Question

ORIGINAL TITLE：在AsyncTask中使用MongoDB游标的android.os.NetworkOnMainThreadException？

我正在使用AndroidStudio和MongoDB后端为Android开发，尽管使用AsyncTask执行与网络相关的所有操作，但我得到了NetworkOnMainThreadException。

这是我们的数据库类（MyDB）中调用GetTasksTask（AsyncTask的子类）的方法：

public void getStoredTasks(CallbackHandler<ArrayList<PAWTask>> handler) {
    GetTasksTask task = new GetTasksTask(mongoDB, handler);
    task.doInBackground();
}

这里是GetTasksTask类（PAWTaskMongo是一个Mongo模型类，PAWTask是整个应用程序中使用的包装器）：

private class GetTasksTask extends AsyncTask<Void, Void, ArrayList<PAWTask>> {

    private DB mongoDB;
    private CallbackHandler handler;

    public GetTasksTask(DB mongoDB, CallbackHandler handler) {
        this.mongoDB = mongoDB;
        this.handler = handler;
    }

    @Override
    protected ArrayList<PAWTask> doInBackground(Void... voids) {
        ArrayList<PAWTask> storedTasks = new ArrayList<PAWTask>();

        DBCollection coll = mongoDB.getCollection(DBMongoParse.PAW_TASK_COLLECTION);
        BasicDBObject query = new BasicDBObject("isDeleted", false);

        List<DBObject> tasks = coll.find(query).toArray();

        for (DBObject task : tasks) {
            storedTasks.add(new PAWTask((PAWTaskMongo) task));
        }

        return storedTasks;
    }

    @Override
    protected void onPostExecute(ArrayList<PAWTask> result) {
        handler.handle(result);
    }

}

CallbackHandler的代码：

public abstract class CallbackHandler<T> {
    public abstract void handle(T result);
}

以下是我如何获取Mongo DB的实例（在我实例化MyDB类时，之前已完成）：

private MyDB() {
    new OpenMongoConnectionTask().execute();
}

private class OpenMongoConnectionTask extends AsyncTask<Void, Void, Void> {
    protected Void doInBackground(Void... voids) {
        try {
            MongoClient mongoClient = new MongoClient();
            mongoDB = mongoClient.getDB("mydb");
            pawTaskCollection = mongoDB.getCollection(PAW_TASK_COLLECTION);
            pawTaskCompleteCollection = mongoDB.getCollection(PAW_TASK_COMPLETE_COLLECTION);
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
        return null;
    }
}

这是我得到的异常（它会被抛出AsyncTask中的coll.find(query);行：

 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mudd.heatlab.pawpal/com.mudd.heatlab.pawpal.tasklist.TaskListActivity}: android.os.NetworkOnMainThreadException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2269)
        at android.app.ActivityThread.access$800(ActivityThread.java:139)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5102)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: android.os.NetworkOnMainThreadException
        at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1145)
        at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
        at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
        at java.net.InetAddress.getByName(InetAddress.java:289)
        at com.mongodb.ServerAddress.getSocketAddress(ServerAddress.java:185)
        at com.mongodb.DBPort.ensureOpen(DBPort.java:255)
        at com.mongodb.DBPort.<init>(DBPort.java:89)
        at com.mongodb.DBPortFactory.create(DBPortFactory.java:28)
        at com.mongodb.PooledConnectionProvider$ConnectionItemFactory.create(PooledConnectionProvider.java:186)
        at com.mongodb.PooledConnectionProvider$ConnectionItemFactory.create(PooledConnectionProvider.java:183)
        at com.mongodb.ConcurrentPool.createNewAndReleasePermitIfFailure(ConcurrentPool.java:150)
        at com.mongodb.ConcurrentPool.get(ConcurrentPool.java:118)
        at com.mongodb.PooledConnectionProvider.get(PooledConnectionProvider.java:75)
        at com.mongodb.DefaultServer.getConnection(DefaultServer.java:60)
        at com.mongodb.BaseCluster$WrappedServer.getConnection(BaseCluster.java:216)
        at com.mongodb.DBTCPConnector$MyPort.getConnection(DBTCPConnector.java:503)
        at com.mongodb.DBTCPConnector$MyPort.get(DBTCPConnector.java:451)
        at com.mongodb.DBTCPConnector.innerCall(DBTCPConnector.java:286)
        at com.mongodb.DBTCPConnector.call(DBTCPConnector.java:271)
        at com.mongodb.DBCollectionImpl.find(DBCollectionImpl.java:84)
        at com.mongodb.DBCollectionImpl.find(DBCollectionImpl.java:66)
        at com.mongodb.DBCursor._check(DBCursor.java:458)
        at com.mongodb.DBCursor._hasNext(DBCursor.java:546)
        at com.mongodb.DBCursor._fill(DBCursor.java:605)
        at com.mongodb.DBCursor.toArray(DBCursor.java:640)
        at com.mongodb.DBCursor.toArray(DBCursor.java:629)
        at com.mudd.heatlab.pawpal.dbonline.GetTasksTask.doInBackground(GetTasksTask.java:32)
        at com.mudd.heatlab.pawpal.dbonline.DBMongoParse.getStoredTasks(DBMongoParse.java:130)
        at com.mudd.heatlab.pawpal.DB.PAWPalDB.getStoredTasks(PAWPalDB.java:106)
        at com.mudd.heatlab.pawpal.tasklist.TaskListFragment.onCreate(TaskListFragment.java:66)
        at android.support.v4.app.Fragment.performCreate(Fragment.java:1477)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:893)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
        at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
        at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
        at com.mudd.heatlab.pawpal.tasklist.TaskListActivity.displayTaskList(TaskListActivity.java:67)
        at com.mudd.heatlab.pawpal.tasklist.TaskListActivity.onCreate(TaskListActivity.java:31)
        at android.app.Activity.performCreate(Activity.java:5248)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2173)

非常感谢任何帮助。谢谢！

Answer 1

public void getStoredTasks(CallbackHandler<ArrayList<PAWTask>> handler) {
GetTasksTask task = new GetTasksTask(mongoDB, handler);
task.doInBackground();
 }

替换为

public void getStoredTasks(CallbackHandler<ArrayList<PAWTask>> handler) {
GetTasksTask task = new GetTasksTask(mongoDB, handler);
task.execute();
}

AsyncTask控制着BackThread ..

AsyncTask中的android.os.NetworkOnMainThreadException？

1 个答案: