In this article am going to look at how you can pass a
custom list from one activity to another. This being one of the things I had to deal with
in my not complete android application, well, I thought it was worthwhile blogging
about it.
Let’s first look at what my code supposedly looks
like before we jump into what is happening.
I have Customer class:
import
android.os.Bundle;
import
android.os.Parcel;
import
android.os.Parcelable;
class Customer implements Parcelable {
private int iProperty1;
private String sProperty2;
public Customer(){
super();
}
public Customer(Parcel
in){
super();
iProperty1 =in.readInt();
sProperty2=in.readString();
}
public int Property1() {return iProperty1;}
public void Property1(int value) {this.iProperty1 = value;}
public String
Property2() {return sProperty2;}
public void
Property2(String value) {this.sProperty2 = value;}
@Override
public void
writeToParcel(Parcel dest, int flags) {
dest.writeInt(iProperty1);
dest.writeString(sProperty2);
}
@Override
public int
describeContents() {
return 0;
}
public static final
Parcelable.Creator<Customer> CREATOR= new
Parcelable.Creator<Customer>() {
public Customer
createFromParcel(Parcel in) {
return new Customer(in);
}
public Customer[]
newArray(int size) {
return new Customer[size];
}
};
}
A customer List,
import android.content.Context;
import java.sql.Array;
import
java.util.ArrayList;
class CustomerList
extends
ArrayList<Customer>{
private Context context;
private CustomerDataSource
oDataSrc;
public CustomerList(){
super();
}
public
CustomerList(Context context){
super();
this.context=context;
oDataSrc = new CustomerDataSource(context);
}
public void Save(){
try{
for(int iItem=0;
iItem<this.size(); iItem++ )
{
Customer
oCustomer=this.get(iItem);
if (oCustomer.IsDirty()){
oDataSrc.Save(oCustomer);
}
}
}
catch(Exception e){
Log.e("ERROR", e.toString());
e.printStackTrace();
}
}
public void Load(){
try{
this.addAll(oDataSrc.GetCustomers());
}
catch(Exception e){
Log.e("ERROR", e.toString());
e.printStackTrace();
}
}
public Boolean
RemoveCustomer(Customer oCustomer){
try{
oDataSrc.Delete(oCustomer);
this.remove(oCustomer);
return true;
}
catch(Exception e){
Log.e("ERROR", e.toString());
e.printStackTrace();
return false;
}
}
}
Lets begin with the customer class, I know
you have realized that it has implemented Parcelable interface. Parcelable is
an extremely efficient, low level Protocol which serializes your objects
into byte stream. Two methods have also been overridden for similar purpose;
- writeParcelable(Parcelable, int) -
This method flattens the object data to the Parcel,
allowing that object to be reconstructed from the appropriate class loader when
later reading. Each element in the object should be parceled individually as I have done with the two class properties.
- describeContents() -This
defines the kind of object you are going to parcel.
To reconstruct the object I have defined a
constructor, which will read data from the parcel and map it back to the object.
public Customer(Parcel
in){
I also have an class "class CustomerList" which extends an ArrayList. This basically loads all
the customers data from the repository and saves back in. This ArrayList object will be used to sustain the customers data within different activities which was also a bit of a pain. So how do I do this?
CustomerList oCustomerList = new CustomerList(this);
oCustomerList.load(); // Load all
the customers
Intent intent = new Intent(this, CustomersActivity.class); //Declare an Intent
intent.putParcelableArrayListExtra("oCustomerList",
oCustomerList); //send the Customer list to
startActivityForResult(intent, EditREQUEST_CODE);
Reconstructing the list, was tricky
because after the object was flattened I could not directly parse it back to a
type
CustomerList therefore I had to manuver.
Declare my custome arraylist to persist the original
customer list ;
CustomerList oCustomerList = new CustomerList();
The declare another Arraylist since the intent will
only return a type arrayList.
ArrayList<Customer> oArraylist = extras.getParcelableArrayList("oCustomerList");
//populate the customer list with the data from arraylist
oCustomerList.addAll(oArraylist);
//Clean up
oArraylist.clear;
oArraylist=null;
