I'm attempting to implement a VERY simple saved games setup on Android. I am providing two buttons to the user-- one is "save" and one is "load."
Both will call simple functions:
Save(name);
Load(name);
When I save, I want it to overwrite whatever exists, if it has the same name-- no matter what. Similary, if I try to load, and the name doesn't exist, I just want to bomb out and say, nope, doesn't exist.
(The game has user created levels, so it would be too dangerous to sync it behind the scenes-- my users will have to do their own conflict management).
Here's my problem... two problems actually. One, I cannot find any sample code that is simpler than a deluxe save/load suite designed for multiple save games, conflict resolution, and a cherry on top. The second problem is, even the complex code is so full of depreciations that I can't even paste it into my code and start playing with it (even the apparently newest stuff is full of unresolvable methods and depreciations).
Can anyone either explain, or point me to, a "simplest" implementation of saved games, that just writes some data to by synced, and then reads it back?
Related
I ve got a problem in a game project. I develop a bot in video game. The game engine of the game is that the game gives every game tick information about the track and i use that information to make decisions about bot strategy. I want to store that information all these game ticks in a txt file. However, i noticed that when i store the data in txt files my bot fails to make correct decision. Actually the behavior of the bot slow down. Is there efficient way to store my data to ram? My project is in java.
If the bot needs the data to make it's decision, it's best to keep all that data in ram.
If you need to save the data for other reasons to disk, you might want to consider only saving the data every minute, and not every game tick, as disk-io tends to be slow.
File writing is comparatively very slow, hence why your game slows down. What information exactly do you need to store? Defining a class (used statically, if necessary, but preferably not) whose members represent the data you need is probably a way to go about it...
I have a game where I draw and move bitmaps over a SurfaceView. The user can interact (drag and drop) these bitmaps. When the player hits the home button then goes back into the game, I want to be able to pause the game, then restore it to where it was before he left it. What is the best way to store my custom objects?
Should I implement onSaveInstanceState(Bundle) and have all of the classes whose objects I want to save implement the Parcelable interface? This would be quite a bit of work, and I'm still not sure how I would save things like bitmaps. I suppose I wouldn't and I would just reload those from disk.
I am also confused about what kind of storage a bundle offers: disk storage that never goes away unless you clear it yourself, or memory storage that goes away if the OS decides to remove your program from memory while it's in the background. According to the comments in this question, it is disk storage. The documentation implies that it is memory storage, saying Note that it is important to save persistent data in onPause(), however I don't find it very clear. This page also implies that it is not persistent: it only lasts as long as the application remains in memory. So which one is it?
The last link above suggests using onRetainNonConfigurationInstance() to keep objects in memory while the application is in the background. This would imply that if the program is taken out of memory by the OS while in the background, everything would be lost. This seems to be what most (all I tested on) games do: if you hit home while playing then go back in, the level resumes. If you hit home, open a lot of stuff (sufficient to make Android remove the game from memory), then go back in, nothing is resumed, the game starts from the main menu. Does that mean this is what they use, and if so, is that a good practice?
Note that the question about a Bundle's persistency is just a secondary curiosity. I don't really care if the state of this game is not permanently saved and can be lost after the game being in the background for a while (as described in 2 above). I'm interested in the best practice for this case.
The basic idea is, IMO, identify the smallest collection of values that will enable you to recreate the state of your game. Save those in shared preferences.
So I have two possible solutions that I want to implement. Firstly I will state my problem. The task I have been assigned to requires me to go to a website called finra.org and do broker checks to see if the brokers in my excel sheet(which gives the name and company among other things) still work A, and if they do work do they still work for the company in the excel sheet. If they do move on to the next one, and if they don't delete them from the sheet. The issue lies in that I have 37k names to check. I calculated this and to do it individually, which is annoying and takes the whole day allows me to do a maximum of 1400 a day. That is on a productive day when I dont have other things to do. So I figured a better use of my time ( I am an intern) would be to write a program which (here are my two suggested solutions:)
1.) Automatically through minimal key strokes copies the data and pastes it into the search box on the page. Ill still have to click and search but at least I would eliminate copying and pasting and switching between screens which takes the majority of the time.
2.) Completely automate the process. I was thinking of copying the names into a text file and then somehow writing a program that takes each name and submits a query to this website which would then show me the result. Perhaps sends the result text to a text file and then i could just GREP the text file for the data that i need.
Any idea if any of this is possible?
Thanks,
Kevin
Definitely possible. I'm doing something similar with a database and an Excel spreadsheet of values using AutoHotKey to automate queries, Chrome console commands and Javascript bookmarklets to scrape data into the clipboard, and Ruby/Nokogiri with more complex and/or structured parsing tasks.
Either of your methods will work - if you have little programming background, I would suggest starting with AutoHotKey since it mimics keyboard and mouse commands, so the programming is much more straightforward and easier to understand. If you have some object-oriented programming skills, learning Ruby/Nokogiri might be your solution, depending on how FINRA's page is structued.
I'm trying to write a painting app for a mobile device (Android) that will have a bit more functionality than MS Paint (e.g. various brushes and brush settings, selections, layers) but won't be as complex as Photoshop. I need my app to have a decent undo/redo feature. Unlimited undo/redo is probably not possible. I'd be happy with being able to undo about the last minute worth of user actions (maybe about 20 actions).
The main approaches I know of for undo/redo is:
save the whole state or just the bits that changed after each operation. Undoing involves updating the state by restoring snapshots. Pros: simple to implement Cons: memory intensive.
use the command pattern where each command has a "do action" and "undo action" method. To undo, you just call the undo action of the previous commands. Pros: memory efficient, Cons: much more complex to implement.
My pathological undo/redo scenarios I have to consider is:
the user paints over the whole canvas in one go, where you would want this whole operation to be undone when the user clicks undo. With option 1, we'd need to store a bitmap the size of the whole canvas.
the user draws something, imports image 1.jpg onto the canvas, does some more drawing, 1.jpg is then deleted/modified at some point by another application and then the user wants to undo then redo all their actions in the paint application. I'm really not sure how to undo correctly here without saving a copy of any imported image while it's on the undo stack.
Can anyone give any recommendations about how best to implement undo/redo on a mobile device where memory and processor speed are low? I like the simplicity of 1 and 3 but it seems like the only realistic option is 2. I'm not sure how to cope with my second pathological example with this option though.
On the iPhone, Core Data has built in support for undo and redo. Just make your data model reflect the objects drawn and you can easily roll it back and forward between saves. Usually you would save the procedures and objects used to create the graphic instead of the graphic itself.
Edit:
OK, but this is just a little API
support for implementing number 2 and
won't help with the examples I gave.
The key idea to making this work is that you don't configure your data model to modal and persist the graphical output of the program, you configure it to modal and persist the process of creating the graphical output.
The naive way of creating a graphical program would be to set up the data flow like:
Input_UI-->Display_UI-->Data_Model
The user manipulates the Input_UI which directly alters the onscreen graphics of the Display_UI. Only when the user saved would the Data_Model come into play. This type of data flow makes undo/redo (and other things) very hard to implement especially in a painting e.g. compositing program. Every single operation has to know how to undo itself and has to be able operate on the altered graphic.
The better way is to set up a data flow like this:
Input_UI-->Data_Model-->Display_UI
The user manipulates the Input_UI which communicates to the Data_Model which manipulations the user chose. The Data_Model records the process e.g. "add file jpg.1 at rect {0,0,100,100}". A change to the Data_Model sends a notification to the Display_UI which reads the changed data and implements the process described.
The Data_Model rolls itself back and the Display_UI simply draws what the Data_Model tells it to. The Display_UI doesn't have to understand the undo process at all.
In a drawing program you would create logical layers of individual graphical objects so that redoing is just a matter of removing layers in the reverse order they were added. For painting/composition programs, you have to start at the last save point and recreate the graphic going forward until the last-1 step.
So, in your examples for a compositing program:
The Data_Model stores the coordinates of the selected area (the entire canvas) which is still just "rect {0,0,canvas.width,canvas.height}" and then the operation "fill with black". For undo, the Display_UI whips the image back to the last save point and then invisibly applies the changes made up to last-1.
You just need to save a cache of the image up until the next save. At that point, the Data_Modal commits all the changes and exports the composition to a file. The next time the app starts, it begins with the image from the last time. If you want infinite undo, then yes you have to save the imported image permanently.
The way to approach this is to ignore the GUI and instead think about how you would design an app to be run from the command line with out any GUI input or output. The Data_Modal would work just the same. It would save the text commands and the data (e.g. imported images) for creating the output image, not just a snapshot of the image on screen.
I like the simplicity of 1 and 3 but
it seems like the only realistic
option is 2.
I'm not sure what "3" is, since you only appear to have two options in your question.
With respect to the memory consumption of #1, it's only an issue if you use memory. Only hold onto history in memory for as long as it takes an AsyncTask (or possibly a regular background thread working off a LinkedBlockingQueue) to write them to the SD card. No SD card -- no undo/redo. On an undo, if your history has already written it to disk, reload it from disk. Just be sure to clean up the SD card (delete history on a clean exit, delete all lingering files on next startup).
Bear in mind that I have never written a painting application, let alone on Android, and so there may yet be performance problems (e.g., undo may take a second to load the bitmap off of the SD card).
I'm creating a grid based game in Java and I want to implement game recording and playback. I'm not sure how to do this, although I've considered 2 ideas:
Several times every second, I'd record the entire game state. To play it back, I write a renderer to read the states and try to create a visual representation. With this, however, I'd likely have a large save file, and any playback attempts would likely have noticeable lag.
I could also write every key press and mouse click into the save file. This would give me a smaller file, and could play back with less lag. However, the slightest error at the start of the game (For example, shooting 1 millisecond later) would result in a vastly different game state several minutes into the game.
What, then, is the best way to implement game playback?
Edit- I'm not sure exactly how deterministic my game is, so I'm not sure the entire game can be pieced together exactly by recording only keystrokes and mouse clicks.
A good playback mechanism is not something that can be simply added to a game without major difiiculties. The best would be do design the game infrastructure with it in mind. The command pattern can be used to achieve such a game infrastructure.
For example:
public interface Command{
void execute();
}
public class MoveRightCommand implements Command {
private Grid theGrid;
private Player thePlayer;
public MoveRightCommand(Player player, Grid grid){
this.theGrid = grid;
this.thePlayer = player;
}
public void execute(){
player.modifyPosition(0, 1, 0, 0);
}
}
And then the command can be pushed in an execution queue both when the user presses a keyboard button, moves the mouse or without a trigger with the playback mechanism. The command object can have a time-stamp value (relative to the beginning of the playback) for precise playback...
Shawn Hargreaves had a recent post on his blog about how they implemented replay in MotoGP. Goes over several different approaches and their pros and cons.
http://blogs.msdn.com/shawnhar/archive/2009/03/20/motogp-replays.aspx
Assuming that your game is deterministic, it might be sufficient if you recorded the inputs of the users (option 2). However, you would need to make sure that you are recognizing the correct and consistent times for these events, such as when it was recognized by the server. I'm not sure how you handle events in the grid.
My worry is that if you don't have a mechanism that can uniformly reference timed events, there might be a problem with the way your code handles distributed users.
Consider a game like Halo 3 on the XBOX 360 for example - each client records his view of the game, including server-based corrections.
Why not record several times a second and then compress your output, or perhaps do this:
recordInitialState();
...
runs 30 times a second:
recordChangeInState(previousState, currentState);
...
If you only record the change in state with a timestamp(and each change is small, and if there is no change, then record nothing), you should end up with reasonable file sizes.
There is no need to save everything in the scene for every frame. Save changes incrementally and use some good interpolation techniques. I would not really use a command pattern based approach, but rather make checks at a fixed rate for every game object and see if it has changed any attribute. If there is a change that change is recorded in some good encoding and the replay won't even become that big.
How you approach this will depend greatly on the language you are using for your game, but in general terms there are many approaches, depending on if you want to use a lot of storage or want some delay. It would be helpful if you could give some thoughts as to what sacrifices you are willing to make.
But, it would seem the best approach may be to just save the input from the user, as was mentioned, and either store the positions of all the actors/sprites in the game at the same time, which is as simple as just saving direction, velocity and tile x,y, or, if everything can be deterministic then ignore the actors/sprites as you can get their information.
How non-deterministic your game is would also be useful to give a better suggestion.
If there is a great deal of dynamic motion, such as a crash derby, then you may want to save information each frame, as you should be updating the players/actors at a certain framerate.
I would simply say that the best way to record a replay of a game depends entirely on the nature of the game. Being grid based isn't the issue; the issue is how predictable behaviour is following a state change, how often there are new inputs to the system, whether there is random data being injected at any point, etc, You can store an entire chess game just by recording each move in turn, but that wouldn't work for a first person shooter where there are no clear turns. You could store a first person shooter by noting the exact time of each input, but that won't work for an RPG where the result of an input might be modified by the result of a random dice roll. Even the seemingly foolproof idea of taking a snapshot as often as possible isn't good enough if important information appears instantaneously and doesn't persist in any capturable form.
Interestingly this is very similar to the problem you get with networking. How does one computer ensure that another computer is made aware of the game state, without having to send that entire game state at an impractically high frequency? The typical approach ends up being a bespoke mixture of event notifications and state updates, which is probably what you'll need here.
I did this once by borrowing an idea from video compression: keyframes and intermediate frames. Basically, every few seconds you save the complete state of the world. Then, once per game update, you save all the changes to the world state that have happened since the last game update. The details (how often do you save keyframes? What exactly counts as a 'change to the world state'?) will depend on what sort of game information you need to preserve.
In our case, the world consisted of many, many game objects, most of which were holding still at any given time, so this approach saved us a lot of time and memory in recording the positions of objects that weren't moving. In yours the tradeoffs might be different.