Как правильно обновлять элемент EDITTEXT?

Спасибо, теперь всё работает.

Из-за чего может вылетать программа на Android при прокрутке кастомизированного списка?

Да, действительно нулл поинтер.
java.lang.NullPointerException
at com.androidlabs.devel.lab3.ExchangeAdapter.getView(ExchangeAdapter.java:49)
at android.widget.HeaderViewListAdapter.getView(HeaderViewListAdapter.java:220)
at android.widget.AbsListView.obtainView(AbsListView.java:2255)
at android.widget.ListView.makeAndAddView(ListView.java:1790)
at android.widget.ListView.fillDown(ListView.java:691)
at android.widget.ListView.fillGap(ListView.java:655)
at android.widget.AbsListView.trackMotionScroll(AbsListView.java:5143)
at android.widget.AbsListView.scrollIfNeeded(AbsListView.java:3243)
at android.widget.AbsListView.onTouchMove(AbsListView.java:3587)
at android.widget.AbsListView.onTouchEvent(AbsListView.java:3431)
at android.view.View.dispatchTouchEvent(View.java:7713)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2210)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1945)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2329)
at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1568)
at android.app.Activity.dispatchTouchEvent(Activity.java:2458)
at android.support.v7.internal.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:60)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2277)
at android.view.View.dispatchPointerEvent(View.java:7893)
at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:3950)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3829)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3395)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3445)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3414)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3521)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3422)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3578)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3395)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3445)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3414)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3422)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3395)
at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5535)
at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5515)
at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5486)
at andr

Из-за чего может вылетать программа на Android при прокрутке кастомизированного списка?

Я новичок и в логах мне мало что понятно

Почему в Elementary OS Freya если сохраняется файл, записанный через функцию write (си) с флагом O_CREAT, к нему невозможен доступ?

Я не смог понять, как его использовать, зато это помогло мне нагуглить другой способ: fchmod(fd, S_IRWXU | S_IRWXG | S_IRWXO).