canvas - Android Null Exception on Calling function -
i want change color on button click passing color integer parameter on click android throws error of null pointer exception. , application crashes .. stuck here kindly me please function name setcolor()
myview class public class myview extends activity { button brushlarge; button brushmeduim; button brushsmall; button erase; button save; button trash; button rainbow; button color1; button color2; button color3; this.color1 = ((button)findviewbyid(r.id.color1)); this.color2 = ((button)findviewbyid(r.id.color2)); this.color3 = ((button)findviewbyid(r.id.color3)); this.color1.setonclicklistener(new view.onclicklistener() { public void onclick(view paramview) { toast.maketext(getapplicationcontext(), "color1", toast.length_long).show(); //myview.this.coloringview.setcolor("#cd5c5c"); } }); this.color2.setonclicklistener(new view.onclicklistener() { public void onclick(view paramview) { //drawview.changepaintcolor(0xffff0000);0); try {coloringview.changepaintcolor(0xffff0000); } catch(exception e) { toast.maketext(getapplicationcontext(), "color1"+e,toast.length_long).show(); } //coloringview.changepaintcolor(0xffff0000); } }); this.color3.setonclicklistener(new view.onclicklistener() { public void onclick(view paramview) { myview.this.coloringview.setcolor("#fa8072"); } }); return; } } drawview class public class drawview extends view { private paint paint = new paint(); private path path = new path(); private paint circlepaint = new paint(); private path circlepath = new path(); canvas mcanvas; string color = "#ffee22"; public drawview(context context, attributeset attrs) { super(context, attrs); paint.setantialias(true); paint.setcolor(color.green); paint.setstyle(paint.style.stroke); paint.setstrokejoin(paint.join.round); paint.setstrokewidth(15f); circlepaint.setantialias(true); circlepaint.setcolor(color.blue); circlepaint.setstyle(paint.style.stroke); circlepaint.setstrokejoin(paint.join.miter); circlepaint.setstrokewidth(4f); mcanvas=new canvas(); } public void changepaintcolor(int color){ this.paint.setcolor(color); } @override protected void ondraw(canvas canvas) { canvas.drawpath(path, paint); canvas.drawpath(circlepath, circlepaint); } @override public boolean ontouchevent(motionevent event) { // gives x , y coordinates on event. float pointx = event.getx(); float pointy = event.gety(); // checks event occurs switch (event.getaction()) { case motionevent.action_down: path.moveto(pointx, pointy); return true; case motionevent.action_move: path.lineto(pointx, pointy); circlepath.reset(); // (circle's center x-coordinate, y-coordinate, radius of // circle, direction wind shape) circlepath.addcircle(pointx, pointy, 30, path.direction.cw); //circlepath.addrect(pointx - 25, pointy - 25, pointx + 25, pointy + 25, path.direction.cw); /* rectf rect = new rectf(pointx - 25, pointy - 25, pointx + 25, pointy + 25); circlepath.addroundrect(rect, 0, 0, path.direction.cw); */ break; case motionevent.action_up: circlepath.reset(); break; default: return false; } // schedules repaint. // force view draw. postinvalidate(); return true; } /////function------------------------------------ public void apple() { // paint.setcolor(ap); //toast.maketext(getcontext(), "rehman", toast.length_short).show(); this.paint.setcolor(0xff0000ff); } public void setcolor(string color) { this.paint.setcolor(0xff0000ff); } public void onsizechange(int paramint) { paint.setstrokewidth(paramint); } public void clear() { if (this.mcanvas != null) { this.paint.setargb(255, 255, 255, 255); mcanvas.drawpaint(this.paint); invalidate(); paint.setcolor(color.parsecolor(this.color)); } } }
you need override oncreate
@override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); this.color1 = ((button)findviewbyid(r.id.color1)); this.color2 = ((button)findviewbyid(r.id.color2)); this.color3 = ((button)findviewbyid(r.id.color3)); ...//rest of code } you need set content of layout activity first , intialize views.
also need add drawing view layout.
in oncreate
linearlayout ll = (linearlayout)findviewbyid(r.layout.linearlayout); // assuming have linear layout in xml add drawing view lineasrlayout // can have relative layout drawingview view = new drawingview(this); ll.addview(view); edit
public class mainactivity extends activity implements colorpickerdialog.oncolorchangedlistener { @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(new myview(this)); //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); //circlepath.reset(); //circlepath.addcircle(mx, my, 30, path.direction.cw); 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(12); 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,circlepath; private paint mbitmappaint,circlepaint; public myview(context c) { super(c); 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); 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) { canvas.drawcolor(0xffaaaaaa); 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; = y; } private void touch_move(float x, float y) { float dx = math.abs(x - mx); float dy = math.abs(y - my); if (dx >= touch_tolerance || dy >= touch_tolerance) { mpath.quadto(mx, my, (x + mx)/2, (y + my)/2); mx = x; = y; } circlepath.reset(); circlepath.addcircle(mx, my, 30, path.direction.cw); } private void touch_up() { mpath.lineto(mx, my); // commit path our offscreen mcanvas.drawpath(mpath, mpaint); // kill don't double draw circlepath.reset(); 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; } } 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; @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'); /**** mechanism extend filter effects? intent intent = new intent(null, getintent().getdata()); intent.addcategory(intent.category_alternative); menu.addintentoptions( menu.alternative, 0, new componentname(this, noteslist.class), null, intent, 0, null); *****/ 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)); return true; case srcatop_menu_id: mpaint.setxfermode(new porterduffxfermode( porterduff.mode.src_atop)); mpaint.setalpha(0x80); return true; } return super.onoptionsitemselected(item); } } colorpickerdialog
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 < 0) { n = 0; } else if (n > 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 <= 0) { return colors[0]; } if (unit >= 1) { return colors[colors.length - 1]; } float p = unit * (colors.length - 1); int = (int)p; p -= i; // p fractional part [0...1) , index int c0 = colors[i]; int c1 = colors[i+1]; int = 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[] = 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) <= 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 turn angle [-pi ... pi] unit [0....1] float unit = angle/(2*pi); if (unit < 0) { unit += 1; } mcenterpaint.setcolor(interpcolor(mcolors, unit)); invalidate(); } break; case motionevent.action_up: if (mtrackingcenter) { if (incenter) { mlistener.colorchanged(mcenterpaint.getcolor()); } mtrackingcenter = false; // 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 color"); } } 
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