Changes

}

</pre>

For the time being, the only changes to this class are to add some import directives and to override the onCreateView() method to make sure the layout file is inflated and displayed when the fragment is used within an activity. The class declaration also needs to indicate that the class extends the Android Fragment class:

Figure 25-5

Once correctly positioned, release the fragment to add it to the layout. Once added, a message panel will appear (Figure 25 6) indicating that the Designer tool needs to know which fragment to display during the preview session. Display the ToolbarFragment fragment by clicking on the Use @layout/toolbar_fragment link within the message:

}

</pre>

Before moving on, we need to take some time to explain the above code changes. First, the class is declared as implementing the OnSeekBarChangeListener interface. This is because the user interface contains a SeekBar instance and the fragment needs to receive notifications when the user slides the bar to change the font size. Implementation of the OnSeekBarChangeListener interface requires that the onProgressChanged(), onStartTrackingTouch() and onStopTrackingTouch() methods be implemented. These methods have been implemented but only the onProgressChanged() method is actually required to perform a task, in this case storing the new value in a variable named seekvalue which has been declared at the start of the class. Also declared is a variable in which to store a reference to the EditText object.

With the code changes as they currently stand, the toolbar fragment will detect when the button is clicked by the user and call a method on the activity passing through the content of the EditText field and the current setting of the SeekBar view. It is now the job of the activity to communicate with the Text Fragment and to pass along these values so that the fragment can update the TextView object accordingly.

== Making the Activity Talk to the Text Fragment ==