About NotePad Tutorial

最新推荐文章于 2025-09-12 17:34:15 发布

转载最新推荐文章于 2025-09-12 17:34:15 发布 · 81 阅读

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原文链接：https://my.oschina.net/u/127911/blog/17307

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本文详细介绍了Android布局文件的基本结构，包括必须的XML头信息、常用的LinearLayout定义及命名空间使用方法。此外，还深入解析了startActivity()与startActivityForResult()的区别，以及如何通过onActivityResult()方法接收返回结果。

2019独角兽企业重金招聘Python工程师标准>>>

今天学习NotePad Tutorial。把自己认为重要的Copy过来。

一，Here are some things you should know about a layout file:

1,All Android layout files must start with the XML header line: <?xml version="1.0" encoding="utf-8"?>.

2,The next definition will often (but not always) be a layout definition of some kind, in this case a LinearLayout.

3,The XML namespace of Android should always be defined in the top level component or layout in the XML so thatandroid: tags can be used through the rest of the file:

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

二，关于startActivity()和startActivityForResult()：

The startActivityForResult() method fires the Intent in a way that causes a method in our Activity to be called when the new Activity is completed. The method in our Activity that receives the callback is calledonActivityResult() and we will implement it in a later step. The other way to call an Activity is usingstartActivity() but this is a "fire-and-forget" way of calling it — in this manner, our Activity is not informed when the Activity is completed, and there is no way to return result information from the called Activity withstartActivity().

三，关于onActivityResult():

onActivityResult() is the overridden method which will be called when an Activity returns with a result. (Remember, an Activity will only return a result if launched withstartActivityForResult.) The parameters provided to the callback are:

1,requestCode — the original request code specified in the Intent invocation (either ACTIVITY_CREATE or ACTIVITY_EDIT for us).

2,resultCode — the result (or error code) of the call, this should be zero if everything was OK, but may have a non-zero code indicating that something failed. There are standard result codes available, and you can also create your own constants to indicate specific problems.

3,intent — this is an Intent created by the Activity returning results. It can be used to return data in the Intent "extras."

转载于:https://my.oschina.net/u/127911/blog/17307