Best way to store SparseBooleanArray in Bundle?

Question

When a config change happens, my ListView Checkbox states get lost, which I understand why. I try to implement

public void onSaveInstanceState(final Bundle outState)

in one of my Fragments. So I'm just wondering what's the easiest way to store my SparseBooleanArray in the outState.

Also, I'm a bit confused, as ListView has the method:

getListView().getCheckedItemPositions();

What's this good for?

Answer 1

In my case, I ended up doing it by implementing a Parcelable wrapper around the SparseBooleanArray, like this:

import android.os.Parcel;
import android.os.Parcelable;
import android.util.SparseBooleanArray;

public class SparseBooleanArrayParcelable extends SparseBooleanArray implements Parcelable {
  public static Parcelable.Creator<SparseBooleanArrayParcelable> CREATOR = new Parcelable.Creator<SparseBooleanArrayParcelable>() {
    @Override
    public SparseBooleanArrayParcelable createFromParcel(Parcel source) {
      SparseBooleanArrayParcelable read = new SparseBooleanArrayParcelable();
      int size = source.readInt();

      int[] keys = new int[size];
      boolean[] values = new boolean[size];

      source.readIntArray(keys);
      source.readBooleanArray(values);

      for (int i = 0; i < size; i++) {
        read.put(keys[i], values[i]);
      }

      return read;
    }

    @Override
    public SparseBooleanArrayParcelable[] newArray(int size) {
      return new SparseBooleanArrayParcelable[size];
    }
  };

  public SparseBooleanArrayParcelable() {

  }

  public SparseBooleanArrayParcelable(SparseBooleanArray sparseBooleanArray) {
    for (int i = 0; i < sparseBooleanArray.size(); i++) {
      this.put(sparseBooleanArray.keyAt(i), sparseBooleanArray.valueAt(i));
    }
  }

  @Override
  public int describeContents() {
    return 0;
  }

  @Override
  public void writeToParcel(Parcel dest, int flags) {
    int[] keys = new int[size()];
    boolean[] values = new boolean[size()];

    for (int i = 0; i < size(); i++) {
      keys[i] = keyAt(i);
      values[i] = valueAt(i);
    }

    dest.writeInt(size());
    dest.writeIntArray(keys);
    dest.writeBooleanArray(values);
  }
}

This allows you to save and load your SparseBooleanArray by just doing:

Bundle bundle; //For your activity/fragment state, to include in an intent, ...
SparseBooleanArray sbarray; //Probably from your listview.getCheckedItemPositions()

//Write it
bundle.putParcelable("myBooleanArray", new SparseBooleanArrayParcelable(sbarray));

//Read it back
sbarray = (SparseBooleanArray) bundle.getParcelable("myBooleanArray");

Just my .02€