【導(dǎo)讀】章中做的一樣，更常見的方法是使用一種基于XML的布局文件。動態(tài)的小部件實例保留更。多，情況復(fù)雜，小工具在編譯時不為人所知。例如，在數(shù)據(jù)檢索了互聯(lián)網(wǎng)基礎(chǔ)上將單選按鈕?？紤]到這一點，現(xiàn)在是時候來學(xué)習(xí)如何用此種方式來布置Androidactivities。器編碼的XML格式。的布局是資源，因此布局文件存儲在res/在你的Android項目布局目錄中。每個XML文件包含一個指定的部件和容器布局元素樹，一種意見認為構(gòu)成層次。是呈現(xiàn)一個粗體字體樣式.Android的SDK中附帶一個使用的布局的工具。這個工具應(yīng)自動調(diào)用你的Android. Eclipse或者一個像DroidDraw1設(shè)計GUI圖形用戶界面建設(shè)者。這樣GUI建設(shè)者們，在原。則上，生成Java代碼而不是XML。生成的XML定義從手寫的Java代碼中分離，使得某人定制的來源意外重新生成不太可能。此外，XML作為一個GUI定義格式是越來越普遍。其他XML為中心的觀點描述語言輕松進入Android。寬度和高度填寫“parent”，這種情況下，整個屏幕。標(biāo)識符生成的R類由android在。被最后按下時顯示的時間。這種邏輯仍然適用，即使

　　

【正文】 lly, they are used to identify adjacent widgets (., a “Name:” label before a field where one fills in a name). In Java, you can create a label by creating a TextView instance. More monly, though, you will create labels in XML layout files by adding a TextView element to the layout, with an android:text property to set the value of the label itself. If you need to swap labels based on certain criteria, such as internationalization, you may wish to use a resource reference in the XML instead, as will be described in Chapter 9. TextView has numerous other properties of relevance for labels, For example, in the Basic/Label project, you will find the following layout file: ?xml version= encoding=utf8? TextView xmlns:android= 中國地質(zhì)大學(xué) (北京 )2021 屆本科生畢業(yè)設(shè)計 外文資料翻譯 13 android:layout_width=fill_parent android:layout_height=wrap_content android:text=You were expecting something profound? / Button, Who’s Got the Button? We’ve already seen the use of the Button widget in Chapters 4 and 5. As it turns out, Button is a subclass of TextView, so everything discussed in the preceding section in terms of formatting the face of the button still holds. Android has two widgets to help you embed images in your activities: ImageView and ImageButton. As the names suggest, they are imagebased analogues to TextView and Button, respectively. Each widget takes an android:src attribute (in an XML layout) to specify what picture to use. These usually reference a drawable resource, described in greater detail in the chapter on resources. You can also set the image content based on a Uri from a content provider via setImageURI(). ImageButton, a subclass of ImageView, mixes in the standard Button behaviors, for responding to clicks and whatnot. For example, take a peek at the layout from the Basic/ImageView sample project: ?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 / 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: 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: 中國地質(zhì)大學(xué) (北京 )2021 屆本科生畢業(yè)設(shè)計 外文資料翻譯 14 ?xml version= encoding=utf8? EditText xmlns:android= android:id=@+id/field android:layout_width=fill_parent android:layout_height=fill_parent 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 + } 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.