Homework 2

Due on: Thursday April 27, 11pm (STRICT)

CrowdGrader URL: https://www.crowdgrader.org/crowdgrader/venues/view_venue/3081

Submission instructions: Follow these instructions

The Assignment

You need to create an application consisting of three activities.

Each activity should display at the top its name: Activity 1, Activity 2, Activity 3, as a big string.

The activities will share information via an AppInfo object (see Lecture 3 and see the code for BackAndForthStudio).

The information shared consists in three strings, string1, string2, string3.

For i = 1, 2, 3, Activity i should:

• Display the values of stringj, for j=1, 2, 3 but j != i (i.e., display the values of the OTHER activity strings)
• Offer a way to enter the value of stringi (the string for its own activity), using an input field and an Enter button.
• Offer a way to go to Activity j=1, 2, 3, j != i, that is, to the other two activities.
• When the RETURN hot-key (at the bottom of the screen) is pressed, the app should always return to Activity 1, using the flag to clear the activity stack.

Here is how Activity 2 should look like, more or less. The blue line is the input field where the user is typing the word "pear".

When the user presses Enter, the value stored in the input field should be stored in Appinfo, and displayed in the other activities.

When a user opens an activity, the initial value of the textfield (before the user edits it) should be the value stored in AppInfo for that activity. That is, if you are in Activity 1, write Orange in the field, go to Activity 2, and then come back to Activity 1, the editable field in Activity 1 should contain "Orange".

In other words, when an activity executes onResume, you should display string1, string2, string3 either in the fields for the respective strings, or as initial value of the editable field, as appropriate.

As an example, if the user finishes writing pear, and clicks on the button to go to Activity 3, this is how Activity 3 should look like:

AppInfo

See here for an example of AppInfo definition. The information in the AppInfo object should be written back to the SharedPreferences, and read upon initialization, so that if your app stops and is destroyed, no information is lost.

Changing activities

When you switch from one activity to another, please use the flag to clear the activity stack as done here.

Starting code

You might find it easier to start your work from the BackAndForthStudio project.

Suggestion

If I had to do this assignment, I would do the following.

• First, write an AppInfo class starting from this, that can save and restore the values of string1, string2, string3.
• Then, write ActivityMain.java, and activity_main.xml.
• Then, create using Android Studio two new activities. You create them by right-clicking on app, and choosing New > Activity > Empty Activity. See here:

• The reason why you want to use that helper to create new activities, rather than just create a file Activity1.java in the proper directory, is that activities need their java code and also they need a "stanza" in AndroidManifest.xml, like this one. They also need their xml layout file. You definitely can create everything by hand, but using Android Studio as helper is likely faster.
• Then, copy the code (cut and paste, whatever) from ActivityMain.java into Activity2.java and Activity3.java
• Likewise, copy activity_main.xml into activity2.xml and activity3.xml
• Now, adapt Activity 2 and 3. Basically, you have to change which string is editable. In detail:
• In onResume, you need to put the text into textView or editView, as appropriate.
• When the user presses the Enter button, you have to write the string to a different place in AppInfo.
• Likely some other change.
• Finally, you have to add the behavior for the "Back" button; see here for how to do this.