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PORunning same background task from two acitivities
 

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    <p>In my app I have a background task (using AsyncTask) that downloads stuff from a web site.</p> <p>This task can be called from two separate activities, and it is possible to call it twice. So in "activity1" the background task "update" is called, and runs for a while (it takes something like 5-10 seconds usually). Then while it's running, user switches to "activity2" and runs "update" again. This gives problems: either a crash when both try to clear the database (command: DELETE FROM table) at the same time, causing a "database locked" error. Or they try to put the same item in the database causing a duplicate.</p> <p>I've tried to solve this by setting a static boolean flag to true when a task is active. When the task is called, it will check for this flag, and if true (i.e. the same task running on another thread) it goes into a wait loop using a handler until this flag clears, and then returns. This to make sure that when the background task returns, the update has been done. I have to use a Looper for that: this sometimes fails with an error "can create only one looper per thread". And I really have it in a way that only one looper can be started, this is the offending code, which appears at the start of the background task:</p> <pre><code> if (active) { Looper.prepare(); handler = new Handler(); handler.postDelayed(new Runnable() { int count = 0; @Override public void run() { if (active) { count++; if (count &lt; 1000) handler.postDelayed(this, 100); } } }, 100); Looper.loop(); active = false; return "done"; } </code></pre> <p>And to make matters worse it often seems to hang in this loop, without returning.</p> <p>Any ideas on how to solve such a situation?</p>
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