Cannot pass custom Object in an Intent: The Method Put Extra is Ambiguous for the type Intent

Question

If I try to write

Car myCarObject=getCar();
Intent details = new Intent(Start.this, DetailsCar.class);
                details.putExtra("Car", myCarObject);
                startActivity(details);

Eclipse show me a compilation error "The Method Put Extra is Ambiguous for the type Intent" in the line

  details.putExtra("Car", myCarObject);

If I use the code

Car myCarObject=getCar();
ArrayList<Car> parcelableExtra = new ArrayList<Car>();
                parcelableExtra.add(myCarObject);

Intent details = new Intent(Start.this, DetailsCar.class);
                details.putExtra("Car", parcelableExtra);
                startActivity(dettagli);

And I try to load the extra with this code in the destination Intent with

ArrayList<Car> parcelableExtra = new ArrayList<Car>();
        parcelableExtra = (ArrayList<Car>) getIntent().getExtras().getParcelable("Car");
        Car c=parcelableExtra.get(0);

I get this warning

12-14 05:30:07.669: W/Bundle(19823): Key Car expected Parcelable but value was a java.util.ArrayList.  The default value <null> was returned.
12-14 05:30:07.679: W/Bundle(19823): Attempt to cast generated internal exception:
12-14 05:30:07.679: W/Bundle(19823): java.lang.ClassCastException: java.util.ArrayList
12-14 05:30:07.679: W/Bundle(19823):    at android.os.Bundle.getParcelable(Bundle.java:1106)
12-14 05:30:07.679: W/Bundle(19823):    at my.app.com.DetailsCar.onCreate(DetailsCar.java:43)
12-14 05:30:07.679: W/Bundle(19823):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
12-14 05:30:07.679: W/Bundle(19823):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
12-14 05:30:07.679: W/Bundle(19823):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
12-14 05:30:07.679: W/Bundle(19823):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
12-14 05:30:07.679: W/Bundle(19823):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
12-14 05:30:07.679: W/Bundle(19823):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-14 05:30:07.679: W/Bundle(19823):    at android.os.Looper.loop(Looper.java:130)
12-14 05:30:07.679: W/Bundle(19823):    at android.app.ActivityThread.main(ActivityThread.java:3687)
12-14 05:30:07.679: W/Bundle(19823):    at java.lang.reflect.Method.invokeNative(Native Method)
12-14 05:30:07.679: W/Bundle(19823):    at java.lang.reflect.Method.invoke(Method.java:507)
12-14 05:30:07.679: W/Bundle(19823):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
12-14 05:30:07.679: W/Bundle(19823):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
12-14 05:30:07.679: W/Bundle(19823):    at dalvik.system.NativeStart.main(Native Method)
12-14 05:30:07.679: W/dalvikvm(19823): threadid=1: thread exiting with uncaught exception (group=0x40018578)

And the app crashes with a Null Point Exception

My Car object is Parcelable

so.... what is wrong?

Answer 1

The first error: 'The Method Put Extra is Ambiguous for the type Intent'.

The class Car is both Serializable and Parcelable, the compiler doesn't know whether to use putExtra(Serializable s) or putExtra(Parcelable p) to handle your request. So you have to cast your Car to one of them when using Intent.putExtra().

Intent.putExtra("car", (Parcelable)myCarObject);
Intent.putExtra("car", (Serializable)myCarObject);

The second error: java.lang.ClassCastException: java.util.ArrayList

You put the Car object in a ArrayList and use putExtra to send to the next activity. An ArrayList is not Parcelable but only Serializable. The putExtra(ArrayList) works as putExtra(Serializable), but you read it by getParcelable(). An ArrayList cannot be cast to Parcelable.