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/**
* Copyright 2013 Alex Yanchenko
*
* 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.droidparts.util.ui;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListAdapter;
import android.widget.ListView;
// https://github.com/vladexologija/PinterestListView/blob/master/src/com/vladimir/pinterestlistview/ItemsActivity.java
public class ListViewSynchronizer implements OnTouchListener, OnScrollListener {
private final ListView leftListView;
private final ListView rightListView;
private int[] leftViewsHeights;
private int[] rightViewsHeights;
public ListViewSynchronizer(ListView first, ListView second) {
leftListView = first;
rightListView = second;
}
public void synchronize() {
ListAdapter leftAdapter = leftListView.getAdapter();
ListAdapter rightAdapter = rightListView.getAdapter();
if (leftAdapter == null || rightAdapter == null) {
throw new IllegalStateException("List adapters must be set.");
}
leftViewsHeights = new int[leftAdapter.getCount()];
rightViewsHeights = new int[rightAdapter.getCount()];
// reset getFirstVisiblePosition()
leftListView.setAdapter(leftAdapter);
rightListView.setAdapter(rightAdapter);
//
leftListView.setOnTouchListener(this);
rightListView.setOnTouchListener(this);
leftListView.setOnScrollListener(this);
rightListView.setOnScrollListener(this);
}
public void desynchronize() {
leftListView.setOnTouchListener(null);
rightListView.setOnTouchListener(null);
leftListView.setOnScrollListener(null);
rightListView.setOnScrollListener(null);
}
/**
* Passing the touch event to the opposite list
*/
@Override
public boolean onTouch(View v, MotionEvent event) {
if (v == leftListView && !dispatched) {
dispatched = true;
rightListView.dispatchTouchEvent(event);
} else if (v == rightListView && !dispatched) {
dispatched = true;
leftListView.dispatchTouchEvent(event);
}
dispatched = false;
return false;
}
private boolean dispatched = false;
/**
* Synchronizing scrolling Distance from the top of the first visible
* element opposite list: sum_heights(opposite invisible screens) -
* sum_heights(invisible screens) + distance from top of the first visible
* child
*/
@Override
public void onScroll(AbsListView listView, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
if (listView.getChildAt(0) != null) {
if (listView == leftListView) {
leftViewsHeights[listView.getFirstVisiblePosition()] = listView
.getChildAt(0).getHeight();
int h = 0;
for (int i = 0; i < rightListView.getFirstVisiblePosition(); i++) {
h += rightViewsHeights[i];
}
int hi = 0;
for (int i = 0; i < leftListView.getFirstVisiblePosition(); i++) {
hi += leftViewsHeights[i];
}
int top = h - hi + listView.getChildAt(0).getTop();
rightListView.setSelectionFromTop(
rightListView.getFirstVisiblePosition(), top);
} else if (listView == rightListView) {
rightViewsHeights[listView.getFirstVisiblePosition()] = listView
.getChildAt(0).getHeight();
int h = 0;
for (int i = 0; i < leftListView.getFirstVisiblePosition(); i++) {
h += leftViewsHeights[i];
}
int hi = 0;
for (int i = 0; i < rightListView.getFirstVisiblePosition(); i++) {
hi += rightViewsHeights[i];
}
int top = h - hi + listView.getChildAt(0).getTop();
leftListView.setSelectionFromTop(
leftListView.getFirstVisiblePosition(), top);
}
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// pass
}
}
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