EventBus源码阅读（17）-EventBusBuilder

我们看到 EventBus，EventBusBuilder，从名字就可以猜到这是建造者模式了。

代码都比较多，还好我们已经把外围的困难都扫平了（异常处理在此先忽略，不影响我们理解，最后的时候在阅读相关代码）

我们先看EventBusBuilder

源码：

/* * Copyright (C) 2012-2016 Markus Junginger, greenrobot (http://greenrobot.org) * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package org.greenrobot.eventbus;import org.greenrobot.eventbus.meta.SubscriberInfoIndex;import java.util.ArrayList;import java.util.List;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * Creates EventBus instances with custom parameters and also allows to install a custom default EventBus instance. * Create a new builder using {@link EventBus#builder()}. */public class EventBusBuilder {    private final static ExecutorService DEFAULT_EXECUTOR_SERVICE = Executors.newCachedThreadPool();//这个就是我们的线程池了，异步任务，后台任务就要靠它来执行了。    boolean logSubscriberExceptions = true;//订阅者异常日志    boolean logNoSubscriberMessages = true;//不要订阅者消息日志    boolean sendSubscriberExceptionEvent = true;//是否发送订阅者异常    boolean sendNoSubscriberEvent = true;//是否发送无订阅者异常    boolean throwSubscriberException;//是否抛出订阅者异常    boolean eventInheritance = true;//是否继承事件    boolean ignoreGeneratedIndex;//是否忽略生成的索引    boolean strictMethodVerification;//是否严格执行方法验证    ExecutorService executorService = DEFAULT_EXECUTOR_SERVICE;//默认线程池    List<Class<?>> skipMethodVerificationForClasses;//需要跳过执行方法验证的类    List<SubscriberInfoIndex> subscriberInfoIndexes;//订阅者信息索引    EventBusBuilder() {    }    /** Default: true */    public EventBusBuilder logSubscriberExceptions(boolean logSubscriberExceptions) {        this.logSubscriberExceptions = logSubscriberExceptions;        return this;    }    /** Default: true */    public EventBusBuilder logNoSubscriberMessages(boolean logNoSubscriberMessages) {        this.logNoSubscriberMessages = logNoSubscriberMessages;        return this;    }    /** Default: true */    public EventBusBuilder sendSubscriberExceptionEvent(boolean sendSubscriberExceptionEvent) {        this.sendSubscriberExceptionEvent = sendSubscriberExceptionEvent;        return this;    }    /** Default: true */    public EventBusBuilder sendNoSubscriberEvent(boolean sendNoSubscriberEvent) {        this.sendNoSubscriberEvent = sendNoSubscriberEvent;        return this;    }    /**     * Fails if an subscriber throws an exception (default: false).     * <p/>     * Tip: Use this with BuildConfig.DEBUG to let the app crash in DEBUG mode (only). This way, you won't miss     * exceptions during development.     */    public EventBusBuilder throwSubscriberException(boolean throwSubscriberException) {        this.throwSubscriberException = throwSubscriberException;        return this;    }    /**     * By default, EventBus considers the event class hierarchy (subscribers to super classes will be notified).     * Switching this feature off will improve posting of events. For simple event classes extending Object directly,     * we measured a speed up of 20% for event posting. For more complex event hierarchies, the speed up should be     * >20%.     * <p/>     * However, keep in mind that event posting usually consumes just a small proportion of CPU time inside an app,     * unless it is posting at high rates, e.g. hundreds/thousands of events per second.     */    public EventBusBuilder eventInheritance(boolean eventInheritance) {        this.eventInheritance = eventInheritance;        return this;    }    /**     * Provide a custom thread pool to EventBus used for async and background event delivery. This is an advanced     * setting to that can break things: ensure the given ExecutorService won't get stuck to avoid undefined behavior.     */    public EventBusBuilder executorService(ExecutorService executorService) {        this.executorService = executorService;        return this;    }    /**     * Method name verification is done for methods starting with onEvent to avoid typos; using this method you can     * exclude subscriber classes from this check. Also disables checks for method modifiers (public, not static nor     * abstract).     */    public EventBusBuilder skipMethodVerificationFor(Class<?> clazz) {        if (skipMethodVerificationForClasses == null) {            skipMethodVerificationForClasses = new ArrayList<>();        }        skipMethodVerificationForClasses.add(clazz);        return this;    }    /** Forces the use of reflection even if there's a generated index (default: false). */    public EventBusBuilder ignoreGeneratedIndex(boolean ignoreGeneratedIndex) {        this.ignoreGeneratedIndex = ignoreGeneratedIndex;        return this;    }    /** Enables strict method verification (default: false). */    public EventBusBuilder strictMethodVerification(boolean strictMethodVerification) {        this.strictMethodVerification = strictMethodVerification;        return this;    }    /** Adds an index generated by EventBus' annotation preprocessor. */    public EventBusBuilder addIndex(SubscriberInfoIndex index) {        if(subscriberInfoIndexes == null) {            subscriberInfoIndexes = new ArrayList<>();        }        subscriberInfoIndexes.add(index);        return this;    }    /**     * Installs the default EventBus returned by {@link EventBus#getDefault()} using this builders' values. Must be     * done only once before the first usage of the default EventBus.     *     * @throws EventBusException if there's already a default EventBus instance in place     */    public EventBus installDefaultEventBus() {        synchronized (EventBus.class) {            if (EventBus.defaultInstance != null) {                throw new EventBusException("Default instance already exists." +                        " It may be only set once before it's used the first time to ensure consistent behavior.");            }            EventBus.defaultInstance = build();            return EventBus.defaultInstance;        }    }    /** Builds an EventBus based on the current configuration. */    public EventBus build() {        return new EventBus(this);    }}

这个真么什么好说的了，看一遍，理解理解字面意思，知道有什么就行了