CODEWITHSUNDEEP
androidandroid-intentserializationlinkedhashmap
user1841702
user1841702

Reputation: 2763

Android - LinkedHashMap cannot be passed between Activities

I have a very strange problem. All I want to do is pass a LinkedHashMap<String,HashMap<String,String>> (I am just experimenting here and the I would like the choice of data structure to remain unchanged regardless of performance overhead) object from one Activity to another via an Intent. I tried two approaches after initializing and populating my data structure:

 LinkedHashMap<String,HashMap<String,String>> mData = new LinkedHashMap<String,HashMap<String,String>>();
//insert data into LinkedHashMap

Approach 1:

 Intent intent = new Intent(this, TestActivity.class);             
 // as a Serializable
 intent.putExtra("DATA",mData)
 startActivity(intent);

Approach 2:

 Intent intent = new Intent(this, TestActivity.class);             
 Bundle bundle = new Bundle();
 bundle.putSerializable("LIST",mData);
 intent.putExtra("DATA",bundle)
 startActivity(intent);

And in the receiving Activity:

For Approach 1:

Intent intent = getIntent();
mData = (LinkedHashMap<String, HashMap<String, String>>) intent.getSerializableExtra("DATA");

For Approach 2:

Intent intent = getIntent();
Bundle bundle = intent.getBundleExtra("DATA");
mData = (LinkedHashMap<String, HashMap<String, String>>) bundle.getSerializable("LIST");

And I keep running into this issue:

 Caused by: java.lang.ClassCastException: java.util.HashMap cannot be cast to java.util.LinkedHashMap
            at com.matchify.TestActivity.onCreate(TestActivity.java:56)
            at android.app.Activity.performCreate(Activity.java:5451)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2377)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2471)
            at android.app.ActivityThread.access$900(ActivityThread.java:175)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5602)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)

What am I doing wrong ? Apologies if I have missed something very obvious.

Upvotes: 2

Views: 1720

Answers (3)

Mohammad nabil
Mohammad nabil

Reputation: 1020

Try this hope you help!

Intent intent = new Intent(this, TestActivity.class);
intent.putExtra("hashmap", hashMap);
startActivity(intent);

//receiving Activity:

hashMap = (HashMap<String,String>)intent.getExtras().getSerializable("hashmap");
LinkedHashMap<String,String> linkedMap = new LinkedHashMap<>(hashMap);

Upvotes: -2

akhil batlawala
akhil batlawala

Reputation: 1066

Bundle bundle = new Bundle();
bundle.putSerializable("factorsDataMap", mData);
Intent intent = new Intent(MainActivity.this, MoodSummary.class); 
intent.putExtras(bundle);
startActivity(intent);

Try this, Hope it works. Tell me if you still have problem.

Upvotes: 0

Kai
Kai

Reputation: 15476

I checked LinkedHashMap's source code and found the data structure that stores iteration order is declared as transient:

transient LinkedEntry<K, V> header;

So even if LinkedHashMap is returned to the new Activity, the map would be broken as far as iteration is concerned, which may be the reason why HashMap is returned instead.

If you don't need guaranteed iteration order, just cast it as HashMap in the 2nd Activity, otherwise you may have to write your own Parcelable to preserve the ordering.

Upvotes: 4

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