Android Common UI Components-Button

button is one of the most common UI components in Android, very small but most commonly used in development. It is typically used in conjunction with a listener to trigger some specific events. Button inherits the TextView. Its function is to provide a button, this button can be clicked by the user, when the user action on the button, trigger the corresponding event, such as Click, Touch. In general, for a button, the most used is the Click event, the button indirectly inherits from view, and all the events in the Android UI are defined in the view.

Example: Buttondemo
Operating effect:


Code Listing:
Layout file: Main.xml

[HTML]View Plaincopy

2. <? XML version= "1.0" encoding="Utf-8"?>
4. <linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
6. android:orientation="vertical"
8. android:layout_width="fill_parent"
10. android:layout_height="fill_parent"
12. >
14. <button android:id="@+id/button1"
16. android:layout_width="fill_parent"
18. android:layout_height= "wrap_content" android:text="Button1" />
20. <button android:id="@+id/button2"
22. android:layout_width="fill_parent"
24. android:layout_height= "wrap_content" android:text="Button2" />
26. </linearlayout>

Java source code file: Activitybutton.java

[Java]View Plaincopy

2. Package Com.rainsong.buttondemo;
6. Import android.app.Activity;
8. Import Android.os.Bundle;
10. Import Android.view.View;
12. Import Android.view.View.OnClickListener;
14. Import Android.widget.Button;
16. Import Android.widget.Toast;
20. Public class Activitybutton extends Activity
22. {
24. Button btn1;
26. Button btn2;
30. Onclicklistener Listener1;
32. Onclicklistener Listener2;
36. /** Called when the activity is first created. * /
38. @Override
40. public void OnCreate (Bundle savedinstancestate)
42. {
44. super.oncreate (savedinstancestate);
46. Setcontentview (R.layout.main);
50. Listener1 = New Onclicklistener () {
52. public void OnClick (View v) {
54. Toast.maketext (Activitybutton.   This, "Button1 clicked", Toast.length_short). Show ();
56. }
58. };
60. Listener2 = New Onclicklistener () {
62. public void OnClick (View v) {
64. Toast.maketext (Activitybutton.   This, "Button2 clicked", Toast.length_short). Show ();
66. }
68. };
72. BTN1 = (Button) Findviewbyid (R.id.button1);
74. Btn1.setonclicklistener (Listener1);
78. BTN2 = (Button) Findviewbyid (R.id.button2);
80. Btn2.setonclicklistener (LISTENER2);
82. }
84. }

API Knowledge points
Activity
public class
Activity
Extends Contextthemewrapper
Implements COMPONENTCALLBACKS2 Keyevent.callback Layoutinflater.factory2 View.oncreatecontextmenulistener Window.callback

View Findviewbyid (int id)
Finds A view that is identified by the id attribute from the XML is processed in OnCreate (Bundle).

void Setcontentview (int layoutresid)
Set the activity content from a layout resource.

View
public class
View
Extends Object
Implements Drawable.callback Keyevent.callback Accessibilityeventsource

void Setonclicklistener (View.onclicklistener l)
Register a callback to being invoked when the this view is clicked.

Button
public class
Button
Extends TextView

View.onclicklistener
public static interface
View.onclicklistener

abstract void OnClick (View v)
Called when a view has been clicked.

Toast
public class
Toast
Extends Object

Constants
int Length_long showthe View or text notification for a LONG period of time.
int Length_short showthe View or text notification for a short period of time.

Static Toast
Maketext (context context, int resId, int duration)
Make a standard toast, the just contains a text view with the text from a resource.

Static Toast
Maketext (Context context, charsequence text, int duration)
Make a standard toast, that just contains a text view.

void
Show ()
Show The View for the specified duration.

Android Common UI Components-Button