How to store sparsearray in bundle

Question

I have a SparseArray<myObject> and want to store it in bundle in onSaveInstanceState method in my activity and restore it in oncreate. I found putSparseParcelableArray method for put SparseArray in bundle and did this in onSaveInstanceState method:

bundle.putSparseParcelableArray("mySparseArray", mySparseArray);

But eclips shows this error:

The method putSparseParcelableArray(String, SparseArray<? extends Parcelable>) in the type Bundle is not applicable for the arguments (String, SparseArray<myObject>)

And the quick fix is casting argument mySparsArray to SparseArray<? extends Parcelable>, but if I do so and get it in onCreate method:

mySparseArray = (SparseArray<myObject>) savedInstanceState.getSparseParcelableArray("mySparseArray");

It gets this error:

Cannot cast from SparseArray<Parcelable> to SparseArray<myObject>

If this way is wrong, what is the solution for put mySparseArray in bundle? Any help would be much appreciated.

Mitchmitchael

What is myObject? Does it implement Parcelable? – Sphacelus

It is a custom class that I defined and does not implement anything. Should it implements of Parcelable? – Mitchmitchael

Yes, look at the arguments putSparseParcelableArray, it is SparseArray<? extends Parcelable>, so only the object that implements Parcelable can be put into the bundle. Do you need help for how to implement Parcelable, it is very straightforward. – Sphacelus

Here is one example. – Sphacelus

Answer 1

Your class should implement Parcelable and should have a static final member variable called CREATOR of type Parcelable.Creator<myObject>.

Idalla

Answer 2

You can extend SparsArray to imlement a Serializable as use it:

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import android.util.SparseArray;



/**
 * @author Asaf Pinhassi www.mobiledev.co.il
 * @param <E>
 *
 */
public class SerializableSparseArray<E> extends SparseArray<E> implements Serializable{

    private static final long serialVersionUID = 824056059663678000L;

    public SerializableSparseArray(int capacity){
        super(capacity);
    }

    public SerializableSparseArray(){
        super();
    }

    /**
     * This method is private but it is called using reflection by java
     * serialization mechanism. It overwrites the default object serialization.
     *
     * <br/><br/><b>IMPORTANT</b>
     * The access modifier for this method MUST be set to <b>private</b> otherwise {@link java.io.StreamCorruptedException}
     * will be thrown.
     *
     * @param oos
     *            the stream the data is stored into
     * @throws IOException
     *             an exception that might occur during data storing
     */
    private void writeObject(ObjectOutputStream oos) throws IOException {
        Object[] data = new  Object[size()];

        for (int i=data.length-1;i>=0;i--){
            Object[] pair = {keyAt(i),valueAt(i)}; 
            data[i] = pair;
        }
        oos.writeObject(data);
    }

    /**
     * This method is private but it is called using reflection by java
     * serialization mechanism. It overwrites the default object serialization.
     *
     * <br/><br/><b>IMPORTANT</b>
     * The access modifier for this method MUST be set to <b>private</b> otherwise {@link java.io.StreamCorruptedException}
     * will be thrown.
     *
     * @param oos
     *            the stream the data is read from
     * @throws IOException
     *             an exception that might occur during data reading
     * @throws ClassNotFoundException
     *             this exception will be raised when a class is read that is
     *             not known to the current ClassLoader
     */
    private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
        Object[] data = (Object[]) ois.readObject();
        for (int i=data.length-1;i>=0;i--){
            Object[] pair = (Object[]) data[i]; 
            this.append((Integer)pair[0],(E)pair[1]);
        }
        return;
    }


}

Bathhouse

Any good reason the for loops works from back to front? Can't it just be a normal for (int i = 0; i < data.length; i++) ? – Susysuter

@Susysuter Is it faster to count down than it is to count up? – Strand

@Strand I would prefer having more readable code, over micro optimisation. – Susysuter

@Susysuter me too, but since I don't find it any harder I don't complain. – Strand