The document discusses event handling in Android applications. It covers XML-based event handling where events are defined in the XML layout. It also covers Java-based event handling where events are handled by implementing listener interfaces in the Java code. It provides examples of handling click and long click events. It also lists some other event listeners that can be used, such as OnFocusChangeListener, OnKeyListener, OnTouchListener, and OnCreateContextMenuListener.

1. 07.1. Event Handling
Oum Saokosal
Master of Engineering in Information Systems, South Korea
855-12-252-752
oum_saokosal@yahoo.com

2. Agenda
• XML-based Event Handling
• Java-based Event Handling
• More Event Listeners

3. XML-based Event Handling

4. XML-based Event Handling (1)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android=
"http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<Button android:text="Show Me!"
android:id="@+id/btnShowMe"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="showMe"
/>
</LinearLayout>
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5. XML-based Event Handling (2)
package com.kosalab;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
public class WidgetContainer extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.eventhandling);
}
public void showMe(View v){
Toast.makeText(this, "This event invoked from XML.",
Toast.LENGTH_SHORT).show();
}
}
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7. Java-based Event Handling

8. Java-based Event Handling (1)
?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android=
"http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<Button android:text="Show Me!"
android:id="@+id/btnShowMe"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>
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9. Java-based Event Handling (2)
public class WidgetContainer extends Activity
implements OnClickListener{
Button btn;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.eventhandling);
btn = (Button)findViewById(R.id.btnShowMe);
btn.setOnClickListener(this);
}
public void onClick(View v) {
Toast.makeText(this, "It's Toast Message! It appears
shortly.“, Toast.LENGTH_SHORT).show();
}
}
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11. Java-based Event Handling –
Another Example

12. public class WidgetContainer extends Activity implements
OnClickListener, OnLongClickListener{
Button btn;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.eventhandling);
btn = (Button)findViewById(R.id.btnShowMe);
btn.setOnClickListener(this);
btn.setOnLongClickListener(this);
}
public void onClick(View v) {
Toast.makeText(this, “Short click!“,
Toast.LENGTH_SHORT).show();
}
public boolean onLongClick(View v) {
Toast.makeText(this, “Long click!",
Toast.LENGTH_SHORT).show();
return true;
}
}
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13. onLongClick() – return true/false
public boolean onLongClick(View v) {
Toast.makeText(this, “Long click!",
Toast.LENGTH_SHORT).show();
return true;
}
Note:
return true: show only the longClick.
return false: show both longclick and then
short click.

14. More Event Listeners
• onFocusChange()
From View.OnFocusChangeListener. This is called when the user navigates onto or
away from the item, using the navigation-keys or trackball.
• onKey()
From View.OnKeyListener. This is called when the user is focused on the item and
presses or releases a key on the device.
• onTouch()
From View.OnTouchListener. This is called when the user performs an action
qualified as a touch event, including a press, a release, or any movement gesture
on the screen (within the bounds of the item).
• onCreateContextMenu()
From View.OnCreateContextMenuListener. This is called when a Context Menu is
being built (as the result of a sustained "long click").

15. Go on to the next slide