. The compiler cannot usually deduce such things.

Good Point.

The strange thing for me however is the change in type information. I created a Hashtable(IS-A Serializable) and inserted just one String(IS-A Serializable) object into it. I passed this Hashtable as an intent extra. On the receiving end, I did a getSerializableExtra() to get Serializable which I was casting to Hashtable. JVM says the cast is Illegal. However, if I cast the object to a HashMap, I can read the values stored in the data structure.

I am wondering how a Hashtable type is converted to a HashMap type??!!

[PrasannaKumar Sathiyanantham]

hashtable is a subclass of java.util.dictionary

as of java1.2 hashtable implements map interface......

I think that may be the reason that hashmap accepts a hashtable object

maybe while reading it again it may have found only the map properties.....

I am given reasons vaguely.....but it may be the starting point of understanding the casting.