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重新打开活动时，AsyncTask（doInBackground方法）存在问题

androidandroid-asynctask
4
最近，我开始使用AsyncTask，在使用时遇到了一些问题。
我有一个ListActivity (CatalogActivity)，我使用AsyncTask重新加载它，因为它是一种树形逻辑。每次我在列表中选择一个项目时，我会在doInBackground方法中做一些计算并显示进度对话框，在onPostExecute中重新加载列表并关闭进度对话框。所有的工作都很好。
当我完成（到达最后一级）后，我启动另一个活动(LoginActivity)。这个新活动有一个“返回”菜单按钮，可以启动我先前提到的列表活动。它启动了活动，但当我在doInBackground方法中点击加载部分时，出现了奇怪的异常。真正有趣的部分是，如果我在我的加载方法上设置断点并单步运行，一切都正常！
我错过了什么？
这里是我的CatalogActivity的doInBackground方法（错误发生的地方）：
    protected String doInBackground(String... params) {
        catalogAdapter.mappingServicesCatalog.loadFromRml(new RIoConnectionManagerImpl(currentActivity.getApplicationContext()), params[0], null, 120000, 500000);
        if (catalogAdapter.urlMapping.size() == 0)
        {
            catalogAdapter.urlMapping.add(params[0]);
        }
        else
        {
            if (catalogAdapter.urlMapping.get(catalogAdapter.urlMapping.size() - 1) != params[0])
            {
                catalogAdapter.urlMapping.add(params[0]);
            }
        }
        return "";
    }

以下是LogCat记录：
06-20 11:38:21.109: ERROR/AndroidRuntime(22789): FATAL EXCEPTION: AsyncTask #4
06-20 11:38:21.109: ERROR/AndroidRuntime(22789): java.lang.RuntimeException: An error occured while executing doInBackground()
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at android.os.AsyncTask$3.done(AsyncTask.java:200)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at java.lang.Thread.run(Thread.java:1096)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789): Caused by: java.lang.NullPointerException
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at si.realis.rmap.android.CatalogActivity$CatalogAdapter.access$1(CatalogActivity.java:35)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at si.realis.rmap.android.CatalogActivity$LoadRMLCatalog.doInBackground(CatalogActivity.java:197)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at si.realis.rmap.android.CatalogActivity$LoadRMLCatalog.doInBackground(CatalogActivity.java:1)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
06-20 11:38:21.109: ERROR/AndroidRuntime(22789):     ... 4 more
06-20 11:38:44.086: ERROR/WindowManager(22789): Activity si.realis.rmap.android.CatalogActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@47f532a0 that was originally added here
06-20 11:38:44.086: ERROR/WindowManager(22789): android.view.WindowLeaked: Activity si.realis.rmap.android.CatalogActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@47f532a0 that was originally added here
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.view.ViewRoot.<init>(ViewRoot.java:247)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.view.Window$LocalWindowManager.addView(Window.java:424)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.app.Dialog.show(Dialog.java:241)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.app.ProgressDialog.show(ProgressDialog.java:107)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.app.ProgressDialog.show(ProgressDialog.java:90)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at si.realis.rmap.android.CatalogActivity.loadRMLCatalog(CatalogActivity.java:135)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at si.realis.rmap.android.CatalogActivity$CatalogAdapter.Initialize(CatalogActivity.java:60)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at si.realis.rmap.android.CatalogActivity$CatalogAdapter.<init>(CatalogActivity.java:45)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at si.realis.rmap.android.CatalogActivity.onCreate(CatalogActivity.java:119)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.os.Looper.loop(Looper.java:123)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at android.app.ActivityThread.main(ActivityThread.java:4627)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at java.lang.reflect.Method.invokeNative(Native Method)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at java.lang.reflect.Method.invoke(Method.java:521)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:871)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:629)
06-20 11:38:44.086: ERROR/WindowManager(22789):     at dalvik.system.NativeStart.main(Native Method)
06-20 11:49:00.402: ERROR/WifiManager(22835): showApDialog
06-20 11:49:04.699: ERROR/HierarchicalStateMachine(2475): TetherMaster - unhandledMessage: msg.what=3
06-20 11:49:07.511: ERROR/WifiManager(22835): showApDialog
06-20 11:49:14.648: ERROR/WifiManager(22835): showApDialog
06-20 11:49:23.109: ERROR/libnetutils(2475): dhcp start cmd 11 : [dhcpcd:-ABK] 
06-20 11:49:23.597: ERROR/HierarchicalStateMachine(2475): TetherMaster - unhandledMessage: msg.what=3
06-20 11:49:23.965: ERROR/gps_BRCM(2475): BrcmLbs_sync() return error.
需要在您的代码摘录中添加行号，以便与NPE堆栈跟踪对齐：si.realis.rmap.android.CatalogActivity$CatalogAdapter.access$1(CatalogActivity.java:35) -- 您的片段中的第35行是哪一行？.access$1()意味着它正在使用合成访问器方法请求私有成员，并且该成员似乎为空。您说它“启动”了上一个活动，但为什么不让BACK键完成其工作并结束顶部活动，恢复上一个活动呢？ - Joe
你是对的。这是一个典型的新手错误。我有一个活动和一个适配器。在适配器构造函数中，我有一些代码启动了这个异步任务。当我调试适配器时是同步的，但在运行时出现了错误。我把代码从适配器的构造函数移到了一个方法中，现在它可以正常工作了。感谢您的时间！这是我粗心的工作... - no9
1个回答
0

我通过修复我的代码（粗心的工作）解决了这个问题。

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