Android Code Templates: Custom Templates with FreeMarker

Custom Android
Code Templates
Paul Murphy
DROIDCON SPAIN 2012

Friday 7 December 12

Agenda
• What are Android Code Templates?
• Default ADT Templates
• Where are ADT Templates Located?
• Tools and Conﬁguration in Eclipse
• Template Directory Structure
• Template Files
• FreeMarker Template Language
• Demo - Animation Template

What are Android
Code Templates?


What are Android Code
Templates?
• A mechanism for generating boilerplate
Android code and assets from the input
of simple UI parameters.
• Intergrated with the Eclipse ADT Plugin
• Templates are written using
FreeMarker - a Java templating engine
• It is relatively lightweight - not a full
metadata driven code generation
solution like EMF

Code Generation Process

recipe.xml.ftl

UI Parameters
FreeMarker

MyActivity.java

MyActivity.java.ftl


Code Generation Process

recipe.xml.ftl

UI Parameters
FreeMarker
output directory

root
(source directory)


Default ADT
Templates


Default ADT Templates

Template Types:
1. Android Application Templates
2. Android Activity Templates
3. Android Object Templates


Android Application Template


Android Activity Template


Android Activity Template

Template Parameters


Android Object Template


Where are
ADT Templates
Located?


<android-sdk>/tools/templates


Application Templates


Activity Templates


Android Object
Templates


Custom Android
Code Template


Tools and
Conﬁguration


Tools and Conﬁg

• Eclipse
• FreeMarker IDE
• Create a location mapping in Eclipse to
• ADT Plugin Preview Releases


FreeMarker IDE

Key Features:
• Syntax Highlighting
• Template Structure Outline

• Developer:
JBoss Tools Sub Project


Install New Software..


Add Site

http://download.jboss.org/jbosstools/updates/development/juno


Conﬁguring Eclipse Workspace

• Create New Eclipse Project
• Set the Project Location to:


Eclipse | New Project...


New Project



tools/templates


Conﬁgured Environment


Template Directory
Structure


Template Directory

Template


template.xml

Template Metadata


root

Source Directory


recipe.xml.ftl

Recipe


globals.xml.ftl

Global Variables


app_package

app_package


FreeMarker Template Files

FreeMarker template


FreeMarker Template Files

FreeMarker templates


Template Files


template.xml

Metadata

UI Parameters

Global Values

Recipe to
Execute


template.xml

Metadata

UI Parameters

Global Values
globals.xml.ftl

Recipe to
Execute

recipe.xml.ftl


template.xml

<?xml version="1.0"?>

<template name="My Template"
description="description...">

<category value="UI Components"/>

<parameter
id="duration"
type="float"
name="Animation Duration"/>

<globals file="globals.xml.ftl" />

<execute file="recipe.xml.ftl" />

</template>


Category Element


<template name="My Template"
description="description...">

<category value="UI Components"/>

<parameter
id="duration"
type="float"
name="Animation Duration"/>

<globals file="globals.xml.ftl" />

<execute file="recipe.xml.ftl" />

</template>


Category Element

• Applications
<template name="MyTemplate">
<category value="Applications"/>
....
</template>


• Activities <category value="Activities"/>
...
</template>


• UI Component <category value="UI Component"/>
...
</template>


recipe.xml

<copy>

<instantiate>

<merge>


recipe.xml

<copy>

<instantiate>
root
output directory
(source directory)
<merge>


recipe.xml.ftl

<recipe>

<copy
from="res/anim/zoom.xml"
to="res/anim/zoom.xml" />

<instantiate
from="res/anim/zoom.xml.ftl"
to="res/anim/${filename}.xml" />

<merge
from="AndroidManifest.xml.ftl" />

<open
file="res/anim/${filename}.xml"/>

</recipe>


recipe.xml.ftl


<globals>
<#-- Animation Defaults -->
<global id="slow" value="500" />
<global id="fast" value="100" />
</globals>


Template Variable Dataflow

UI Parameters Global Values
globals.xml.ftl

Recipe Execution


FreeMarker
Template Language


FreeMarker Template Language
• It is a Java Template Language used
for over 10 years
• It is an example of a DSL for generating
text output of any kind
• It has a small subset of programming
language constructs
• Similar to: Velocity Template Language,
C Preprocessor, PHP, Django templates
• http://freemarker.org

Introduction to FreeMarker
Template Data

<manifest>
<activity name="{activityName}"> <global id="HomeActivity" value=
<manifest> "HomeActivity"/>

FreeMarker

Merge

<manifest>
<activity name="HomeActivity">
<manifest>

Output


FreeMarker “Markup”

• Interpolations
${duration}

• FTL Tags
<#if animationType == "zoom">

</#if>

• Comments
<#-- FreeMarker Comment -->


Interpolations

package ${packageName};

public class ${activityClass} extends Activity {
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.${layoutName});
}
}


Conditional Tags

• If Statement:

</#if>

• Else Statement:

<#else>

</#if>


http://freemarker.org/docs/index.html


Extra Template Functions
string slashedPackageName(string)
This function converts a full Java package name to its corresponding directory path.

For example, if the given argument is com.example.foo, the return value will be com/
example/foo.

<global id="srcOut" value="src/${slashedPackageName(packageName)}" />

string underscoreToCamelCase(string)
This function converts an underscore-delimited string, such as foo_bar, to its
corresponding camel-case string, such as FooBar.

string activityToLayout(string)

This function converts an activity class-like identifer string, such as FooActivity, to a
corresponding resource-friendly identiﬁer string, such as activity_foo.


Demo
Animation Template


Review


Ideas for Custom ADT?

• Custom SDK Templates
• Rapid Development Templates
• Templates enabling easy access to an
organisations visual assets colour
schemes etc...
• Generating the boiler plate code
required for Content Providers etc...


Questions?
Twitter: @murphonic


References

• Ofﬁcial FreeMarker Docs:
http://freemarker.org/docs/index.html
• Roman Nurik Android Template Article:
https://dl.dropbox.com/u/231329/
android/templatedocs/index.html


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