Develop Reference

Can I switch activities from a SurfaceView?

I am trying to adapt a snake game in Android Studio so that game over triggers a GameOverActivity. The problem is that the game over text is currently written to the screen in the redrawCanvas() function:
public void redrawCanvas(Canvas canvas) {
if (this.snake.isEnabled()) {
this.snake.draw(canvas);
this.apple.draw(canvas);
this.score.draw(canvas);
} else {
Paint p = getPaint();
p.setTextSize(50);
p.setColor(Color.BLACK);
canvas.drawText("Game over!", 100, 100, p);
// LAUNCH PLAY AGAIN ACTIVITY HERE?
}
}
and this redrawCanvas code is contained in a class extending SurfaceView. I would ordinarily call an intent, but I can't call startActivity() from within a SurfaceView class. My SnakeGameActivity just sets the content view, and all the code occurs in this surface view. Here is the code in SnakeGameActivity:
public class SnakeGameActivity extends com.codepath.simplegame.GameActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//before activity is created : cold start
//switch back to original Theme (App Theme)
setTheme(R.style.AppTheme);
switchFullscreen();
setContentView(new SnakeGamePanel(this));
}
}
And here is the full code in SnakeGamePanel:
public class SnakeGamePanel extends AbstractGamePanel {
public SnakeGamePanel(Context context) {
super(context);
}
private SnakeActor snake;
private AppleActor apple ;
private ScoreBoard score;
private boolean isPaused = false;
#Override
public void onStart() {
this.snake = new SnakeActor(100, 100);
this.apple = new AppleActor(200, 50);
this.score = new ScoreBoard(this);
}
#Override
public void onTimer() {
if (!isPaused) {
if (this.snake.checkBoundsCollision(this)) {
this.snake.setEnabled(false);
}
this.snake.move();
if (this.apple.intersect(this.snake)) {
this.snake.grow();
this.score.earnPoints(50);
this.apple.reposition(this);
}
}
}
#Override
public void redrawCanvas(Canvas canvas) {
if (this.snake.isEnabled()) {
this.snake.draw(canvas);
this.apple.draw(canvas);
this.score.draw(canvas);
} else {
Paint p = getPaint();
p.setTextSize(50);
p.setColor(Color.BLACK);
canvas.drawText("Game over!", 100, 100, p);
// LAUNCH PLAY AGAIN ACTIVITY?
}
}
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
this.snake.handleKeyInput(keyCode);
if (keyCode == KeyEvent.KEYCODE_G) {
this.onStart();
}
if (keyCode == KeyEvent.KEYCODE_P) {
isPaused = !isPaused;
}
return true;
}
#Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
this.snake.handleTouchInput(event);
return true;
}
return false;
}
}
Is there any way to start an activity when the game ends?

One alternative to your inner class solution is to pass a Context object to the constructor of your SurfaceView subclass. Then you can call startActivity() on that context.

I found what seems to be a solution so far. I just made the SurfaceView extension class be an inner class in my activity. That way, it has an activity as a containing class.

Android pause an observer when view is removed

I have two custom views (canvas views) and both of them have an observer which triggers an event on the screen and draw something on canvas. I am reusing the container and rendering the canvas in the same parent layout by removing other views. Right now, no matter what my both view observer values.
I have tried an dirty hack where I am passing a boolan to both views as true being one and other being false on switch which kinda work but I don't want that. Because it is just a hack. Can anyone tell me an android way to do it?
public class FakeViewOne extends View {
private EventViewModel eventViewModel;
private float l = 0.0f;
public FakeViewOne(Context context, View ParentView) {
super(context);
eventViewModel = new ViewModelProvider((ViewModelStoreOwner) getContext()).get(EventViewModel.class);
eventViewModel.getTrigger().observe((LifecycleOwner) getContext(), new Observer<Float>() {
#Override
public void onChanged(Float val) {
l = val;
}
});
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
/*
* if l > 50 change background of a linearlayout
* draw a line on a canvas
* */
invalidate();
}
}
public class FakeViewTwo extends View {
private EventViewModel eventViewModel;
private float l = 0.0f;
public FakeViewTwo(Context context, View ParentView) {
super(context);
eventViewModel = new ViewModelProvider((ViewModelStoreOwner) getContext()).get(EventViewModel.class);
eventViewModel.getTrigger().observe((LifecycleOwner) getContext(), new Observer<Float>() {
#Override
public void onChanged(Float val) {
l = val;
}
});
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
/*
* if l > 50 change background of a tile
*
* */
invalidate();
}
}
CODE Inside a Fragment where I am switch between those two FakeViews. How can I make those not observe values when they are not-rendered/inactive/removed from the view. I am using mycanvas.removeAllViews();.
final RelativeLayout mycanvas = view.findViewById(R.id.myCanvas);
gestureViewModel.getGestureType().observe(getActivity(), new Observer<String>() {
#Override
public void onChanged(#Nullable String s) {
assert s != null;
mycanvas.removeAllViews();
switch (s){
case "shake":
ShakeControl(view,myView,mycanvas);
break;
case "move":
MoveControl(view,myView,mycanvas);
break;
}
}
});

I have solved the problem with removing the observers on window detach in each FakeView.
#Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
Log.d("Detached","Head");
if (eventViewModel != null && eventViewModel.getTrigger().hasObservers()) {
eventViewModel.getTrigger().removeObservers((LifecycleOwner) ctx);
}
}

[Android]onTouch in child View is not responding

I have been working on making Sudoku grid whose cell's value changes whenever I touch on a cell. So I have implemented this sudoku grid in a LinearLayout by Child View, and tried using OnTouch method, but it is not working. I tried using log method to check whether onTouch is actually called, but it seemes that this method is perfectly ignored. I have been searching for solutions on other question, but it seems none of those solutions helped. I feel kinda suck here, and any help would be greatly appreciated.
Here is my code:
SudokuActivity.java
package snacker.nonogramsolver;
import ...; /*many things are imported here*/
public class SudokuActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sudoku);
Button btn = (Button)findViewById(R.id.btn_clear);
Sudoku sdk = new Sudoku(this);
sdk.setOnTouchListener(sdk);
}
}
;
Sudoku.java
package snacker.nonogramsolver;
import ...;
public class Sudoku extends View implements View.OnTouchListener {
int mWidth = 9;
int mHeight = 9;
int mCellWidth, mCellHeight;
int mCellMargin;
int mEdgeThick;
int mStatus;
int mTextSize;
int mXNow = -1, mYNow = -1;
int[][] mBoard = new int[9][9];
Point mBoardPt;
Paint mTextPaint, mTileEdgePaint;
final static int VALID = 0;
public Sudoku(Context context){
super(context);
initializeBoard();
}
public Sudoku(Context context, AttributeSet attrs){
super(context, attrs);
initializeBoard();
}
#Override
protected void onDraw(Canvas canvas){
/* There are some codes here */
Log.d("LogTest","OnDraw Complete");
}
public void initializeBoard(){
for (int x=0; x< mWidth; x++){
for (int y=0; y< mHeight; y++){
mBoard[x][y] = 0;
}
}
invalidate();
}
public boolean onTouch(View v, MotionEvent event){
Log.d("LogTest","Touched?"); /* LOG NOT ACTIVE HERE */
if(event.getAction() == MotionEvent.ACTION_DOWN){
mXNow = getBoardX(event.getX());
Log.d("LogTest","" + mXNow); /* LOG NOT ACTIVE HERE */
mYNow = getBoardY(event.getY());
Log.d("LogTest","" + mYNow); /* LOG NOT ACTIVE HERE */
mBoard[mXNow][mYNow] = mBoard[mXNow][mYNow] + 1;
invalidate();
return true;
}
else return false;
}
int getBoardX(float scrx){
int x = (int)((scrx) / mCellWidth);
if (x < 0) x = 0;
if (x > 8) x= 8;
return x;
}
int getBoardY(float scry){
int y = (int)((scry) / mCellHeight);
if (y < 0) y = 0;
if (y > 8) y = 8;
return y;
}
}
Edit: added activity XML file.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:id="#+id/activity_sudoku"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="snacker.nonogramsolver.SudokuActivity">
<snacker.nonogramsolver.Sudoku
android:id="#+id/SudokuGrid"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn_clear"
android:layout_width="150dp"
android:layout_height="30dp"
android:layout_weight="0.06"
android:text="Clear" />
</LinearLayout>

You cannot directly add touchListener by just creating object of
Sudoku class. You should add view in xml or programatically.
Your Activity
public class MyActivity extends Activity{
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
//initializing custom views
MyCustomView1 myCustomView1 = new MyCustomView1(parameterList);
MyCustomView2 myCustomView2 = new MyCustomView2(parameterList);
//adding both custom views to the main activity
mainView.addView(myCustomView1);
mainView.addView(myCustomView1);
//adding custom listener to the custom view 1
myCustomView1.setCustomEventListener(new OnCustomEventListener() {
#Override
public void onEvent() {
//firing an event of custom view 1
Toast.makeText(MainActivity.this, "Touched custom view 1",
Toast.LENGTH_SHORT).show();
}
});
//adding custom listener to the custom view 2
myCustomView2.setCustomEventListener(new OnCustomEventListener() {
#Override
public void onEvent() {
//firing an event of custom view 2
Toast.makeText(MainActivity.this, "Touched custom view 2",
Toast.LENGTH_SHORT).show();
}
});
}
}
Your CustomView 1
public class MyCustomView1 extends LinearLayout{
OnCustomEventListener myCustomEventListener;
public MyCustomView1(ParameterList){
super(ContextFromParameterList);
//Just adding something to the custom view 1 in order to distinguish it on the screen
TextView tv = new TextView(ContextFromParameterList);
tv.setText("Hello world from custom view 1");
addView(tv);
this.setOnTouchListener(new OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
//delegating one event to another (delegating touch event to custom event)
if (MyCustomView1.this.myCustomEventListener != null)
MyCustomView1.this.myCustomEventListener.onEvent();
return false;
}
}); }
public void setCustomEventListener(OnCustomEventListener
eventListener) {
//setting custom listener from activity
myCustomEventListener = eventListener; } }
Your CustomView2
public class MyCustomView2 extends LinearLayout {
OnCustomEventListener myCustomEventListener;
public MyCustomView2(ParameterList) {
super(ContextFromParameterList);
//Just adding something to the custom view 1 in order to distinguish it on the screen
TextView tv = new TextView(ContextFromParameterList);
tv.setText("Hello world from custom view 2");
addView(tv);
this.setOnTouchListener(new OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
//delegating one event to another (delegating touch event to custom event)
if (MyCustomView2.this.myCustomEventListener != null)
MyCustomView2.this.myCustomEventListener.onEvent();
return false;
}
});
}
public void setCustomEventListener(OnCustomEventListener eventListener) {
//setting custom listener from activity
myCustomEventListener = eventListener;
}
}
Your listener interface:
public interface OnCustomEventListener{
//interface defines one method. Can be more and methods may have parameters
public void onEvent();
}

How can I change the picture that draws on the screen

This might seem like a silly qustion but how do you change the picture that draws on the screen.I have already been able to program a app were it draws a little icon where you touch the screen.So natually after I completed that I want to make it better by adding a option menu and the ability to change what icon you were being drown but when I ran the code the icon picture stayed the same.When I looked at it I found that when you click on any of the menu item it does do it's job and change the image id but when you go back to the main screen and try to create a new image it revertes back to the old image.I have no idea why it doesn't change because when I look at it everything make sense for it to change icon properly.If any one has any idea on what i am doing wrong or any suggestion on how to do this it would be greatly appreciate
Main
public class main extends Activity {
/** Called when the activity is first created. */
MenuItem item2;
int item3=R.drawable.ic_launcher;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FrameLayout sv = new FrameLayout(this);
LinearLayout ll = new LinearLayout(this);
Panel test = new Panel(this);
//ImageButton button = new ImageButton(this);
ll.setOrientation(LinearLayout.VERTICAL);
sv.addView(test);
//ll.addView(button);
sv.addView(ll);
setContentView(sv);
}
public boolean onCreateOptionsMenu(Menu menu) {
// TODO Auto-generated method stub
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
return super.onCreateOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// TODO Auto-generated method stub
Log.v("test", "item3 before is: "+item3);
item3=R.drawable.box;
Log.v("test", "item3 after is: "+item3);
return super.onOptionsItemSelected(item);
}
}
Panel
public class Panel extends SurfaceView implements SurfaceHolder.Callback {
private Bitmap image;
private ViewThread mThread;
private int x;
private int y;
private ArrayList<Element> mElements = new ArrayList<Element>();
public Panel(Context context) {
super(context );
image = BitmapFactory.decodeResource(getResources(),yantz.imageapp4.R.drawable.test);
getHolder().addCallback(this);
mThread = new ViewThread(this);
}
public void doDraw(Canvas canvas) {
canvas.drawColor(Color.CYAN);
canvas.drawBitmap(image, x, y, null);
synchronized (mElements){
for(Element element : mElements){
element.doDraw(canvas);
}
}
}
#Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
Log.v("test", "you have touched the sreen: ");
synchronized (mElements){
mElements.add(new Element(getResources(),(int) event.getX(),(int) event.getY()));
}
return super.onTouchEvent(event);
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
// TODO Auto-generated method stub
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
if (!mThread.isAlive()) {
mThread = new ViewThread(this);
mThread.setRunning(true);
mThread.start();
}
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
if (mThread.isAlive()) {
mThread.setRunning(false);
}
}
}
Elements
public class Element extends main{
private int mX;
private int mY;
int location ;
private Bitmap mBitmap;
public Element(Resources res, int x, int y) {
Log.v("element", "item3 before location is: "+item3);
location =item3;
mBitmap = BitmapFactory.decodeResource(res, location);
mX = x - mBitmap.getWidth() / 2;
mY = y - mBitmap.getHeight() / 2;
Log.v("element", "item3 before location is: "+item3);
}
public void doDraw(Canvas canvas) {
canvas.drawBitmap(mBitmap, mX, mY, null);
}
public void setlocation(int location2){
location=location2;
}
}
ViewThread
public class ViewThread extends Thread {
private Panel mPanel;
private SurfaceHolder mHolder;
private boolean mRun = false;
public ViewThread(Panel panel) {
mPanel = panel;
mHolder = mPanel.getHolder();
}
public void setRunning(boolean run) {
mRun = run;
}
#Override
public void run() {
Canvas canvas = null;
while (mRun) {
canvas = mHolder.lockCanvas();
if (canvas != null) {
mPanel.doDraw(canvas);
mHolder.unlockCanvasAndPost(canvas);
}
}
}
}

you can use
#Override
protected void onResume() {
super.onResume();
id="what ever you want";
//and set it to imagevIew;
}
if i have understood the uestion correctly,this happens because your activity pauses when it is not focused and resumes with default values.

Android animation acting strange with .sleep() onTouchEvent

I currently have (among others) these classes:
public class Main extends Activity {
Panel p;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
p = new Panel(this);
setContentView(p);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
p.onTouchEvent(event);
// Make your UI thread sleep.
try {
Thread.sleep(30);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return true;
}
and
public class Panel extends SurfaceView implements SurfaceHolder.Callback {
private ViewThread mThread;
private ArrayList<GraphicsElement> mElements = new ArrayList<GraphicsElement>();
public static int panelHeight;
public static int panelWidth;
private int numberOfElements = 0;
private Paint mPaint;
public Panel(Context context) {
super(context);
getHolder().addCallback(this);
mThread = new ViewThread(this);
mPaint = new Paint();
mPaint.setColor(Color.CYAN);
mPaint.setTextSize(20);
}
public void doDraw(long elapsed, Canvas canvas) {
canvas.drawColor(Color.parseColor("#003045"));
if (!(mElements.size() > 15)) {
synchronized (mElements) {
for (GraphicsElement element : mElements) {
element.doDraw(canvas);
}
canvas.drawText("FPS: " + Math.round(1000f / elapsed) + " Elements: " + numberOfElements, 10, 30, mPaint);
}
} else {
mElements.clear();
numberOfElements = 0;
}
}
public void animate(long elapsedTime) {
synchronized (mElements) {
for (GraphicsElement element : mElements) {
element.animate(elapsedTime);
}
}
}
#Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
int xspeed = 0;
int yspeed = 0;
if (action == MotionEvent.ACTION_DOWN || action == MotionEvent.ACTION_MOVE) {
if (event.getX() > panelWidth / 2) {
xspeed = 5;
} else if (event.getX() < panelWidth / 2) {
xspeed = -5;
}
synchronized (mElements) {
for (GraphicsElement element : mElements) {
element.changeSpeed(xspeed, yspeed);
}
}
}
return true;
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
#Override
public void surfaceCreated(SurfaceHolder holder) {
if (!mThread.isAlive()) {
mThread = new ViewThread(this);
mThread.setRunning(true);
mThread.start();
}
mElements.add(new GraphicsElement(getResources(), 80, 300));
numberOfElements += 1;
}
public void surfaceDestroyed(SurfaceHolder holder) {
I also have ViewThread, just my animation thread, and GraphicsElement, which defines the moving object. My animation is going very slow(on touch), and I think it has something to do with my .sleep() method. Could anyone please help me ?
Edit: I'm using .sleep() because I don't want to flood TouchEvents.
i'm trying to get it like: Check for TouchEvent, Sleep, Check for TouchEvent, Sleep.. etc...

I've had the same issues with touch slowing things down and ended up with a similar approach to yours (sleeping the UI thread on touch events, as recommended by a Google game developer). The thing that seemed to help me was playing with the length of the sleep time. Try increasing it to 70 ms or even more and see if that helps. Most apps don't need a super high sample rate for touch input.

Firstly, you should initialize your Panel inside your onCreate() method.
Panel p = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
p = new Panel(this);
setContentView(p);
}
Secondly, I do not understand why you are doing a sleep in your onTouchEvent() handler. Try taking that out, and things should speed up, especially if you think that may be the cause!