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LarphoidLarphoid
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the class
the overscroll listview class
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‎src/com/larphoid/overscrolllistview/OverscrollListview.java‎

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package com.larphoid.overscrollinglistview;
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import android.content.Context;
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import android.os.Handler;
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import android.util.AttributeSet;
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import android.view.GestureDetector;
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import android.view.MotionEvent;
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import android.view.View;
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import android.view.GestureDetector.OnGestureListener;
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import android.view.WindowManager;
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import android.widget.AbsListView;
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import android.widget.AdapterView;
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import android.widget.ListView;
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import android.widget.AbsListView.OnScrollListener;
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public class OverscrollListview extends ListView implements OnScrollListener, View.OnTouchListener, android.widget.AdapterView.OnItemSelectedListener {
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public Handler mHandler = new Handler();
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private View measure;
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public int nHeaders = 1, nFooters = 1, divHeight, delay = 10;
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public boolean rebound = false;
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private int firstVis, visibleCnt, lastVis, totalItems, scrollstate;
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private boolean bounce = true, recalcV = false, trackballEvent = false;
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private long flingTimestamp = 0;
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private float velocity = 0;
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private static final float BREAKSPEED = 4.0f, BOUNCEBRAKE = -.5f;
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private GestureDetector gesture;
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public OverscrollListview(Context context) {
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super(context);
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initialize(context);
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}
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public OverscrollListview(Context context, AttributeSet attrs) {
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super(context, attrs);
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initialize(context);
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}
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public OverscrollListview(Context context, AttributeSet attrs, int defStyle) {
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super(context, attrs, defStyle);
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initialize(context);
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}
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@Override
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public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
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firstVis = firstVisibleItem;
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visibleCnt = visibleItemCount;
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totalItems = totalItemCount;
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lastVis = firstVisibleItem + visibleItemCount;
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}
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@Override
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public void onScrollStateChanged(AbsListView view, int scrollState) {
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scrollstate = scrollState;
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if (scrollState != OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
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rebound = true;
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mHandler.postDelayed(checkListviewTopAndBottom, delay);
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}
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}
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@Override
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public void onItemSelected(AdapterView<?> av, View v, int position, long id) {
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rebound = true;
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mHandler.postDelayed(checkListviewTopAndBottom, delay);
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}
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@Override
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public void onNothingSelected(AdapterView<?> av) {
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rebound = true;
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mHandler.postDelayed(checkListviewTopAndBottom, delay);
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}
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@Override
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public boolean onTrackballEvent(MotionEvent event) {
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trackballEvent = true;
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rebound = true;
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mHandler.postDelayed(checkListviewTopAndBottom, delay);
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return super.onTrackballEvent(event);
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}
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@Override
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public boolean onTouch(View v, MotionEvent event) {
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gesture.onTouchEvent(event);
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return false;
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}
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private class thisGestureListener implements OnGestureListener {
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@Override
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public boolean onDown(MotionEvent e) {
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rebound = false;
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recalcV = false;
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velocity = 0;
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return false;
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}
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@Override
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public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
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rebound = true;
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recalcV = true;
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velocity = velocityY / 25.0f;
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flingTimestamp = System.currentTimeMillis();
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return false;
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}
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@Override
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public void onLongPress(MotionEvent e) {
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}
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@Override
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public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
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return false;
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}
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@Override
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public void onShowPress(MotionEvent e) {
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}
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@Override
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public boolean onSingleTapUp(MotionEvent e) {
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rebound = true;
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recalcV = false;
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velocity = 0;
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return false;
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}
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};
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public void initialize(Context context) {
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View header = new View(context);
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header.setMinimumHeight(((WindowManager) context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay().getHeight());
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addHeaderView(header, null, false);
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addFooterView(header, null, false);
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gesture = new GestureDetector(new thisGestureListener());
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gesture.setIsLongpressEnabled(false);
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flingTimestamp = System.currentTimeMillis();
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setHeaderDividersEnabled(false);
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setFooterDividersEnabled(false);
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setOnTouchListener(this);
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setOnScrollListener(this);
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setOnItemSelectedListener(this);
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}
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public void initializeValues() {
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nHeaders = getHeaderViewsCount();
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nFooters = getFooterViewsCount();
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divHeight = getDividerHeight();
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firstVis = 0;
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visibleCnt = 0;
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lastVis = 0;
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totalItems = 0;
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scrollstate = 0;
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}
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public void setBounce(boolean bouncing) {
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bounce = bouncing;
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}
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public Runnable checkListviewTopAndBottom = new Runnable() {
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@Override
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public void run() {
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mHandler.removeCallbacks(checkListviewTopAndBottom);
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if (rebound) {
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if (trackballEvent && firstVis < nHeaders && lastVis >= totalItems) {
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trackballEvent = false;
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rebound = false;
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return;
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}
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if (firstVis < nHeaders) {
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// hack to avoid strange behaviour when there aren't enough items to fill the entire listview
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if (lastVis >= totalItems) {
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smoothScrollBy(0, 0);
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rebound = false;
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recalcV = false;
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velocity = 0;
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}
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if (recalcV) {
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recalcV = false;
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velocity /= (1.0f + ((System.currentTimeMillis() - flingTimestamp) / 1000.0f));
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}
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if (firstVis == nHeaders) {
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recalcV = false;
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}
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measure = getChildAt(nHeaders);
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try {
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if (measure.getTop() + velocity < divHeight) {
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velocity *= BOUNCEBRAKE;
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if (!bounce || Math.abs(velocity) < 1.0f) {
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rebound = false;
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recalcV = false;
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velocity = 0;
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} else {
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setSelectionFromTop(nHeaders, divHeight - 1);
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}
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}
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} catch (Exception e) {
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if (velocity > 0) velocity = -velocity;
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}
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if (rebound) {
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smoothScrollBy((int) -velocity, 0);
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if (velocity > BREAKSPEED) velocity /= BREAKSPEED;
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else velocity -= BREAKSPEED;
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}
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} else if (lastVis >= totalItems) {
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if (recalcV) {
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recalcV = false;
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velocity /= (1.0f + ((System.currentTimeMillis() - flingTimestamp) / 1000.0f));
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}
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if (lastVis == totalItems - nHeaders - nFooters) {
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rebound = false;
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recalcV = false;
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velocity = 0;
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} else {
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measure = getChildAt(visibleCnt - nHeaders - nFooters);
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try {
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if (measure.getBottom() + velocity > getHeight() - divHeight) {
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velocity *= BOUNCEBRAKE;
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if (!bounce || Math.abs(velocity) < 1.0f) {
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rebound = false;
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recalcV = false;
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velocity = 0;
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} else {
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setSelectionFromTop(lastVis - nHeaders - nFooters, getHeight() - divHeight - measure.getHeight() + 1);
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}
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}
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} catch (Exception e) {
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if (velocity < 0) velocity = -velocity;
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}
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}
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if (rebound) {
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smoothScrollBy((int) -velocity, 0);
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if (velocity < -BREAKSPEED) velocity /= BREAKSPEED;
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else velocity += BREAKSPEED;
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}
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} else if (scrollstate == OnScrollListener.SCROLL_STATE_IDLE) {
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rebound = false;
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recalcV = false;
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velocity = 0;
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}
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mHandler.postDelayed(checkListviewTopAndBottom, delay);
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return;
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}
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if (scrollstate != OnScrollListener.SCROLL_STATE_IDLE) return;
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if (totalItems == (nHeaders + nFooters) || firstVis < nHeaders) {
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setSelectionFromTop(nHeaders, divHeight);
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smoothScrollBy(0, 0);
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} else if (lastVis == totalItems) {
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int offset = getHeight() - divHeight;
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measure = getChildAt(visibleCnt - nHeaders - nFooters);
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if (measure != null) offset -= measure.getHeight();
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setSelectionFromTop(lastVis - nHeaders - nFooters, offset);
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smoothScrollBy(0, 0);
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}
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}
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};
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}

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