【導(dǎo)讀】雖然純粹通過(guò)Java代碼在activity上創(chuàng)建和添加部件，在技術(shù)上是可行的，我們?cè)诘?章中做的一樣，更常見(jiàn)的方法是使用一種基于XML的布局文件。索了互聯(lián)網(wǎng)基礎(chǔ)上將單選按鈕填充柱。他們的容器編碼的XML格式。對(duì)XML元素的屬性，描述一個(gè)部件應(yīng)如何看或者一個(gè)容器應(yīng)如何運(yùn)轉(zhuǎn)。的表面應(yīng)該是呈現(xiàn)一個(gè)粗體字體樣式.Android的SDK中附帶一個(gè)使用的布局的工具。者像Eclipse或者一個(gè)像DroidDraw1設(shè)計(jì)GUI圖形用戶界面建設(shè)者。目前的挑戰(zhàn)是重新閱讀用戶界面的。此外，XML作為一個(gè)GUI定義格式是越來(lái)越普遍。程智慧資料放在源文件。戶界面框架，如ZK，還使用視圖定義的XML。而“隨大流”并不一定是最好的政。策，但他們有優(yōu)勢(shì)幫助從任何其他XML為中心的觀點(diǎn)描述語(yǔ)言輕松進(jìn)入Android。所有其他要素將成為子根并繼承該命名空間的聲明。android：文字表示的初始文本將顯示在按鈕。寬度和高度填寫(xiě)“parent”，這種情況下，整個(gè)屏幕。用戶界面將需要整個(gè)樹(shù)的元素，代表工具和容器，控制自己的定位。這種邏輯仍然適用，即使在該修訂演示中。

　　

【正文】 from the Basic/ImageView sample project which is found along with all other code samples at ?xml version= encoding=utf8? ImageView xmlns:android= android:id=@+id/icon android:layout_width=fill_parent android:layout_height=fill_parent android:adjustViewBounds=true android:src=@drawable/molecule / The result, just using the codegenerated activity, is shown in Figure 62. Figure 62. The ImageViewDemo sample application 第 27 頁(yè) 共 35 頁(yè) Fields of Green. Or Other Colors. Along with buttons and labels, fields are the third “anchor” of most GUI toolkits. In Android, they are implemented via the EditText widget, which is a subclass of the TextView used for labels. Along with the standard TextView properties (., android:textStyle), EditText has many others that will be useful for you in constructing fields, including: ? android:autoText, to control if the field should provide automatic spelling assistance ? android:capitalize, to control if the field should automatically capitalize the first letter of entered text (., first name, city) ? android:digits, to configure the field to accept only certain digits ? android:singleLine, to control if the field is for singleline input or multipleline input (., does Enter move you to the next widget or add a newline?) Beyond those, you can configure fields to use specialized input methods, such as android:numeric for numericonly input, android:password for shrouded password input, and android:phoneNumber for entering in phone numbers. If you want to create your own input method scheme (., postal codes, Social Security numbers), you need to create your own implementation of the InputMethod interface, then configure the field to use it via android: inputMethod. For example, from the Basic/Field project, here is an XML layout file showing an EditText: ?xml version= encoding=utf8? EditText xmlns:android= android:id=@+id/field android:layout_width=fill_parent android:layout_height=fill_parent 第 28 頁(yè) 共 35 頁(yè) android:singleLine=false / Note that android:singleLine is false, so users will be able to enter in several lines of text. For this project, the file populates the input field with some prose: package 。 import 。 import 。 import 。 public class FieldDemo extends Activity { @Override public void onCreate(Bundle icicle) { (icicle)。 setContentView()。 EditText fld=(EditText)findViewById()。 (Licensed under the Apache License, Version + (the \License\)。 you may not use this file + except in pliance with the License. You may + obtain a copy of the License at + } } The result, once built and installed into the emulator, is shown in Figure 63. 第 29 頁(yè) 共 35 頁(yè) Figure 63. The FieldDemo sample application Note Android’s emulator only allows one application in the launcher per unique Java package. Since all the demos in this chapter share the package, you will only see one of these demos in your emulator’s launcher at any one time. Another flavor of field is one that offers autopletion, to help users supply a value without typing in the whole text. That is provided in Android as the AutoCompleteTextView widget and is discussed in Chapter 8. Just Another Box to Check The classic checkbox has two states: checked and unchecked. Clicking the checkbox toggles between those states to indicate a choice (., “Add rush delivery to my order”). In Android, there is a CheckBox widget to meet this need. It has TextView as an ancestor, so you can use TextView properties like 第 30 頁(yè) 共 35 頁(yè) android:textColor to format the widget. Within Java, you can invoke: ? isChecked() to determine if the checkbox has been checked ? setChecked() to force the checkbox into a checked or unchecked state ? toggle() to toggle the checkbox as if the user checked it Also, you can register a listener object (in this case, an instance of OnCheckedChangeListener) to be notified when the state of the checkbox changes. For example, from the Basic/CheckBox project, here is a simple checkbox layout: ?xml version= encoding=utf8? CheckBox xmlns:android= android:id=@+id/check android:layout_width=wrap_content android:layout_height=wrap_content android:text=This checkbox is: unchecked / The corresponding retrieves and configures the behavior of the checkbox: public class CheckBoxDemo extends Activity implements { CheckBox cb。 @Override public void onCreate(Bundle icicle) { (icicle)。 setContentView()。 cb=(CheckBox)findViewById()。 (this)。 } public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { if (isChecked) { (This checkbox is: checked)。 } else { (This checkbox is: unchecked)。 第 31 頁(yè) 共 35 頁(yè) } } } Note that the activity serves as its own listener for checkbox state changes since it implements the OnCheckedChangeListener interface (via (this)). The callback for the listener is onCheckedChanged(), which receives the checkbox whose state has changed and what the new state is. In this case, we update the text of the checkbox to reflect what the actual box contains. The result? Clicking the checkbox immediately updates its text, as you can see in Figures 64 and 65. Figure 64. The CheckBoxDemo sample application, with the checkbox unchecked 第 32 頁(yè) 共 35 頁(yè) Figure 65. The same application, now with the checkbox checked Turn the Radio Up As with other implementations of radio buttons in other toolkits, Android’s radio buttons are twostate, like checkboxes, but can be grouped such that only one radio button in the group can be checked at any time. Like CheckBox, RadioButton inherits from CompoundButton, which in turn inherits f