1. Basic Functionality in Android

2. Functionality in Android Events in Java – mouse related mouse clicked button down or up mouse entered – many others key pressed item selected (checkbox, table, list box) tabbed pane selection made others…

3. Tying a method to a Button 3 approaches – By implementing the OnClickListener interface – By using an anonymous inner class Most common Same way it is done in typical Graphical programming – Within xml

4. .xml file used in following examples <LinearLayout xmlns:android=“http://schemas.android.com/apk/res/android” … <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Print Hello" android:id="@+id/pb1" /> <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Print Goodbye" android:id="@+id/pb2" /> <EditText android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/et1" />

5. Approach 1 Implementing the OnClickListener interface

6. Implementing OnClickListener OnClickListenerInterface – android.view.View.OnClickListener – one abstract method: public abstract void onClick (View v); – widget must ‘listen’ for this event

7. Implementing OnClickListener Implementing the interface and “Listening” for the event public class OnClickWithSwitch extends Activity implements OnClickListener { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); View button1 = findViewById(R.id.pb1); button1.setOnClickListener(this); View button2 = findViewById(R.id.pb2); button2.setOnClickListener(this); }

8. Implementing OnClickListener Implementing onClick() public void onClick (View v) { switch (v.getId()) { case R.id.pb1: ((TextView)findViewById(R.id.et1)).setText("Hello"); break; case R.id.pb2: ((TextView)findViewById(R.id.et1)).setText("Goodbye"); break; default: ((TextView)findViewById(R.id.et1)).setText("Nothing"); }

9. Method 2 Using an anonymous inner class

10. Using an anonymous inner class With anonymous inner class – OnClickListener not explicitly implemented – Each widget must still ‘listen’ for the event when the listener is set, an anonymous inner class is used – inner class is a subclass of OnClickListener – onClick is implemented Each widget implements functionality accordingly

11. Using anonymous inner class Utilizing an anonymous inner class public class OnClickWithInner extends Activity { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); (findViewById(R.id.pb1)).setOnClickListener(new OnClickListener () { public void onClick (View v) { ((TextView)findViewById(R.id.et1)).setText("Hello"); } }); (findViewById(R.id.pb2)).setOnClickListener(new OnClickListener () { public void onClick (View v) { ((TextView)findViewById(R.id.et1)).setText("Goodbye"); } }); }

12. Method 3 Implementing onClick via XML

13. Using onClick XML attribute With XML – onClick is an attribute in XML – Attribute value is set to the name of the method that is tied to the button android:onClick=“methodName” – Method is written with the following signature: public void methodName(View v)

14. Using onClick XML attribute.xml file used in the following example: <LinearLayout xmlns:android=“http://schemas.android.com/apk/res/android” … <Button android:layout_width=“match_parent" android:layout_height="wrap_content" android:text="Print Hello" android:id="@+id/pb1“ android:onClick=“displayHello“ /> <Button android:layout_width=“match_parent" android:layout_height="wrap_content" android:text="Print Goodbye" android:id="@+id/pb2“ android:onClick= " displayGoodbye " /> <EditText android:layout_width= " match_parent" android:layout_height="wrap_content" android:id="@+id/et1" />

15. Using onClick XML attribute Implementing the methods named in XML public class OnClickWithXML extends Activity { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); } public void displayHello(View v) { ((TextView)findViewById(R.id.et1)).setText("Hello"); } public void displayGoodbye(View v) { ((TextView)findViewById(R.id.et1)).setText("Goodbye"); }