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Build a Simple Android App with Java

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Adding the OnClick Method

2:36 with Ben Deitch

The OnClick method is called when the button is actually clicked (or tapped). Any code in the OnClick method will run each time we tap the button!

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    We just left off with a lot of code that was generated by auto complete. 0:00
    We use on click listeners like this a lot in Android. 0:05
    So it'll make more and more sense the more you use it. 0:08
    This on click method, 0:11
    will run when ever this listener detects a click on our button. 0:14
    Just like opening our app triggers the onCreate method, 0:18
    typing on our button will trigger this onClick method. 0:21
    So anytime we click on our button, 0:24
    the code that we write inside these curly brackets will run. 0:26
    Let's add a comment in the onClick method to describe what we'd like to do. 0:31
    The button was clicked, 0:34
    so update the fact TextView with a new fact. 0:38
    All right, now we need a new fact. 0:44
    On the line below our comment, let's create a new string variable named fact. 0:47
    And let's set it equal to in quotation marks Ostriches 0:52
    can run faster than horses. 0:57
    And don't forget the semicolon. 1:01
    Now we need to update our text view to show this new fact. 1:03
    Remember when we were editing the layout? 1:07
    We can change the text of a text view by editing it's text property or 1:09
    by changing it directly in the layout's XML file. 1:13
    Android also allows us to make these kinds of changes in code. 1:17
    On a new line type factTextView.setText and then hit Enter to autocomplete. 1:21
    Notice that there's a list of different parameters down here. 1:30
    This is because there are different versions of this set text method. 1:33
    Each taken different parameters. 1:38
    We want this first one because it only has one parameter for the text. 1:40
    Now the data type here, CharSequence, 1:44
    might be a little confusing since we're using a String. 1:47
    But a String is just a sequence of characters, so 1:51
    it shouldn't be too surprising that all Strings are also CharSequences. 1:54
    Kind of like how text views are also views or how dogs are also animals. 2:00
    In Android, 2:06
    whenever you see a Charsequence, you can just pass in a string. 2:07
    All right, let's type fact in between the parenthesis to pass in our fact variable 2:11
    and now we are ready for the moment of truth. 2:16
    Let's click on the Run button, or hit Ctrl + Alt on Mac, 2:18
    or Shift + F10 on Windows to run our app. 2:22
    Looks good. 2:27
    Let's click on the button to test it. 2:29
    Did you know that ostriches can run faster than horses? 2:32

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