1 files changed, 125 insertions, 0 deletions
diff --git a/java/com/android/contacts/common/list/AutoScrollListView.java b/java/com/android/contacts/common/list/AutoScrollListView.java
new file mode 100644
index 000000000..601abf528
--- /dev/null
+++ b/java/com/android/contacts/common/list/AutoScrollListView.java
@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2010 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.contacts.common.list;
+
+import android.content.Context;
+import android.os.Build;
+import android.util.AttributeSet;
+import android.widget.ListView;
+
+/**
+ * A ListView that can be asked to scroll (smoothly or otherwise) to a specific position. This class
+ * takes advantage of similar functionality that exists in {@link ListView} and enhances it.
+ */
+public class AutoScrollListView extends ListView {
+
+  /** Position the element at about 1/3 of the list height */
+  private static final float PREFERRED_SELECTION_OFFSET_FROM_TOP = 0.33f;
+
+  private int mRequestedScrollPosition = -1;
+  private boolean mSmoothScrollRequested;
+
+  public AutoScrollListView(Context context) {
+    super(context);
+  }
+
+  public AutoScrollListView(Context context, AttributeSet attrs) {
+    super(context, attrs);
+  }
+
+  public AutoScrollListView(Context context, AttributeSet attrs, int defStyle) {
+    super(context, attrs, defStyle);
+  }
+
+  /**
+   * Brings the specified position to view by optionally performing a jump-scroll maneuver: first it
+   * jumps to some position near the one requested and then does a smooth scroll to the requested
+   * position. This creates an impression of full smooth scrolling without actually traversing the
+   * entire list. If smooth scrolling is not requested, instantly positions the requested item at a
+   * preferred offset.
+   */
+  public void requestPositionToScreen(int position, boolean smoothScroll) {
+    mRequestedScrollPosition = position;
+    mSmoothScrollRequested = smoothScroll;
+    requestLayout();
+  }
+
+  @Override
+  protected void layoutChildren() {
+    super.layoutChildren();
+    if (mRequestedScrollPosition == -1) {
+      return;
+    }
+
+    final int position = mRequestedScrollPosition;
+    mRequestedScrollPosition = -1;
+
+    int firstPosition = getFirstVisiblePosition() + 1;
+    int lastPosition = getLastVisiblePosition();
+    if (position >= firstPosition && position <= lastPosition) {
+      return; // Already on screen
+    }
+
+    final int offset = (int) (getHeight() * PREFERRED_SELECTION_OFFSET_FROM_TOP);
+    if (!mSmoothScrollRequested) {
+      setSelectionFromTop(position, offset);
+
+      // Since we have changed the scrolling position, we need to redo child layout
+      // Calling "requestLayout" in the middle of a layout pass has no effect,
+      // so we call layoutChildren explicitly
+      super.layoutChildren();
+
+    } else {
+      // We will first position the list a couple of screens before or after
+      // the new selection and then scroll smoothly to it.
+      int twoScreens = (lastPosition - firstPosition) * 2;
+      int preliminaryPosition;
+      if (position < firstPosition) {
+        preliminaryPosition = position + twoScreens;
+        if (preliminaryPosition >= getCount()) {
+          preliminaryPosition = getCount() - 1;
+        }
+        if (preliminaryPosition < firstPosition) {
+          setSelection(preliminaryPosition);
+          super.layoutChildren();
+        }
+      } else {
+        preliminaryPosition = position - twoScreens;
+        if (preliminaryPosition < 0) {
+          preliminaryPosition = 0;
+        }
+        if (preliminaryPosition > lastPosition) {
+          setSelection(preliminaryPosition);
+          super.layoutChildren();
+        }
+      }
+
+      smoothScrollToPositionFromTop(position, offset);
+    }
+  }
+
+  @Override
+  protected void onLayout(boolean changed, int l, int t, int r, int b) {
+    super.onLayout(changed, l, t, r, b);
+
+    // Workaround for b/31160338 and b/32778636.
+    if (android.os.Build.VERSION.SDK_INT == Build.VERSION_CODES.N
+        || android.os.Build.VERSION.SDK_INT == Build.VERSION_CODES.N_MR1) {
+      layoutChildren();
+    }
+  }
+}