This covers how you can create a basic 2D game using SurfaceView.
First, we need an activity:
public class GameLauncher extends AppCompatActivity {
private Game game;
@Override
public void onCreate(Bundle sis){
super.onCreate(sis);
game = new Game(GameLauncher.this);//Initialize the game instance
setContentView(game);//setContentView to the game surfaceview
//Custom XML files can also be used, and then retrieve the game instance using findViewById.
}
}
The activity also has to be declared in the Android Manifest.
Now for the game itself. First, we start by implementing a game thread:
public class Game extends SurfaceView implements SurfaceHolder.Callback, Runnable{
/**
* Holds the surface frame
*/
private SurfaceHolder holder;
/**
* Draw thread
*/
private Thread drawThread;
/**
* True when the surface is ready to draw
*/
private boolean surfaceReady = false;
/**
* Drawing thread flag
*/
private boolean drawingActive = false;
/**
* Time per frame for 60 FPS
*/
private static final int MAX_FRAME_TIME = (int) (1000.0 / 60.0);
private static final String LOGTAG = "surface";
/*
* All the constructors are overridden to ensure functionality if one of the different constructors are used through an XML file or programmatically
*/
public Game(Context context) {
super(context);
init();
}
public Game(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public Game(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
@TargetApi(21)
public Game(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init();
}
public void init(Context c) {
this.c = c;
SurfaceHolder holder = getHolder();
holder.addCallback(this);
setFocusable(true);
//Initialize other stuff here later
}
public void render(Canvas c){
//Game rendering here
}
public void tick(){
//Game logic here
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height)
{
if (width == 0 || height == 0){
return;
}
// resize your UI
}
@Override
public void surfaceCreated(SurfaceHolder holder){
this.holder = holder;
if (drawThread != null){
Log.d(LOGTAG, "draw thread still active..");
drawingActive = false;
try{
drawThread.join();
} catch (InterruptedException e){}
}
surfaceReady = true;
startDrawThread();
Log.d(LOGTAG, "Created");
}
@Override
public void surfaceDestroyed(SurfaceHolder holder){
// Surface is not used anymore - stop the drawing thread
stopDrawThread();
// and release the surface
holder.getSurface().release();
this.holder = null;
surfaceReady = false;
Log.d(LOGTAG, "Destroyed");
}
@Override
public boolean onTouchEvent(MotionEvent event){
// Handle touch events
return true;
}
/**
* Stops the drawing thread
*/
public void stopDrawThread(){
if (drawThread == null){
Log.d(LOGTAG, "DrawThread is null");
return;
}
drawingActive = false;
while (true){
try{
Log.d(LOGTAG, "Request last frame");
drawThread.join(5000);
break;
} catch (Exception e) {
Log.e(LOGTAG, "Could not join with draw thread");
}
}
drawThread = null;
}
/**
* Creates a new draw thread and starts it.
*/
public void startDrawThread(){
if (surfaceReady && drawThread == null){
drawThread = new Thread(this, "Draw thread");
drawingActive = true;
drawThread.start();
}
}
@Override
public void run() {
Log.d(LOGTAG, "Draw thread started");
long frameStartTime;
long frameTime;
/*
* In order to work reliable on Nexus 7, we place ~500ms delay at the start of drawing thread
* (AOSP - Issue 58385)
*/
if (android.os.Build.BRAND.equalsIgnoreCase("google") && android.os.Build.MANUFACTURER.equalsIgnoreCase("asus") && android.os.Build.MODEL.equalsIgnoreCase("Nexus 7")) {
Log.w(LOGTAG, "Sleep 500ms (Device: Asus Nexus 7)");
try {
Thread.sleep(500);
} catch (InterruptedException ignored) {}
}
while (drawing) {
if (sf == null) {
return;
}
frameStartTime = System.nanoTime();
Canvas canvas = sf.lockCanvas();
if (canvas != null) {
try {
synchronized (sf) {
tick();
render(canvas);
}
} finally {
sf.unlockCanvasAndPost(canvas);
}
}
// calculate the time required to draw the frame in ms
frameTime = (System.nanoTime() - frameStartTime) / 1000000;
if (frameTime < MAX_FRAME_TIME){
try {
Thread.sleep(MAX_FRAME_TIME - frameTime);
} catch (InterruptedException e) {
// ignore
}
}
}
Log.d(LOGTAG, "Draw thread finished");
}
}
That is the basic part. Now you have the ability to draw onto the screen.
Now, let’s start by adding to integers:
public final int x = 100;//The reason for this being static will be shown when the game is runnable
public int y;
public int velY;
For this next part, you are going to need an image. It should be about 100x100 but it can be bigger or smaller. For learning, a Rect can also be used(but that requires change in code a little bit down)
Now, we declare a Bitmap:
private Bitmap PLAYER_BMP = BitmapFactory.decodeResource(getResources(), R.drawable.my_player_drawable);
In render, we need to draw this bitmap.
...
c.drawBitmap(PLAYER_BMP, x, y, null);
...
BEFORE LAUNCHING there are still some things to be done
We need a boolean first:
boolean up = false;
in onTouchEvent, we add: