center zoom around focused point...

README.md

@@ -105,6 +105,8 @@ You can customize the look of the `WeekView` in xml. Use the following attribute
 - `eventTextColor`
 - `eventTextSize`
 - `firstDayOfWeek`
+- `zoomFocusPoint` The focused point (percentage of the view height) where the week view is zoomed around. This point will not move while zooming. You can declare it as a fraction `app:focusPoint="30%"` and if is not declared the top of the view is used.
+- `zoomFocusPointEnabled` If you set this to ``false`` the zoomFocusPoint won't take effect any more while zooming. The zoom will always be focused at the center of your gesture.
 - `headerColumnBackground`
 - `headerColumnPadding`
 - `headerColumnTextColor`

library/src/main/java/com/alamkanak/weekview/WeekView.java

@@ -142,7 +142,9 @@ private enum Direction {
     private boolean mShowDistinctPastFutureColor = false;
     private boolean mHorizontalFlingEnabled = true;
     private boolean mVerticalFlingEnabled = true;
-    private int mAllDayEventHeight = 100;
+    private int mAllDayEventHeight= 100;
+    private float mZoomFocusPoint = 0;
+    private boolean mZoomFocusPointEnabled = true;
     private int mScrollDuration = 250;
 
     // Listeners.
@@ -352,6 +354,8 @@ public WeekView(Context context, AttributeSet attrs, int defStyleAttr) {
             mHorizontalFlingEnabled = a.getBoolean(R.styleable.WeekView_horizontalFlingEnabled, mHorizontalFlingEnabled);
             mVerticalFlingEnabled = a.getBoolean(R.styleable.WeekView_verticalFlingEnabled, mVerticalFlingEnabled);
             mAllDayEventHeight = a.getDimensionPixelSize(R.styleable.WeekView_allDayEventHeight, mAllDayEventHeight);
+            mZoomFocusPoint = a.getFraction(R.styleable.WeekView_zoomFocusPoint, 1, 1, mZoomFocusPoint);
+            mZoomFocusPointEnabled = a.getBoolean(R.styleable.WeekView_zoomFocusPointEnabled, mZoomFocusPointEnabled);
             mScrollDuration = a.getInt(R.styleable.WeekView_scrollDuration, mScrollDuration);
         } finally {
             a.recycle();
@@ -443,26 +447,7 @@ private void init() {
         // Set default event color.
         mDefaultEventColor = Color.parseColor("#9fc6e7");
 
-        mScaleDetector = new ScaleGestureDetector(mContext, new ScaleGestureDetector.OnScaleGestureListener() {
-            @Override
-            public void onScaleEnd(ScaleGestureDetector detector) {
-                mIsZooming = false;
-            }
-
-            @Override
-            public boolean onScaleBegin(ScaleGestureDetector detector) {
-                mIsZooming = true;
-                goToNearestOrigin();
-                return true;
-            }
-
-            @Override
-            public boolean onScale(ScaleGestureDetector detector) {
-                mNewHourHeight = Math.round(mHourHeight * detector.getScaleFactor());
-                invalidate();
-                return true;
-            }
-        });
+        mScaleDetector = new ScaleGestureDetector(mContext, new WeekViewGestureListener());
     }
 
     // fix rotation changes
@@ -586,7 +571,6 @@ private void drawHeaderRowAndEvents(Canvas canvas) {
             else if (mNewHourHeight > mMaxHourHeight)
                 mNewHourHeight = mMaxHourHeight;
 
-            mCurrentOrigin.y = (mCurrentOrigin.y/mHourHeight)*mNewHourHeight;
             mHourHeight = mNewHourHeight;
             mNewHourHeight = -1;
         }
@@ -1798,6 +1782,45 @@ public void setAllDayEventHeight(int height) {
         mAllDayEventHeight = height;
     }
 
+    /**
+     * Enable zoom focus point
+     * If you set this to false the `zoomFocusPoint` won't take effect any more while zooming.
+     * The zoom will always be focused at the center of your gesture.
+     */
+    public void setZoomFocusPointEnabled(boolean zoomFocusPointEnabled) {
+        mZoomFocusPointEnabled = zoomFocusPointEnabled;
+    }
+
+    /*
+     * Is focus point enabled
+     * @return fixed focus point enabled?
+     */
+    public boolean isZoomFocusPointEnabled() {
+        return mZoomFocusPointEnabled;
+    }
+
+    /*
+     * Get focus point
+     * 0 = top of view, 1 = bottom of view
+     * The focused point (multiplier of the view height) where the week view is zoomed around.
+     * This point will not move while zooming.
+     * @return focus point
+     */
+    public float getZoomFocusPoint() {
+        return mZoomFocusPoint;
+    }
+
+    /**
+     * Set focus point
+     * 0 = top of view, 1 = bottom of view
+     * The focused point (multiplier of the view height) where the week view is zoomed around.
+     * This point will not move while zooming.
+     */
+    public void setZoomFocusPoint(int zoomFocusPoint) {
+        mZoomFocusPoint = zoomFocusPoint;
+    }
+
+
     /**
      * Get scroll duration
      * @return scroll duration
@@ -2039,4 +2062,52 @@ public interface ScrollListener {
          */
         void onFirstVisibleDayChanged(Calendar newFirstVisibleDay, Calendar oldFirstVisibleDay);
     }
+
+    /**
+     * A simple GestureListener that holds the focused hour while scaling.
+     */
+    private class WeekViewGestureListener implements ScaleGestureDetector.OnScaleGestureListener {
+
+        float mFocusedPointY;
+
+        @Override
+        public void onScaleEnd(ScaleGestureDetector detector) {
+            mIsZooming = false;
+        }
+
+        @Override
+        public boolean onScaleBegin(ScaleGestureDetector detector) {
+            mIsZooming = true;
+            goToNearestOrigin();
+
+            // Calculate focused point for scale action
+            if (mZoomFocusPointEnabled) {
+                // Use fractional focus, percentage of height
+                mFocusedPointY = (getHeight() - mHeaderHeight - mHeaderRowPadding * 2 - mHeaderMarginBottom) * mZoomFocusPoint;
+            } else {
+                // Grab focus
+                mFocusedPointY = detector.getFocusY();
+            }
+
+            return true;
+        }
+
+        @Override
+        public boolean onScale(ScaleGestureDetector detector) {
+            final float scale = detector.getScaleFactor();
+
+            mNewHourHeight = Math.round(mHourHeight * scale);
+
+            // Calculating difference
+            float diffY = mFocusedPointY - mCurrentOrigin.y;
+            // Scaling difference
+            diffY = diffY * scale - diffY;
+            // Updating week view origin
+            mCurrentOrigin.y -= diffY;
+
+            invalidate();
+            return true;
+        }
+
+    }
 }

library/src/main/res/values/attrs.xml

@@ -50,6 +50,8 @@
         <attr name="horizontalFlingEnabled" format="boolean"/>
         <attr name="verticalFlingEnabled" format="boolean"/>
         <attr name="allDayEventHeight" format="dimension"/>
+        <attr name="zoomFocusPoint" format="fraction"/>
+        <attr name="zoomFocusPointEnabled" format="boolean"/>
         <attr name="scrollDuration" format="integer"/>
     </declare-styleable>
 </resources>