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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
一.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)
二.为什么会崩溃
从上面的stacktrace,我们可以分析到,发生了NullPointerException。发生了崩溃。
等等,我记得OkHttp有处理异常的情况呢。
嗯,确实,OkHttp有处理异常的情况,比如发生异常会调用onFailure
。比如下面的Callback的内容介绍。
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)
}
是的.
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。
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
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
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。
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