Android 开发工具

ADT (Android 开发工具) is a plugin for Eclipse that provides a suite of tools that are integrated with the Eclipse IDE. It offers you access to many features that help you develop Android applications quickly. ADT provides GUI access to many of the command line SDK tools as well as a UI design tool for rapid prototyping, designing, and building of your application's user interface.

Because ADT is a plugin for Eclipse, you get the functionality of a well-established IDE, along with Android-specific features that are bundled with ADT. The following describes important features of Eclipse and ADT:

Integrated Android project creation, building, packaging, installation, and debugging

ADT integrates many development workflow tasks into Eclipse, making it easy for you to rapidly develop and test your Android applications.

SDK Tools integration

Many of the SDK tools are integrated into Eclipse's menus, perspectives, or as a part of background processes ran by ADT.

Java programming language and XML editors

The Java programming language editor contains common IDE features such as compile time syntax checking, auto-completion, and integrated documentation for the Android framework APIs. ADT also provides custom XML editors that let you edit Android-specific XML files in a form-based UI. A graphical layout editor lets you design user interfaces with a drag and drop interface.

Integrated documentation for Android framework APIs

You can access documentation by hovering over classes, methods, or variables.

You can find the most up-to-date and more detailed information about changes and new features on the Recent Changes page at the Android Tools Project site.

SDK Tools Integration

Many of the tools that you can start or run from the command line are integrated into ADT. They include:

• Traceview: Allows you to profile your program's execution (Window > Open Perspective > Traceview).
• android: Provides access to the Android SDK Manager and AVD Manager. Other android features such as creating or updating projects (application and library) are integrated throughout the Eclipse IDE.
• Hierarchy Viewer: Allows you to visualize your application's view hierarchy to find inefficiencies (Window > Open Perspective > Hierarchy Viewer).
• Pixel Perfect: Allows you to closely examine your UI to help with designing and building. (Window > Open Perspective > Pixel Perfect).
• DDMS: Provides debugging features including: screen capturing, thread and heap information, and logcat (Window > Open Perspective > DDMS).
• adb: Provides access to a device from your development system. Some features of adb are integrated into ADT such as project installation (Eclipse run menu), file transfer, device enumeration, and logcat (DDMS). You must access the more advanced features of adb, such as shell commands, from the command line.
• ProGuard: Allows code obfuscation, shrinking, and optimization. ADT integrates ProGuard as part of the build, if you enable it.

Code Editors

In addition to Eclipse's standard editor features, ADT provides custom XML editors to help you create and edit Android manifests, resources, menus, and layouts in a form-based or graphical mode. Double-clicking on an XML file in Eclipse's package explorer opens the appropriate XML editor.

Note: You can edit Android-specific XML files (such as a layout or manifest) in both a graphical mode and also an XML markup mode. You can switch between these modes with the pair of tabs at the bottom of each custom XML editor.

In addition, some special file types that don't have custom editors, such as drawables, animations, and color files offer editing enhancements such as XML tag completion.

ADT provides the following custom, form-based XML editors:

Graphical Layout Editor

Edit and design your XML layout files with a drag and drop interface. The layout editor renders your interface as well, offering you a preview as you design your layouts. This editor is invoked when you open an XML file with a view declared (usually declared in res/layout. For more information, see Graphical Layout Editor.

Android Manifest Editor

Edit Android manifests with a simple graphical interface. This editor is invoked when you open an AndroidManifest.xml file.

Menu Editor

Edit menu groups and items with a simple graphical interface. This editor is invoked when you open an XML file with a <menu> declared (usually located in the res/menu folder).

Resources Editor

Edit resources with a simple graphical interface. This editor is invoked when you open an XML file with a <resources> tag declared.

XML Resources Editor

Edit XML resources with a simple graphical interface. This editor is invoked when you open an XML file.

Resource linking enhancements

In addition to the normal code editing features of Eclipse, ADT provides enhancements to the Android development experience that allow you to quickly jump to declarations of various types of resources such as strings or layout files. You can access these enhancements by holding down the control key and clicking on the following items:

• A resource identifier, such as R.id.button1, jumps to the XML definition of the view.
• A declaration in the R.java file, such as public static final int Button01=0x7f050000", jumps to the corresponding XML definition.
• An activity or service definition in your manifest, such as <activity android:name=".TestActivity">, jumps to the corresponding Java class. You can jump from an activity definition (or service definition) into the corresponding Java class.
• You can jump to any value definition (e.g. @string:foo), regardless of which XML file "foo" is defined in.
• Any file-based declaration, such as @layout/bar, opens the file.
• Non-XML resources, such as @drawable/icon, launches Eclipse's default application for the given file type, which in this case is an image.
• @android namespace resources opens the resources found in the SDK install area.
• Custom views in XML layouts, such as <foo.bar.MyView></foo.bar.MyView>, or <view class="foo.bar.MyView">) jump to the corresponding custom view classes.
• An XML attribute such as @android:string/ok or android.R.string.id in Java code opens the file that declares the strings. The XML tab opens when doing this, not the form-based editor.

Graphical Layout Editor

ADT provides many features to allow you to design and build your application's user interface. Many of these features are in the graphical layout editor, which you can access by opening one of your application's XML layout files in Eclipse.

The graphical layout editor is the main screen that you use to visually design and build your UI. It is split up into the following parts:

Canvas

In the middle of the editor is the canvas. It provides the rendered view of your layout and supports dragging and dropping of UI widgets directly from the palette. You can select the platform version used to render the items in the canvas. Each platform version has its own look and feel, which might be the similar to or radically different from another platform version. The canvas renders the appropriate look and feel for the currently selected platform version. This platform version does not need to be the same as the version that your application targets.

The canvas also provides context-sensitive actions in the layout actions bar, such as adjusting layout margins and orientation. The layout actions bar displays available actions depending on the selected UI element in the canvas.

Outline

On the right side of the editor is the outline view. It displays a hierarchical view of your layout where you can do things such as reorder of views. The outline view exposes similar functionality as the canvas but displays your layout in an ordered list instead of a rendered preview.

Palette

On the left side of the editor is the palette. It provides a set of widgets that you can drag onto the canvas. The palette shows rendered previews of the widgets for easy lookup of desired UI widgets.

Configuration Chooser

At the top of the editor is the configuration chooser. It provides options to change a layout's rendering mode or screen type.

Figure 1. Graphical layout editor

Canvas and outline view

The canvas is the area where you can drag and drop UI widgets from the palette to design your layout. The canvas offers a rendered preview of your layout depending on factors such as the selected platform version, screen orientation, and currently selected theme that you specify in the configuration chooser. You can also drag and drop items into the outline view, which displays your layout in a hierarchical list. The outline view exposes much of the same functionality as the canvas but offers another method of organization that is beneficial for ordering and quickly selecting items. When you right-click a specific item in the canvas or outline view, you can access a context-sensitive menu that lets you modify the following attributes of the layout or view:

View and layout properties

When you right-click a view or layout in the canvas or outline view, it brings up a context-sensitive menu that lets you set things such as:

• ID of the view or layout
• Text of the view
• Layout width
• Layout height
• Properties such as alpha or clickable

Animation preview and creation

If your layout or view is animated, you can preview the animation directly in the canvas (when you select Android 3.0 or later as the platform version in the configuration chooser). Right-click an item in the canvas and select Play Animation. If animation is not associated with item, an option is available in the menu to create one.

View the segment on the animation features for more information.

Extract as Include

You can extract parts of a current layout into its own layout file, which you can then include in any layout with a single line of XML. See Layout Refactoring Support for more information.

Other canvas features

The canvas has additional features not available in the outline view:

• Edit views with the layout actions bar: The context-sensitive layout actions bar allows you to edit how a view is laid out in your UI. The available actions depend on the currently selected view and its parent layout. Some common actions include toggling the fill mode of the view and specifying margins. For instance, if you select a Button in a LinearLayout, you see actions related to the LinearLayout, such as a toggle to switch between horizontal and vertical layout, and a toggle to control whether its children are aligned along their text baseline. You will also see toolbar actions to control the individual layout attributes of the child, such as whether the child should stretch out to match its parent's width and height, a dropdown action to set the child's layout gravity, a button to open a margin editor, and a layout weight editor.
• Edit a nested layout in its current context: If you are editing a layout that includes another layout, you can edit the included layout in the layout that included it.
• Preview drag and drop location: When you drag and drop a UI widget onto the canvas, ruler markers appear showing you the approximate location of the UI widget depending on the type of layout, such as RelativeLayout or LinearLayout.
• Preview animations: You can preview view and layout animations when you select Android 2.1 or later for the platform version in the configuration bar.
• Render layouts in real-time: Layouts are rendered as accurately as possible according to the platform version, including the appropriate system and action bars.
• Support for fragments: Fragments can be rendered in the same screen as the layout that includes the fragments.

Figure 2. Canvas portion of the layout editor showing a rendered preview of an application

Figure 3. Outline view showing current layout's structure

Palette

The palette contains the UI widgets that you can drag and drop onto the canvas and add to your layout. The pallete categorizes the widgets and shows rendered previews for easier lookup. The main features of the palette include:

• Different modes of rendered previews include: icons only, icons and text, tiny previews, small previews, and previews (rendered in real size). Previews are only available for layouts rendered with the latest revisions of Android 2.1 (API Level 7) or later.
• Custom views in your project or library projects are added under custom views category.
• Arrange UI widgets alphabetically or by category.

Figure 4. Palette showing available UI widgets

Configuration chooser

The configuration chooser allows you to create and configure different configurations of a layout for different situations, such as one for landscape and one for portrait mode. You can set the following options for each configuration of a layout:

• Screen type combo box: Predefined screen settings for common device configurations. You can also create your own by selecting Custom....
• Screen orientation combo box: Portrait or Landscape screen orientation.
• Theme combo box: Predefined themes or a custom theme that you have created.
• Platform combo box: Platform version used to render the canvas and palette as well as displaying appropriate themes.
• Custom layout combo boxes: The locale, dock, and time of day combo boxes let you select different versions of the same layout depending on the device's current state. You can create a new version of a layout with the Create button.

Figure 5. Configuration chooser

Layout Refactoring Support

In both the graphical and XML layout editor, there are many features that help you quickly refactor your layouts. The following list describes the major refactoring support:

Change layout

This lets you change the layout on the fly and re-renders the canvas for you. You can apply this refactoring to any layout and the layout is converted to the new type if possible. In many cases, the opening and closing tags of the layout's XML element are changed along with things such as ID attributes and their references. However, for some supported types, ADT attempts to preserve the layout, such as changing a LinearLayout to a RelativeLayout.

Change widget

This lets you select one or more widgets and converts them to a new widget type. In addition to changing the element name, it also removes any attributes that are not supported by the new widget type and adds in any mandatory attributes required by the new widget type. If the current ID of a widget includes the current widget type in its ID (such as a <Button> widget named "button1"), then the ID is changed to match the new widget type and all references are updated.

Extract as include

This lets you extract views inside of an existing layout into their own separate layout file. An include tag that points to the newly created layout file is inserted into the existing layout file. Right-click the view or layout and select Extract as Include....

Extract string

Extract strings from either XML or Java files into their own separate resource file.

Extract style

Extract style-related attributes from a layout and define them in a new styles.xml file. You can select multiple views and this refactoring extracts all of the same styles into one style and assigns that style to all the views that use it.

Wrap-in container

This lets you select one or more sibling elements and wrap them in a new container. This can be applied to the root element as well, in which case the namespace declaration attributes will be transferred to the new root. This refactoring also transfers layout_ attribute references to the new root, For example, suppose you have a RelativeLayout. If other widgets have layout constraints pointing to your widget, wrapping the widget causes these constraints to point to the parent instead.

Quick Assistant

Provides refactoring suggestions depending on the current context. Press Ctrl-1 (or Cmd-1 on Mac) in an editor, and Eclipse provides a list of possible refactorings depending on the context. The Quick Assistant provides fast access to all of the above refactorings, where applicable. For example, if you are editing an XML value and decide you want to extract it out as a string, place the text cursor in the string and press Ctrl-1 to see the refactoring context menu.