Android Even Handling By Oum Saokosal Note: This tutorial is for ADT - Eclipse

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