I have a Main Activity and in the corresponding XML Layout I have a Custom View that draws game objects (my tank and 10 enemies), a few buttons to control my tank and fire bullets and a TextView to show my score. My custom view is a GameSurfaceView java class that is a half screen game board.
Here is some of my code:
public class GameSurfaceView extends SurfaceView implements Runnable {
private static Context gContext;
public GameSurfaceView(Context context, AttributeSet attributeSet) {
super(context, attributeSet);
holder = getHolder();
holder.addCallback(new SurfaceHolder.Callback() {
resume();
gContext = context;
}
public void resume() {
isRunning = true;
gameThread = new Thread(this);
gameThread.start();
}
public void pause() {
isRunning = false;
boolean retry = true;
while (retry) {
try {
gameThread.join();
retry = false;
} catch (InterruptedException e) {
// try again shutting down the thread
}
}
}
#Override
public void run() {
while (isRunning) {
// We need to make sure that the surface is ready
if (!holder.getSurface().isValid()) {
continue;
}
long started = System.currentTimeMillis();
// update
step();
// draw
Canvas canvas = holder.lockCanvas();
if (canvas != null) {
render(canvas);
holder.unlockCanvasAndPost(canvas);
}
//detect all possible collisions
detectCollisions();
float deltaTime = (System.currentTimeMillis() - started);
int sleepTime = (int) (FRAME_PERIOD - deltaTime);
if (sleepTime > 0) {
try {
gameThread.sleep(sleepTime);
} catch (InterruptedException e) {
}
}
while (sleepTime < 0) {
step();
sleepTime += FRAME_PERIOD;
}
}
}
//Called from MainActivity
public void dispatchKey(int tDirection) {
Toast.makeText(gContext, "Hi", Toast.LENGTH_LONG).show();
gameStarted = true;
if (tDirection == FIRE)
Fire();
else if (tDirection != tank.Direction)
turnTankDirection = tDirection;
}
private void detectCollisions() {
//Collision Detection between tank and enemy
Toast.makeText(gContext, "Collision", Toast.LENGTH_LONG).show();
}
}
My questions:
1- Why the Toast in dispatchKey() runs correctly but Toast in detectCollisions() makes a force close?
2- How to update TextView in detectCollisions() method?
3- How to show a DialogAlert when a collision detected in detectCollisions() method?
My problem relates mainly to gContext variable.
Thanks.
Regarding question 1: Maybe this effects the second thread. While dispatchKey() is called from Activity, detectCollision() is invoked from the sureface-thread. Did you tried to call detectCollision() from activity?
Regarding question 3: let your activity implement a listener, which will be called if collision is detected. The same thing you could use as solution of question 1 and 2.
You should try:
MainActivity.this.runOnUiThread(new Runnable() {
public void run() {
//Make toast or manipulate TextView
}
});
I write a simple game with the following structure. Main xml layout have user View:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/menuRL"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<com.sokolovlev.UFOtest03.MenuView
android:id="#+id/menuView"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
</RelativeLayout>
This View have two files. First is user MenuView:
package com.sokolovlev.UFOtest03;
import android.content.Context;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MenuView extends SurfaceView implements SurfaceHolder.Callback
{
private SurfaceHolder mSurfaceHolder; //Draw surface
public static MenuManager mMenuManager; //Draw manager
public MenuView(Context context, AttributeSet attrs)
{
super(context, attrs);
// Surface events registration
mSurfaceHolder = getHolder();
mSurfaceHolder.addCallback(this);
mMenuManager = new MenuManager(mSurfaceHolder, context);
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height)
{
mMenuManager.initPositions(height, width);
}
#SuppressWarnings("static-access")
#Override
public void surfaceCreated(SurfaceHolder holder)
{
mMenuManager.setRunning(true);
try
{
mMenuManager.start();
}
catch (Exception e) { }
}
#SuppressWarnings("static-access")
#Override
public void surfaceDestroyed(SurfaceHolder holder)
{
boolean retry = true;
mMenuManager.setRunning(false);
while (retry)
{
try
{
mMenuManager.join();
retry = false;
}
catch (InterruptedException e) { }
}
}
}
And second file is this draw manager:
package com.sokolovlev.UFOtest03;
import ...
public class MenuManager extends Thread
{
private SurfaceHolder mSurfaceHolder;
private static boolean mRunning;
private int _screenHeight;
private int _screenWidth;
private ...
Context c;
private ...
public MenuManager(SurfaceHolder surfaceHolder, Context context)
{
mSurfaceHolder = surfaceHolder;
mRunning = false;
c = context;
...
}
public static void setRunning(boolean running)
{
mRunning = running;
}
#Override
public void run()
{
while (mRunning)
{
Canvas canvas = null;
try
{
// подготовка Canvas-а
canvas = mSurfaceHolder.lockCanvas();
canvas.drawRGB(0, 0, 0);
synchronized (mSurfaceHolder)
{
//All drawing
}
}
catch (Exception e) { }
finally
{
if (canvas != null)
{
mSurfaceHolder.unlockCanvasAndPost(canvas);
}
}
}
}
}
Everything works fine! (step №1) But if I press central button, or I have incoming call, or I call task manager (step №2) and go back to my app - I haven't my drawing, only black screen (step №3). But if I go next to step №2 and then in my app, I see that everything works.
I don't understand, where there is a reloading which influences such on my drawings! Help please!
To solve this problem, I need to save the settings and restart my surface. Then load the settings. (See LunarLander Example)
HI! I have a surfaceView inside a horizontal scrollview that I want to fill with images with a onDraw() call. However, nothing is drawn.
I have a class in which the drawing is done from the thread CanvasThread.
public class PanelChart extends SurfaceView implements SurfaceHolder.Callback {
private CanvasThread canvasthread ;
public PanelChart(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
getHolder().addCallback(this);
canvasthread = new CanvasThread(getHolder(), this);
setFocusable(true);
I have tried to change the
`synchronized (_surfaceHolder) {
_panel.postInvalidate();
}`
to
synchronized (_surfaceHolder) {
_panel.postInvalidate();
}
I have also tried to add the call setWillNotDraw(false) without luck:
#Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
canvasthread.setRunning(true);
canvasthread.start();
setWillNotDraw(false);
This seems to be a common issue, but none of the solutions I have come across have worked for me.
Thanks!
postInvalidate will not call onDraw with surfaceView. You need to unlock canvas, draw things and then lock canvas. Here is an example of a thread for surfaceView:
class CanvasThread extends Thread {
private SurfaceHolder surfaceHolder;
private PanelChart panel;
private boolean run = false;
public CanvasThread(SurfaceHolder surfaceHolder, PanelChart panel) {
this.surfaceHolder = surfaceHolder;
this.panel = panel;
}
public void setRunning(boolean run) {
this.run = run;
}
public SurfaceHolder getSurfaceHolder() {
return surfaceHolder;
}
#Override
public void run() {
Canvas c;
while (run) {
c = null;
//limit the frame rate to maximum 60 frames per second (16 miliseconds)
timeNow = System.currentTimeMillis();
timeDelta = timeNow - timePrevFrame;
if ( timeDelta < 16){
try{
Thread.sleep(16 - timeDelta);
}catch(InterruptedException e){
}
}
timePrevFrame = System.currentTimeMillis();
try {
c = surfaceHolder.lockCanvas(null);
synchronized (surfaceHolder) {
panel.onDraw(c); //draw canvas
computePhysics(); //calculate next frame
}
} finally {
if (c != null) {
surfaceHolder.unlockCanvasAndPost(c); //show canvas
}
}//try finally
} //while
}//run
}//thread
I'm trying to work with 3 SurfaceViews on one screen, one on top half (BoardView), one on bottom half (StatusView), and the last one as an extra layer above the top half (TileView) (see main.xml).
I created a class MySurfaceView, which is extended by BoardView, StatusView and TileView.
I've got multiple problems with this.
Let me first give the code.
main.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#color/main_background">
<com.niek.test.BoardView
android:id="#+id/boardview"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
<FrameLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_below="#+id/boardview">
<com.niek.test.StatusView
android:id="#+id/statusview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#F0931E"
android:layout_below="#+id/boardview" />
<com.niek.test.TileView
android:id="#+id/tileview"
android:layout_width="180dip"
android:layout_height="60dip"
android:layout_gravity="bottom"/>
</FrameLayout>
</RelativeLayout>
MainActivity.java:
package com.niek.test;
public class MainActivity extends Activity {
private Board board;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
board = new Board();
BoardView boardView = (BoardView) findViewById(R.id.boardview);
boardView.setBoard(board);
StatusView statusView = (StatusView) findViewById(R.id.statusview);
statusView.setBoard(board);
}
}
MySurfaceView.java
package com.niek.test;
public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback {
protected DrawThread drawThread;
public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
getHolder().addCallback(this);
setFocusable(true);
drawThread = new DrawThread(getHolder());
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
// TODO Auto-generated method stub
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
drawThread.setRunning(true);
drawThread.start();
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
// we have to tell thread to shut down & wait for it to finish, or else
// it might touch the Surface after we return and explode
boolean retry = true;
drawThread.setRunning(false);
while (retry) {
try {
drawThread.join();
retry = false;
} catch (InterruptedException e) {
// we will try it again and again...
}
}
}
protected class DrawThread extends Thread {
private SurfaceHolder surfaceHolder;
private boolean isRunning;
public DrawThread(SurfaceHolder surfaceHolder) {
this.surfaceHolder = surfaceHolder;
isRunning = false;
}
public void setRunning(boolean run) {
isRunning = run;
}
public void run() {
Canvas c;
while (isRunning) {
try {
Thread.sleep(100);
} catch (Exception e) {
// TODO: handle exception
}
c = null;
try {
c = surfaceHolder.lockCanvas(null);
synchronized (surfaceHolder) {
onDraw(c);
postInvalidate();
}
} finally {
// do this in a finally so that if an exception is thrown
// during the above, we don't leave the Surface in an
// inconsistent state
if (c != null) {
surfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
}
}
These three classes extend MySurfaceView:
BoardView.java
package com.niek.test;
public class BoardView extends MySurfaceView {
private int squareSize, marginX, marginY;
private Board board;
Paint boardBorder;
public BoardView(Context context, AttributeSet attrs) {
super(context, attrs);
board = null;
}
public void setBoard(Board board) {
this.board = board;
}
private void init(SurfaceHolder holder) {
Canvas canvas = null;
try {
canvas = holder.lockCanvas();
/* Initialize the board */
squareSize = canvas.getWidth() / Board.GRIDSIZE;
/* Size the view */
LayoutParams lp = getLayoutParams();
lp.height = (squareSize * Board.GRIDSIZE) + 4;
setLayoutParams(lp);
/* Place the board neatly in the center */
marginX = (canvas.getWidth() - (squareSize * Board.GRIDSIZE)) / 2;
marginY = 1;
} finally {
holder.unlockCanvasAndPost(canvas);
}
boardBorder = new Paint();
boardBorder.setColor(Color.RED);
boardBorder.setStyle(Style.STROKE);
}
#Override
public void onDraw(Canvas canvas) {
drawBoard(board, canvas);
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
init(holder);
super.surfaceCreated(holder);
}
private void drawBoard(Board board, Canvas canvas) {
synchronized (board) {
if (board != null) {
for (Square[] ys : board.getSquares()) {
for (Square xs : ys) {
xs.onDraw(canvas, squareSize, squareSize, marginX, marginY);
}
}
}
canvas.drawRect(marginX - 1, marginY - 1, marginX + squareSize * Board.GRIDSIZE + 1, marginY + squareSize * Board.GRIDSIZE + 1, boardBorder);
}
}
}
StatusView.java
package com.niek.test;
public class StatusView extends MySurfaceView {
private Board board;
private Paint textPaint;
public StatusView(Context context, AttributeSet attrs) {
super(context, attrs);
board = null;
textPaint = new Paint();
textPaint.setColor(Color.BLACK);
textPaint.setTextSize(20);
textPaint.setTypeface(Typeface.DEFAULT_BOLD);
}
public void setBoard(Board board) {
this.board = board;
}
int tmp=0;
#Override
public void onDraw(Canvas c) {
if (board != null) {
c.drawText(tmp+"", 10, 20, textPaint);
tmp++;
System.out.println(tmp);
}
}
}
TileView.java
package com.niek.test;
public class TileView extends MySurfaceView {
public TileView(Context context, AttributeSet attrs) {
super(context, attrs);
System.out.println(0);
}
int tmp =0;
#Override
public void onDraw(Canvas c) {
System.out.println(2);
Paint p= new Paint();
p.setColor(Color.RED);
c.drawColor(Color.RED);
c.drawText(tmp+"",10,10,p);
tmp++;
}
}
Now what are my problems?
First off, as you can see in MySurfaceView I've got this:
try {
c = surfaceHolder.lockCanvas(null);
synchronized (surfaceHolder) {
onDraw(c);
postInvalidate();
}
}
When I only use onDraw(c), only the BoardView gets drawn, the StatusView doesn't get drawn, but the tmp increments in the onDraw of StatusView are being executed.
When I only use postInvalidate(), same story, but only StatusView gets drawn, BoardView doesn't.
So that's why I use both methods, and both Views get drawn.
Then there's TileView, the System.out(2) is being shown in logcat, but the view doesn't get drawn. It is a black square instead of the red square I ask it to be in the onDraw method.
When I turn the screen off and then on again, the TileView does get drawn, and the tmp increments are shown.
Who can help me?
For clarity, I've created this based on this tutorial.
You can have multiple SurfaceViewsin one layout. The "Multi-surface test" activity in Grafika has three.
The first post cited in #nonsleepr's answer was followed up 9 months later with this post by the same author, which mentioned the existence of SurfaceView#setZOrderMediaOverlay().
The key thing to understand is that SurfaceView is not a regular view. When your app comes to the foreground it gets a surface to draw on. Everything in your app's UI is rendered onto the app's surface by the app, and then that surface is composited with other surfaces (like the status bar and navigation bar) by the system compositor. When you create a SurfaceView, it's actually creating an entirely new surface that is composited by the system, not by your app.
You can control the Z-ordering (i.e. "depth") of the SurfaceView surface very loosely. There are four positions, from top to bottom:
SurfaceView + ZOrderOnTop
(app UI goes here)
SurfaceView + ZOrderMediaOverlay
SurfaceView (default)
If you have two SurfaceViews at the same depth, and they overlap, the results are undefined -- one will "win", but you can't control which.
The system compositor on modern devices is very efficient when you have N surfaces. At N+1 surfaces you hit a performance cliff. So while you can have three SurfaceViews, you're generally better off keeping the number down. The value of N varies from device to device.
Update: if you really want to understand how SurfaceView works, see the Android System-Level Graphics doc.
It looks like you are not supposed to create multiple SurfaceViews on one Layout.
According to this two posts written by Android framework engineer:
The way surface view is implemented is that a separate surface is created and Z-ordered behind its containing window, and transparent pixels drawn into the rectangle where the SurfaceView is so you can see the surface behind. We never intended to allow for multiple surface view.
and
you should effectively think of SurfaceView as an overlay you embed inside your window,
giving you an area in which you can directly draw independently of the normal view update system.
So, what you can do, is use one SurfaceView to draw all the graphics you want.
It sounds like the SurfaceViews are being drawn, but transparency is not enabled for whichever one is on top. In your MySurfaceView class in the surfaceCreated() method, make sure you are calling holder.setFormat(PixelFormat.TRANSPARENT);
I'm experimenting with SurfaceView and creating simple animations with it, I don't understand why my animation (changins screen color from black to white) is working here (without using SurfaceHolder.Callback)
public class MySurface extends SurfaceView {
private boolean playing = true;
private int counter = 0;
public MySurface(Context context){
super(context);
new Anim().start();
}
private class Anim extends Thread {
#Override
public void run() {
while (playing) {
try {
sleep(1000);
draw();
counter++;
} catch (Exception e){
e.printStackTrace();
}
}
}
private void draw() {
SurfaceHolder holder = getHolder();
Canvas canvas = holder.lockCanvas();
if (canvas != null) {
if (counter % 2 == 0) {
canvas.drawColor(Color.WHITE);
} else
canvas.drawColor(Color.BLACK);
holder.unlockCanvasAndPost(canvas);
}
}
}
}
But it's not working here, what's the difference? I think it might be caused by calling .run() instead of .start()
public class MySurface extends SurfaceView implements SurfaceHolder.Callback {
Anim anim;
private boolean playing = true;
private int counter = 0;
public MySurface(Context context){
super(context);
}
// all Callbacks are overrided i didn add them to make code easier to read
#Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
anim = new Anim();
anim.run();
}
private class Anim extends Thread {
#Override
public void run() {
while (playing) {
try {
sleep(1000);
draw();
counter++;
} catch (Exception e){
e.printStackTrace();
}
}
}
private void draw() {
SurfaceHolder holder = getHolder();
Canvas canvas = holder.lockCanvas();
if (canvas != null) {
if (counter % 2 == 0) {
canvas.drawColor(Color.WHITE);
} else
canvas.drawColor(Color.BLACK);
holder.unlockCanvasAndPost(canvas);
}
}
}
}
EDIT: I forgot to add getHolder().addCallback(this) that caused the issue.
Could someone still point out the differnces between those two methods and tell which one is better?
EDIT2: anim.start() was also needed