Draw in Canvas by finger Android

Question

I need to build a project for drawing on canvas by fingers   to get the touch event and motion event of my finger  and thence draw   Any one can advice me how to get start in project   and what is best component to do thing like this

User · Answer

You can use this class simply   public class DoodleCanvas  extends View       private Paint mPaint      private Path mPath       public DoodleCanvas Context context  AttributeSet attrs            super context  attrs           mPaint   new Paint            mPaint setColor Color RED           mPaint setStyle Paint Style STROKE           mPaint setStrokeJoin Paint Join ROUND           mPaint setStrokeCap Paint Cap ROUND           mPaint setStrokeWidth 10           mPath   new Path                 Override     protected void onDraw Canvas canvas            canvas drawPath mPath  mPaint           super onDraw canvas                Override     public boolean onTouchEvent MotionEvent event             switch  event getAction                  case MotionEvent ACTION DOWN                  mPath moveTo event getX    event getY                     break               case MotionEvent ACTION MOVE                  mPath lineTo event getX    event getY                     invalidate                    break               case MotionEvent ACTION UP                  break                     return true

User · Answer

I think it s important to add a thing  if you use the layout inflation that constructor in the drawview is not correct  add these constructors in the class   public DrawingView Context c  AttributeSet attrs        super c  attrs              public DrawingView Context c  AttributeSet attrs  int defStyle        super c  attrs  defStyle               or the android system fails to inflate the layout file  I hope this could to help

User · Answer

In addition to Ishan s answer  if you want to draw programatically without user interaction  you can edit the class just a little like this    public class DrawingCanvas extends View    private Paint mPaint  private Path mPath  private boolean isUserInteractionEnabled   false   public DrawingCanvas Context context  AttributeSet attrs        super context  attrs       mPaint   new Paint        mPaint setColor Color RED       mPaint setStyle Paint Style STROKE       mPaint setStrokeJoin Paint Join ROUND       mPaint setStrokeCap Paint Cap ROUND       mPaint setStrokeWidth 10       mPath   new Path         Override protected void onDraw Canvas canvas        canvas drawPath mPath  mPaint       super onDraw canvas        Override public boolean onTouchEvent MotionEvent event        if  isUserInteractionEnabled            switch  event getAction                  case MotionEvent ACTION DOWN                  mPath moveTo event getX    event getY                     break              case MotionEvent ACTION MOVE                  mPath lineTo event getX    event getY                     invalidate                    break              case MotionEvent ACTION UP                  break                       return true     public void moveCursorTo float x  float y        mPath moveTo x  y      public void makeLine float toX  float toY        mPath lineTo toX  toY      public void setUserInteractionEnabled boolean userInteractionEnabled        isUserInteractionEnabled   userInteractionEnabled        And then use it like   drawingCanvas setUserInteractionEnabled true     to enable user interaction drawingCanvas setUserInteractionEnabled true     to disable user interaction   To Draw programatically  drawingCanvas moveCursorTo 70f  70f     Move the cursor  Define starting point  drawingCanvas makeLine 200f  200f     End point  To where you need to draw

User · Answer

tutorial to draw line use Bitmap  Canvas  and Paint class  draw-line-on-finger-touch and androiddraw  here one simple class to draw line using canvas as show below       public class TestLineView extends View        private Paint paint      private PointF startPoint  endPoint      private boolean isDrawing       public TestLineView Context context                super context           init               private void init                 paint   new Paint            paint setColor Color RED           paint setStyle Style STROKE           paint setStrokeWidth 2           paint setAntiAlias true               Override     protected void onDraw Canvas canvas                if isDrawing                        canvas drawLine startPoint x  startPoint y  endPoint x  endPoint y  paint                          Override     public boolean onTouchEvent MotionEvent event                switch  event getAction                          case MotionEvent ACTION DOWN                  startPoint   new PointF event getX    event getY                     endPoint   new PointF                    isDrawing   true                  break              case MotionEvent ACTION MOVE                  if isDrawing                                        endPoint x   event getX                        endPoint y   event getY                        invalidate                                      break              case MotionEvent ACTION UP                  if isDrawing                                        endPoint x   event getX                        endPoint y   event getY                        isDrawing   false                      invalidate                                      break              default                  break                    return true

User · Answer

Start By going through the Fingerpaint demo in the sdk sample    Another Sample   public class MainActivity extends Activity        DrawingView dv       private Paint mPaint            Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           dv   new DrawingView this           setContentView dv           mPaint   new Paint            mPaint setAntiAlias true           mPaint setDither true           mPaint setColor Color GREEN           mPaint setStyle Paint Style STROKE           mPaint setStrokeJoin Paint Join ROUND           mPaint setStrokeCap Paint Cap ROUND           mPaint setStrokeWidth 12              public class DrawingView extends View            public int width          public  int height          private Bitmap  mBitmap          private Canvas  mCanvas          private Path    mPath          private Paint   mBitmapPaint          Context context          private Paint circlePaint          private Path circlePath           public DrawingView Context c                super c               context c              mPath   new Path                mBitmapPaint   new Paint Paint DITHER FLAG               circlePaint   new Paint                circlePath   new Path                circlePaint setAntiAlias true               circlePaint setColor Color BLUE               circlePaint setStyle Paint Style STROKE               circlePaint setStrokeJoin Paint Join MITER               circlePaint setStrokeWidth 4f                       Override         protected void onSizeChanged int w  int h  int oldw  int oldh                super onSizeChanged w  h  oldw  oldh                mBitmap   Bitmap createBitmap w  h  Bitmap Config ARGB 8888               mCanvas   new Canvas mBitmap                       Override         protected void onDraw Canvas canvas                super onDraw canvas                canvas drawBitmap  mBitmap  0  0  mBitmapPaint               canvas drawPath  mPath   mPaint               canvas drawPath  circlePath   circlePaint                      private float mX  mY          private static final float TOUCH TOLERANCE   4           private void touch start float x  float y                mPath reset                mPath moveTo x  y               mX   x              mY   y                     private void touch move float x  float y                float dx   Math abs x - mX               float dy   Math abs y - mY               if  dx  gt   TOUCH TOLERANCE    dy  gt   TOUCH TOLERANCE                    mPath quadTo mX  mY   x   mX  2   y   mY  2                   mX   x                  mY   y                   circlePath reset                    circlePath addCircle mX  mY  30  Path Direction CW                                    private void touch up                 mPath lineTo mX  mY               circlePath reset                   commit the path to our offscreen             mCanvas drawPath mPath   mPaint                  kill this so we don t double draw             mPath reset                        Override         public boolean onTouchEvent MotionEvent event                float x   event getX                float y   event getY                 switch  event getAction                      case MotionEvent ACTION DOWN                      touch start x  y                       invalidate                        break                  case MotionEvent ACTION MOVE                      touch move x  y                       invalidate                        break                  case MotionEvent ACTION UP                      touch up                        invalidate                        break                            return true                      Snap shot    Explanation    You are creating a view class then extends View  You override the onDraw    You add the path of where finger touches and moves  You override the onTouch   of this purpose  In your onDraw   you draw the paths using the paint of your choice  You should call invalidate   to refresh the view   To choose options you can click menu and choose the options   The below can be used as a reference  You can modify the below according to your needs   public class FingerPaintActivity extends Activity         implements ColorPickerDialog OnColorChangedListener        MyView mv      AlertDialog dialog        Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState            mv  new MyView this           mv setDrawingCacheEnabled true           mv setBackgroundResource R drawable afor    set the back ground if you wish to         setContentView mv           mPaint   new Paint            mPaint setAntiAlias true           mPaint setDither true           mPaint setColor 0xFFFF0000           mPaint setStyle Paint Style STROKE           mPaint setStrokeJoin Paint Join ROUND           mPaint setStrokeCap Paint Cap ROUND           mPaint setStrokeWidth 20           mEmboss   new EmbossMaskFilter new float     1  1  1                    0 4f  6  3 5f           mBlur   new BlurMaskFilter 8  BlurMaskFilter Blur NORMAL              private Paint       mPaint      private MaskFilter  mEmboss      private MaskFilter  mBlur       public void colorChanged int color            mPaint setColor color              public class MyView extends View            private static final float MINP   0 25f          private static final float MAXP   0 75f          private Bitmap  mBitmap          private Canvas  mCanvas          private Path    mPath          private Paint   mBitmapPaint          Context context           public MyView Context c                super c               context c              mPath   new Path                mBitmapPaint   new Paint Paint DITHER FLAG                        Override         protected void onSizeChanged int w  int h  int oldw  int oldh                super onSizeChanged w  h  oldw  oldh               mBitmap   Bitmap createBitmap w  h  Bitmap Config ARGB 8888               mCanvas   new Canvas mBitmap                        Override         protected void onDraw Canvas canvas                super onDraw canvas                canvas drawBitmap mBitmap  0  0  mBitmapPaint               canvas drawPath mPath  mPaint                      private float mX  mY          private static final float TOUCH TOLERANCE   4           private void touch start float x  float y                  showDialog                 mPath reset                mPath moveTo x  y               mX   x              mY   y                     private void touch move float x  float y                float dx   Math abs x - mX               float dy   Math abs y - mY               if  dx  gt   TOUCH TOLERANCE    dy  gt   TOUCH TOLERANCE                    mPath quadTo mX  mY   x   mX  2   y   mY  2                   mX   x                  mY   y                                   private void touch up                 mPath lineTo mX  mY                  commit the path to our offscreen             mCanvas drawPath mPath  mPaint                  kill this so we don t double draw             mPath reset                mPaint setXfermode new PorterDuffXfermode PorterDuff Mode SCREEN                  mPaint setMaskFilter null                       Override         public boolean onTouchEvent MotionEvent event                float x   event getX                float y   event getY                 switch  event getAction                      case MotionEvent ACTION DOWN                      touch start x  y                       invalidate                        break                  case MotionEvent ACTION MOVE                       touch move x  y                       invalidate                        break                  case MotionEvent ACTION UP                      touch up                        invalidate                        break                            return true                       private static final int COLOR MENU ID   Menu FIRST      private static final int EMBOSS MENU ID   Menu FIRST   1      private static final int BLUR MENU ID   Menu FIRST   2      private static final int ERASE MENU ID   Menu FIRST   3      private static final int SRCATOP MENU ID   Menu FIRST   4      private static final int Save   Menu FIRST   5        Override     public boolean onCreateOptionsMenu Menu menu            super onCreateOptionsMenu menu            menu add 0  COLOR MENU ID  0   Color   setShortcut  3    c            menu add 0  EMBOSS MENU ID  0   Emboss   setShortcut  4    s            menu add 0  BLUR MENU ID  0   Blur   setShortcut  5    z            menu add 0  ERASE MENU ID  0   Erase   setShortcut  5    z            menu add 0  SRCATOP MENU ID  0   SrcATop   setShortcut  5    z            menu add 0  Save  0   Save   setShortcut  5    z             return true              Override     public boolean onPrepareOptionsMenu Menu menu            super onPrepareOptionsMenu menu           return true              Override     public boolean onOptionsItemSelected MenuItem item            mPaint setXfermode null           mPaint setAlpha 0xFF            switch  item getItemId                  case COLOR MENU ID                  new ColorPickerDialog this  this  mPaint getColor    show                    return true              case EMBOSS MENU ID                  if  mPaint getMaskFilter      mEmboss                        mPaint setMaskFilter mEmboss                     else                       mPaint setMaskFilter null                                     return true              case BLUR MENU ID                  if  mPaint getMaskFilter      mBlur                        mPaint setMaskFilter mBlur                     else                       mPaint setMaskFilter null                                     return true              case ERASE MENU ID                  mPaint setXfermode new PorterDuffXfermode PorterDuff Mode CLEAR                    mPaint setAlpha 0x80                   return true              case SRCATOP MENU ID                   mPaint setXfermode new PorterDuffXfermode                          PorterDuff Mode SRC ATOP                    mPaint setAlpha 0x80                   return true              case Save                  AlertDialog Builder editalert   new AlertDialog Builder FingerPaintActivity this                   editalert setTitle  Please Enter the name with which you want to Save                    final EditText input   new EditText FingerPaintActivity this                   LinearLayout LayoutParams lp   new LinearLayout LayoutParams                          LinearLayout LayoutParams FILL PARENT                          LinearLayout LayoutParams FILL PARENT                   input setLayoutParams lp                   editalert setView input                   editalert setPositiveButton  OK   new DialogInterface OnClickListener                         public void onClick DialogInterface dialog  int whichButton                             String name  input getText   toString                            Bitmap bitmap   mv getDrawingCache                             String path   Environment getExternalStorageDirectory   getAbsolutePath                            File file   new File   sdcard   name   png                            try                                                       if  file exists                                                                  file createNewFile                                                              FileOutputStream ostream   new FileOutputStream file                               bitmap compress CompressFormat PNG  10  ostream                               ostream close                                mv invalidate                                                      catch  Exception e                                                        e printStackTrace                             finally                                                        mv setDrawingCacheEnabled false                                                                                        editalert show                    return true                    return super onOptionsItemSelected item             Color Picker  public class ColorPickerDialog extends Dialog        public interface OnColorChangedListener           void colorChanged int color              private OnColorChangedListener mListener      private int mInitialColor       private static class ColorPickerView extends View           private Paint mPaint          private Paint mCenterPaint          private final int   mColors          private OnColorChangedListener mListener           ColorPickerView Context c  OnColorChangedListener l  int color                super c               mListener   l              mColors   new int                         0xFFFF0000  0xFFFF00FF  0xFF0000FF  0xFF00FFFF  0xFF00FF00                      0xFFFFFF00  0xFFFF0000                            Shader s   new SweepGradient 0  0  mColors  null                mPaint   new Paint Paint ANTI ALIAS FLAG               mPaint setShader s               mPaint setStyle Paint Style STROKE               mPaint setStrokeWidth 32                mCenterPaint   new Paint Paint ANTI ALIAS FLAG               mCenterPaint setColor color               mCenterPaint setStrokeWidth 5                      private boolean mTrackingCenter          private boolean mHighlightCenter            Override         protected void onDraw Canvas canvas                float r   CENTER X - mPaint getStrokeWidth   0 5f               canvas translate CENTER X  CENTER X                canvas drawOval new RectF -r  -r  r  r   mPaint               canvas drawCircle 0  0  CENTER RADIUS  mCenterPaint                if  mTrackingCenter                    int c   mCenterPaint getColor                    mCenterPaint setStyle Paint Style STROKE                    if  mHighlightCenter                        mCenterPaint setAlpha 0xFF                     else                       mCenterPaint setAlpha 0x80                                     canvas drawCircle 0  0                          CENTER RADIUS   mCenterPaint getStrokeWidth                            mCenterPaint                    mCenterPaint setStyle Paint Style FILL                   mCenterPaint setColor c                                     Override         protected void onMeasure int widthMeasureSpec  int heightMeasureSpec                setMeasuredDimension CENTER X 2  CENTER Y 2                      private static final int CENTER X   100          private static final int CENTER Y   100          private static final int CENTER RADIUS   32           private int floatToByte float x                int n   java lang Math round x               return n                     private int pinToByte int n                if  n  lt  0                    n   0                else if  n  gt  255                    n   255                            return n                     private int ave int s  int d  float p                return s   java lang Math round p    d - s                       private int interpColor int colors    float unit                if  unit  lt   0                    return colors 0                             if  unit  gt   1                    return colors colors length - 1                              float p   unit    colors length - 1               int i    int p              p -  i                  now p is just the fractional part  0   1  and i is the index             int c0   colors i               int c1   colors i 1               int a   ave Color alpha c0   Color alpha c1   p               int r   ave Color red c0   Color red c1   p               int g   ave Color green c0   Color green c1   p               int b   ave Color blue c0   Color blue c1   p                return Color argb a  r  g  b                      private int rotateColor int color  float rad                float deg   rad   180   3 1415927f              int r   Color red color               int g   Color green color               int b   Color blue color                ColorMatrix cm   new ColorMatrix                ColorMatrix tmp   new ColorMatrix                 cm setRGB2YUV                tmp setRotate 0  deg               cm postConcat tmp               tmp setYUV2RGB                cm postConcat tmp                final float   a   cm getArray                 int ir   floatToByte a 0    r    a 1    g    a 2    b               int ig   floatToByte a 5    r    a 6    g    a 7    b               int ib   floatToByte a 10    r   a 11    g   a 12    b                return Color argb Color alpha color   pinToByte ir                       pinToByte ig   pinToByte ib                       private static final float PI   3 1415926f            Override         public boolean onTouchEvent MotionEvent event                float x   event getX   - CENTER X              float y   event getY   - CENTER Y              boolean inCenter   java lang Math sqrt x x   y y   lt   CENTER RADIUS               switch  event getAction                      case MotionEvent ACTION DOWN                      mTrackingCenter   inCenter                      if  inCenter                            mHighlightCenter   true                          invalidate                            break                                        case MotionEvent ACTION MOVE                      if  mTrackingCenter                            if  mHighlightCenter    inCenter                                mHighlightCenter   inCenter                              invalidate                                                    else                           float angle    float java lang Math atan2 y  x                              need to turn angle  -PI     PI  into unit  0    1                          float unit   angle  2 PI                           if  unit  lt  0                                unit    1                                                    mCenterPaint setColor interpColor mColors  unit                            invalidate                                              break                  case MotionEvent ACTION UP                      if  mTrackingCenter                            if  inCenter                                mListener colorChanged mCenterPaint getColor                                                       mTrackingCenter   false        so we draw w o halo                         invalidate                                              break                            return true                       public ColorPickerDialog Context context                               OnColorChangedListener listener                               int initialColor            super context            mListener   listener          mInitialColor   initialColor              Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           OnColorChangedListener l   new OnColorChangedListener                 public void colorChanged int color                    mListener colorChanged color                   dismiss                                      setContentView new ColorPickerView getContext    l  mInitialColor            setTitle  Pick a Color

User · Answer

Regarding the beautiful code of Raghunandan above   Many have asked how to  clear  the drawing  Here s how to do that   public void clearDrawing             Utils Log  RaghunandanDraw  how to clear             setDrawingCacheEnabled false          don t forget that one and the match below         or you just keep getting a duplicate when you save       onSizeChanged width  height  width  height       invalidate         setDrawingCacheEnabled true           Override protected void onSizeChanged int w  int h  int oldw  int oldh            super onSizeChanged w  h  oldw  oldh        width   w          don t forget these     height   h       mBitmap   Bitmap createBitmap width  height  Bitmap Config ARGB 8888       mCanvas   new Canvas mBitmap           Many have asked how to  save  the drawing  Here s how to do that   public DrawingView Context c        circlePaint setStrokeJoin Paint Join MITER     circlePaint setStrokeWidth 4f      etc          in the class where you set up the view  add this    setDrawingCacheEnabled  true         public void saveDrawing         Bitmap whatTheUserDrewBitmap   getDrawingCache         don t forget to clear it  see above  or you just get duplicates       almost always you will want to reduce res from the very high screen res   whatTheUserDrewBitmap            ThumbnailUtils extractThumbnail whatTheUserDrewBitmap  256  256        NOTE that s an incredibly useful trick for cropping resizing squares      while handling all memory problems etc      http   stackoverflow com a 17733530 294884       you can now save the bitmap to a file  or display it in an ImageView    ImageView testArea         testArea setImageBitmap  whatTheUserDrewBitmap          these days you often need a  byte array   for example       to save to parse com or other cloud services   ByteArrayOutputStream baos   new ByteArrayOutputStream      whatTheUserDrewBitmap compress Bitmap CompressFormat PNG  0  baos     byte   yourByteArray    yourByteArray   baos toByteArray          Hope it helps someone as this has helped me

[android] Draw in Canvas by finger, Android

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