title: ColorPicker in android not working
body: <p>I have made a simple drawing android program for learning ,I have put a colorDialog which is displayed properly bu after selecting any color ,The pen color is not changing ,It still remains "black" the default color.I have tried as below,Please help me for it,My code is as below:</p>
  
  <p><strong>Main.java</strong></p>
  
  <pre><code>   package com.example.singletouch;
  
  import java.util.AbstractMap;
  import java.util.Map;
  import java.util.concurrent.ConcurrentLinkedQueue;
  
  import com.example.singletouch.SingleTouchView.DrawingPens;
  
  import android.os.Bundle;
  import android.app.ActionBar.LayoutParams;
  import android.app.Activity;
  import android.content.Context;
  import android.graphics.Bitmap;
  import android.graphics.Canvas;
  import android.graphics.Color;
  import android.graphics.Paint;
  import android.graphics.Path;
  import android.util.AttributeSet;
  import android.view.MotionEvent;
  import android.view.View;
  import android.view.View.OnClickListener;
  import android.widget.HorizontalScrollView;
  import android.widget.ImageView;
  import android.widget.LinearLayout;
  import android.widget.RelativeLayout;
  import android.widget.TextView;
  
  public class MainActivity extends Activity implements
          ColorPickerDialog.OnColorChangedListener {
      ImageView pen, color;
      SingleTouchView mDrawView;
      RelativeLayout layout, layout1;
      ImageView remove;
      ImageView eraser;
      Paint mPaint;
      private LinearLayout list_color;
      LinearLayout pens;
  
      private TextView select_color;
      private int selectedColor = 0x00FF0000;
      HorizontalScrollView myplate;
  
  
  
  
      private Path mPath;
  
      public Canvas mCanvas;
      LinearLayout pen1, pen2, pen3, pen4;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          mDrawView = (SingleTouchView) findViewById(R.id.myview);
  
          layout = (RelativeLayout) findViewById(R.id.layout);
          pen = (ImageView) findViewById(R.id.pen);
          pens = (LinearLayout) findViewById(R.id.linear);
          pens.setVisibility(View.GONE);
          pen1 = (LinearLayout) findViewById(R.id.pen1);
          pen2 = (LinearLayout) findViewById(R.id.pen2);
          pen3 = (LinearLayout) findViewById(R.id.pen3);
          pen4 = (LinearLayout) findViewById(R.id.pen4);
          eraser = (ImageView) findViewById(R.id.eraser);
          remove = (ImageView) findViewById(R.id.remove);
          color = (ImageView) findViewById(R.id.color);
  
  
          pen.setOnClickListener(new OnClickListener() {
  
              public void onClick(View v) {
                  // TODO Auto-generated method stub
                  pens.setVisibility(View.VISIBLE);
  
              }
          });
          pens.setVisibility(View.GONE);
          pen1.setOnClickListener(new OnClickListener() {
  
              @Override
              public void onClick(View v) {
                  mDrawView.setPen(SingleTouchView.DrawingPens.PEN_1);
                  pens.setVisibility(View.GONE);
  
              }
          });
          pen2.setOnClickListener(new OnClickListener() {
  
              @Override
              public void onClick(View v) {
                  mDrawView.setPen(SingleTouchView.DrawingPens.PEN_2);
                  pens.setVisibility(View.GONE);
  
              }
          });
          pen3.setOnClickListener(new OnClickListener() {
  
              @Override
              public void onClick(View v) {
                  pens.setVisibility(View.GONE);
                  mDrawView.setPen(SingleTouchView.DrawingPens.PEN_3);
  
              }
          });
          pen4.setOnClickListener(new OnClickListener() {
  
              @Override
              public void onClick(View v) {
                  pens.setVisibility(View.GONE);
                  mDrawView.setPen(SingleTouchView.DrawingPens.PEN_4);
  
              }
          });
  
          remove.setOnClickListener(new OnClickListener() {
  
              @Override
              public void onClick(View v) {
  
                  layout.removeView(mDrawView);
                  mDrawView = new SingleTouchView(MainActivity.this);
                  layout.addView(mDrawView);
              }
          });
  
          eraser.setOnClickListener(new OnClickListener() {
  
              @Override
              public void onClick(View v) {
  
  
              }
          });
  
          color.setOnClickListener(new OnClickListener() {
  
              @Override
              public void onClick(View v) {
                  // TODO Auto-generated method stub
                  // myplate.setVisibility(View.VISIBLE);
                  new ColorPickerDialog(MainActivity.this, MainActivity.this,
                  mPaint.getColor()).show();
  
              }
          });
  
      }
  
      @Override
      public void colorChanged(int color) {
          // TODO Auto-generated method stub
          mPaint.getColor();
      }
  
  
  
  }
   class SingleTouchView extends View {
      public static int width;
      public int height;
      public Bitmap mBitmap;
      public Canvas mCanvas;
      public Path mPath;
      public Paint mBitmapPaint;
      Context context;
      public Paint mPaint;
      public Paint circlePaint;
      public Path circlePath;
  
      public enum DrawingPens {
          PEN_1(6), PEN_2(4), PEN_3(2), PEN_4(1);
  
          public Paint mPaint;
  
          private DrawingPens(final int width) {
              mPaint = new Paint();
  
              mPaint.setAntiAlias(true);
              mPaint.setStrokeWidth(width);
  
              mPaint.setStyle(Paint.Style.STROKE);
              mPaint.setStrokeJoin(Paint.Join.ROUND);
          }
  
          Paint getPaint() {
              return mPaint;
          }
      }
  
      public SingleTouchView(final Context context) {
          super(context);
  
          init(context);
      }
  
      public SingleTouchView(final Context context, final AttributeSet attrs) {
          super(context, attrs);
  
          init(context);
          mBitmap = Bitmap.createBitmap(400, 400, Bitmap.Config.ARGB_8888);
          mCanvas = new Canvas(mBitmap);
          mPath = new Path();
          mBitmapPaint = new Paint(Paint.DITHER_FLAG);
  
          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);
      }
  
      public SingleTouchView(final Context context, final AttributeSet attrs,
              final int defStyle) {
          super(context, attrs, defStyle);
  
          init(context);
      }
  
      private ConcurrentLinkedQueue&lt;Map.Entry&lt;Path, DrawingPens&gt;&gt; mPaths = new ConcurrentLinkedQueue&lt;Map.Entry&lt;Path, DrawingPens&gt;&gt;();
  
      private Path mCurrentPath;
  
      private void init(final Context context) {
  
          setPen(DrawingPens.PEN_3);
  
      }
  
      @Override
      public void onDraw(Canvas canvas) {
  
          super.onDraw(canvas);
  
          for (Map.Entry&lt;Path, DrawingPens&gt; entry : mPaths) {
              canvas.drawPath(entry.getKey(), entry.getValue().getPaint());
          }
      }
  
      @Override
      public boolean onTouchEvent(MotionEvent me) {
          float eventX = me.getX();
          float eventY = me.getY();
  
          switch (me.getAction()) {
          case MotionEvent.ACTION_DOWN:
              mCurrentPath.moveTo(eventX, eventY);
              return true;
          case MotionEvent.ACTION_MOVE:
              mCurrentPath.lineTo(eventX, eventY);
              break;
          case MotionEvent.ACTION_UP:
              break;
          }
  
          invalidate();
  
          return true;
      }
  
      public void setPen(final DrawingPens pen) {
  
          mCurrentPath = new Path();
          mPaths.add(new AbstractMap.SimpleImmutableEntry&lt;Path, DrawingPens&gt;(
                  mCurrentPath, pen));
      }
  </code></pre>
  
  <p><strong>ColorPickerDialog.java</strong></p>
  
  <pre><code>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;
  
          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);
              }
          }
  
          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");
      }
  }
  </code></pre>
  
  <p>Crash log:</p>
  
  <pre><code>08-06 15:44:00.427: E/AndroidRuntime(3617): java.lang.NullPointerException
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at com.example.singletouch.MainActivity$8.onClick(MainActivity.java:134)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at android.view.View.performClick(View.java:3511)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at android.view.View$PerformClick.run(View.java:14109)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at android.os.Handler.handleCallback(Handler.java:605)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at android.os.Handler.dispatchMessage(Handler.java:92)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at android.os.Looper.loop(Looper.java:137)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at android.app.ActivityThread.main(ActivityThread.java:4424)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at java.lang.reflect.Method.invokeNative(Native Method)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at java.lang.reflect.Method.invoke(Method.java:511)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
      08-06 15:44:00.427: E/AndroidRuntime(3617):     at dalvik.system.NativeStart.main(Native Method)
  </code></pre>