Achieve goals:
- Automatic ID binding via @bindView ()
- Click events are automatically bound with @onclick ()
ButterKnife simple principle analysis:
- Get the ID and type of the control via @bindView () and @onclick () annotations
- Once you get the control ID, a Java file named XXActivity_ViewBinding is automatically generated
- While generating the XXActivity_ViewBinding Java file (class file), declare a bind(Activity target) method and write the following statement: Target. TextView = (WidgetType) fb (viewId), fb (viewId). SetOnClickListener ()
- Pass in an Activity instance through butterknife. bind(Activity Activity) and execute the statement in Step 4
Step analysis
Through the above analysis, we can define the following minimalist steps:
- Declare two annotations @bindView (), @onclick ()
- Implementing annotation handlers
- Execute the methods in the class file generated by the annotation handler
Began to lu code
Code preparation, environment configuration
- Create two new modules, called Annotations and Annotation_compiler, for processing annotations.
- Module-annptation_compiler build. Gradle add dependency packages to compileOnly (AS3.4.1)
annotationProcessor 'com. Google. Auto. Services: auto - service: 1.0 rc4'
compileOnly 'com. Google. Auto. Services: auto - service: 1.0 rc4'
Copy the codeConveniently under the Sync
- Module dependencies Main Module (APP) dependencies
implementation project(path: ':annotations')
annotationProcessor project(path: ':annotation_compiler')
Copy the codeAnnotation_compiler module relies on
implementation project(path: ':annotations')
Copy the codeThat’s the end of the preparations
Project directory
Look at the structure first and then look at the code
Implement Step 1- Declare annotations
Create two new annotation classes in the Annotation Module
Remark:
- Notice the @ notation before the interface keyword
- METHOD – annotation on methods, ElementType.FIELD – annotation on member variables)
- @rentention: is to clarify when the annotation is in effect (eg: RetentionPolicy.SOURCE – SOURCE period, retentionPolicy. RUNTIME – RUNTIME)
- Default The default value is -1= view. NoId
Implement Step 2- annotation processing
So let’s get our thoughts straight here
Each Activity class with the @bindView / @onclick annotation declaration generates an XXActivity_ViewBinding class and declares a bind(Activity target) method in the class. This method can receive different Activity objects;
- Declare an interface class
Due to each automatically generatedXXActivity_ViewBindingEach class has onebind(Activity target)Method, so we abstract an interface out and finally letXXActivity_ViewBindingClass implements the interface and uses generics to ensure that every method that implements the interface receives itDifferent Activity objects 在 module(app)Let’s go ahead and create a new oneBinder interfaceHere:TWill be used toPassing an Activity object, so that we can be inbind()Methodfb(),setOnClcikListner()
- Create annotation handling classes
The functionality of the annotation handling class is really the a. that does the annotation processing and creates the Java class files we need. Create a new AnnotationComPiler class under module(annotation_compiler)
@AutoService(Processor.class) // Register the annotation handler, which uses the AutoService library that the environment configuration relies on
public class AnnotationCompiler extends AbstractProcessor {}
Copy the codeB. Declare the Filer object. Note that the Filer object and the Writer object can create a file with content
// Declare file objects (member variables)
private Filer filer;
@Override
public synchronized void init(ProcessingEnvironment processingEnvironment) {
super.init(processingEnvironment);
// Don't ask
filer = processingEnvironment.getFiler();
}
Copy the codeC. rewrite getSupportedAnnotationTypes (), screening of our target annotation
/** * specifies the annotation handler to process */
@Override
public Set<String> getSupportedAnnotationTypes(a) {
Set<String> types = new HashSet<>();
//getCanonicalName() gets the package name + class name
types.add(BindView.class.getCanonicalName());
types.add(OnClick.class.getCanonicalName());
return types;
}
Copy the codeD. rewrite getSupportedSourceVersion (), statement of support we can use the default Java version here
/** * Specifies the Java version supported by the annotation processor */
@Override
public SourceVersion getSupportedSourceVersion(a) {
//processingEnv this is the parent variable
return processingEnv.getSourceVersion();
}
Copy the codeD. Rewrite process() to generate the XXActivity_ViewBinding class file
// Declare the package path
package com.junt.annotationdemo;
// Declare the import of Binder because the Binder interface is implemented
import com.junt.annotationdemo.Binder;
// Click events need to instantiate the view.onClickListener () interface, so declare the import View package
import android.view.View;
public class MainActivity_ViewBinding implements Binder<com.junt.annotationdemo.MainActivity>{
@Override
public void bind(final com.junt.annotationdemo.MainActivity target) {
// First, for the @bindView and @onclick controls, we should need the following when generating code
//textView- we need to get the name of the control,
//(Android.widget.textView)- We also need to know the type of the control
//2131165319- Control Id
target.textView=(android.widget.TextView)target.findViewById(2131165319);
target.textView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
try {
target.onClick(view);
} catch(Exception e) { e.printStackTrace(); }}});// Second, for a control that only uses @onclick, only an Id is required
target.findViewById(2131165320).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
try {
target.onClick(view);
} catch(Exception e) { e.printStackTrace(); }}}); }}Copy the codeWriting code in the generated Java class file says for example we need to write
package com.junt.annotationdemo;
Copy the codeYou just call
writer.write("package com.junt.annotationdemo; \n")
Copy the codeAll process code
*/ @override public Boolean process(Set<? extends TypeElement>set, RoundEnvironment RoundEnvironment) {// Get all elements using @bindView Set<? extends Element> elementsAnnotatedWith = roundEnvironment.getElementsAnnotatedWith(BindView.class); // Classify nodes according to the Activity they are in (an Activity can have multiple @bindbiew), Map<String, List<VariableElement>> mapBindView = new HashMap<>();for(Element Element: elementsAnnotatedWith) {// Get control Element VariableElement VariableElement = (VariableElement) Element; // Get the parent element of the control element Name (Activity or fragment) String activityName = variableElement.getEnclosingElement().getSimpleName().toString(); List<VariableElement> variableElements = mapBindView.get(activityName);if(variableElements == null) { variableElements = new ArrayList<>(); mapBindView.put(activityName, variableElements); } variableElements.add(variableElement); } // get all nodes that use @onclick Set<? extends Element> elementsAnnotatedWithClick=roundEnvironment.getElementsAnnotatedWith(OnClick.class); Map<String, Element> mapClickView = new HashMap<>();for(Element element : elementsAnnotatedWithClick) { String activityName = element.getEnclosingElement().getSimpleName().toString(); mapClickView.put(activityName, element); } // start creating XXActivity_ViewBinding. Writer = null; // Write a xxActivity_ViewBinding each time through the For loopfor(String activityName : Mapbindview.keyset ()) {// Fetch the annotated control elements under activityName List<VariableElement> variableElements = mapBindView.get(activityName); // Get the package name of the activity. (All elements under the same activity have parent elements of that activity, so just pick one of them. Element enclosingElement = variableElements.get(0).getenClosingElement (); String packageName = processingEnv.getElementUtils().getPackageOf(enclosingElement).toString(); Try {// instantiate a JavaFileObject (we're writing.java files -- class files) JavaFileObjectsourceFile = filer.createSourceFile(
packageName + "." + activityName + "_ViewBinding"); // Instantiate the writer object to write the code writer = to a. Java filesourceFile.openWriter(); //1. Write - writer.write("package " + packageName + "; \n");
writer.write("import " + packageName + ".Binder; \n");
writer.write("import android.view.View; \n"); //2. Write - declare class and implement interface code writer.write("public class " + activityName + "_ViewBinding implements Binder<"
+ packageName + "." + activityName + ">{\n"); //3. Write - implement interface method code writer.write(" @Override\n" +
" public void bind(final " + packageName + "." + activityName + " target) {\n"); Element clickVariableElement = mapClickView.get(activityName); int[] clickIds = clickVariableElement.getAnnotation(OnClick.class).value(); List<Integer> id = new ArrayList<>(clickIds.length); //4. Write - all controls findViewById codefor(VariableElement variableElement : VariableElements) {/ / access controls the Name String variableName = variableElement. GetSimpleName (), toString (); / / access controls ID int variableId = variableElement. GetAnnotation (BindView. Class). The value (); // Get control Type TypeMirrortypeMirror = variableElement.asType(); // writeFindViewById writeFindViewById(writer, variableName,typeMirror, variableId); // See if the control element has an @onclick annotation, if so, write it at the same timesetOnClickListener
if(contains(clickIds, variableId)) {// All control ids that set the click event id.add(variableId); writeSetOnClickListener(writer, packageName, activityName, variableName); }}for(int clickId: clickIds) {// If the clickId is not present in the id collection, the space needs to set the click event, but has not set the click event yetif(! id.contains(clickId)) { writeSetOnClickListenerWithoutName(writer, packageName, activityName, clickId); }} //5. Write writer.write()" \n }\n}\n"); } catch (Exception e) { e.printStackTrace(); } finally {// This Activity has its Id bound to the click event, so remove mapClickView.remove(activityName);if(writer ! = null) { try { writer.close(); writer = null; } catch (Exception e) { e.printStackTrace(); }}}} // Handle the @onclick binding only. The above step only handles all activities that contain @bindView (click events are also handled and removed from mapClickView).if (mapClickView.size() <= 0) {
return false;
}
for (String activityName : mapClickView.keySet()) {
Element element = mapClickView.get(activityName);
String packageName = processingEnv.getElementUtils().getPackageOf(element.getEnclosingElement()).toString();
try {
JavaFileObject sourceFile = filer.createSourceFile(
packageName + "." + activityName + "_ViewBinding");
writer = sourceFile.openWriter(); //1. Write - writer.write("package " + packageName + "; \n");
writer.write("import " + packageName + ".Binder; \n");
writer.write("import android.view.View; \n"); //2. Write - declare class and implement interface code writer.write("public class " + activityName + "_ViewBinding implements Binder<"
+ packageName + "." + activityName + ">{\n"); //3. Write - implement interface method code writer.write(" @Override\n" +
" public void bind(final " + packageName + "." + activityName + " target) {\n"); Int [] clickViewIds = element.getannotation (onclick.class).value(); int[] clickViewIds = element.getannotation (onclick.class).value(); //4. Write the -setonClickListener codefor(int clickViewId : clickViewIds) { writeSetOnClickListenerWithoutName(writer, packageName, activityName, clickViewId); } //5. Complete class writer.write(" \n }\n}\n");
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if(writer! =null){ writer.close(); writer = null; } } catch (IOException e) { e.printStackTrace(); }}}return false; } /** * Write findViewById code * @param writer writer * @param variableName control name * @paramtypeMirror control type * @param variableId Control Id * @throws IOException Write exception */ private void writeFindViewById(Writer Writer, String variableName, TypeMirrortypeMirror, int variableId) throws IOException {
writer.write(" target." + variableName + "=" + typeMirror + ")target.findViewById(" + variableId + "); \n"); @param writer writer @param variableName Control name * @throws IOException Write exception */ private void writeSetOnClickListener(Writer writer, String packageName, String className, String variableName) throws IOException { writer.write(" target." + variableName + ".setOnClickListener(new View.OnClickListener() {\n" +
" @Override\n" +
" public void onClick(View view) {\n" +
" try {\n" +
" target.onClick(view); \n" +
" } catch (Exception e) {\n" +
" e.printStackTrace(); \n" +
" }\n" +
" }\n" +
"}); \n"); @param writer writer @param viewId control Id * @throws IOException Write exception */ private void writeSetOnClickListenerWithoutName(Writer writer, String packageName, String className, int viewId) throws IOException { writer.write(" target.findViewById(" + viewId + ")" + ".setOnClickListener(new View.OnClickListener() {\n" +
" @Override\n" +
" public void onClick(View view) {\n" +
" try {\n" +
" target.onClick(view); \n" +
" } catch (Exception e) {\n" +
" e.printStackTrace(); \n" +
" }\n" +
" }\n" +
"}); \n"); } /** * check whether the array contains a value * Is @bindView * @param arr the Id of all the @onclick controls in an Activity * @param arg The @bindView control Id * @ is set under an Activityreturn true/false
*/
private boolean contains(int[] arr, int arg) {
boolean isContain = false;
if (arr.length == 0) {
isContain = false;
} else {
for (int i : arr) {
if (i == arg) {
isContain = true;
break; }}}return isContain;
}
Copy the codeImplement Step 3- execute the onBind() method in XXActivity_ViewBinding
Module (app) creates a new ButterKnife class
Used in an Activity
