1 files changed, 168 insertions, 0 deletions
diff --git a/src/org/cyanogenmod/theme/widget/AutoSnapHorizontalScrollView.java b/src/org/cyanogenmod/theme/widget/AutoSnapHorizontalScrollView.java
new file mode 100644
index 0000000..29534f7
--- /dev/null
+++ b/src/org/cyanogenmod/theme/widget/AutoSnapHorizontalScrollView.java
@@ -0,0 +1,168 @@
+/*
+ * Copyright (C) 2016 Cyanogen, Inc.
+ * Copyright (C) 2016 The CyanogenMod 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.
+ */
+
+package org.cyanogenmod.theme.widget;
+
+import android.content.Context;
+import android.graphics.Rect;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.HorizontalScrollView;
+import android.widget.LinearLayout;
+
+public class AutoSnapHorizontalScrollView extends HorizontalScrollView {
+    private static final int SNAP_ON_UP_DELAY = 250;
+
+    private int mScrollPositionOnUp;
+
+    enum EventStates {
+        SCROLLING,
+        FLING
+    }
+
+    private EventStates mSystemState = EventStates.SCROLLING;
+
+    public AutoSnapHorizontalScrollView(Context context) {
+        super(context);
+    }
+
+    public AutoSnapHorizontalScrollView(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public AutoSnapHorizontalScrollView(Context context, AttributeSet attrs, int defStyle) {
+        super(context, attrs, defStyle);
+    }
+
+    Runnable mSnapRunnable = new Runnable(){
+        @Override
+        public void run() {
+            snapItems();
+            mSystemState = EventStates.SCROLLING;
+        }
+    };
+
+    /**
+     * Added runnable for snapping on an item when the user lifts up their finger and
+     * there is no scrolling taking place (i.e. no flinging)
+     */
+    Runnable mSnapOnUpRunnable = new Runnable(){
+        @Override
+        public void run() {
+            int scrollX = getScrollX();
+            if (scrollX != mScrollPositionOnUp) {
+                mScrollPositionOnUp = scrollX;
+                postDelayed(mSnapOnUpRunnable, SNAP_ON_UP_DELAY);
+            } else {
+                snapItems();
+                mSystemState = EventStates.SCROLLING;
+            }
+        }
+    };
+
+    @Override
+    public boolean onTouchEvent(MotionEvent ev) {
+        int action = ev.getAction();
+        if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
+            mSystemState = EventStates.FLING;
+            removeCallbacks(mSnapRunnable);
+            mScrollPositionOnUp = getScrollX();
+            postDelayed(mSnapOnUpRunnable, SNAP_ON_UP_DELAY);
+        } else if (action == MotionEvent.ACTION_DOWN) {
+            mSystemState = EventStates.SCROLLING;
+            removeCallbacks(mSnapRunnable);
+            removeCallbacks(mSnapOnUpRunnable);
+        }
+        return super.onTouchEvent(ev);
+    }
+
+    private void snapItems() {
+        Rect parentBounds = new Rect();
+        getDrawingRect(parentBounds);
+        Rect childBounds = new Rect();
+        ViewGroup parent = (ViewGroup) getChildAt(0);
+        for (int i = 0; i < parent.getChildCount(); i++) {
+            View view = parent.getChildAt(i);
+            view.getHitRect(childBounds);
+            if (childBounds.right >= parentBounds.left && childBounds.left <= parentBounds.left) {
+                // First partially visible child
+                if ((childBounds.right - parentBounds.left) >=
+                        (parentBounds.left - childBounds.left)) {
+                    smoothScrollTo(Math.abs(childBounds.left), 0);
+                } else {
+                    /**
+                     * Added code to take into account dividers so that we do not see
+                     * one on the edge of the screen when items snap in place.
+                     */
+                    int dividerWidth = 0;
+                    if (parent instanceof LinearLayout) {
+                        dividerWidth = ((LinearLayout) parent).getDividerWidth();
+                    }
+                    smoothScrollTo(Math.abs(childBounds.right) + dividerWidth, 0);
+                }
+                break;
+            }
+        }
+    }
+
+    // Overwrite measureChildX as we want our child to be able to tell the
+    // parents width but do not impose any limits (AT_MOST; AT_MAX)
+    @Override
+    protected void measureChild(View child, int parentWidthMeasureSpec,
+            int parentHeightMeasureSpec) {
+        ViewGroup.LayoutParams lp = child.getLayoutParams();
+
+        int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop
+                + mPaddingBottom, lp.height);
+
+        int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
+                MeasureSpec.getSize(parentWidthMeasureSpec) - (mPaddingLeft + mPaddingRight),
+                MeasureSpec.UNSPECIFIED);
+
+        child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
+    }
+
+    @Override
+    protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed,
+            int parentHeightMeasureSpec, int heightUsed) {
+        MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
+
+        int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec,
+                mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin
+                        + heightUsed, lp.height);
+
+        int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
+                MeasureSpec.getSize(parentWidthMeasureSpec) -
+                        (mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin
+                        + widthUsed), MeasureSpec.UNSPECIFIED);
+
+        child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
+    }
+
+    @Override
+    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
+        if (mSystemState == EventStates.SCROLLING) {
+            return;
+        }
+        if (Math.abs(l - oldl) <= 1 && mSystemState == EventStates.FLING) {
+            removeCallbacks(mSnapRunnable);
+            postDelayed(mSnapRunnable, 100);
+        }
+    }
+}