Color Picker Dialog Android example

Select color from menu and touch the screen.
color-picker-android

// MainActivity.java
public class MainActivity extends Activity implements
		ColorPickerDialog.OnColorChangedListener {
	// http://www.apache.org/licenses/LICENSE-2.0
	protected int _color = Color.GREEN;
 
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		mPaint = new Paint();
		mPaint.setColor(Color.RED);
		setContentView(new SampleView(this));
	}
 
	private Paint mPaint;
 
	private static final int MY_MENU_1 = Menu.FIRST;
	private static final int MY_MENU_2 = Menu.FIRST + 1;
	private static final int MY_MENU_3 = Menu.FIRST + 2;
 
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		super.onCreateOptionsMenu(menu);
 
		menu.add(0, MY_MENU_1, 0, "Color").setShortcut('3', 'c');
		menu.add(0, MY_MENU_2, 0, "About").setShortcut('4', 's');
		menu.add(0, MY_MENU_3, 0, "Help").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 MY_MENU_1:
			Toast.makeText(getApplicationContext(), "Color", Toast.LENGTH_LONG)
					.show();
			// Paint mPaint = new Paint();
			mPaint.setColor(Color.BLUE);
			new ColorPickerDialog(this, this, mPaint.getColor()).show();
 
			return true;
		case MY_MENU_2:
 
			Toast.makeText(getApplicationContext(), item.getTitle(),
					Toast.LENGTH_LONG).show();
			return true;
		case MY_MENU_3:
			Toast.makeText(getApplicationContext(), item.getTitle(),
					Toast.LENGTH_LONG).show();
			return true;
		}
		return super.onOptionsItemSelected(item);
	}
 
	public class SampleView extends View {
 
		// CONSTRUCTOR
		public SampleView(Context context) {
			super(context);
			setFocusable(true);
 
		}
        @Override
        public boolean onTouchEvent(MotionEvent event) {
            float x = event.getX();
            float y = event.getY();
 
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    invalidate();
                    break;
                case MotionEvent.ACTION_MOVE:
                    invalidate();
                    break;
                case MotionEvent.ACTION_UP:
                    invalidate();
                    break;
            }
            return true;
        }
 
		@Override
		protected void onDraw(Canvas canvas) {
			int nColor = _color;
			// canvas.drawColor(nColor);
			canvas.drawColor(Color.GREEN);
 
			Bitmap b = Bitmap.createBitmap(200, 200, Bitmap.Config.ALPHA_8);
			Canvas c = new Canvas(b);
			c.drawRect(0, 0, 200, 200, mPaint);
			canvas.drawBitmap(b, 10, 10, mPaint);
		}
 
	}
 
	@Override
	public void colorChanged(int color) {
		mPaint.setColor(color);
		_color = color;
 
	}
}
/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
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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