Android: Passing value from one activity to another

Objective : To pass some data from one activity to another. Here the user's selection of listview item from main activity to another activity.

Scenario: Main activity has a ViewGroup -  ListView. Based on the user's selection of the item from the ListView another activity (Second activity here)gets started. But the selected item value needs to be passed from the main activity to the Second Activity.

//attaching a listener on listview

MainActivity - onCreate()

…..

    listview.setOnItemClickListener(new AdapterView.OnItemClickListener(){

            public void onItemClick(AdapterView<?> parent, final View view,

                      int position, long id){

            

                            Intent intent = new Intent(getApplicationContext(), SecondActivity.class);

                            String value = (String)parent.getItemAtPosition(position);

// putExtra is called to send key-value pair to the SecondActivity

                            intent.putExtra("key", value);

                            startActivity(intent);

                            

               }

    });

SecondActivity - onCreate()

…

Intent intent = getIntent();

//retrieving extras that are sent in bundle.

Bundle bundle = intent.getExtras();

String value = bundle.getString("key");

Android: ListViews

Android : ListViews

The Steps that need to be followed in order to create a ListView are:
1. Create an array of data source
2. Create a ListAdapter and specify it how to display the array elements (here an individual view - TextView is created for each array item)
3. Define the action that needs to be taken when the user interacts with the ListView (by adding appropriate listener to it)

ListView is a view group which has a set of scrollable elements or items in it. To create a ListView with three items, these are the steps that need to be followed:

1. Open the layout file (.xml)

2. Drag and drop ListView item from under the Composite widget. A ListView gets created with the id listView1

3. Open the Java file and do the following steps:

     //Get the resource of the listview from the R file      

final ListView listview = (ListView) findViewById(R.id.listView1);

    //Create an array of Strings (the elements that you want the listview to display

String[] values = new String[] { "Pride & Prejudice", "David Copperfield", "To Sir, With Love" };

    //Create an ArrayList from the string array

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

    for (int i = 0; i < values.length; ++i) {

      list.add(values[i]);

    }

    //List items are added to the list with the help of an adapter. Create and ArrayAdapter

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.activity_list_item, android.R.id.text1, list);

   //set the adapter with the listview

    listview.setAdapter(adapter);

  

The Constructor for ArrayAdapter that is used here is:

public ArrayAdapter (Context context, int resource, int textViewResourceId, List<T>objects)

context : The current context (used this here)

resource : The resource ID for a layout file containing a layout to use when instantiating views (used the activity_list_item here - it gets populated automatically)

textViewResourceId : The id for the TextView within the layout resource to be populated (used text1 -it gets populated automatically)

objects : the array ArrayList that has been created with the items

This will make your ListView appear with the list items in it.