StartActivtyForResult.md

Start an Activity for result in a Fragment

See Also:

• Android Developers/ Activity
• Android Developers/ Fragment

Start a Activity for result

When you start an Activity, usually you don't expect any callback from it. However, sometimes you have to get some result from an Activty you just launched. That's when startActivtyForResult() comes in. This method launchs an Activty and call onActivityResult() after the it finished.

Using startActivtyForResult

Let's say we wish to show ThatActivity from ThisActivity and capture user's input from ThatActivity.

ThisActivity.java

  ...
  // create an Intent.
  Intent intent = new Intent();
  intent.setClass(ThisActivity.this, ThatActivity.class);

  // start actviity
  startActivityForResult(intent,REQUEST_CODE);
  ...

In the code REQUEST_CODE is a constant which will let you know what you've tell the second Activity do.

And here's how you tell the results to ThisActivity in ThatActivity.

ThatActivity.java

  ...
  // after  you get result
  Intent resultDataIntent = new Intent();

  Bundle args = new Bundle();
  args.putString(KEY_RESULT_STRING,"some string");

  intent.putExtras(args);

  // THIS LINE IS HOW YOU TELL LAST ACTIVITY YOUR RESULTS ARE
  setResult(RESULT_OK, resultDataIntent);
  ...

After ThatActivity is finished and we're back to ThisActivity. onActivityResult() is called.

ThisActivity.java

  ...

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        Log.d(TAG, "onActivityResult: requestCode =" + requestCode + ", resultCode =" + resultCode);

        if (requestCode == REQUEST_CODE) {
            switch (resultCode) {
                case RESULT_OK:
                    Bundle bundle = data.getExtras();

                    if (bundle != null) {
                        String resultString = bundle.getString(ThatActivity.KEY_RESULT_STRING);

                    } else {
                        Log.w(TAG, "onActivityResult: argument bundle == null");
                    }
            }
        }


    }

And that's it. We can pass data back to the Activty which launchs current Activty easily. But how about Fragments?

In Fragments

There's two ways to invoke startActvitiy() in a Fragment.

1. Simply call startActvitiy().
2. use getActivity().startActvitiy().

There's a startActvitiy() inside Fragment class. Similarly, there's a startActivityForResult() method inside Fragment clas. However, that's the tricky part.

Using startActivtyForResult in Fragment

If you call startActivtyForResult() directly. You have to override onActivityResult() inside your Fragment. Otherwise, if you wish to use the same onActivityResult() in the Activity. You have to use getActivity().startActivtyForResult() instead.

That's it!

And that's it. A quick tip with this method.

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