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Android Null Exception Function

I want to change the color when I click the button, passing an integer of color as a parameter, but when I click on the android, a Null Pointer exception error is thrown. and application crashes .. I'm stuck here, please help me please the 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 you x and y coordinates on the Event. float pointX = event.getX(); float pointY = event.getY(); // Checks for the event that 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 center x-coordinate, y-coordinate, radius of the // circle, direction to wind the 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 a repaint. // Force a view to 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)); } } }
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You need to 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 the code }

First you need to customize the contents of your layout, and then re-view the views.

You also need to add a drawing to your layout.

In onCreate

  LinearLayout ll = (LinearLayout)findViewById(R.layout.linearlayout); // Assuming you have linear layout in your xml add your drawing view to lineasrlayout // you can have relative layout also 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; mY = 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; mY = y; } circlePath.reset(); circlePath.addCircle(mX, mY, 30, Path.Direction.CW); } 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 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'); /**** Is this the mechanism to extend with 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 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) <= 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 < 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"); } }
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Source: https://habr.com/ru/post/1497825/

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