Application.ProcessMessages command, what is the alternative on
android?
lazarus / 43-Android

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loaded · 2019-02-14 08:07

Hello to everyone,
I used the Application.ProcessMessages command in my windows
application to keep the application breathing. I'm looking for an
alternative method for the Android application.
Thank you in advance for your help.

Example Code
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TAndroidModule1.jDrawingView1Draw(Sender: TObject; countXY: integer; 
X: array of single; Y: array of single; flingGesture: TFlingGesture; 
pinchZoomScaleState: TPinchZoomScaleState; zoomScale: single);begin 
 randomize;   jDrawingView1.BackgroundColor:=colbrBlack;   for i:=0 to
5000 do // ~100000 do   begin 
 jDrawingView1.PaintColor:=TARGBColorBridge(Random(144)); 
 jDrawingView1.DrawLine(0,0,i,jDrawingView1.Height); 
 //Application.ProcessMessages;   end;end;

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Remy Lebeau · 2019-02-14 18:15

Quote from: loaded on February 14, 2019, 09:07:21 amI used the
Application.ProcessMessages command in my windows application to keep
the application breathing.

Don't do that.  It is always a sign of bad UI/code design.

Quote from: loaded on February 14, 2019, 09:07:21 amI'm looking for an
alternative method for the Android application.

Redesign your approach, for all platforms, even Windows.

First off, you should not call Randomize() more than once per
process.  Call it at program startup.

Second, and most importantly, don't block the UI thread for lengthy
operations.  ESPECIALLY important on mobile platforms, but even for
desktop platforms, too.  UI painting is done frequently and should be
fast.  If your painting is so slow that the user notices it, and the
OS thinks the app is unresponsive because of it, then move the actual
drawing to a worker thread instead, and have it draw onto an in-memory
bitmap, and then notify the UI thread whenever a new bitmap is ready
for use so it can trigger a repaint.  Every time the UI needs to be
painted, let the UI thread paint by simply drawing the latest bitmap
onto the UI, and keep that bitmap around for subsequent paints until a
new bitmap is ready.

For example (may need tweaking to suit your needs, but you should get
the idea):

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i type 
TDrawingThread = class(TThread)  private    FBitmap: TBitmap;   
FOnNewBitmap: TNotifyEvent;    procedure NewBitmapReady;  protected  
procedure Execute; override;      public    constructor Create(Width,
Height: Integer); reintroduce;    destructor Destroy; override;   
property Bitmap: TBitmap read FBitmap;    property OnNewBitmap:
TNotifyEvent read FOnNewBitmap write FOnNewBitmap;  end; constructor
TDrawingThread.Create(Width, Height: Integer);begin  inherited
Create(True);  FBitmap := TBitmap.Create;  FBitmap.Width := Width; 
FBitmap.Height := Height;end; destructor TDrawingThread.Destroy;begin 
FBitmap.Free;  inherited;end; procedure TDrawingThread.Execute;
override;    begin  while not Terminated do  begin   
FBitmap.Canvas.Lock;    try      FBitmap..Canvas.Brush.Color :=
clBlack;      FBitmap..Canvas.FillRect(Rect(0, 0, FBitmap.Width,
FBitmap.Height));      for i := 0 to FBitmap.Width-1 do      begin   
   FBitmap.Canvas.Pen.Color := TColor(Random(144));       
FBitmap.Canvas.MoveTo(0, 0);        FBitmap.Canvas.DrawLine(i,
FBitmap.Height);      end;    finally      FBitmap.Canvas.Unlock;   
end;    if Assigned(FOnNewBitmap) then     
Synchronize(NewBitmapReady);  end;end; procedure
TDrawingThread.NewBitmapReady;begin  if Assigned(FOnNewBitmap) then  
FOnNewBitmap(Self);end; var  DrawingThread: TThread;  CurrentBitmap:
TBitmap; procedure TAndroidModule1.ModuleCreate(Owner:
TComponent);begin  Randomize;  CurrentBitmap := TBitmap.Create; 
DrawingThread := TDrawingThread.Create(5000, jDrawingView1.Height); 
DrawingThread.OnNewBitmap := NewBitmapReady; 
DrawingThread.Resume;end; procedure
TAndroidModule1.NewBitmapReady(Sender: TObject);begin 
CurrentBitmap.Assign(DrawingThread.Bitmap); 
jDrawingView1.Invalidate;end; procedure
TAndroidModule1.jDrawingView1Draw(Sender: TObject; countXY: integer; 
X: array of single; Y: array of single; flingGesture: TFlingGesture; 
pinchZoomScaleState: TPinchZoomScaleState; zoomScale: single);begin 
// draw CurrentBitmap onto jDrawingView1 as needed...end;

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Handoko · 2019-02-14 18:42

Quote from: loaded on February 14, 2019, 09:07:21 amCode: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i    for i:=0
to 5000 do // ~100000 do   begin 
If you have high amount of items needed to draw on the screen, it is
usually good to use a buffer.

Not sure about Android. On PC, drawing on the screen directly is slow.
So we draw all the items on a buffer and copy the buffer to the screen
in one single pass. This trick can reduce flickering and improve
performance.

You can learn more about using buffer here (PC version):
https://forum.lazarus.freepascal.org/index.php/topic,38136.msg263143.h
tml#msg263143

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loaded · 2019-02-14 19:02

Remy Lebeau and Handoko
Thank you for taking your precious time and writing your answer. I
understand that I have to work more.