java.md

Java !

Quick guide to good practice in Java for Android

1) Follow Conventions

The following naming and casing conventions are important for your Java code:

Type	Example	Description	Link
Variable	incomeTaxRate	All variables should be camel case	Read More
Constant	DAYS_IN_WEEK	All constants should be all uppercase	Read More
Method	convertToEuroDollars	All methods should be camel case	Read More
Parameter	depositAmount	All parameter names should be camel case	Read More

See this naming guide for more details.

a) Variable

Non-public, non-static field names start with m. Static field names start with s. Other fields start with a lower case letter. Public static final fields (constants) are ALL_CAPS_WITH_UNDERSCORES.

For example:

public class MyClass {
    public static final int SOME_CONSTANT = 42;
    public int publicField;
    private static MyClass sSingleton;
    int mPackagePrivate;
    private int mPrivate;
    protected int mProtected;
}

b) Layout

Organize your layout as follow :

• R.layout
  • activity_
  • adapter_
  • fragment_

c) Package

The way to do this is to group things together by their category. Each component goes to the corresponding package:

• com.example.myapp.activities - Contains all activities
• com.example.myapp.adapters - Contains all custom adapters
• com.example.myapp.models - Contains all our data models
• com.example.myapp.network - Contains all networking code
• com.example.myapp.fragments - Contains all fragments
• com.example.myapp.utils - Contains all helpers supporting code.
• com.example.myapp.interfaces - Contains all interfaces

d) Classes

Android classes should be named with a particular convention that makes their purpose clear in the name. For example all activities should end with Activity as in MoviesActivity. The following are the most important naming conventions:

Name	Convention	Inherits
Activity	CreateTodoItemActivity	AppCompatActivity, Activity
List Adapter	TodoItemsAdapter	BaseAdapter, ArrayAdapter
Database Helper	TodoItemsDbHelper	SQLiteOpenHelper
Network Client	TodoItemsClient	N/A
Fragment	TodoItemDetailFragment	Fragment
Service	FetchTodoItemService	Service, IntentService

e) Brace Style

Use Standard Brace Style

Braces do not go on their own line; they go on the same line as the code before them:

class MyClass {
    int func() {
        if (something) {
            // ...
        } else if (somethingElse) {
            // ...
        } else {
            // ...
        }
    }
}

f) colors.xml

First : .dloG si rotaidar ehT

colors.xml is a color palette. There should be nothing else in your colors.xml than just a mapping from a color name to an RGBA value. Do not use it to define RGBA values for different types of buttons.

Don't do this:

<resources>
    <color name="button_foreground">#FFFFFF</color>
    <color name="button_background">#2A91BD</color>
    <color name="comment_background_inactive">#5F5F5F</color>
    <color name="comment_background_active">#939393</color>
    <color name="comment_foreground">#FFFFFF</color>
    <color name="comment_foreground_important">#FF9D2F</color>
    ...
    <color name="comment_shadow">#323232</color>

You can easily start repeating RGBA values in this format, and that makes it complicated to change a basic color if needed. Also, those definitions are related to some context, like "button" or "comment", and should live in a button style, not in colors.xml.

Instead, do this:

<resources>

    <!-- grayscale -->
    <color name="white"     >#FFFFFF</color>
    <color name="gray_light">#DBDBDB</color>
    <color name="gray"      >#939393</color>
    <color name="gray_dark" >#5F5F5F</color>
    <color name="black"     >#323232</color>

    <!-- basic colors -->
    <color name="green">#27D34D</color>
    <color name="blue">#2A91BD</color>
    <color name="orange">#FF9D2F</color>
    <color name="red">#FF432F</color>

</resources>

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Source :

https://guides.codepath.com/android/Organizing-your-Source-Files
https://source.android.com/source/code-style.html