Stuff

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;

public abstract class DetachableTask<Params> extends AsyncTask<Params, String, String> {

	protected Activity owner;
	protected Context ctx;

	private ProgressDialog dialog;
	private String dialogMessage = "";
	private String dialogTitle = "";
    	
	// An Activity's onCreate should use this if it might have previously
	// owned some retained task, e.g.
	//     myTask = DetachableTask.doRestore(getLastNonConfigurationInstance(), this))
	@SuppressWarnings("unchecked")
	public static <Params> DetachableTask<Params> doRestore(Object task, Activity owner) {
		// We can't check that the desired parameter is correct, but we can
		// at least make sure it's some kind of DetachableTask.
		DetachableTask<?> checkTask = (DetachableTask<?>)task;
		DetachableTask<Params> aTask = (DetachableTask<Params>)checkTask;
		if (aTask != null)
			aTask.attach(owner);
		return aTask;
	}

	// An Activity's onRetainNonInstanceState should use this if it might own
	// some task, e.g.:
	//     return DetachableTask.doRetain(myTask, this);
	public static Object doRetain(DetachableTask<?> task, Activity maybeOwner) {
		if (task != null && maybeOwner == task.owner)
			task.detach();
		return task;
	}

	// An Activity's onDestroy should use this if it might own some task, e.g.:
	//     return DetachableTask.doDestroy(myTask, this);
	public static boolean doDestroy(DetachableTask<?> task, Activity maybeOwner, boolean mayInterrupt) {
		if (task != null)
			return task.cancelIfOwned(maybeOwner, mayInterrupt);
		return false;
	}

	protected DetachableTask(Activity owner, String titleId, String msgId) {
		ctx = owner.getApplicationContext();
		dialogTitle = titleId;
		setDialogMessage(msgId);
		attach(owner);
	}

	protected DetachableTask(Activity owner, int titleId, int msgId) {
		this(owner, owner.getString(titleId), owner.getString(msgId));
	}

	protected void setDialogMessage(int id) {
		setDialogMessage(ctx.getString(id));
	}

	protected void setDialogMessage(String msg) {
		dialogMessage = msg;
		if (dialog != null)
			dialog.setMessage(msg);
	}

	public void detach() {
		attach(null);
	}

	public boolean isAttached() {
		return owner != null;
	}
	
	public boolean cancelIfOwned(Activity maybeOwner, boolean mayInterrupt) {
		if (maybeOwner == owner)
			return cancel(mayInterrupt);
		return false;
	}

	public static boolean isActive(AsyncTask<?, ?, ?> task) {
		return task != null && task.getStatus() != AsyncTask.Status.FINISHED;
	}
	
	protected void cancelDialog() {
		if (dialog != null)
			dialog.cancel();
		dialog = null;
	}
	
	protected void publishProgress(int msgId) {
		publishProgress(ctx.getString(msgId));
	}
    	
	public void attach(Activity owner) {
		if (owner != this.owner)
    		cancelDialog();

		this.owner = owner;

		if (isAttached() && getStatus() != AsyncTask.Status.FINISHED && dialog == null)
			dialog = ProgressDialog.show(owner, dialogTitle, dialogMessage, true, false);    			
	}

	@Override
	protected void onProgressUpdate(String... message) {
		setDialogMessage(message[0]);
	}
	
	@Override
	protected void onPostExecute(String finalMessage) {
		cancelDialog();
	}
}