Respond to the Send Button

  1. In Android Studio, from the res/layout directory, edit the content_my.xml file.

  2. Add the android:onClick attribute to the <Button> element.

res/layout/content_my.xml

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/button_send"
    android:onClick="sendMessage" />

The android:onClick attribute’s value, "sendMessage", is the name of a method in your activity that the system calls when the user clicks the button.

  1. In the java/com.mycompany.myfirstapp directory, open the MyActivity.java file.

  2. Within the MyActivity class, add the sendMessage() method stub shown below.

java/com.mycompany.myfirstapp/MyActivity.java

/** Called when the user clicks the Send button */
public void sendMessage(View view) {
    // Do something in response to button
}

In order for the system to match this method to the method name given to android:onClick, the signature must be exactly as shown. Specifically, the method must:

  • Be public
  • Have a void return value
  • Have a View as the only parameter (this will be the View that was clicked)

Next, you’ll fill in this method to read the contents of the text field and deliver that text to another activity.