Android HashMap in Bundle?
AndroidDictionaryBundleAndroid Problem Overview
The android.os.Message
uses a Bundle
to send with it's sendMessage-method. Therefore, is it possible to put a HashMap
inside a Bundle
?
Android Solutions
Solution 1 - Android
try as:
Bundle extras = new Bundle();
extras.putSerializable("HashMap",hashMap);
intent.putExtras(extras);
and in second Activity
Bundle bundle = this.getIntent().getExtras();
if(bundle != null) {
hashMap = bundle.getSerializable("HashMap");
}
because Hashmap by default implements Serializable
so you can pass it using putSerializable
in Bundle and get in other activity using getSerializable
Solution 2 - Android
According to the doc, Hashmap
implements Serializable
, so you can putSerializable
I guess. Did you try it ?
Solution 3 - Android
Please note: If you are using a AppCompatActivity, you will have to call the
protected void onSaveInstanceState(Bundle outState) {}
(NOT public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {}
) method.
Example code...
Store the map:
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putSerializable("leftMaxima", leftMaxima);
outState.putSerializable("rightMaxima", rightMaxima);
}
And receive it in onCreate:
if (savedInstanceState != null) {
leftMaxima = (HashMap<Long, Float>) savedInstanceState.getSerializable("leftMaxima");
rightMaxima = (HashMap<Long, Float>) savedInstanceState.getSerializable("rightMaxima");
}
Sorry if it's some kind of a duplicate answer - maybe someone will find it useful. :)
Solution 4 - Android
If you want to send all the keys in the bundle, you can try
for(String key: map.keySet()){
bundle.putStringExtra(key, map.get(key));
}
Solution 5 - Android
public static Bundle mapToBundle(Map<String, Object> data) throws Exception {
Bundle bundle = new Bundle();
for (Map.Entry<String, Object> entry : data.entrySet()) {
if (entry.getValue() instanceof String)
bundle.putString(entry.getKey(), (String) entry.getValue());
else if (entry.getValue() instanceof Double) {
bundle.putDouble(entry.getKey(), ((Double) entry.getValue()));
} else if (entry.getValue() instanceof Integer) {
bundle.putInt(entry.getKey(), (Integer) entry.getValue());
} else if (entry.getValue() instanceof Float) {
bundle.putFloat(entry.getKey(), ((Float) entry.getValue()));
}
}
return bundle;
}
Solution 6 - Android
I am using my kotlin implementation of Parcelable to achieve that and so far it works for me. It is useful if you want to avoid the heavy serializable.
Also in order for it to work, I recommend using it with these
Declaration
class ParcelableMap<K,V>(val map: MutableMap<K,V>) : Parcelable {
constructor(parcel: Parcel) : this(parcel.readMap(LinkedHashMap<K,V>()))
override fun writeToParcel(parcel: Parcel, flags: Int) {
parcel.writeMap(map)
}
override fun describeContents(): Int {
return 0
}
companion object CREATOR : Parcelable.Creator<ParcelableMap<Any?,Any?>> {
@JvmStatic
override fun createFromParcel(parcel: Parcel): ParcelableMap<Any?,Any?> {
return ParcelableMap(parcel)
}
@JvmStatic
override fun newArray(size: Int): Array<ParcelableMap<Any?,Any?>?> {
return arrayOfNulls(size)
}
}
}
Use
write
val map = LinkedHashMap<Int, String>()
val wrap = ParcelableMap<Int,String>(map)
Bundle().putParcelable("your_key", wrap)
read
val bundle = fragment.arguments ?: Bundle()
val wrap = bundle.getParcelable<ParcelableMap<Int,String>>("your_key")
val map = wrap.map
Don't forget that if your map K,V
are not parceled by default they must implement Parcelable
Solution 7 - Android
In Kotlin:
hashMap = savedInstanceState?.getSerializable(ARG_HASH_MAP) as? HashMap<Int, ValueClass>
putSerializable(ARG_HASH_MAP, hashMap)