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OkHttp是可以说是Android开发中,每个项目都必需依赖的网络库,我们可以很便捷高效的处理网络请求,极大的提升了编码效率。但是有时候,我们使用OkHttp也会遇到这样的问题

崩溃的stacktrace

 E AndroidRuntime: FATAL EXCEPTION: OkHttp Dispatcher
 E AndroidRuntime: Process: com.example.okhttpexceptionsample, PID: 13564
 E AndroidRuntime: java.lang.NullPointerException: blablabla
 E AndroidRuntime:    at com.example.okhttpexceptionsample.MainActivity$createNPEInterceptor$1.intercept(MainActivity.kt:61)
 E AndroidRuntime:    at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:112)
 E AndroidRuntime:    at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:87)
 E AndroidRuntime:    at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.kt:184)
 E AndroidRuntime:    at okhttp3.RealCall$AsyncCall.run(RealCall.kt:136)
 E AndroidRuntime:    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
 E AndroidRuntime:    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
 E AndroidRuntime:    at java.lang.Thread.run(Thread.java:784)
interface Callback {
   * Called when the request could not be executed due to cancellation, a connectivity problem or
   * timeout. Because networks can fail during an exchange, it is possible that the remote server
   * accepted the request before the failure.
  fun onFailure(call: Call, e: IOException)
   * Called when the HTTP response was successfully returned by the remote server. The callback may
   * proceed to read the response body with [Response.body]. The response is still live until its
   * response body is [closed][ResponseBody]. The recipient of the callback may consume the response
   * body on another thread.
   * Note that transport-layer success (receiving a HTTP response code, headers and body) does not
   * necessarily indicate application-layer success: `response` may still indicate an unhappy HTTP
   * response code like 404 or 500.
  @Throws(IOException::class)
  fun onResponse(call: Call, response: Response)
  • OkHttp只处理了IOException的情况,
  • NullPointerException不是IOException的子类
  • 所以没有被处理,发生了崩溃。

    那么有没有办法解决,让这种崩溃不发生,对用户不进行干扰呢?其实是可以的。

    使用Interceptor

    package com.example.okhttpexceptionsample
    import okhttp3.Interceptor
    import okhttp3.Response
    import java.io.IOException
     * 对于Interceptor的intercept中可能出现的Throwable包裹成IOExceptionWrapper,转成网络请求失败,而不是应用崩溃
    class SafeGuardInterceptor : Interceptor {
        override fun intercept(chain: Interceptor.Chain): Response {
            try {
                return chain.proceed(chain.request())
            } catch (t: Throwable) {
                throw IOExceptionWrapper("SafeGuarded when requesting ${chain.request().url}", t)
     * 将chain.proceed处理中发生的Throwable包装成IOExceptionWrapper
    class IOExceptionWrapper(message: String?, cause: Throwable?) : IOException(message, cause)
    

    上面的代码,我们将任何Throwable的转成IOExceptionWrapper(伪装成IOException),然后添加到OkHttpClient中

    fun createOKHttpClient(): OkHttpClient {
            return OkHttpClient.Builder()
                .addInterceptor(SafeGuardInterceptor())
                .build()
    

    当我们再次执行有NPE的代码,日志就发生了改变(不再是崩溃的日志,而是异常的日志)

      W System.err: com.example.okhttpexceptionsample.IOExceptionWrapper: SafeGuarded=blablabla
      W System.err:   at com.example.okhttpexceptionsample.SafeGuardInterceptor.intercept(SafeGuardInterceptor.kt:12)
      W System.err:   at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:112)
      W System.err:   at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:87)
      W System.err:   at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.kt:184)
      W System.err:   at okhttp3.RealCall$AsyncCall.run(RealCall.kt:136)
      W System.err:   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
      W System.err:   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
      W System.err:   at java.lang.Thread.run(Thread.java:784)
      W System.err: Caused by: java.lang.NullPointerException: blablabla
      W System.err:   at com.example.okhttpexceptionsample.MainActivity$createNPEInterceptor$1.intercept(MainActivity.kt:61)
      W System.err:   at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:112)
      W System.err:   at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:87)
      W System.err:   at com.example.okhttpexceptionsample.SafeGuardInterceptor.intercept(SafeGuardInterceptor.kt:10)
      W System.err:   ... 7 more
    

    上述需要注意两点

  • 添加的是Interceptor,而不是NetworkInterceptor
  • 顺序很重要,一定要放在第一个位置
  • 这么做有什么问题

    这么做,当然可以明显增强请求的稳定性和应用的崩溃率。但是是不是也有一些问题呢?比如

  • 将问题情况吞掉,不利于发现问题呢
  • 是的,确实可能存在上述的问题,但是我们可以利用下面的方式减轻或者解决问题

  • 只针对release情况应用SafeGuardInterceptor,这样便于debug情况下更容易发现
  • 针对不同的build variants进行配置,便于尽可能的小范围发现问题
  • 实行更加智能的动态开启策略。
  • 在软件工程中,很多决定都是trade-off的体现,具体的实施方案大家可以自行平衡选择。