Android教程：步进式学习NotePadv1项目

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"这篇外文资料是关于Android开发的学习资源，特别关注了Android应用的实践步骤，适合已经对HelloAndroid教程有一定了解的开发者。提供的示例项目是Notepadv1，它作为起点，处理了一些基础工作，如界面构建和数据管理。资料中还涉及到错误修复和数据库帮助类DBHelper的使用，以及对ContentProvider的简要提及。" 在Android开发中，Notepadv1项目是一个起始模板，它旨在帮助开发者快速进入应用开发状态，尤其是对于那些已经完成过HelloAndroid教程的人来说。通过Eclipse集成开发环境（IDE），可以导入这个项目。右键点击Package Explorer，选择“Import” -> “General” -> “Existing Projects into Workspace”，然后找到并选择复制到本地的工作空间中的Notepadv1项目，点击“OK”。如果遇到AndroidManifest.xml错误或者与Android库相关的问题，可以通过右键点击项目，选择“Android Tools” -> “Fix Project Properties”来修复。资料中提到的DBHelper类是一个关键组件，它封装了对SQLite数据库的数据访问，用于存储和更新笔记数据。在实际的Android应用开发中，通常会用到ContentProvider来实现对数据的管理和共享，但在这个示例中，DBHelper可能是为了简化教学而设计的。ContentProvider是Android四大组件之一，它负责应用程序间的数据共享和访问，遵循标准的CRUD（创建、读取、更新、删除）操作。 DBHelper的实现可能包括创建数据库、定义表结构、插入、查询、更新和删除数据的方法。使用此类，开发者可以更专注于业务逻辑，而不是底层数据库操作的细节。此外，资料中虽然没有详细展开ContentProvider的使用，但它的重要性不容忽视，因为ContentProvider是规范数据交互的标准方式，尤其是在不同应用之间共享数据时。在深入学习Notepadv1项目的过程中，开发者可以了解到如何在Android应用中处理用户输入、持久化数据以及如何处理基本的UI交互。这对于进一步掌握Android应用开发至关重要，同时也为理解和使用ContentProvider打下基础。通过这种方式，开发者可以逐步构建复杂的应用，并理解Android生态系统的核心组件和工作原理。

Android

Step 1 Open up the Notepadv1 project in Eclipse

Notepadv1 is a project that is provided as a starting point - it takes care of some of the

boilerplate work that you have already seen if you followed the Hello Android tutorial.

Right click in the Package Explorer, select Import.../General/Existing Projects into

Workspace. Hit the browse button, and navigate to where you copied the three exercise

folders, select Notepadv1 and hit OK. You should see Notepadv1 listed in the projects with

a check mark next to it. Hit Finish. The exercise project should be open and ready to go in

your Eclipse package explorer. If you see an error about AndroidManifest.xml, or some

problems related to an Android zip file, right click on the project and select Android Tools-

>Fix Project Properties from the popup menu (the project is looking in the wrong location

for the library file, this will fix it for you).

Step 2

Take a look at the DBHelper class — this class is provided to encapsulate data access to

a SQLite database that will hold our notes data and allow us to update it.

Typically you would implement this using a ContentProvider, and in fact the full

Notepad application included with the SDK does implement such a ContentProvider.

However, there is no reason you can't just use your own SQLite database directly as we do

here. The main thing to notice about this class is that it takes care of the details of storing,

retrieving and updating data in the SQLite database for us. There are methods for retrieving

all the rows, retrieving a row based on rowIds, creating a new row, deleting an existing row

and updating a row. If you want a quick primer in how to use the SQLite Database for your

own applications, either take a look at this class or better yet, look at the full Notepad

application included with the SDK in the samples/ folder as the sample uses a

ContentProvider.

Step 3

Open the notepad_list.xml file in res/layout and take a look at it:

This is a layout definition file with a default starting point in it, we have provided this as

a convenience to get you going quickly.

a.All Android layout files must start with the XML header line:

<?xml version="1.0" encoding="utf-8"?>.

b.Also, the next definition will often (but not always) be a layout definition of some

kind, in this case a LinearLayout.

c.Note also that the xml namespace of Android should always be defined in the top level

component or layout in the XML so that android: tags can be used through the rest of

the file: xmlns:android="http://schemas.android.com/apk/res/android"

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Android教程：步进式学习NotePadv1项目

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