Question

我有一个问题android listview中的AsyncTask在正常运行时并不是真正的问题，所以当asyntask运行时用户将页面向下滚动到下一页时，直接应用力关闭。

我已经尝试了所有条件：

if (AsyncTask.Status.RUNNING == null) {
    / / My code do in backgroud here
}

if (backgroundtask.getStatus! = STATUS.RUNNING) {
    / / My code do in backgroud here
}

总是失败......

public abstract View getAmazingView(int position, View convertView,
            ViewGroup parent);


public final View getView(int position, View convertView, ViewGroup parent) {
        View res = getAmazingView(position, convertView, parent);

        if (position == getCount() - 1 && automaticNextPageLoading) {
            onNextPageRequested(page + 1);
        }

        final int section = getSectionForPosition(position);
        boolean displaySectionHeaders = (getPositionForSection(section) ==  position);

        bindSectionHeader(res, position, displaySectionHeaders);

        return res;
    }


protected void onNextPageRequested(int page) {

            backgroundTask = new AsyncTask<Integer, Void, List<Bola>>() {
                protected List<Bola> doInBackground(
                        Integer... params) {
                    int page = params[0];
                    return Adapter.getRows(page);
                }

                protected void onPostExecute(
                        List<Bola> result) {
                    if (isCancelled()){
                        backgroundTask.cancel(true);                        
                    }

                    list.addAll(result);
                    nextPage();
                    notifyDataSetChanged();

                    if (result.size() > 0) {
                        // still have more pages
                        notifyMayHaveMorePages();
                    } else {
                        notifyNoMorePages();
                    }
                };
            }.execute(page);
        }

如何使用AsyncTask运行条件运行，用户使用向下滚动事件？

=======更新我的日志=======

11-02 23:22:42.330: ERROR/AndroidRuntime(25830): FATAL EXCEPTION: main
11-02 23:22:42.330: ERROR/AndroidRuntime(25830): java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. [in ListView(2131034281, class com.dhika.bola.application.ui.ListUtils) with Adapter(class android.widget.HeaderViewListAdapter)]
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.widget.ListView.layoutChildren(ListView.java:1548)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.widget.AbsListView.onTouchEvent(AbsListView.java:3490)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at com.dhika.bola.application.ui.ListUtils.onTouchEvent(ListUtils.java:445)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.View.dispatchTouchEvent(View.java:7262)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2235)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1932)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1968)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1420)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.app.Activity.dispatchTouchEvent(Activity.java:2428)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1916)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.View.dispatchPointerEvent(View.java:7442)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3610)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3538)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4790)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4750)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4902)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:179)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:171)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:4870)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:4924)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:776)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.Choreographer.doCallbacks(Choreographer.java:579)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.Choreographer.doFrame(Choreographer.java:546)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:762)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.os.Handler.handleCallback(Handler.java:725)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.os.Handler.dispatchMessage(Handler.java:92)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.os.Looper.loop(Looper.java:153)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at android.app.ActivityThread.main(ActivityThread.java:5297)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at java.lang.reflect.Method.invokeNative(Native Method)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at java.lang.reflect.Method.invoke(Method.java:511)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
11-02 23:22:42.330: ERROR/AndroidRuntime(25830):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

如果我理解正确（根据您的尝试），您希望在运行时避免调用AsyncTask。这应该做的工作：

// class variable
// boolean isRunning = false;

protected void onNextPageRequested(int page) {


    if (!isRunning) {

        isRunning = true;

        backgroundTask = new AsyncTask<Integer, Void, List<Bola>>() {

            protected List<Bola> doInBackground(
                    Integer... params) {
                int page = params[0];
                return Adapter.getRows(page);
            }

            protected void onPostExecute(
                    List<Bola> result) {
                if (isCancelled()){
                    backgroundTask.cancel(true);                        
                }

                list.addAll(result);
                nextPage();
                notifyDataSetChanged();

                if (result.size() > 0) {
                    // still have more pages
                    notifyMayHaveMorePages();
                } else {
                    notifyNoMorePages();
                }


            };
        }.execute(page);
            isRunning = false;
       }

    }

Answer 2

根据您的LogCat错误，您可以在另一个线程上修改ListView数据，然后修改主线程..正如它所说：

11-02 23:22:42.330: ERROR/AndroidRuntime(25830): java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. [in ListView(2131034281, class com.dhika.bola.application.ui.ListUtils) with Adapter(class android.widget.HeaderViewListAdapter)]

也不允许多次启动单个AsyncTask。

但还有一些事情我不清楚：

为什么要在异步任务中执行getRows（）？
这个Adapter.getRows(page)做了什么（因为这应该是静态方法）？确实改变了什么？
你通常想要达到什么目的？你想一次只有一个AsyncTask吗？

还有一点需要注意：我没有看到你在AsyncTask中更改适配器内容，但那里（如例外）应该是...

如果您在其他地方执行此操作，请使用onPostExecution或使用runOnUiThread方法。

runOnUiThread(new Runnable() {

public void run() 
{
    //Update UI here                        
}
});

滚动事件时AsyncTask崩溃

2 个答案: