In this post we will discuss about how to pass data between two activities. This is very important feature in perspective of the any application that it always needed to pass data between two activities. Here we will use two activities two pass the data first calling activity is called as the parent activity and other is invoked activity child activity.
For simplicity sake, We use an explicit intent for
invoking the child activity. For simple invocation without expecting any data
back, we use the method startActivity(). However, when we
want a result to be returned by the child activity, we need to call it by the method
startActivityForResult().
When the child activity finishes with the job, it should set the data in an
intent and call the method setResult(resultcode, intent)
to return the data through the intent.
When the parent activity expecting result from the invoked activity. The parent activity should have overridden the
method onActivityResult(…)
in order to be able to get the data and act upon it.
After the setting up the set activity setResult(...) please call finish() function to return to the parrent activity.
Here we need two methods to impliment on the parrent activity.
- startActivtyForResult(..)
- onActivityResult(..)
- setResult(..)
- finish()
Here in this example we can see easily our calling activity having two buttons to view He or She. Either selecting one of them HeAcitivty or SheActivity which display a list using listview of selected type of objects. The user can select any of the object then the object will return it to the parent activity with data.
Since we are expecting to get back the selected object,
the calling Activity’s code is like this:
Intent HeIntent = new Intent(); heIntent.setClass(Home.this,HeActivity.class);
startActivityForResult(heIntent,HE_SELECT);
where HE_SELECT is just a constant to help us
identify from which child activity the is result obtained, when there is more
than 1 child activity, as in this case.
At this point the control is handed over to the BooksActivity.
This displays the list of books and the user can scroll through and select a
book. When the user selects a book, the selected book needs to be passed back
to the CallingActivity.
This is how it is done:
Object
o = this.getListAdapter().getItem(position);
String
book = o.toString();
Intent
returnIntent = new Intent();
returnIntent.putExtra("Selected He",book);
setResult(RESULT_OK,returnIntent);
finish();
The first 2 lines show how to get the selected
he from the ListView. Then, you create a new intent object, set the selected
book as an extra and pass it back through the setResult(…)
method call. The result code is set to RESULT_OK
since the job has been successfully done. After that the finish()
method is called to give the control back to the parent activity.
In the parent, the method that gets the control is
onActivityResult(…)
protected void
onActivityResult(int requestCode, int resultCode, Intent data)
{
switch(requestCode) {
case HE_SELECT:
if (resultCode == RESULT_OK) {
String name =
data.getStringExtra("Selected He");
Toast.makeText(this, "You have
chosen the He: " + " " + name, Toast.LENGTH_LONG).show();
break;
}
……….
}
}
