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POmultiTouch android | getting Action of each touch point
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copied!<p>I am trying to handle multiTouch in android, my plan is to use 2 fingers in the app. I know how to use one touch point, but I am not sure about how to use more than one touch point.</p> <p>Here is my code, OnTouch:</p> <pre><code> public boolean onTouch(View view, MotionEvent event) { for(int i = 0; i < event.getPointerCount(); i++){ float x = event.getX(i); float y = event.getY(i); // using the data here... //.... } return true; } </code></pre> <p>now after i get the x and y coordinates for each point, how would i get the action that happens? i want to use <code>event.getAction</code>, but it doesn't take a parameter such as the point index. how can i get the action type for each touch point?</p> <p>UPDATE: ok, so now i can successfully manage and handle two fingers, now, after I've done that, I made a simple class called <code>Finger</code> to handle each touch point, now whenever i have two fingers on the screen, and i try to remove one of them, and then move/remove the other finger, the game just crashes! </p> <p>OnTouch:</p> <pre><code>public boolean onTouch(View view, MotionEvent event) { int pointerCount = event.getPointerCount(); if(pointerCount > 2){ pointerCount = 2; System.out.println("too many fingers!"); } // since i want to handle only two fingers, every other finger will be ignored. for (int i = 0; i < pointerCount; i++) { float x = event.getX(i); float y = event.getY(i); int id = event.getPointerId(i); int action = event.getActionMasked(); int actionIndex = event.getActionIndex(); if (action == MotionEvent.ACTION_DOWN || action == MotionEvent.ACTION_POINTER_DOWN) { if (fingers.get(i) == null) fingers.set(i, new Finger(x, y, id)); } if (fingers.get(i).type == Finger.SCREEN_FINGER) { switch (action) { case MotionEvent.ACTION_UP: fingers.set(i, null); System.out.println(id + " action_up!"); break; case MotionEvent.ACTION_POINTER_UP: fingers.set(i, null); System.out.println(id + " pointer_up!"); break; case MotionEvent.ACTION_MOVE: fingers.get(i).setPos(x, y); System.out.println(id + " action_move!, x: "+fingers.get(i).x+", y: "+fingers.get(i).y); break; default: } }else if (fingers.get(i).type == Finger.DPAD_FINGER) { switch (action) { case MotionEvent.ACTION_UP: fingers.set(i, null); System.out.println(id + " action_up! - dpad"); break; case MotionEvent.ACTION_POINTER_UP: fingers.set(i, null); System.out.println(id + " pointer_up! - dpad"); break; case MotionEvent.ACTION_MOVE: fingers.get(i).setPos(x, y); System.out.println(id + " action_move! - dpad, x: "+fingers.get(i).x+", y: "+fingers.get(i).y); break; default: } } } return true; } </code></pre> <p>i create a List for the Fingers:</p> <p>List fingers = new LinkedList();</p> <p>in the constructor i put:</p> <pre><code>fingers.add(0, null); fingers.add(1, null); </code></pre> <p>Finally, the Finger Class:</p> <pre><code>public class Finger { public final static int DPAD_FINGER = 0; public final static int SCREEN_FINGER = 1; public float x, y; public int type; public int id; public Finger(float x, float y,int id) { this.id = id; checkType(x, y); } public void checkType(float x, float y) { if(x>Dpad.x && x < Dpad.x+Dpad.Width && y> Dpad.y && y<Dpad.y+Dpad.Height){ System.out.println("inside DPAD"); type = DPAD_FINGER; }else{ System.out.println("Outside DPAD"); type = SCREEN_FINGER; } } public void setPos(float x, float y){ this.x = x; this.y = y; } } </code></pre> <p>now when i do all that, everything is fine, until i remove one finger and move/remove the other one, i get the following error in the LogCat:</p> <pre><code> 05-18 15:22:03.812: E/InputEventReceiver(20124): Exception dispatching input event. 05-18 15:22:03.812: W/dalvikvm(20124): threadid=1: thread exiting with uncaught exception (group=0x41e00438) 05-18 15:22:03.822: E/AndroidRuntime(20124): FATAL EXCEPTION: main 05-18 15:22:03.822: E/AndroidRuntime(20124): java.lang.NullPointerException 05-18 15:22:03.822: E/AndroidRuntime(20124): at smellychiz.projects.ogc.util.ChizView$1.onTouch(ChizView.java:70) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.View.dispatchTouchEvent(View.java:7241) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2185) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1928) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2185) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1928) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2185) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1928) 05-18 15:22:03.822: E/AndroidRuntime(20124): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2116) 05-18 15:22:03.822: E/AndroidRuntime(20124): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1469) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.app.Activity.dispatchTouchEvent(Activity.java:2477) 05-18 15:22:03.822: E/AndroidRuntime(20124): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2064) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.View.dispatchPointerEvent(View.java:7430) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3457) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3389) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4483) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4461) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4565) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:171) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:163) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:4533) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:4584) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.Choreographer.doCallbacks(Choreographer.java:555) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.Choreographer.doFrame(Choreographer.java:523) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.os.Handler.handleCallback(Handler.java:615) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.os.Handler.dispatchMessage(Handler.java:92) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.os.Looper.loop(Looper.java:137) 05-18 15:22:03.822: E/AndroidRuntime(20124): at android.app.ActivityThread.main(ActivityThread.java:4950) 05-18 15:22:03.822: E/AndroidRuntime(20124): at java.lang.reflect.Method.invokeNative(Native Method) 05-18 15:22:03.822: E/AndroidRuntime(20124): at java.lang.reflect.Method.invoke(Method.java:511) 05-18 15:22:03.822: E/AndroidRuntime(20124): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004) 05-18 15:22:03.822: E/AndroidRuntime(20124): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771) 05-18 15:22:03.822: E/AndroidRuntime(20124): at dalvik.system.NativeStart.main(Native Method) </code></pre> <p>UPDATE: </p> <p>instead of re-setting the fingers and setting them to null and then re-setting them again, i just removed them when finger was up and re created them when finger was down and updated when the finger moved. Now it works perfectly fine!</p> <p>UPDATE....</p> <p>eventually the problem is not solved, even though the app does not crash, when one of the fingers get lifted, it acts as if both fingers get lifted. </p> <p>here is the current code of <code>onTouch</code> method:</p> <pre><code>public boolean onTouch(View view, MotionEvent event) { int pointerCount = event.getPointerCount(); if(pointerCount > 2){ pointerCount = 2; System.out.println("too many fingers!"); } // since i want to handle only two fingers, every other finger will be ignored. for (int i = 0; i < pointerCount; i++) { float x = event.getX(i); float y = event.getY(i); int id = event.getPointerId(i); int action = event.getActionMasked(); int actionIndex = event.getActionIndex(); if (action == MotionEvent.ACTION_DOWN || action == MotionEvent.ACTION_POINTER_DOWN) { if (fingers.get(i) == null) fingers.add(i, new Finger(x, y, id)); } if (fingers.get(i).type == Finger.SCREEN_FINGER) { switch (action) { case MotionEvent.ACTION_UP: fingers.remove(i); System.out.println(id + " action_up!"); break; case MotionEvent.ACTION_POINTER_UP: fingers.remove(i); System.out.println(id + " pointer_up!"); break; case MotionEvent.ACTION_MOVE: fingers.get(i).setPos(x, y); System.out.println(id + " action_move!, x: "+fingers.get(i).x+", y: "+fingers.get(i).y); break; default: } }else if (fingers.get(i).type == Finger.DPAD_FINGER) { switch (action) { case MotionEvent.ACTION_UP: fingers.remove(i); System.out.println(id + " action_up! - dpad"); break; case MotionEvent.ACTION_POINTER_UP: fingers.remove(i); System.out.println(id + " pointer_up! - dpad"); break; case MotionEvent.ACTION_MOVE: fingers.get(i).setPos(x, y); System.out.println(id + " action_move! - dpad, x: "+fingers.get(i).x+", y: "+fingers.get(i).y); break; default: } } } </code></pre> <p>so whenever the one of the fingers get lifted, the logCat writes as if both fingers were lifted off the screen. any ideas? </p>

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