Droidcon madrid CFP

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1. ANDROID ANNOTATIONS UNDERSTANDING SURAJ SHIRVANKAR @h0lyalg0rithm
2. WHAT ARE ANNOTATIONS
3. Annotations, a form of metadata, provide data about a program that is not part of the program itself. Annotations have no direct effect on the operation of the code they annotate http://docs.oracle.com/javase/1.5.0/docs/guide/apt/mirror/overview-summary.html
4. Since annotations have no effect on the code.What the hell do I talk about
5. WHY USE ANNOTATIONS
6. REMOVE BOILERPLATE
7. TEXT ANNOTATIONS ALLOW THE DEVELOPER TO ▸ Information for the compiler — Annotations can be used by the compiler to detect errors or suppress warnings. ▸ Compile-time and deployment-time processing — Software tools can process annotation information to generate code, XML files, and so forth. ▸ Runtime processing — Some annotations are available to be examined at runtime. https://docs.oracle.com/javase/tutorial/java/annotations/
8. OUR FIRST ANNOTATIONS
9. Similar to @Deprecated @NotNull @Nullable ….. public @interface MyAnnotation {}
10. LETS GET META USE ANNOTATIONS TO DEFINE OUR ANNOTATIONS
11. @Retention(RetentionPolicy.CLASS) @Target(ElementType.TYPE) @interface MyAnnotation { String arg1(); int arg2 default 1; String[] arg3; }
12. WHATS AN ANNOTATION PROCESSOR?
13. Annotation Processing is a technique that hooks into the Java compile process. It allows to produce compiler errors and warnings and to generate source code and byte code.
14. EXTEND ABSTRACT PROCESSOR public class MyProcessor extends AbstractProcessor { @Override public synchronized void init(ProcessingEnvironment env){} @Override public boolean process(Set<? extends TypeElement> annoations, RoundEnvironment env) { } @Override public Set<String> getSupportedAnnotationTypes() { } @Override public SourceVersion getSupportedSourceVersion() { } }
15. REGISTERING YOUR PROCESSOR
16. ▸ Package your processor into Jar ▸ Create a file called javax.annotation.processing.Processor in the META-INF/services directory ▸ Write the fully qualified names of the processors in the javax.annotation.processing.Processor file. Steps
17. UNDERSTANDING THE PROCESSING ‣Elements ‣Types ‣Filer ‣Messager
18. JAVAPOET https://github.com/square/javapoet package com.example.helloworld; public final class HelloWorld { public static void main(String[] args) { System.out.println("Hello, JavaPoet!"); } }
19. Using JavaPoet MethodSpec main = MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC, Modifier.STATIC) .returns(void.class) .addParameter(String[].class, "args") .addStatement("$T.out.println($S)", System.class, "Hello, JavaPoet!") .build(); TypeSpec helloWorld = TypeSpec.classBuilder(“HelloWorld") .addModifiers(Modifier.PUBLIC, Modifier.FINAL) .addMethod(main) .build(); JavaFile javaFile = JavaFile.builder("com.example.hellowo rld", helloWorld).build(); javaFile.writeTo(System.out);
20. DEMO
21. EXAMPLES ‣ButterKnife ‣RetroFit ‣Dagger 2
22. @Theend