Android应用开发基础篇(1)-----Button

 

一、概述

       Button,顾名思义就是按钮的意思,它主要的功能是响应用户按下按钮时的动作。

二、应用

     新建一个工程,名字为MyButton,在/res/layout/main.xml文件中添加以下内容:

1 <Button
2 android:id="@+id/button"
3 android:layout_width="fill_parent"
4 android:layout_height="wrap_content"
5 android:text="Click"
6 />

添加后main.xml文件的内容为:

 1 <?xml version="1.0" encoding="utf-8"?>
2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
3 android:layout_width="fill_parent"
4 android:layout_height="fill_parent"
5 android:orientation="vertical" >
6
7 <TextView
8 android:layout_width="fill_parent"
9 android:layout_height="wrap_content"
10 android:text="@string/hello" />
11
12 <Button
13 android:id="@+id/button"
14 android:layout_width="fill_parent"
15 android:layout_height="wrap_content"
16 android:text="Click"
17 />
18
19 </LinearLayout>

接着修改MyButtonActivity.java文件,在MyButtonActivity类里声明一个Button对象mButton

private Button mButton = null;

在onCreate()函数里通过findViewById()函数实例化mButton

mButton = (Button)findViewById(R.id.button);

紧接着编写mButton的监听函数

mButton.setOnClickListener(new View.OnClickListener()
{ @Override
public void onClick(View v)
{
// TODO Auto-generated method stub
PlayToast("You Clicked Button");
}
});

其中PlayToast()函数是通过Toast类用来显示"You Clicked Button"这串字符串的,比较简单,如下所示:

private void PlayToast(String s)
{
Toast toast = Toast.makeText(this, s , Toast.LENGTH_LONG);
toast.show();
}

好了。下面是MyButtonActivity.java文件的完整内容:

 1 package com.nan.button;
2
3 import android.app.Activity;
4 import android.os.Bundle;
5 import android.view.View;
6 import android.widget.Button;
7 import android.widget.Toast;
8
9
10
11 public class MyButtonActivity extends Activity
12 {
13 private Button mButton = null;
14
15
16 /** Called when the activity is first created. */
17 @Override
18 public void onCreate(Bundle savedInstanceState)
19 {
20 super.onCreate(savedInstanceState);
21 setContentView(R.layout.main);
22
23 mButton = (Button)findViewById(R.id.button);
24 mButton.setOnClickListener(new View.OnClickListener()
25 {
26
27 @Override
28 public void onClick(View v)
29 {
30 // TODO Auto-generated method stub
31 PlayToast("You Clicked Button");
32 }
33 });
34
35 }
36
37
38 private void PlayToast(String s)
39 {
40 Toast toast = Toast.makeText(this, s , Toast.LENGTH_LONG);
41 toast.show();
42 }
43
44 }

运行程序,并点击按钮,效果如下: