1 files changed, 130 insertions, 0 deletions
diff --git a/java/com/android/dialer/contactsfragment/FastScroller.java b/java/com/android/dialer/contactsfragment/FastScroller.java
new file mode 100644
index 000000000..0223c5f1f
--- /dev/null
+++ b/java/com/android/dialer/contactsfragment/FastScroller.java
@@ -0,0 +1,130 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+package com.android.dialer.contactsfragment;
+
+import android.content.Context;
+import android.support.annotation.NonNull;
+import android.support.v7.widget.LinearLayoutManager;
+import android.support.v7.widget.RecyclerView;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import android.view.View;
+import android.widget.RelativeLayout;
+import android.widget.TextView;
+
+/** Widget to add fast scrolling to {@link ContactsFragment}. */
+public class FastScroller extends RelativeLayout {
+
+  private final int touchTargetWidth;
+
+  private ContactsAdapter adapter;
+  private LinearLayoutManager layoutManager;
+
+  private TextView container;
+  private View scrollBar;
+
+  private boolean dragStarted;
+
+  public FastScroller(Context context, AttributeSet attrs) {
+    super(context, attrs);
+    touchTargetWidth =
+        context.getResources().getDimensionPixelSize(R.dimen.fast_scroller_touch_target_width);
+  }
+
+  @Override
+  protected void onFinishInflate() {
+    super.onFinishInflate();
+    container = findViewById(R.id.fast_scroller_container);
+    scrollBar = findViewById(R.id.fast_scroller_scroll_bar);
+  }
+
+  void setup(ContactsAdapter adapter, LinearLayoutManager layoutManager) {
+    this.adapter = adapter;
+    this.layoutManager = layoutManager;
+    setVisibility(VISIBLE);
+  }
+
+  @Override
+  public boolean onTouchEvent(@NonNull MotionEvent event) {
+    // Don't override if touch event isn't within desired touch target and dragging hasn't started.
+    if (!dragStarted && getWidth() - touchTargetWidth - event.getX() > 0) {
+      return super.onTouchEvent(event);
+    }
+
+    switch (event.getAction()) {
+      case MotionEvent.ACTION_DOWN:
+        dragStarted = true;
+        container.setVisibility(VISIBLE);
+        scrollBar.setSelected(true);
+        // fall through
+      case MotionEvent.ACTION_MOVE:
+        setContainerAndScrollBarPosition(event.getY());
+        setRecyclerViewPosition(event.getY());
+        return true;
+      case MotionEvent.ACTION_UP:
+      case MotionEvent.ACTION_CANCEL:
+        dragStarted = false;
+        container.setVisibility(INVISIBLE);
+        scrollBar.setSelected(false);
+        return true;
+    }
+    return super.onTouchEvent(event);
+  }
+
+  private void setRecyclerViewPosition(float y) {
+    final int itemCount = adapter.getItemCount();
+    float scrolledPosition = getScrolledPercentage(y) * (float) itemCount;
+    int targetPos = getValueInRange(0, itemCount - 1, (int) scrolledPosition);
+    layoutManager.scrollToPositionWithOffset(targetPos, 0);
+    container.setText(adapter.getHeaderString(targetPos));
+  }
+
+  // Returns a float in range [0, 1] which represents the position of the scroller.
+  private float getScrolledPercentage(float y) {
+    if (scrollBar.getY() == 0) {
+      return 0f;
+    } else if (scrollBar.getY() + scrollBar.getHeight() >= getHeight()) {
+      return 1f;
+    } else {
+      return y / (float) getHeight();
+    }
+  }
+
+  private int getValueInRange(int min, int max, int value) {
+    int minimum = Math.max(min, value);
+    return Math.min(minimum, max);
+  }
+
+  void updateContainerAndScrollBarPosition(RecyclerView recyclerView) {
+    if (!scrollBar.isSelected()) {
+      int verticalScrollOffset = recyclerView.computeVerticalScrollOffset();
+      int verticalScrollRange = recyclerView.computeVerticalScrollRange();
+      float proportion = (float) verticalScrollOffset / ((float) verticalScrollRange - getHeight());
+      setContainerAndScrollBarPosition(getHeight() * proportion);
+    }
+  }
+
+  private void setContainerAndScrollBarPosition(float y) {
+    int scrollBarHeight = scrollBar.getHeight();
+    int containerHeight = container.getHeight();
+    scrollBar.setY(
+        getValueInRange(0, getHeight() - scrollBarHeight, (int) (y - scrollBarHeight / 2)));
+    container.setY(
+        getValueInRange(
+            0, getHeight() - containerHeight - scrollBarHeight / 2, (int) (y - containerHeight)));
+  }
+}