Add checkstyle with a small config

It doesn't include all of the Android style checks as found in Android Studio,
but it's a start.

Bump Gradle to 2.7 because the checkstyle plugin in earlier versions is just
not good enough.

.gitlab-ci.yml

@@ -19,9 +19,9 @@ before_script:
   - echo " == Installing Android emulator images"
   - echo y | android -s update sdk --no-ui -a -t android-10
   - echo " == Installing Gradle"
-  - wget -q -O gradle.zip https://services.gradle.org/distributions/gradle-2.4-bin.zip
+  - wget -q -O gradle.zip https://services.gradle.org/distributions/gradle-2.7-bin.zip
   - unzip -q gradle.zip
-  - export PATH="$PWD/gradle-2.4/bin:$PATH"
+  - export PATH="$PWD/gradle-2.7/bin:$PATH"
 
 test:
   script:

F-Droid/build.gradle

@@ -1,5 +1,6 @@
 apply plugin: 'com.android.application'
 apply plugin: 'witness'
+apply plugin: 'checkstyle'
 if (!hasProperty('sourceDeps')) {
 
     repositories {
@@ -182,6 +183,14 @@ android {
     }
 
 }
+task checkstyle(type: Checkstyle) {
+    configFile file("${project.rootDir}/config/checkstyle/checkstyle.xml")
+    source 'src'
+    include '**/*.java'
+    exclude '**/gen/**'
+
+    classpath = files()
+}
 // This person took the example code below from another blogpost online, however
 // I lost the reference to it:
 // http://stackoverflow.com/questions/23297562/gradle-javadoc-and-android-documentation

build.gradle

@@ -7,3 +7,7 @@ buildscript {
         classpath files('libs/gradle-witness.jar')
     }
 }
+
+task wrapper(type: Wrapper) {
+    gradleVersion = '2.7'
+}

config/checkstyle/checkstyle.xml

@@ -0,0 +1,80 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE module PUBLIC
+    "-//Puppy Crawl//DTD Check Configuration 1.2//EN"
+    "http://www.puppycrawl.com/dtds/configuration_1_2.dtd">
+<module name="Checker">
+
+    <module name="FileTabCharacter" />
+
+    <module name="RegexpSingleline">
+        <property name="format" value="\s+$" />
+        <property name="minimum" value="0" />
+        <property name="maximum" value="0" />
+        <property name="message" value="Line has trailing spaces." />
+        <property name="severity" value="info" />
+    </module>
+
+    <module name="TreeWalker">
+
+        <!--<module name="ConstantName" />-->
+        <!--<module name="LocalFinalVariableName" />-->
+        <!--<module name="LocalVariableName" />-->
+        <!--<module name="MemberName" />-->
+        <!--<module name="MethodName" />-->
+        <module name="PackageName" />
+        <!--<module name="ParameterName" />-->
+        <!--<module name="StaticVariableName" />-->
+        <module name="TypeName" />
+
+        <module name="AvoidStarImport" />
+        <!--<module name="IllegalImport" />-->
+        <module name="RedundantImport" />
+        <module name="UnusedImports" />
+
+        <!--<module name="LineLength">-->
+        <!--<module name="MethodLength" />-->
+        <!--<module name="ParameterNumber" />-->
+
+        <module name="EmptyForIteratorPad" />
+        <module name="GenericWhitespace" />
+        <module name="MethodParamPad" />
+        <!--<module name="NoWhitespaceAfter" />-->
+        <!--<module name="NoWhitespaceBefore" />-->
+        <!--<module name="OperatorWrap" />-->
+        <module name="ParenPad" />
+        <module name="TypecastParenPad" />
+        <!--<module name="WhitespaceAfter" />-->
+        <!--<module name="WhitespaceAround" />-->
+
+        <!--<module name="ModifierOrder" />-->
+        <module name="RedundantModifier" />
+
+        <!--<module name="AvoidNestedBlocks" />-->
+        <!--<module name="EmptyBlock">
+            <property name="option" value="text" />
+        </module>-->
+        <!--<module name="LeftCurly" />-->
+        <!--<module name="NeedBraces" />-->
+        <!--<module name="RightCurly" />-->
+
+        <module name="EmptyStatement" />
+        <!--<module name="EqualsHashCode" />-->
+        <!--<module name="HiddenField" />-->
+        <module name="IllegalInstantiation" />
+        <!--<module name="InnerAssignment" />-->
+        <!--<module name="MagicNumber" />-->
+        <!--<module name="MissingSwitchDefault" />-->
+        <!--<module name="SimplifyBooleanExpression" />-->
+        <!--<module name="SimplifyBooleanReturn" />-->
+
+        <!--<module name="FinalClass" />-->
+        <!--<module name="HideUtilityClassConstructor" />-->
+        <!--<module name="InterfaceIsType" />-->
+        <!--<module name="VisibilityModifier" />-->
+
+        <module name="ArrayTypeStyle" />
+        <module name="UpperEll" />
+
+    </module>
+
+</module>