Runs a Loader synchronously and returns the result of the load. The loader will
be started, stopped, and destroyed by this method so it cannot be reused.
// Force class loading of AsyncTask on the main thread so that it's handlers are tied to
// the main thread and responses from the worker thread get delivered on the main thread.
// The tests are run on another thread, allowing them to block waiting on a response from
// the code running on the main thread. The main thread can't block since the AysncTask
// results come in via the event loop.
new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... args) {return null;}
@Override
protected void onPostExecute(Void result) {}
};
// The test thread blocks on this queue until the loader puts it's result in
final ArrayBlockingQueue<T> queue = new ArrayBlockingQueue<T>(1);
// This callback runs on the "main" thread and unblocks the test thread
// when it puts the result into the blocking queue
final OnLoadCompleteListener<T> listener = new OnLoadCompleteListener<T>() {
@Override
public void onLoadComplete(Loader<T> completedLoader, T data) {
// Shut the loader down
completedLoader.unregisterListener(this);
completedLoader.stopLoading();
completedLoader.reset();
// Store the result, unblocking the test thread
queue.add(data);
}
};
// This handler runs on the "main" thread of the process since AsyncTask
// is documented as needing to run on the main thread and many Loaders use
// AsyncTask
final Handler mainThreadHandler = new Handler(Looper.getMainLooper()) {
@Override
public void handleMessage(Message msg) {
loader.registerListener(0, listener);
loader.startLoading();
}
};
// Ask the main thread to start the loading process
mainThreadHandler.sendEmptyMessage(0);
// Block on the queue waiting for the result of the load to be inserted
T result;
while (true) {
try {
result = queue.take();
break;
} catch (InterruptedException e) {
throw new RuntimeException("waiting thread interrupted", e);
}
}
return result;
