Passing a List from one Activity to another

问题:

How to pass Collections like ArrayList, etc from one Activity to another as we used to pass Strings, int with help of putExtra method of Intent?

Can anyone please help me as i want to pass a List<String> from one Activity to another?

回答1:

You can pass an ArrayList<E> the same way, if the E type is Serializable.

You would call the putExtra (String name, Serializable value) of Intent to store, and getSerializableExtra (String name) for retrieval.

Example:

ArrayList<String> myList = new ArrayList<String>();
intent.putExtra("mylist", myList);

In the other Activity:

ArrayList<String> myList = (ArrayList<String>) getIntent().getSerializableExtra("mylist");

---

Please note that serialization can cause performance issues: it takes time, and a lot of objects will be allocated (and thus, have to be garbage collected).

回答2:

First you need to create a Parcelable object class, see the example

public class Student implements Parcelable {

        int id;
        String name;

        public Student(int id, String name) {
            this.id = id;
            this.name = name;

        }

        public int getId() {
            return id;
        }

        public String getName() {
            return name;
        }


        @Override
        public int describeContents() {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public void writeToParcel(Parcel dest, int arg1) {
            // TODO Auto-generated method stub
            dest.writeInt(id);
            dest.writeString(name);
        }

        public Student(Parcel in) {
            id = in.readInt();
            name = in.readString();
        }

        public static final Parcelable.Creator<Student> CREATOR = new Parcelable.Creator<Student>() {
            public Student createFromParcel(Parcel in) {
                return new Student(in);
            }

            public Student[] newArray(int size) {
                return new Student[size];
            }
        };
    }

And the list

ArrayList<Student> arraylist = new ArrayList<Student>();

Code from Calling activity

Intent intent = new Intent(this, SecondActivity.class);
Bundle bundle = new Bundle();
bundle.putParcelableArrayList("mylist", arraylist);
intent.putExtras(bundle);       
this.startActivity(intent);

Code on called activity

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_second);   

    Bundle bundle = getIntent().getExtras();
    ArrayList<Student> arraylist = bundle.getParcelableArrayList("mylist");
}

回答3:

use putExtra to pass value to an intent. use getSerializableExtra method to retrieve the data like this

Activity A :

ArrayList<String> list = new ArrayList<String>();

intent.putExtra("arraylist", list);
startActivity(intent);

Activity B:

ArrayList<String> list = getIntent().getSerializableExtra("arraylist");

回答4:

I tried all the proposed techniques but none of them worked and stopped my app from working and then I finally succedded. Here is how I did it... In main activity I did this:

            List<String> myList...;
            Intent intent = new Intent...;
            Bundle b=new Bundle();
            b.putStringArrayList("KEY",(ArrayList<String>)myList);            
            intent_deviceList.putExtras(b);
            ....startActivity(intent);

To get the data in the new Activity:

    List<String> myList...
    Bundle b = getIntent().getExtras();
    if (b != null) {
        myList = bundle.getStringArrayList("KEY");
    }

I hope this will help someone...

回答5:

To pass ArrayList from one activity to another activity, one should include

intent.putStringArrayListExtra(KEY, list); //where list is ArrayList which you want to pass

before starting the activity.And to get the ArrayList in another activity include

Bundle bundle = getIntent().getExtras();
        if (bundle != null) {
            temp = bundle.getStringArrayList(KEY); // declare temp as ArrayList
                }

you will be able to pass ArrayList through this.Hope this will be helpful to you.