Retrofit2源码解析01-创建过程

青旅半醒 2023-10-17 16:44 60阅读 0赞

Retrofit通过建造者模式进行创建

Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl(url)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();

build方法主要进行了初始化赋值

public Retrofit build() {
        
          //...
          okhttp3.Call.Factory callFactory = this.callFactory;
          //如果callFactory为null，则赋值为OkHttpClient
          if (callFactory == null) {
        
            callFactory = new OkHttpClient();
          }
    
          Executor callbackExecutor = this.callbackExecutor;
          //如果callbackExecutor为null，赋值为相应平台默认的Excutor，用作回调回UI线程
          if (callbackExecutor == null) {
        
            callbackExecutor = platform.defaultCallbackExecutor();
          }
    
          //将Call对象转化的合适执行类的List，比如RxJavaCallAdapterFactory
          List<CallAdapter.Factory> adapterFactories = new ArrayList<>(this.adapterFactories);
          //根据不同平台 添加默认CallAdapterFactory
          adapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));
    
          //转化数据对象的List，比如GsonConverterFactory
          List<Converter.Factory> converterFactories = new ArrayList<>(this.converterFactories);
    
          //传入参数，创建Retroft对象
          return new Retrofit(callFactory, baseUrl, converterFactories, adapterFactories,
              callbackExecutor, validateEagerly);
        }

其中，这里的platform对象在Builder对象构造方法中初始化

public Builder() {
        
          this(Platform.get());
        }

来看`Platform.get()`，get方法想到于是一个工厂模式，而Platform显然是策略模式，根据不同的平台，执行不同的操作。

class Platform {
        
            private static final Platform PLATFORM = findPlatform();
            
            static Platform get() {
        
            return PLATFORM;
            }
            
            private static Platform findPlatform() {
        
                try {
        
                  Class.forName("android.os.Build");
                  //如果是Android平台
                  if (Build.VERSION.SDK_INT != 0) {
        
                    return new Android();
                  }
                } catch (ClassNotFoundException ignored) {
        
                }
                try {
        
                  //如果是Java平台
                  Class.forName("java.util.Optional");
                  return new Java8();
                } catch (ClassNotFoundException ignored) {
        
                }
                try {
        
                  //如果是IOS平台
                  Class.forName("org.robovm.apple.foundation.NSObject");
                  return new IOS();
                } catch (ClassNotFoundException ignored) {
        
                }
                return new Platform();
            }
        }