Fennec/NativeUI/CodingStyle: Difference between revisions

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= Coding Style =
This page has been consolidated into [[Mobile/Fennec/Android#Coding_Style]].
 
== XML files (layout, resources, styles, etc) ==
 
* Each child tag should be indented with 4 spaces.
* The properties should be aligned with the first property of a tag.
* Each element should have "android:id" first, "style" (if exists) second, and the other properties follow. The root will have "xmlns:android" as first property.
* A Line break after every tag.
 
== Java ==
 
* We use the [http://www.oracle.com/technetwork/java/codeconvtoc-136057.html Java Coding Style]. Quick summary:
** FirstLetterUpperCase for class names
** camelCase for method and variable names
** One declaration per line
int x, y; // this is BAD!
int a;    // split it over
int b;    // two lines
** Braces should be placed like so (generally opening braces on same line, closing braces on a new line):
public void func(int arg) {
    if (arg != 0) {
        while (arg > 0) {
            arg--;
        }
    } else {
        arg++;
    }
}
 
* Places we differ from the Java coding style:
** Start class variable names with m (e.g. mSomeClassVariable)
** Don't use wilcard imports.
** 4-space indents
** spaces, not tabs
** Don't restrict yourself to 80-character lines. Java code tends to be long horizontally, so use appropriate judgement when wrapping. Avoid deep indents on wrapping. Note that aligning the wrapped part of a line with some previous part of the line (rather than just using a fixed indent) may require shifting the code every time the line changes, resulting in spurious whitespace changes.
* The [http://source.android.com/source/code-style.html Android Coding Style] has some useful guidelines too.
 
== Java Idioms ==
 
=== Closing resources ===
 
A good way to ensure things get closed properly is to use a try/finally block like so:
 
Cursor c = gimmeNewCursor();
try {
    useCursor(c);
    cursorMightThrowException(c);
    if (checkSomething(c)) {
        return extractReturnValue(c);
    }
} catch (SomeSpecificException sse) {
    log(sse);
} finally {
    if (c != null) {
        c.close();
    }
}
 
Once the try block is entered, the finally block will *always* get executed upon exit of the try block. The one exception is if there is a System.exit call inside the try block, which immediately exits the program and makes everything moot anyway. The finally block will get executed on caught and uncaught exceptions, as well as normal returns.
 
If you are casting the resource to something, make sure that you do the cast inside the try block, like so:
 
// GOOD!
InputStream is = getInputStream();
try {
    FileInputStream fis = (FileInputStream)is;
    ...
} finally {
    ...
}
 
rather than doing this:
 
// BAD!
FileInputStream fis = (FileInputStream)getInputStream();
try {
    ...
} finally {
    ...
}
 
This is so that in case of ClassCastExceptions you don't get a dangling open resource left behind.

Latest revision as of 20:49, 12 August 2013

This page has been consolidated into Mobile/Fennec/Android#Coding_Style.

Retrieved from "https://wiki.mozilla.org/index.php?title=Fennec/NativeUI/CodingStyle&oldid=693552"