我在下面创建了一个非常简化的版本.
严格模式通过以下策略设置:
StrictMode.setThreadPolicy(
StrictMode.ThreadPolicy.Builder()
.detectDiskReads()
.detectDiskWrites()
.detectNetwork() // or .detectAll() for all detectable problems
.penaltyLog()
.penaltyDeath()
.build()
)
视图模型只有一个函数,该函数在调用时会使应用程序崩溃.该函数不执行任何操作(其主体为空)
class Myviewmodel : viewmodel() {
fun foo() {
viewmodelScope.launch(Dispatchers.IO){ }
}
}
该活动在onCreate上调用viewmodel.foo(),从而使带有以下跟踪信息的应用程序崩溃.
--------- beginning of crash
2019-04-08 22:07:49.579 1471-1471/com.example.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.myapplication,PID: 1471
java.lang.RuntimeException: StrictMode ThreadPolicy violation
at android.os.StrictMode$AndroidBlockGuardPolicy.onThreadPolicyViolation(StrictMode.java:1705)
at android.os.StrictMode$AndroidBlockGuardPolicy.lambda$handleViolationWithTimingAttempt$0(StrictMode.java:1619)
at android.os.-$$Lambda$StrictMode$AndroidBlockGuardPolicy$9nBulCQKaMajrWr41SB7f7YRT1I.run(Unknown Source:6)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: android.os.strictmode.DiskReadViolation
at android.os.StrictMode$AndroidBlockGuardPolicy.onReadFromDisk(StrictMode.java:1504)
at java.io.UnixFileSystem.getBooleanAttributes(UnixFileSystem.java:241)
at java.io.File.isDirectory(File.java:845)
at dalvik.system.DexPathList$Element.maybeInit(DexPathList.java:696)
at dalvik.system.DexPathList$Element.findResource(DexPathList.java:729)
at dalvik.system.DexPathList.findResources(DexPathList.java:526)
at dalvik.system.BaseDexClassLoader.findResources(BaseDexClassLoader.java:174)
at java.lang.ClassLoader.getResources(ClassLoader.java:839)
at java.util.ServiceLoader$LazyIterator.hasNextService(ServiceLoader.java:349)
at java.util.ServiceLoader$LazyIterator.hasNext(ServiceLoader.java:402)
at java.util.ServiceLoader$1.hasNext(ServiceLoader.java:488)
at kotlin.collections.CollectionsKt___CollectionsKt.toCollection(_Collections.kt:1145)
at kotlin.collections.CollectionsKt___CollectionsKt.toMutableList(_Collections.kt:1178)
at kotlin.collections.CollectionsKt___CollectionsKt.toList(_Collections.kt:1169)
at kotlinx.coroutines.internal.MainDispatcherLoader.loadMainDispatcher(MainDispatchers.kt:15)
at kotlinx.coroutines.internal.MainDispatcherLoader.<clinit>(MainDispatchers.kt:10)
at kotlinx.coroutines.Dispatchers.getMain(Dispatchers.kt:55)
at androidx.lifecycle.viewmodelKt.getviewmodelScope(viewmodel.kt:41)
at com.example.myapplication.Myviewmodel.foo(MainActivity.kt:35)
at com.example.myapplication.MainActivity.onCreate(MainActivity.kt:28)
at android.app.Activity.performCreate(Activity.java:7136)
at android.app.Activity.performCreate(Activity.java:7127)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
根据堆栈跟踪,有磁盘读取冲突,但是该代码中的任何内容都不应访问磁盘.
感兴趣的行是:
at com.example.myapplication.Myviewmodel.foo(MainActivity.kt:35)
at com.example.myapplication.MainActivity.onCreate(MainActivity.kt:28)
第35行:viewmodelScope.launch(Dispatchers.IO){}
第28行:viewmodel.foo()
更进一步,如果我删除了刑罚日志(),则应用程序不会崩溃.
所以我的问题是:
如何使用上述严格模式配置防止崩溃?
协程或严格模式本身存在问题吗?
最佳答案
解决方案是使用您自己初始化的调度程序,而不在主线程上执行I / O.
实施起来有点棘手,因为要避免由于默认情况下在Handler上启用了vsync(可能会延迟多达16ms的代码,根本不需要vsync)而导致应用程序变慢,则必须使用API 28构造函数,并使用反映旧版本的Android.之后,您可以对Handler使用asCoroutineDispatcher()扩展函数,并使用生成的调度程序.
为了使它对我和其他人更简单,我制作了一个(小)库,该库提供了Dispatchers.MainAndroid扩展,它无需任何I / O即可延迟初始化,并且可以代替Dispatchers.Main使用.它还将生命周期与协同程序范围集成在一起.
在这里,您可以查看如何获取依赖关系(在jcenter上可用)以及如何实现依赖关系:https://github.com/LouisCAD/Splitties/tree/master/modules/lifecycle-coroutines