I have the following problem and I'm not quite sure how to go about solving it. I am requesting data from several different servers with each server returning a list of objects of a different type (every server has it's own specific unique POJO object type) - but what all these lists of objects have in common is that all the objects have a date parameter. I then need to display the objects from all the lists as one huge mixed list for the user, with all the various objects sorted by date.
I made an adapter that extends baseadapter and I've passed all the arraylists of objects to that adapter - but how can I sort all these lists of objects by date and display them all together? I could create a "super object" that has the properties of all the other objects and then make one sorted array of this super object to pass to the adapter, but that seems like a messy and crude solution. Is there a more or less elegant way to do this?
public class someAdapter extends BaseAdapter
{
...
public someAdapter(ArrayList<ObjectOne> objectOneArray, ArrayList<ObjectTwo> objectTwoArray) {
if (objectOneArray != null) {
this.localObjectOneList.addAll(objectOneArray);
}
...
}
}
Example of an object type:
public class ObjectOne implements Serializable {
private String date;
private String someFieldOne;
private String someFieldTwo;
...
//getters and setters
...
}
To reiterate - the final list has to be a mix of all the different object types in the order of their dates.
The way you expected initially to have a super class would be nice if there weren't a huge plumbing associated. A better approach can be as follows: Assuming that all the POJOs have getDate() method.
Comparator to compare datesSort the objects
If the POJOs don't have getters i.e, getDate() method, replace getDateFromMethod() with getDateFromProperty() in the comparator .
public class Sorter{ public void sortList()
{
Collections.sort(objList, comparator);
// Now consume / print your objList to get sorted by date
}
ArrayList<Object> objList = new ArrayList<Object>();
Comparator<Object> comparator = new Comparator<Object>()
{
@Override
public int compare(Object object1, Object o2)
{
Date o1Date = getDateFromMethod(object1);
Date o2Date = getDateFromMethod(o2);
if (o1Date != null && o2Date != null)
{
if (o1Date.before(o2Date))
return -1;
else if (o1Date.after(o2Date))
return 1;
else
return 0;
}
else
return -1;
}
};
public Date getDateFromMethod(Object obj)
{
Date date = null;
String getDate = "getDate";
try
{
Method method = obj.getClass().getMethod(getDate, (Class<?>[]) null);
if (method != null)
date = (Date) method.invoke(obj, (Object[]) null);
}
catch (NoSuchMethodException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (SecurityException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (IllegalAccessException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (IllegalArgumentException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (InvocationTargetException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
return date;
}public Date getDateFromProperty(Object obj)
{
Date date=null;
try
{
Field dateField= obj.getClass().getField("date");
if(dateField!=null)
date=(Date) dateField.get(obj);
}
catch (NoSuchFieldException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (SecurityException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (IllegalArgumentException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (IllegalAccessException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
return date;
}
}
Now say for instance you have Obj1,Obj2 and Obj3 as follows, create objects using these POJOS and populate the objList and test the solution.
class Obj1 { int id; int name; Date date;
public Date getDate()
{ return date; } public int getId() { return id; }
public void setId(int id)
{
this.id = id;
}
public int getName()
{
return name;
}
public void setName(int name)
{
this.name = name;
}
}
class Obj2 { int sequence; int location; Date date;
public Date getDate()
{ return date; } public int getSequence() { return sequence; }
public void setSequence(int sequence)
{
this.sequence = sequence;
}
public int getLocation()
{
return location;
}
public void setLocation(int location)
{
this.location = location;
}
}
class Obj3 { int type; int origin; Date date;
public Date getDate()
{ return date; }
public void setDate(Date date) { this.date = date; }
public int getType()
{
return type;
}
public void setType(int type)
{
this.type = type;
}
public int getOrigin()
{
return origin;
}
public void setOrigin(int origin)
{
this.origin = origin;
}
}