如何将SharedPreferences存储的token添加到OkHttp拦截器中

步骤1：创建全局Application类提供ApplicationContext #

因为SharedPreferences需要Context才能访问，使用Application级别的全局Context不会造成内存泄漏，是最稳妥的方案：

1. 新建自定义Application类：

public class MyApp extends Application {
    private static Context appContext;

    @Override
    public void onCreate() {
        super.onCreate();
        appContext = getApplicationContext();
    }

    // 对外提供全局Context
    public static Context getAppContext() {
        return appContext;
    }
}

2. 在AndroidManifest.xml的<application>标签中注册这个自定义Application：

<application
    android:name=".MyApp"
    <!-- 其余原有配置不变 -->
    >
    <!-- 四大组件配置 -->
</application>

步骤2：修改ApiClient拦截器逻辑，动态读取token #

直接在拦截器中通过全局Context读取SharedPreferences中存储的token即可：

public class ApiClient {

        private static Retrofit getRetrofit() {

            HttpLoggingInterceptor httpLoggingInterceptor = new HttpLoggingInterceptor();
            httpLoggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);

            OkHttpClient client =  new OkHttpClient.Builder()
                    .addInterceptor(httpLoggingInterceptor)
                    .addInterceptor(chain -> {
                        Request.Builder requestBuilder = chain.request().newBuilder();
                        // 读取SharedPreferences中的token
                        SharedPreferences preferences = MyApp.getAppContext().getSharedPreferences("logged", Context.MODE_PRIVATE);
                        String token = preferences.getString("token", "");
                        // 仅当token不为空时添加请求头，避免未登录请求携带无效头
                        if (!token.isEmpty()) {
                            requestBuilder.addHeader("Authorization", token);
                        }
                        return chain.proceed(requestBuilder.build());
                    })
                    .build();

            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl("http://192.168.1.60:8080/")
                    .addConverterFactory(GsonConverterFactory.create())
                    .client(client)
                    .build();

            return retrofit;
        }

        public static UserService getUserService() {
            return getRetrofit().create(UserService.class);
        }
    }

可选优化：Retrofit单例化 #

你现有代码每次调用getUserService都会重新创建Retrofit、OkHttpClient实例，会造成不必要的性能损耗，建议改成单例模式：

public class ApiClient {
    // 缓存Retrofit单例
    private static Retrofit retrofitInstance;

    private static Retrofit getRetrofit() {
        if (retrofitInstance == null) {
            HttpLoggingInterceptor httpLoggingInterceptor = new HttpLoggingInterceptor();
            httpLoggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);

            OkHttpClient client =  new OkHttpClient.Builder()
                    .addInterceptor(httpLoggingInterceptor)
                    .addInterceptor(chain -> {
                        Request.Builder requestBuilder = chain.request().newBuilder();
                        SharedPreferences preferences = MyApp.getAppContext().getSharedPreferences("logged", Context.MODE_PRIVATE);
                        String token = preferences.getString("token", "");
                        if (!token.isEmpty()) {
                            requestBuilder.addHeader("Authorization", token);
                        }
                        return chain.proceed(requestBuilder.build());
                    })
                    .build();

            retrofitInstance = new Retrofit.Builder()
                    .baseUrl("http://192.168.1.60:8080/")
                    .addConverterFactory(GsonConverterFactory.create())
                    .client(client)
                    .build();
        }
        return retrofitInstance;
    }

    public static UserService getUserService() {
        return getRetrofit().create(UserService.class);
    }
}

后续你登出账号清空SharedPreferences中的token后，拦截器会自动停止携带Authorization头，无需额外处理。

内容的提问来源于stack exchange，提问作者Pollongz