button（Button）是Android其中一个经常使用的UI组件。非常小可是在开发中最经常使用到。一般通过与监听器结合使用。从而触发一些特定事件。

Button继承了TextView。它的功能就是提供一个button，这个button能够供用户点击。当用户对button进行操作的时候，触发对应事件，如点击。触摸。一般对于一个button而言，用的最多的就是点击事件，Button间接继承自View。而Android UI中的全部事件。都是定义在View中的。

实例：ButtonDemo

执行效果：





代码清单：

布局文件：main.xml

<?

xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    >

    <Button android:id="@+id/button1"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content" android:text="Button1" />

    <Button android:id="@+id/button2"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content" android:text="Button2" />

</LinearLayout>

Java源码文件：ActivityButton.java

package com.rainsong.buttondemo;

import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.Toast;

public class ActivityButton extends Activity

{

    Button btn1;

    Button btn2;

    OnClickListener listener1;

    OnClickListener listener2;

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState)

    {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        listener1 = new OnClickListener() {

            public void onClick(View v) {

                Toast.makeText(ActivityButton.this, "Button1 clicked",Toast.LENGTH_SHORT).show();

            }

        };

        listener2 = new OnClickListener() {

            public void onClick(View v) {

                Toast.makeText(ActivityButton.this, "Button2 clicked",Toast.LENGTH_SHORT).show();

            }

        };

        btn1 = (Button)findViewById(R.id.button1);

        btn1.setOnClickListener(listener1);

        btn2 = (Button)findViewById(R.id.button2);

        btn2.setOnClickListener(listener2);

    }

}

API知识点

Activity

public class

Activity

extends ContextThemeWrapper

implements ComponentCallbacks2 KeyEvent.Callback LayoutInflater.Factory2 View.OnCreateContextMenuListener Window.Callback



View     findViewById(int id)

Finds a view that was identified by the id attribute from the XML that was 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 be invoked when 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 that 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.