Develop Reference

Android app crashes upon attempt to switch to a different Activity

I am running into an issue in my app. When my game ends (when life == 0) I am attempting to switch to a game over screen by using a different activity. When the game ends, the app simply crashes. I have included the XML for the activity I am trying to switch from as well as indicating where the app crashes. If anyone could help out, that would be great! Thanks.
activity_game.XML:
SurfaceView I am trying to switch from once game ends:
public class SVGameView extends SurfaceView implements Runnable {
private SurfaceHolder holder;
Thread thread = null;
volatile boolean running = false;
static final long FPS = 30;
private Sprite sprite;
private long lastClick;
private Bitmap ball, gameOver;
//private int x = 200, y = 200;
private int scorePosX = 100;
private int scorePosY = 100;
private int countScore = 0;
private int life = 1;
public SVGameView(Context context) {
super(context);
thread = new Thread(this);
holder = getHolder();
holder.addCallback(new SurfaceHolder.Callback() {
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
boolean retry = true;
running = false;
while (retry) {
try {
thread.join();
retry = false;
} catch (InterruptedException e) {
}
}
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
running = true;
thread.start();
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format,
int width, int height) {
}
});
ball = BitmapFactory.decodeResource(getResources(), R.drawable.ball2);
gameOver = BitmapFactory.decodeResource(getResources(),R.drawable.endscreen);
sprite = new Sprite(this, ball);
}
#Override
public void run() {
long ticksPS = 1000 / FPS;
long startTime;
long sleepTime;
while (running) {
Canvas c = null;
startTime = System.currentTimeMillis();
try {
c = getHolder().lockCanvas();
synchronized (getHolder()) {
update();
draw(c);
}
} finally {
if (c != null) {
getHolder().unlockCanvasAndPost(c);
}
}
sleepTime = ticksPS-(System.currentTimeMillis() - startTime);
try {
if (sleepTime > 0)
thread.sleep(sleepTime);
else
thread.sleep(10);
} catch (Exception e) {}
}
}
private void update(){
sprite.update();
}
#Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.WHITE);
Paint paint = new Paint();
canvas.drawPaint(paint);
paint.setColor(Color.WHITE);
paint.setTextSize(48);
canvas.drawText("Score: " + countScore, scorePosX, scorePosY, paint);
canvas.drawText("Lives: " + life, 500, 100, paint);
sprite.onDraw(canvas);
//Crashes here
if(life == 0) {
getContext().startActivity(new Intent(getContext(), SVGameOver.class));
}
}
#Override
public boolean onTouchEvent(MotionEvent event) {
if(System.currentTimeMillis()-lastClick > 300){
lastClick = System.currentTimeMillis();
}
synchronized (getHolder()){
if(sprite.isHit(event.getX(), event.getY())){
countScore += 1;
sprite.increase();
}else{
life --;
}
}
return super.onTouchEvent(event);
}
}
Activity I am trying to reach once the game ends:
public class SVGameOver extends Activity {
private Bitmap gameOverScreen;
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game);
gameOverScreen = BitmapFactory.decodeResource(getResources(), R.drawable.endscreen);
}
protected void onDraw(Canvas canvas){
canvas.drawBitmap(gameOverScreen, 0,0,null);
}
}

I think logcat is asking you the right question: "have you declared this activity in your AndroidManifest.xml" ?
If you think you did it, It's highly probable you did it in a wrong way, most of the times that you think you added an Activity to the manifest but you are receiving this kind of crash, 99,9% of the time you declared it with a wrong namespace

Declare SVGameOver activity in your AndroidManifest.xml:
<activity
android:name="com.example.welcome.assignment2.SVGameOver">
...
</activity>

Best Practice: How to draw a Countdown within a Service

i´m new to Android programming and I have a Question.
I have a Countdown that will count down from 60 to zero when i am touching the screen.
I want now that this Countdown will survive the Activity lifecycling even when onDestroy is called. So I need a Service for that.
Wenn the countdown is finished a notification will be send. But if the user want to open the App again before the countdown in the Service is finished, no notification should be sended and the service has to be stopped.
What is the best practice to implement those features? What is here the way to go?
Thank you very much for answers!
My approach is that I have a class with the countdown methods and the service
//Countdownclass
TimerClass.java
public class TimerClass {
private static final String TAG = "MyLog";
private static final long TIMERINTERVAL = 1000;
//Eigenschaften --------------------------------------------------------------------
private boolean isActiv = false;
private Paint paint;
private long timerTime;
private double actualTime;
private int x;
private int y;
private CountDownTimer countDownTimer;
private String timeString;
//Konstruktor --------------------------------------------------------------------
public TimerClass(int x, int y) {
this.x = x;
this.y = y;
paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.YELLOW);
paint.setAntiAlias(true);
paint.setTextAlign(Align.RIGHT);
paint.setTextSize(70);
}
public TimerClass() {
}
//Methoden --------------------------------------------------------------------
public void draw(Canvas canvas) {
if(isActiv) {
canvas.drawText(timeString, x, y, paint);
}
}
public void createTimer(long timerTime) {
this.timerTime = timerTime;
countDownTimer = new CountDownTimer(timerTime, TIMERINTERVAL) {
#Override
public void onTick(long millisUntilFinished) {
actualTime = (double) millisUntilFinished / TIMERINTERVAL;
NumberFormat nf = new DecimalFormat("##.#");
nf.format(actualTime);
if(actualTime < 10) {
new DecimalFormat();
timeString = "0:0" + nf.format(actualTime - 1);
} else {
timeString = "0:" + nf.format(actualTime - 1);
}
}
#Override
public void onFinish() {
isActiv = false;
}
};
}
public void timerStart() {
countDownTimer.start();
isActiv = true;
}
public void timerStop() {
if(isActiv) {
countDownTimer.cancel();
}
isActiv = false;
}
public boolean isActiv() {
return isActiv;
}
public void setActiv(boolean isActiv) {
this.isActiv = isActiv;
}
public double getActualTime() {
return actualTime;
}
public void setActualTime(double actualTime) {
this.actualTime = actualTime;
}
And my Service:
public class TimerService extends Service {
//class with the countdowntimer
private TimerClass timerClass;
private long startTime;
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onCreate() {
super.onCreate();
timerClass = new TimerClass();
startTime = (long) timerClass.getActualTime();
timerClass.createTimer(startTime);
}
#Override
public void onDestroy() {
timerClass.timerStop();
super.onDestroy();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
timerClass.timerStart();
if(timerClass.getActualTime() <= 0) {
// send the notification
}
return super.onStartCommand(intent, flags, startId);
}
I wanted to start the Service in my mainActivies onPause method and stop it when onResume is called. But i´ve have tried it many times and failed.. so i have no code for my service in my activity.
( Sorry for my broken english :( )

ProgressBar causing constant onDraw calls for all the UI

I have an activity which has a ProgressBar. This bar is used to show the elapsed time on the game level.
I'm updating this bar and a TextView with a CountdownTimer, called every 100ms. The problem is that every time I call setProgress, it seems to be causing an invalidate() that makes my whole UI to be redrawn. If I delete the line where the ProgressBar get updated everything works fine, even setText for the TextView that show the time left.
This is a problem for me because I also have a custom view which needs to be redrawn only when I need it, or at least a few times but not constantly because it'll affect performance.
This is a piece of my code:
private CountDownTimer timer;
private long ttime;
private long ctime;
private ProgressBar bar;
private TextView clock;
#Override
protected void onCreate(Bundle savedInstanceState) {
...
startTimer(500);
...
}
#Override
protected void onResume() {
super.onResume();
if(!checkFlags()){
startTimer(500);
}
}
#Override
protected void onPause() {
super.onPause();
if(!checkFlags()){
timer.cancel();
}
}
private void startTimer(long delay){
timer = new CountDownTimer(ctime,100){
public void onTick(long millisUntilFinished){
ctime = millisUntilFinished;
clock.setText(formatTime(millisUntilFinished));
bar.setProgress((int) (1000 - ((ctime * 1000)/ttime)));
}
public void onFinish(){
clock.setText("00:00");
gameOver(false);
}
};
if(delay > 0){
Handler handler = new Handler();
handler.postDelayed(new Runnable(){
public void run(){
timer.start();
}
},delay);
}else{
timer.start();
}
}
How could I prevent the ProgressBar to cause this onDraw calls for every element of the UI?

According to 'sources/android-18/android/widget/ProgressBar.java' in Android SDK the call of setProgress() will result in the call of invalidate().
private synchronized void doRefreshProgress(int id, int progress, boolean fromUser,
boolean callBackToApp) {
float scale = mMax > 0 ? (float) progress / (float) mMax : 0;
final Drawable d = mCurrentDrawable;
if (d != null) {
Drawable progressDrawable = null;
if (d instanceof LayerDrawable) {
progressDrawable = ((LayerDrawable) d).findDrawableByLayerId(id);
if (progressDrawable != null && canResolveLayoutDirection()) {
progressDrawable.setLayoutDirection(getLayoutDirection());
}
}
final int level = (int) (scale * MAX_LEVEL);
(progressDrawable != null ? progressDrawable : d).setLevel(level);
} else {
>>> invalidate();
}
if (callBackToApp && id == R.id.progress) {
onProgressRefresh(scale, fromUser);
}
}
Try to use setProgressDrawable(). It seems that invalidate() is not called in that case.

Surfaceview ANR onResume

I'm working on a Android game using SurfaceView, the game works fine, so I want to pause it when the user hits HOME key but when getting back the SurfaceView disappears(black background Edit: sometimes the drawing appears) and buttons are inactive in both cases then I get ANR.
public class MainActivity extends Activity {
private Game game;
MainPanel mp;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
game = new Game();
LoadLevel();
Init();
setContentView(R.layout.main);//contains surfaceview and buttons
mp = (MainPanel) findViewById(R.id.SurfaceView01);
mp.Init(game,this);
Button btnTop = (Button) findViewById(R.id.buttonTop);
Button btnBottom = (Button) findViewById(R.id.buttonBottom);
Button btnLeft = (Button) findViewById(R.id.buttonLeft);
Button btnRight = (Button) findViewById(R.id.buttonRight);
btnTop.setOnClickListener...
}
private void Init() {
...
}
public void LoadLevel() {
...
}
#Override
protected void onResume() {
super.onResume();
Log.d("Tag","Resume");
}
#Override
protected void onPause() {
super.onPause();
Log.d("Tag","Pause");
}
}
public class MainPanel extends SurfaceView implements SurfaceHolder.Callback {
private MainThread thread;
private Game game;
private MainActivity act;
public MainPanel(Context context, AttributeSet attrs) {
super(context,attrs);
getHolder().addCallback(this);
}
public MainThread getThread() {
return thread;
}
public void Init(Game game, MainActivity act){
this.game = game;
this.act = act;
}
public void Move(int dir) {
...
}
public void update() {
...
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {}
#Override
public void surfaceCreated(SurfaceHolder holder) {
if (thread == null) {
thread = new MainThread(getHolder(), this);
thread.Start();
thread.start();
}
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
thread.Stop();
boolean retry = true;
while (retry) {
try {
thread.join();
retry = false;
} catch (InterruptedException e) {}
}
thread = null;
}
#Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.BLACK);
//drawing...
}
}
public class MainThread extends Thread {
private final static int MAX_FPS = 30;
private final static int MAX_FRAME_SKIPS = 3;
private final static int FRAME_PERIOD = 1000 / MAX_FPS;
private SurfaceHolder surfaceHolder;
private MainPanel gamePanel;
private boolean run = false;
private boolean start = false;
public MainThread(SurfaceHolder surfaceHolder, MainPanel gamePanel) {
super();
this.surfaceHolder = surfaceHolder;
this.gamePanel = gamePanel;
}
public void Start() {
this.run = true;
this.start = true;
}
public void Pause() {
this.start = false;
}
public void Resume() {
this.start = true;
}
public void Stop() {
this.run = false;
}
#Override
public void run() {
Canvas c = null;
long beginTime; // the time when the cycle begun
long timeDiff; // the time it took for the cycle to execute
int sleepTime; // ms to sleep (<0 if we're behind)
int framesSkipped; // number of frames being skipped
while(run) {
while(start) {
try {
c = surfaceHolder.lockCanvas(null);
synchronized (surfaceHolder) {
beginTime = System.currentTimeMillis();
framesSkipped = 0; // resetting the frames skipped
// update game state
gamePanel.update();
// render state to the screen draws the canvas on the panel
if(c!=null) gamePanel.onDraw(c);
// calculate how long did the cycle take
timeDiff = System.currentTimeMillis() - beginTime;
// calculate sleep time
sleepTime = (int)(FRAME_PERIOD - timeDiff);
if (sleepTime > 0) {
// if sleepTime > 0 we're OK
try {
// send the thread to sleep for a short period very useful for battery saving
Thread.sleep(sleepTime);
} catch (InterruptedException e) {}
}
while (sleepTime < 0 && framesSkipped < MAX_FRAME_SKIPS) {
// we need to catch up update without rendering
gamePanel.update();
// add frame period to check if in next frame
sleepTime += FRAME_PERIOD;
framesSkipped++;
}
}
} finally {
if (c != null) surfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
}

Thx to this post why is my runnable giving ANR? I could solve the problem, I isolated the MainThread from the UI thread for further details check the best answer.

Refreshing canvas?

I try to display one from list of bitmaps during onDraw.
When i'm passing list to the canvas all are display and stay in their places.
When I pass one random bitmaps it's redrawing canvas all the time.
All works when i'm using public void drawEnemy(Canvas canvas) but not exactly like I want when using public void drawEn(Canvas canvas).
I want to display one random bitmap, then after a few seconds, delete it and display other bitmap. I think the problem is how I implemented onDrow() method. It's redrawing canvas all the time.
Activity:
public class NewGameActivity extends Activity{
NewGame newgame;
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
// Landscape mode
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
// no title
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
// content Newgame.java
newgame = new NewGame(this);
setContentView(newgame);
}
Thread:
public class MainThread extends Thread{
private SurfaceHolder surfaceHolder;
private NewGame screen;
public MainThread(SurfaceHolder surfaceHolder, NewGame ekran) {
super();
this.surfaceHolder = surfaceHolder;
this.screen= screen;
}
private boolean running;
public void setRunning(boolean running) {
this.running = running;
}
#Override
public void run() {
Canvas canvas;
while (running) {
canvas = null;
try {
canvas = this.surfaceHolder.lockCanvas();
synchronized (surfaceHolder) {
this.screen.onDraw(canvas);
}
} finally {
if (canvas != null) {
surfaceHolder.unlockCanvasAndPost(canvas);
}
}
}
}
}
SurfaceView:
public class NewGame extends SurfaceView implements SurfaceHolder.Callback{
private MainThread thread;
private EnemyManager manager;
public NewGame(Context context) {
super(context);
getHolder().addCallback(this);
thread = new MainThread(getHolder(), this);
manager = new EnemyManager();
// TODO Auto-generated constructor stub
//adding enemy
Enemy e1 = new Enemy(BitmapFactory.decodeResource(getResources(), R.drawable.card), 1);
Enemy e2 = new Enemy(BitmapFactory.decodeResource(getResources(), R.drawable.horse), 2);
EnemyLocation l1 = new EnemyLocation(60, 180);
EnemyLocation l2 = new EnemyLocation(60, 50);
manager.AddEnemy(e1, l1);
manager.AddEnemy(e2, l2);
setFocusable(true);
}
#Override
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.saloon), 0, 0, null);
manager.drawEn(canvas);
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
thread.setRunning(true);
thread.start();
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
thread.setRunning(false);
thread.stop();
}
#Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
manager.handleActionDown((int)event.getX(), (int)event.getY());
}
return true;
}
}
EnemyManager:
public class EnemyManager {
private ArrayList<Enemy> enemyList;
private ArrayList<Enemy> suspects;
private Enemy cow;
private String message;
private int suspectID;
private Random rnd;
public String getMessage() {
return message;
}
public EnemyManager(){
enemyList = new ArrayList<Enemy>();
suspects = new ArrayList<Enemy>();
}
public void AddEnemy(Enemy enemy, EnemyLocation loc){
// set x,y enemy localization
enemy.setX(loc.getX());
enemy.setY(loc.getY());
enemyList.add(enemy);
}
public void clearEnemy() {
enemyList.clear();
}
// message if enemy touched
public void handleActionDown(int x, int y) {
for (Enemy enemy: enemyList) {
if (enemy.wasTouched(x, y)) {
message = enemy.getId();
return;
}
}
}
public void PrepareEnemy(){
suspectID = enemyList.get(rnd.nextInt(enemyList.size()+1)).getId();
suspects = new ArrayList<Enemy>();
suspects.add(getSuspectByID(suspectID));
}
private Enemy SingleEnemy(){
Double i = 1 + Math.random() * ((enemyList.size()-1)+1);
cow = getSuspectByID(i.intValue());
return cow;
}
private Enemy getSuspectByID(int suspectID) {
for (Enemy s: enemyList) {
if (s.getId() == suspectID) {
return s;
}
}
return null;
}
public void drawEn(Canvas canvas){
try {
Enemy k = SingleEnemy();
canvas.drawBitmap(cow.picture, cow.x, cow.y, null);
} catch (Exception e) {
// TODO: handle exception
}
}
// draw enemy
public void drawEnemy(Canvas canvas) {
try {
for (Enemy enemy: enemyList) {
canvas.drawBitmap(enemy.picture, enemy.x, enemy.y, null);
}
} catch (Exception e) {
// TODO: handle exception
}
}
}
das

As for as understand you are trying to do something like this (if it's not, please correct me):
This is rendering the canvas with all components:
Draw background
Draw enemy
To "refresh" the canvas you simply do something like this:
Draw background
Update
To pause the rendering you could do something like this:
int lastUpdateTime;
int delayTime = 2000; 2 seconds
if(System.currenttimeMillis() > lastUpdateTime + delayTime) {
// Finished waiting
}
You should only define lastUpdateTime when you want to wait and not in every iteration.
NB: Don't call Thread.sleep() in a rendering thread!