This project contains an unfinished Android application to convert temperatures measured in celsius to farenheit and vice-versa. It is thought to be used as a (VERRY) short tutorial for Android development. You will make slight changes to a layout file and add some code which is responding to a button press.

The corresponding slides can be found here.

You will need Android Studio for this tutorial. An Android device is nice to have, but you can use the emulator, too (which is available in Android Studio).

• Get the code from github
  • Open Adnroid Studio and Click File > New > Project from Version Control > GitHub
  • The Git Repository URL is https://github.com/leifb/temperature.git
  • Follow the instructions, you can't to much wrong here
• Add the missing “To Celsius”-button
  • Go to the layout file: Double-press shift and enter content_main.xml
  • If the Design view is shown, switch to the Text view to edit the xml
  • Search for the Button attribute at the bottom of the file
  • Copy and paste the attribute and adjust the id of the new button (for examle to @+id/button_to_c)
  • Change the text of your new button:
    • In the android:text attribute, change @string/to_fahrenheit to To celsius
  • Change the android:layout_below value to @+id/button_to_f
• Add the functionality to convert
  • You can write methods for this either in the MainActivity class, or create a new class
    • Java code is generally placed in app/java/...
    • to convert farenheit to celsius use this formula: c = (f - 32) * 5/9
    • to convert celsius to farenheit use this formula: f = c * 9/5 + 32
  • Get the button and textfield references and add the event listeners
    • You will have to do this in the MainActivity class and there in the onCreate method
    • To get a button reference, you can use Button b = (Button) findViewById(R.id.buttonID);
    • To get a text view reference, you can use TextView t = (TextView) findViewById(R.id.textViewID);
    • To add an event listener, you can use b.setOnClickListener(new View.OnClickListener() {...});, or create a new class which implements the OnClickListener interface
    • In the OnClick method of your event listener, get the text of the text filed, do the calculation and update the other text field
• Use refactoring
  • Switch back to the layout file
  • In your new button attribute, place your coursor on the android:text line
  • press ALT+ENTER and select Extract string resource by pressing enter
  • confirm by pressing enter
• If you want further practice, you could add the functionality to calculate to kelvin!

If you have problems or just want to check, if you have done everything correct, you can check my given solution. For each step I have created a branch. Just check the commits or compare the branches to see what I have done to solve the problems.