深入理解ButterKnife源码并掌握原理（二）
2016-09-10 本文已影响472人
后厂村追寻
好，我们接着parseBindView的步骤3 ，忘记了在哪里了，咦。
不知所措
可以看下上一篇，哈哈。
步骤3
BindingClass bindingClass = targetClassMap.get(enclosingElement);
if (bindingClass != null) {
ViewBindings viewBindings = bindingClass.getViewBinding(getId(id));
if (viewBindings != null && viewBindings.getFieldBinding() != null) {
FieldViewBinding existingBinding = viewBindings.getFieldBinding();
error(element, "Attempt to use @%s for an already bound ID %d on '%s'. (%s.%s)",
BindView.class.getSimpleName(), id, existingBinding.getName(),
enclosingElement.getQualifiedName(), element.getSimpleName());
return;
}
} else {
bindingClass = getOrCreateTargetClass(targetClassMap, enclosingElement);
}
如果map（缓存）中已经有了就直接到到这个BindingClass实例。BindingClass这个我们后面还会再说。
1.如果不为空，则根据id获取保存在bindingClass中的ViewBindings实例，
如果viewBindings不为空且viewBindings.getFieldBinding不为空则抛出异常，什么意思呢？就是说一个id不能bind多次。
2.如果为空，则bindingClass = getOrCreateTargetClass(targetClassMap, enclosingElement);
获取并返回，参数是最初的那个map和父节点。
private BindingClass getOrCreateTargetClass(Map<TypeElement, BindingClass> targetClassMap,
TypeElement enclosingElement) {
BindingClass bindingClass = targetClassMap.get(enclosingElement);
//再次判断
if (bindingClass == null) {
//获取父节点的类型名字，这个不用太关系
TypeName targetType = TypeName.get(enclosingElement.asType());
if (targetType instanceof ParameterizedTypeName) {
targetType = ((ParameterizedTypeName) targetType).rawType;
}
//获取该enclosingElement就是父节点所在的包名称
String packageName = getPackageName(enclosingElement);
//类名字
String className = getClassName(enclosingElement, packageName);
//根据包名称和类名称获取bindingClassName实体
//并且加入了_ViewBinding 哈哈，有点意思是了。不是吗？？
ClassName bindingClassName = ClassName.get(packageName, className + "_ViewBinding");
//是否是final 类
boolean isFinal = enclosingElement.getModifiers().contains(Modifier.FINAL);
//创建了一个BindingClass实例
bindingClass = new BindingClass(targetType, bindingClassName, isFinal);
//加入集合，缓存
targetClassMap.put(enclosingElement, bindingClass);
}
return bindingClass;
}
到此我们的parseBindView的步骤3就完了。
步骤4：parseBindView步骤4
//@BindView(R.id.word)
// TextView word;
//name就是word
String name = element.getSimpleName().toString();
//类型的名字
TypeName type = TypeName.get(elementType);
//是否要求可为空
boolean required = isFieldRequired(element);
//生成FieldViewBinding实体
FieldViewBinding binding = new FieldViewBinding(name, type, required);
步骤5.
添加到bindingClass中的成员变量的实体的集合中，方便生成java源文件也就是xxxxx_ViewBinding文件的成员变量的初始化存在
bindingClass.addField(getId(id), binding);
其它的注解都是一样的。至此查找并解析成员变量的流程就完了。
接下来是处理控件事件的监听的流程。
注解事件源码流程分析（OnClick，OnItemClick等）
我们回到findAndParseTargets方法。
//... 省略成员变量的注解
// Process each annotation that corresponds to a listener.
//处理方法的比如一些OnClick，OnItemClick等
for (Class<? extends Annotation> listener : LISTENERS) {
findAndParseListener(env, listener, targetClassMap, erasedTargetNames);
}
// Try to find a parent binder for each.
for (Map.Entry<TypeElement, BindingClass> entry : targetClassMap.entrySet()) {
TypeElement parentType = findParentType(entry.getKey(), erasedTargetNames);
if (parentType != null) {
BindingClass bindingClass = entry.getValue();
BindingClass parentBindingClass = targetClassMap.get(parentType);
bindingClass.setParent(parentBindingClass);
}
}
return targetClassMap;
}
处理注解事件同样也分为查找和解析2个大步骤。
LISTENERS是butterknife支持的注解集合
private static final List<Class<? extends Annotation>> LISTENERS = Arrays.asList(//
OnCheckedChanged.class, //
OnClick.class, //
OnEditorAction.class, //
OnFocusChange.class, //
OnItemClick.class, //
OnItemLongClick.class, //
OnItemSelected.class, //
OnLongClick.class, //
OnPageChange.class, //
OnTextChanged.class, //
OnTouch.class //
);
private void findAndParseListener(RoundEnvironment env,
Class<? extends Annotation> annotationClass, Map<TypeElement, BindingClass> targetClassMap,
Set<TypeElement> erasedTargetNames) {
for (Element element : env.getElementsAnnotatedWith(annotationClass)) {
//检查合法性问题
if (!SuperficialValidation.validateElement(element)) continue;
try {
//解析注解
parseListenerAnnotation(annotationClass, element, targetClassMap, erasedTargetNames);
} catch (Exception e) {
StringWriter stackTrace = new StringWriter();
e.printStackTrace(new PrintWriter(stackTrace));
error(element, "Unable to generate view binder for @%s.\n\n%s",
annotationClass.getSimpleName(), stackTrace.toString());
}
}
}
我们看一下parseListenerAnnotation方法，传入了注解类annotationClass，该节点element，最初的那个集合targetClassMap。
比较长，我在方法里注释效果会比较好，哈哈
private void parseListenerAnnotation(Class<? extends Annotation> annotationClass, Element element,
Map<TypeElement, BindingClass> targetClassMap, Set<TypeElement> erasedTargetNames)
throws Exception {
// This should be guarded by the annotation's @Target but it's worth a check for safe casting.
//必需是方法类型的，节点元素为ExecutableElement
if (!(element instanceof ExecutableElement) || element.getKind() != METHOD) {
throw new IllegalStateException(
String.format("@%s annotation must be on a method.", annotationClass.getSimpleName()));
}
//方法对应的是ExecutableElement，前文我们已经简单的说明了一下
ExecutableElement executableElement = (ExecutableElement) element;
//获取父节点
TypeElement enclosingElement = (TypeElement) element.getEnclosingElement();
// Assemble information on the method.
// 获取注解信息
Annotation annotation = element.getAnnotation(annotationClass);
//该注解value方法，每一个注解都有（butterknife提供的都是数组）
//为什么是数组？因为支持下面这种
@OnClick(｛R.id.hello，R.id.hello2｝)
void sayHello() {
｝
//反射注解方法value
Method annotationValue = annotationClass.getDeclaredMethod("value");
//不是数组抛出异常
if (annotationValue.getReturnType() != int[].class) {
throw new IllegalStateException(
String.format("@%s annotation value() type not int[].", annotationClass));
}
//反射调用
int[] ids = (int[]) annotationValue.invoke(annotation);
//方法名字
String name = executableElement.getSimpleName().toString();
boolean required = isListenerRequired(executableElement);
// Verify that the method and its containing class are accessible via generated code.
//检查方法的修饰符，和成员变量一样，这里就不写了，嘻嘻
boolean hasError = isInaccessibleViaGeneratedCode(annotationClass, "methods", element);
hasError |= isBindingInWrongPackage(annotationClass, element);
//一个注解的方法不能有形同的id，or抛出异常
Integer duplicateId = findDuplicate(ids);
if (duplicateId != null) {
error(element, "@%s annotation for method contains duplicate ID %d. (%s.%s)",
annotationClass.getSimpleName(), duplicateId, enclosingElement.getQualifiedName(),
element.getSimpleName());
hasError = true;
}
//获取该注解ListenerClass.class注解，什么意思呢？就是
//butterknife提供的方法注解 包含了另外一个注解
//可以跳过代码看下面的文字说明。
ListenerClass listener = annotationClass.getAnnotation(ListenerClass.class);
if (listener == null) {
throw new IllegalStateException(
String.format("No @%s defined on @%s.", ListenerClass.class.getSimpleName(),
annotationClass.getSimpleName()));
}
//检查id的合法性，里面有个Optional注解
for (int id : ids) {
//id 为 -1 ，不合法
if (id == NO_ID.value) {
if (ids.length == 1) {
//一个参数情况，且方法的参数适用了Optional注解，则抛出异常
if (!required) {
error(element, "ID-free binding must not be annotated with @Optional. (%s.%s)",
enclosingElement.getQualifiedName(), element.getSimpleName());
hasError = true;
}
} else {
error(element, "@%s annotation contains invalid ID %d. (%s.%s)",
annotationClass.getSimpleName(), id, enclosingElement.getQualifiedName(),
element.getSimpleName());
hasError = true;
}
}
}
／／获取实现的方法
ListenerMethod method;
ListenerMethod[] methods = listener.method();
// methods就是OnItemClick 注解的ListenerClass注解的初始化值，
比如下面这种，肯定是个
// method = @ListenerMethod(
// name = "onItemClick",
// parameters = {
// "android.widget.AdapterView<?>",
// "android.view.View",
// "int",
// "long"
// }
// )
if (methods.length > 1) {
//抛异常，不可能走到这因为butterknife提供的都是1个默认的，能骗到我，我可是上过小学的人，哈哈
throw new IllegalStateException(String.format("Multiple listener methods specified on @%s.",
annotationClass.getSimpleName()));
} else if (methods.length == 1) {
//如果有method属性值即这种onItemClick，则callbacks必须为空，也就是2者不能同时使用
if (listener.callbacks() != ListenerClass.NONE.class) {
throw new IllegalStateException(
String.format("Both method() and callback() defined on @%s.",
annotationClass.getSimpleName()));
}
method = methods[0];
} else {
// 否则使用callback
//反射ListenerClass注解中的callback方法
Method annotationCallback = annotationClass.getDeclaredMethod("callback");
Enum<?> callback = (Enum<?>) annotationCallback.invoke(annotation);
Field callbackField = callback.getDeclaringClass().getField(callback.name());
method = callbackField.getAnnotation(ListenerMethod.class);
//如果没有ListenerMethod.class注解 抛出异常，也就是说你使用了callback，则必须提供ListenerMethod.class注解
if (method == null) {
throw new IllegalStateException(
String.format("No @%s defined on @%s's %s.%s.", ListenerMethod.class.getSimpleName(),
annotationClass.getSimpleName(), callback.getDeclaringClass().getSimpleName(),
callback.name()));
}
}
//检查方法的合法性，就是你使用的注解的方法的参数不能butterknife的参数的个数（也就是android系统的那种）
// Verify that the method has equal to or less than the number of parameters as the listener.
List<? extends VariableElement> methodParameters = executableElement.getParameters();
if (methodParameters.size() > method.parameters().length) {
error(element, "@%s methods can have at most %s parameter(s). (%s.%s)",
annotationClass.getSimpleName(), method.parameters().length,
enclosingElement.getQualifiedName(), element.getSimpleName());
hasError = true;
}
//检查返回值，就是你使用的注解的方法的参数不能butterknife的参数的个数（也就是android系统的那种）
// Verify method return type matches the listener.
TypeMirror returnType = executableElement.getReturnType();
if (returnType instanceof TypeVariable) {
TypeVariable typeVariable = (TypeVariable) returnType;
returnType = typeVariable.getUpperBound();
}
if (!returnType.toString().equals(method.returnType())) {
error(element, "@%s methods must have a '%s' return type. (%s.%s)",
annotationClass.getSimpleName(), method.returnType(),
enclosingElement.getQualifiedName(), element.getSimpleName());
hasError = true;
}
if (hasError) {
return;
}
//下面是方法参数的检查，不做分析了，太细了。记住一点就行了，你写的不和系统的实现方法一样就抛出异常
Parameter[] parameters = Parameter.NONE;
if (!methodParameters.isEmpty()) {
parameters = new Parameter[methodParameters.size()];
BitSet methodParameterUsed = new BitSet(methodParameters.size());
String[] parameterTypes = method.parameters();
for (int i = 0; i < methodParameters.size(); i++) {
VariableElement methodParameter = methodParameters.get(i);
TypeMirror methodParameterType = methodParameter.asType();
if (methodParameterType instanceof TypeVariable) {
TypeVariable typeVariable = (TypeVariable) methodParameterType;
methodParameterType = typeVariable.getUpperBound();
}
for (int j = 0; j < parameterTypes.length; j++) {
if (methodParameterUsed.get(j)) {
continue;
}
if (isSubtypeOfType(methodParameterType, parameterTypes[j])
|| isInterface(methodParameterType)) {
parameters[i] = new Parameter(j, TypeName.get(methodParameterType));
methodParameterUsed.set(j);
break;
}
}
if (parameters[i] == null) {
StringBuilder builder = new StringBuilder();
builder.append("Unable to match @")
.append(annotationClass.getSimpleName())
.append(" method arguments. (")
.append(enclosingElement.getQualifiedName())
.append('.')
.append(element.getSimpleName())
.append(')');
for (int j = 0; j < parameters.length; j++) {
Parameter parameter = parameters[j];
builder.append("\n\n Parameter #")
.append(j + 1)
.append(": ")
.append(methodParameters.get(j).asType().toString())
.append("\n ");
if (parameter == null) {
builder.append("did not match any listener parameters");
} else {
builder.append("matched listener parameter #")
.append(parameter.getListenerPosition() + 1)
.append(": ")
.append(parameter.getType());
}
}
builder.append("\n\nMethods may have up to ")
.append(method.parameters().length)
.append(" parameter(s):\n");
for (String parameterType : method.parameters()) {
builder.append("\n ").append(parameterType);
}
builder.append(
"\n\nThese may be listed in any order but will be searched for from top to bottom.");
error(executableElement, builder.toString());
return;
}
}
}
//最后构造MethodViewBinding实体，形成方法的实体
MethodViewBinding binding = new MethodViewBinding(name, Arrays.asList(parameters), required);
//构造BindingClass
BindingClass bindingClass = getOrCreateTargetClass(targetClassMap, enclosingElement);
for (int id : ids) {
//将生成的方法加入到bindingClass的方法集合中，一切都是为了生存java代码而准备。
if (!bindingClass.addMethod(getId(id), listener, method, binding)) {
error(element, "Multiple listener methods with return value specified for ID %d. (%s.%s)",
id, enclosingElement.getQualifiedName(), element.getSimpleName());
return;
}
}
// Add the type-erased version to the valid binding targets set.
erasedTargetNames.add(enclosingElement);
}
ListenerClass／ListenerMethod 注解说明
@Target(METHOD)
@Retention(CLASS)
@ListenerClass(
targetType = "android.widget.AdapterView<?>",
setter = "setOnItemClickListener",
type = "android.widget.AdapterView.OnItemClickListener",
method = @ListenerMethod(
name = "onItemClick",
parameters = {
"android.widget.AdapterView<?>",
"android.view.View",
"int",
"long"
}
)
)
public @interface OnItemClick {
/** View IDs to which the method will be bound. */
@IdRes int[] value() default { View.NO_ID };
}
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
@Retention(RUNTIME) @Target(ANNOTATION_TYPE)
public @interface ListenerClass {
String targetType();
/** Name of the setter method on the {@linkplain #targetType() target type} for the listener. */
String setter();
/**
* Name of the method on the {@linkplain #targetType() target type} to remove the listener. If
* empty {@link #setter()} will be used by default.
*/
String remover() default "";
/** Fully-qualified class name of the listener type. */
String type();
/** Enum which declares the listener callback methods. Mutually exclusive to {@link #method()}. */
Class<? extends Enum<?>> callbacks() default NONE.class;
/**
* Method data for single-method listener callbacks. Mutually exclusive with {@link #callbacks()}
* and an error to specify more than one value.
*/
ListenerMethod[] method() default { };
/** Default value for {@link #callbacks()}. */
enum NONE { }
}
package butterknife.internal;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
@Retention(RUNTIME) @Target(FIELD)
public @interface ListenerMethod {
/** Name of the listener method for which this annotation applies. */
String name();
/** List of method parameters. If the type is not a primitive it must be fully-qualified. */
String[] parameters() default { };
/** Primitive or fully-qualified return type of the listener method. May also be {@code void}. */
String returnType() default "void";
/** If {@link #returnType()} is not {@code void} this value is returned when no binding exists. */
String defaultReturn() default "null";
}
可以把这3个整体来看。ListenerMethod 这个注解包含了方法的返回值，名字，参数，是实现的那些方法；ListenerClass是set的那些方法属性，包含setter等，我们看到了OnItemClick设置的值就是我们平常写的那种，嘻嘻。
至此，我们的findAndParseTargets方法算是走完了。里面有很多细节。
为什么要分析有关细节呢？可以学习下大神的方法和理解有关处理的细节啊，哈哈。
深入理解ButterKnife源码并掌握原理（三)
