everything is mainly explained in the title ill go in as much detail as i can. I am making an android game app i created a unique id for a circle that is drawn in canvas in the DrawingView class since this cannot be referenced in xml i had to create the id as an int in java so that java could find the id and use it as the button. Im sure you are all very confused by now i will continue will putting in my best effort to explain. below is the code for the Main file that gets called
public class Main extends Activity {
DrawingView v;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
LinearLayout layout1 = new LinearLayout (this);
FrameLayout game = new FrameLayout(this);
DrawingView v = new DrawingView (this);
TextView myText = new TextView(this);
int w = getResources().getInteger(DrawingView.redColor);
Button redCircle = (Button) findViewById(w);
redCircle.setWidth(300);
redCircle.setText("Start Game");
layout1.addView(myText);
layout1.addView(redCircle);
//redCircle.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
game.addView(v);
game.addView(layout1);
setContentView(game);
redCircle.setOnClickListener((OnClickListener) this);
}
public void onClick(View v) {
Intent intent = new Intent(this, Main.class);
startActivity(intent);
// re-starts this activity from game-view. add this.finish(); to remove from stack
}
@Override
public boolean onCreateOptionsMenu(Menu menu){
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
and not really neccessary but to help you understand what i am trying to accomplish here is the DrawingView class that creates random circles either green or red below.
public class DrawingView extends View {
public DrawingView(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
RectF rectf = new RectF(0, 0, 200, 0);
private static final int w = 100;
public static int lastColor = Color.BLACK;
private final Random random = new Random();
private final Paint paint = new Paint();
private final int radius = 230;
private final Handler handler = new Handler();
public static int redColor = Color.RED;
public static int greenColor = Color.GREEN;
private final Runnable updateCircle = new Runnable() {
@Override
public void run() {
lastColor = random.nextInt(2) == 1 ? redColor : greenColor;
paint.setColor(lastColor);
invalidate();
handler.postDelayed(this, 1000);
}
};
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
handler.post(updateCircle);
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
handler.removeCallbacks(updateCircle);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// your other stuff here
canvas.drawCircle(random.nextInt(canvas.getWidth()-radius/2) + radius/2f, random.nextInt(canvas.getHeight()-radius/2) + radius/2f, radius, paint);
}
//Bitmap.Config conf = Bitmap.Config.ARGB_8888; // see other conf types
//private int h = 100;
//@SuppressLint("DrawAllocation")
//Bitmap bmp = Bitmap.createBitmap(w, h, conf); // this creates a MUTABLE bitmap
//Canvas canvas = new Canvas(bmp);
/*
private Object canvas(Bitmap bmp) {
// TODO Auto-generated method stub
return null;
}
*/
}
and more importantly the log cat errors that display after the app crashes
03-30 02:27:27.903: E/AndroidRuntime(3104): FATAL EXCEPTION: main
03-30 02:27:27.903: E/AndroidRuntime(3104): Process: com.Tripps.thesimplegame, PID: 3104
03-30 02:27:27.903: E/AndroidRuntime(3104): java.lang.NullPointerException: Attempt to invoke virtual method 'int android.graphics.Bitmap.getWidth()' on a null object reference
03-30 02:27:27.903: E/AndroidRuntime(3104): at com.Tripps.thesimplegame.DrawingView.onDraw(DrawingView.java:67)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.draw(View.java:15114)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.updateDisplayListIfDirty(View.java:14048)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.getDisplayList(View.java:14071)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.draw(View.java:14838)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.updateDisplayListIfDirty(View.java:14043)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.getDisplayList(View.java:14071)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.draw(View.java:14838)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.updateDisplayListIfDirty(View.java:14043)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.getDisplayList(View.java:14071)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.draw(View.java:14838)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.updateDisplayListIfDirty(View.java:14043)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.getDisplayList(View.java:14071)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.draw(View.java:14838)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.draw(View.java:15117)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.widget.FrameLayout.draw(FrameLayout.java:592)
03-30 02:27:27.903: E/AndroidRuntime(3104): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:2595)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.updateDisplayListIfDirty(View.java:14048)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.View.getDisplayList(View.java:14071)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ThreadedRenderer.updateViewTreeDisplayList(ThreadedRenderer.java:266)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ThreadedRenderer.updateRootDisplayList(ThreadedRenderer.java:272)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ThreadedRenderer.draw(ThreadedRenderer.java:311)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewRootImpl.draw(ViewRootImpl.java:2492)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2337)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1968)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.Choreographer.doCallbacks(Choreographer.java:580)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.Choreographer.doFrame(Choreographer.java:550)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.os.Handler.handleCallback(Handler.java:739)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.os.Handler.dispatchMessage(Handler.java:95)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.os.Looper.loop(Looper.java:135)
03-30 02:27:27.903: E/AndroidRuntime(3104): at android.app.ActivityThread.main(ActivityThread.java:5221)
03-30 02:27:27.903: E/AndroidRuntime(3104): at java.lang.reflect.Method.invoke(Native Method)
03-30 02:27:27.903: E/AndroidRuntime(3104): at java.lang.reflect.Method.invoke(Method.java:372)
03-30 02:27:27.903: E/AndroidRuntime(3104): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
03-30 02:27:27.903: E/AndroidRuntime(3104): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
03-30 02:38:46.269: D/OpenGLRenderer(3167): Render dirty regions requested: true
03-30 02:38:46.276: D/(3167): HostConnection::get() New Host Connection established 0xae0add60, tid 3167
03-30 02:38:46.287: D/Atlas(3167): Validating map...
03-30 02:38:46.379: D/(3167): HostConnection::get() New Host Connection established 0xa6c52140, tid 3182
03-30 02:38:46.427: I/OpenGLRenderer(3167): Initialized EGL, version 1.4
03-30 02:38:46.473: D/OpenGLRenderer(3167): Enabling debug mode 0
03-30 02:38:46.550: W/EGL_emulation(3167): eglSurfaceAttrib not implemented
03-30 02:38:46.550: W/OpenGLRenderer(3167): Failed to set EGL_SWAP_BEHAVIOR on surface 0xae0ed4a0, error=EGL_SUCCESS
03-30 03:01:54.523: W/ResourceType(3228): No known package when getting value for resource number 0xffff0000
03-30 03:01:54.523: D/AndroidRuntime(3228): Shutting down VM
03-30 03:01:54.524: E/AndroidRuntime(3228): FATAL EXCEPTION: main
03-30 03:01:54.524: E/AndroidRuntime(3228): Process: com.Tripps.thesimplegame, PID: 3228
03-30 03:01:54.524: E/AndroidRuntime(3228): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.Tripps.thesimplegame/com.Tripps.thesimplegame.Main}: android.content.res.Resources$NotFoundException: Resource ID #0xffff0000
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.app.ActivityThread.access$800(ActivityThread.java:144)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.os.Handler.dispatchMessage(Handler.java:102)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.os.Looper.loop(Looper.java:135)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.app.ActivityThread.main(ActivityThread.java:5221)
03-30 03:01:54.524: E/AndroidRuntime(3228): at java.lang.reflect.Method.invoke(Native Method)
03-30 03:01:54.524: E/AndroidRuntime(3228): at java.lang.reflect.Method.invoke(Method.java:372)
03-30 03:01:54.524: E/AndroidRuntime(3228): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
03-30 03:01:54.524: E/AndroidRuntime(3228): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
03-30 03:01:54.524: E/AndroidRuntime(3228): Caused by: android.content.res.Resources$NotFoundException: Resource ID #0xffff0000
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.content.res.Resources.getValue(Resources.java:1233)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.content.res.Resources.getInteger(Resources.java:989)
03-30 03:01:54.524: E/AndroidRuntime(3228): at com.Tripps.thesimplegame.Main.onCreate(Main.java:34)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.app.Activity.performCreate(Activity.java:5933)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
03-30 03:01:54.524: E/AndroidRuntime(3228): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
03-30 03:01:54.524: E/AndroidRuntime(3228): ... 10 more
03-30 03:03:04.088: W/ResourceType(3288): No known package when getting value for resource number 0xffff0000
03-30 03:03:04.089: D/AndroidRuntime(3288): Shutting down VM
03-30 03:03:04.089: E/AndroidRuntime(3288): FATAL EXCEPTION: main
03-30 03:03:04.089: E/AndroidRuntime(3288): Process: com.Tripps.thesimplegame, PID: 3288
03-30 03:03:04.089: E/AndroidRuntime(3288): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.Tripps.thesimplegame/com.Tripps.thesimplegame.Main}: android.content.res.Resources$NotFoundException: Resource ID #0xffff0000
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.app.ActivityThread.access$800(ActivityThread.java:144)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.os.Handler.dispatchMessage(Handler.java:102)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.os.Looper.loop(Looper.java:135)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.app.ActivityThread.main(ActivityThread.java:5221)
03-30 03:03:04.089: E/AndroidRuntime(3288): at java.lang.reflect.Method.invoke(Native Method)
03-30 03:03:04.089: E/AndroidRuntime(3288): at java.lang.reflect.Method.invoke(Method.java:372)
03-30 03:03:04.089: E/AndroidRuntime(3288): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
03-30 03:03:04.089: E/AndroidRuntime(3288): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
03-30 03:03:04.089: E/AndroidRuntime(3288): Caused by: android.content.res.Resources$NotFoundException: Resource ID #0xffff0000
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.content.res.Resources.getValue(Resources.java:1233)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.content.res.Resources.getInteger(Resources.java:989)
03-30 03:03:04.089: E/AndroidRuntime(3288): at com.Tripps.thesimplegame.Main.onCreate(Main.java:34)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.app.Activity.performCreate(Activity.java:5933)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
03-30 03:03:04.089: E/AndroidRuntime(3288): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
03-30 03:03:04.089: E/AndroidRuntime(3288): ... 10 more
03-30 03:03:34.502: I/Process(3288): Sending signal. PID: 3288 SIG: 9
You are getting error at :
canvas.drawCircle(random.nextInt(canvas.getWidth()-radius/2) + radius/2f, random.nextInt(canvas.getHeight()-radius/2) + radius/2f, radius, paint);
Because the Object canvas do not have width or height (it is null)
Reason :
Your code adds views like :
LinearLayout layout1 = new LinearLayout (this);
FrameLayout game = new FrameLayout(this);
DrawingView v = new DrawingView (this);
TextView myText = new TextView(this);
int w = getResources().getInteger(DrawingView.redColor);
Button redCircle = (Button) findViewById(w);
redCircle.setWidth(300);
redCircle.setText("Start Game");
layout1.addView(myText);
layout1.addView(redCircle);
//redCircle.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
game.addView(v);
game.addView(layout1);
But at the time of
game.addView(v);v do not have any views referenced so the null object view is added in game
So pls add some view i.e. Text or Images in v first and then call
game.addView(v);
This is solution for your error