For Android Developers, see the document: Android development specifications.

Android DevelopmentStandardization is the content to be introduced in this article, mainly to understand and learnAndroid DevelopmentFor more information, seeAndroid DevelopmentFor more information about the standard content, see this article.

I. Android coding specifications

1. the java code does not contain Chinese characters. A maximum of Chinese characters can appear in comments.

2. Local variable naming and static member variable naming

It can only contain letters. The first letter of a word must be in upper case and the other letters must be in lower case.

3. Constant naming

It can only contain letters and _. All letters are in uppercase. Words are separated _.

4. Name the id in layout

Naming mode: view abbreviation _ module name_view logical name

The abbreviated view details are as follows:

 
 

  
  
LayoutView：lv  
  
  
RelativeView:rv  
  
  
TextView:tv  
  
  
ImageView:iv  
  
  
ImageButton:im  
  
  
Button:btn 
 
 

5. Name the view variable in the activity

Naming mode: Logical name + view abbreviation

Suggestion: If the layout file is complex, we recommend that you divide layout into multiple modules. Each module defines a moduleViewHolder whose member variables contain the view

6. id naming in strings. xml

Naming mode: activity name_function module name_logic name/activity name_logic name/common _ logic name

In strings. xml, use activity name annotations to differentiate the file content.

Name the image in drawable

Naming mode: activity name_logical name/common _ logical name

7. styles. xml: extract the styles that are repeatedly reproduced in layout into general style components and put them in styles. xml;

8. Use layer-list and selector

9. Split images into multiple reusable images as much as possible

10. What the server can achieve is not to be placed on the client.

11. Exercise caution when referencing a third-party library. Avoid using a large third-party library, resulting in a large client package.

12. Handle global application exceptions and errors and send the errors to the server by email.

13. process images in. 9

14. Exercise caution when using static variables to share Interfaces

15. Log (system name module Name Interface Name, detailed description)

16. unit test logic test and Interface Test)

17. Do not reuse the handler of the parent class. The handler of the corresponding class should not be used by its subclass. Otherwise, the message. what conflict will occur.

18. process all logic in a View. OnClickListener in the activity

19. Use % 1 $ s in strings. xml for character string wildcard

20. If multiple activities contain common UI processing, you can extract a CommonActivity and call the common part for processing. Other activities only need to inherit it.

21. When you use button + activitgroup to implement the tab effect, use Button. setSelected (true) to make sure that the button is in the selected State and that the current activity of activitygroup corresponds to the button.

22. If a common component is developed, prefix the file name in the drawable/layout/menu/values directory to avoid conflicts.

23. data must be validated, such

The numeric type must have a default value if the conversion fails;

Determine whether the response data of the Android development server is valid;

Ii. Android development performance optimization

1. Use gzip for http compression and set the connection timeout and response timeout.

Http requests can be divided into cache and non-cache based on business needs. In a network-less environment, some data is still browsed through the cached httpresponse for offline reading.

2. listview Performance Optimization

1) Reuse convertView

In getItemView, determine whether convertView is empty. If it is not empty, it can be reused. If you need to add listerner to the view in couvertview, the Code must be out of if (convertView = null.

2) asynchronously load images

If the item contains a webimage, it is best to load it asynchronously.

3) the image is not displayed during fast sliding.

SCROLL_STATE_FLING) When you slide the list quickly. The image in the item or the view that consumes resources can be retrieved without being displayed. The SCROLL_STATE_IDLE and SCROLL_STATE_TOUCH_SCROLL statuses are in the other two States ), the view is displayed.

3. Use a thread pool, which can be divided into a core thread pool and a common thread pool. Download images and other time-consuming tasks are placed in the common thread pool to prevent time-consuming tasks from blocking the thread pool, as a result, all asynchronous tasks must wait.

4. asynchronous tasks are divided into core tasks and common tasks. Only system-level errors in core tasks report errors. The ui operation of asynchronous tasks needs to determine whether the original activity is active.

5. Avoid using static member variables to reference instances that consume too much resources, such as Context

6. Use WeakReference to replace strong references. Weak references allow you to keep references to objects, and allow GC to release objects and reclaim memory when necessary. For those objects that create cheap but consume a large amount of memory, that is, you want to keep the object and use it when the application needs it. If you want GC to recycle it when necessary, you can consider using weak references.

7. Super fat Bitmap

Timely destruction (bitmap is recycled when the onDestroy of the Activity is used by the UI component. RuntimeException: Canvas: tryingtousearecycledbitmapandroid is thrown when it is recycled immediately after it is used by the UI component. graphics. bitmap) sets a certain sampling rate (sampling is not required for images provided by developers. For images uploaded by users or uncontrolled by third parties, sampling can be performed to reduce the memory occupied by images ), when returning images from the server, we recommend that you use soft references to the resid resources of the drawable image. bitmap corresponds to any type of images of other resources. If the image cannot be obtained, for example, the file does not exist, or an OutOfMemory exception occurs when reading the file. The default image corresponding to the default image should be placed in the apk and obtained through resid );

8. Ensure that the memory occupied by Cursor is promptly released, rather than waiting for GC to process. In addition, Android obviously prefers programmers to manually close Cursorclose.

9. threads are also an important source of Memory leakage. The main cause of thread Memory leakage is the uncontrollable thread lifecycle.

10. If the ImageView image is from the network, load it asynchronously.

11. During custom views in application development, do not write the interaction part as a thread to constantly refresh the interface display. Instead, update the interface based on the TouchListener event.

12. Drawable

The image used by the ui component is included in the apk package. Therefore, setImageResource or setBackgroundResource is used instead of resourceid.

Note: get (getResources (), R. drawable. btn_achievement_normal) This method is converted to drawable through resid. You need to consider the recycling problem. If drawable is a private object of the object, the memory will not be released before the object is destroyed.

3. UI Optimization for Android Development

1. layout componentization, use merge and include reuse whenever possible

2. Use styles to reuse style definitions

3. the pop-up control of the soft keyboard should not overwrite the input box

4. Placement of numbers, letters, and Chinese characters: All numbers and letters are divided into different types. In most cases, because our input is half-width, the placeholder values of letters and numbers cannot be determined. However, once fully divided, the placeholder values of numbers and letters are the same as those of a Chinese character, in this way, the layout problem caused by placeholder can be avoided.

5. English Document Layout: When textview is automatically changed, the word integrity should be maintained. The solution is to calculate the string length, and then manually set the number of letters displayed in each row with '\ n' added'

6. Use RelativeLayout for complex la s

7. adaptive screen; Use dp to replace pix

8. Use android: layout_weight or TableLayout to create an equals layout.

9. Use animation-list to create an animation.

Summary:Android DevelopmentDocument for beginners:Android DevelopmentThe contents of the specification have been introduced.Android DevelopmentContent learning is helpful to you. If you want to learn moreAndroid DevelopmentFor more information, see edit recommended articles.