Android 4.4创建The Master/Detail Flow应用程序 翻译

res/values-large/refs.xml 和res/values-sw600dp/refs.xml 两个附加的文件，纯属为了有助于理解这个程序如何帮助辨别是否使用双面板模式。

Handling Different Android Devices and Displays 这一章有着更加详细的勾勒。每个应用程序项目都拥有多套针对不同显示器大小的资源。运行时，安卓系统自动地使用哪些最为匹配物理设备大小的资源集。当然，values-large 和values-sw600dp用于大显示器的设备。在这些文件夹中ref.xml文件仅仅是声明一个导致所双窗口布局可以被使用的别名：

@layout/activity_item_twopane

Modifying the Master/Detail Flow Template

虽然 Master/Detail Flow模板的结构在一开始显示的很混乱，但是随着默认模板在本章的随后部分被修改，它的概念将会变得更加清晰。随之出现的是，其中很大一部分由模板提供的功能，在许多Master/Detail实现中是不需要修改的。

在本章的剩余部分，该MasterDetailFlow项目将被修改，以使主列表显示网站名称的列表，并改变以包含web视图对象，而不是目前的TextView的详细信息窗格中。当一个网站是由用户选择，相应的网页将随后加载和在细节窗格中显示

In the rest of this chapter, the MasterDetailFlow project will be modified such that the master list displays a list of web site names and the detail pane altered to contain a WebView object instead of the current TextView. When a web site is selected by the user, the corresponding web page will subsequently load and display in the detail pane.

在随后的章节中，MasterDetailFlow project将会被修改，以至于Master列表显示的是一列网址名称，Detail面板变为包含一个WebView对象，而不是当前的TextView。当用户选择了一个网址，相应的网页将被随后加载并显示在Detail pane中

Changing the Content Model

The content for the example as it currently stands is defined by the DummyContent class file。因此，开始通过选择DummyContent.java文件，并检查代码。在文件的底部是一个声明了一个名为DummyItem类，这是目前能够存储两个String对象，分别表示content string和一个ID 。另一方面，更新后的项目，将需要每个item object包含一个ID string，用于网站名称的字符串，和一个网址URL。要添加这些功能，修改DummyItem类，以便它的内容如下：

public static class DummyItem {	public String id;	public String website_name;	public String website_url;	public DummyItem(String id, String website_name,              String website_url) 	{		this.id = id;		this.website_name = website_name;		this.website_url = website_url;	}		@Override	public String toString() {		return website_name;	}}

注意到这个类现在添加了3个Items。分别显示为 “Item 1”, “Item 2” and “Item 3”:

public static Map ITEM_MAP =           new HashMap();static {	// Add 3 sample items.	addItem(new DummyItem(1, Item 1));	addItem(new DummyItem(2, Item 2));	addItem(new DummyItem(3, Item 3));}

his code needs to be modified to initialize the data model with the required web site data:

public static Map ITEM_MAP =           new HashMap();static {	// Add 3 sample items.	addItem(new DummyItem(1, eBookFrenzy, 		http://www.ebookfrenzy.com));	addItem(new DummyItem(2, Google, 		http://www.google.com));	addItem(new DummyItem(3, Android, 		http://www.android.com));}

The code now takes advantage of the modified DummyItem class to store an ID, web site name and URL for each item.

上面几句话只可意会，意思是把

addItem(new DummyItem(1, Item 1));

addItem(new DummyItem(1, eBookFrenzy, http://www.ebookfrenzy.com));

修改Detail Pane：

Changing the Detail Pane

The detail information shown to the user when an item is selected from the master list is currently displayed via the layout contained in the fragment_website_detail.xml file. By default this contains a single view in form of a TextView. Since the TextView class is not capable of displaying a web page, this needs to be changed to a WebView object for the purposes of this tutorial. To achieve this, navigate to the res -> layout -> fragment_website_detail.xml file in the Project Explorer panel and double click on it to load it. Switch to the Graphical Layout tool display if it is not already displayed before right-clicking on the white background of the display canvas (which represents the TextView). From the resulting menu, select the Change Widget Type… menu option. In the Change Widget Type dialog, change the widget type from TextView to WebView before clicking on OK to commit the change.（下面是意译，因为直译对我来说，实在是太痛苦了，不过我还是能看懂英文的）

双击打开res -> layout ->fragment__detail.xml文件。在Graphical Laout中显示一个图形界面，点击右上角的MaxMize按钮，不是编成软件最外面的那个放大按钮。在Structure的Outline中显示(TextView),因为它默认显示的是一个TextView，为了显示网页，需要把它修改为WebView。右击白色区域，选择Change Widget Type，弹出Change Widget Type对话框，选择WebView。

Modifying the WebsiteDetailFragment Class

At this point the user interface detail panel has been modified but the corresponding Java class is still designed for working with a TextView object instead of a WebView. Load the source code for this class by double clicking on the WebsiteDetailFragment.java file in the Project Explorer panel. Within the source file locate the onCreateView() method which should read as outlined in the following listing:（以下为意译）

虽然res -> layout ->fragment__detail.xml里面的用户界面已经被修改，但相应的Java类没有变，仍然是TextView而不是WebView，所以我们要进入WebsiteDetailFragment.java文件。修改onCreateView（）方法如下：

把((TextView) rootView.findViewById(R.id.item_detail)).setText(mItem.content);修改为：((WebView) rootView.findViewById(R.id.item_detail)).loadUrl(mItem.website_url);即可。

package com.example.masterdetailflow;import android.os.Bundle;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.TextView;...@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,		Bundle savedInstanceState) {	View rootView = 		inflater.inflate(R.layout.fragment_website_detail,			container, false);	// Show the dummy content as text in a TextView.	if (mItem != null) {		((TextView) rootView.findViewById(R.id.website_detail))				.setText(mItem.content);	}	return rootView;}

In order to load the web page URL corresponding to the currently selected item only one line of code needs to be changed. Once this change has been made, the method should read as follows (note also the addition of the import directive for the android.webkit.WebView library):

package com.example.masterdetailflow;import android.os.Bundle;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.webkit.WebView;...@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,		Bundle savedInstanceState) {	View rootView = 		inflater.inflate(R.layout.fragment_website_detail,			container, false);	// Show the dummy content as text in a TextView.	if (mItem != null) {		((WebView) rootView.findViewById(R.id.website_detail))			.loadUrl(mItem.website_url);	return rootView;}

All that this change does is find the view with the ID of website_detail (this was formally the TextView but is now a WebView), extracts the URL of the web site from the selected item and instructs the WebView object to load that page.

Adding Manifest Permissions

最后一步是通过manifest文件添加网络权限到应用程序中。这将会允许WebView 对象访问网络下载网络页面。修改项目中的 AndroidManifest.xml文件 。 添加合适的权限行到该文件中:

            ...

Running the Application

Compile and run the application on a suitably configured emulator or an attached Android device. Depending on the size of the display, the application will appear either in small screen or two-pane mode. Regardless, the master list should appear primed with the names of the three web sites defined in the content model. Selecting an item should cause the corresponding web site to appear in the detail panel as illustrated in two-pane mode in Figure 23-5:

一个master/detail用户界面由项目的Master列表，选中它，一个细节面板中会显示有关该选择的更多信息。master/detail Flow 是Android ADT bundle提供的一个模板，允许一个master/detail管理被快速和相对容易创建。在本章中的演示中，对默认模板文件稍加修改，各种基于Master/Detail的功能可以通过少量的修改和设计付出即可实现。