Android常用UI组件 - Button - android

按钮（Button）是Android当中一个常用的UI组件，很小但是在开发中最常用到。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按钮，这个按钮可以供用户点击，当用户对按钮进行操作的时候，触发相应事件，如点击，触摸。一般对于一个按钮而言，用的最多的就是点击事件，Button间接继承自View，而Android UI中的所有事件，都是定义在View中的。

实例：ButtonDemo
运行效果：

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源代码文件：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.

Android常用UI组件 - Button

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