Reading MotionEvent.getPressure()
lazarus / 43-Android

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meanderix · 2012-06-22 13:04

Hi,

I'm planning to write an app where I need to be able to read the
pressure of at least one of the touch points.

The MotionEvent class has a getPressure() method that allows you to
retrieve this information.

The way I'm thinking of reading this would be by modifying the
LCLOnTouch JNI callback to include a third parameter, by making the
following changes:

Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i    
@Override public boolean onTouchEvent (MotionEvent event)    {     
int eventResult = LCLOnTouch(event.getX(), event.getY(),
event.getPressure(0), event.getAction());      if ((eventResult | 1)
!= 0) postInvalidate();      return true;    }    
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i        
function Java_com_pascal_lclproject_LCLActivity_LCLOnTouch(env:PJNIEnv
;this:jobject; x, y, pressure: single; action: jint): jint; cdecl; 
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i        
function Java_com_pascal_lclproject_LCLActivity_LCLOnTouch(env:PJNIEnv
;this:jobject; x, y, pressure: single; action: jint): jint; cdecl;var 
lCurForm: TCDNonNativeForm;  lTarget: TWinControl;  lEventPos:
TPoint;begin  {$ifdef VerboseCDEvents} 
__android_log_write(ANDROID_LOG_INFO,'lclapp',PChar(Format('LCLOnTouch
called x=%f y=%f action=%d', [x, y, action])));  {$endif}  eventResult
:= 0;   // Declare a global variable 'TouchPressure', e.g. in
lazdeviceapis.pas  // read pressure value in MouseDown/MouseUp event
handlers  TouchPressure := pressure;    lCurForm :=
GetCurrentForm();   case action of    ACTION_DOWN:    begin     
CallbackMouseDown(lCurForm, Round(X), Round(Y), mbLeft, []);    end; 
 ACTION_UP:    begin      CallbackMouseUp(lCurForm, Round(X),
Round(Y), mbLeft, []);    end;    ACTION_MOVE:
CallbackMouseMove(lCurForm, Round(X), Round(Y), []);  end;   // This
sends messages like Invalidate requests  Result := eventResult;end;  
Some questions:
Is this a good approach?Do I need to make any other changes besides
the above?
Thanks in advance.

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felipemdc · 2012-06-22 14:05

It is a good approach and will probably work. If you want to make a
patch to be merged into the general codebase it would need to be
refined, however. For example, send the entire object event and call
getPressure in the Pascal side, since we might want to call other
things from this object in the future.

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meanderix · 2012-06-22 14:37

Hi Felipe,

Quote from: felipemdc on June 22, 2012, 04:05:54 pmIt is a good
approach and will probably work. If you want to make a patch to be
merged into the general codebase it would need to be refined, however.
For example, send the entire object event and call getPressure in the
Pascal side, since we might want to call other things from this object
in the future.

Is there any simple way to invoke a method of a java object on the
pascal side?

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felipemdc · 2012-06-23 09:08

Quote from: meanderix on June 22, 2012, 04:37:46 pmIs there any simple
way to invoke a method of a java object on the pascal side?
Yes, JNI:

http://wiki.lazarus.freepascal.org/Android_Programming#Example_1:_Crea
ting_a_Java_object_and_calling_a_Java_method

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meanderix · 2012-06-23 20:03

Quote from: felipemdc on June 23, 2012, 11:08:46 amQuote from:
meanderix on June 22, 2012, 04:37:46 pmIs there any simple way to
invoke a method of a java object on the pascal side?
Yes, JNI:

http://wiki.lazarus.freepascal.org/Android_Programming#Example_1:_Crea
ting_a_Java_object_and_calling_a_Java_method
Excellent, I might do this later on -- for now on I've modified the
function prototype.