Android development specifications and android Development

Android development specifications and android Development

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.

7. Name the image in drawable

Naming mode: activity name_logical name/common _ logical name

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

9. Use layer-list and selector

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

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

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

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

14. process the. 9 Image

15. Exercise caution when using static variables to share Interfaces

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

17. unit test (logical test and Interface Test)

18. 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.

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

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

21. 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.

22. When you use button + activitgroup to implement the tab effect, use Button. setSelected (true) to ensure that the button is in the selected state and make the current activity of activitygroup correspond to the button

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

24. data must be validated, such

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

Whether the server response data is effectively judged;

25. If the same client is to be placed in different markets and the data downloaded and used in various markets must be counted

For inconsistent client-end packages, the only difference is versionname, and the APK file name is versionname.apk.

During the upgrade, you must pass your versionCode and versionName to the server. If you need to upgrade, download the apk corresponding to versionName.

About whether to force upgrade:

1). Force upgrade in any situation

2) determine the version of the user and the latest version. if the version is compatible, force upgrade; otherwise, the upgrade is optional;

26. Some buttons should be avoided from repeated clicks

 

Ii. Android Performance Optimization

1. http uses gzip compression to 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.

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

4 ). if the images asynchronously loaded in the list are not within the visible range, they are recycled in a timely manner according to certain algorithms (for example, the pictures outside the current visible range of 10 items are recycled, or cache the image, set a size, and recycle more than half according to the latest minimum usage principle)

5). BaseAdapter to avoid memory overflow

If the entity class of BaseAdapter has attributes that consume a lot of memory, it can be saved to files. To improve performance, you can cache and limit the cache size.

3. the thread pool can be divided into the Core Thread Pool and general thread pool. time-consuming tasks such as image download are placed in the General thread pool to avoid waiting for all asynchronous tasks after time-consuming tasks block the thread pool.

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.

1) The main thread should not process the network;

2) The main thread should not process the database;

3) The main thread should not process files;

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: trying to use a recycled bitmap android. graphics. Bitmap)
Set a certain sampling rate (sampling is not required for images provided by developers. For images uploaded by users or uncontrolled third parties, sampling can be performed to reduce the memory occupied by images ), returns an image from the server. We recommend that you provide the size of the image at the same time.
Clever Use of soft references
Drawable corresponds to resid resources, and bitmap corresponds to other resources
If an image of any type cannot be obtained (for example, the file does not exist or an OutOfMemory exception occurs when the file is read), there should be a corresponding default image (the default image is placed in the apk, 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 Cursor.

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.

13. Reuse and Recycle Activity objects

Temporary activity finish in time

Set the main interface to singleTask.

Set the interface to singleTop

14. Location Information

When obtaining the user's geographic location information, turn on the GPS when you need to obtain the data, and then close it in time

15. Set the power management for this interface during onResume and cancel the setting during onPause.

 

3. AndroidUI Optimization

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 digits 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

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