這篇文章將介紹在之前版本的橫向ListView中添加左/右拉伸及回彈功能(採用阻尼式算法)。
之前的代碼存在許多bug,這個版本處理添加功能以外,還修補了之前版本的bug,在代碼中都有相應的註解。
實現思路如下:
1.在原來的版本上擴展滾動的邊界值
在之前的版本代碼中,列表的滾動無法超出界面的可視區域,爲了實現左/右拉伸及回彈功能,必須擴展其滾動邊界值(在代碼中對應的屬性:maxScrollValue、minScrollValue);還必須考慮兼容以前的版本功能。
2.在OnGestureListener.onScroll()方法中採用阻尼算法重新計算滾動值
3.onTouchEvent()中採用事件攔截,實現回彈功能
4.居中顯示功能和左/右拉伸功能不兼容,做好排異處理
5.爲左/右拉伸功能添加回調事件,同時設置啓動開關
先上完整代碼(ScrollBar.java的源碼請參考文章:《橫向ListView(四) —— 添加滾動條》):
package com.hss.os.horizontallistview.history_version;
import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Rect;
import android.os.Build;
import android.support.annotation.RequiresApi;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.Scroller;
import com.hss.os.horizontallistview.ScrollBar;
import java.util.LinkedList;
import java.util.Queue;
/**
* Created by sxyx on 2017/7/6.
*/
public class HorizontalListView5 extends AdapterView<ListAdapter> {
private Queue<View> cacheView = new LinkedList<>();//列表項緩存視圖
private ListAdapter adapter = null;
private GestureDetector mGesture;
private int firstItemIndex = 0;//顯示的第一個子項的下標
private int lastItemIndex = -1;//顯示的最後的一個子項的下標
private int scrollValue=0;//列表已經發生有效滾動的位移值
private int hasToScrollValue=0;//接下來列表發生滾動所要達到的位移值
private int maxScrollValue=Integer.MAX_VALUE;//列表發生滾動所能達到的最大位移值(這個由最後顯示的列表項決定)
private int minScrollValue=Integer.MIN_VALUE;//列表發生滾動所能達到的最小位移值(值爲0表示不能發生類似下拉刷新的操作,負值表示可以)
private int displayOffset=0;//列表顯示的偏移值(用於矯正列表顯示的所有子項的顯示位置)
private Scroller mScroller;
private int firstItemLeftEdge=0;//第一個子項的左邊界
private int lastItemRightEdge=0;//最後一個子項的右邊界
private View headView;
private View footView;
private boolean hasHeadView=false;
private boolean hasFootView=false;
private boolean canShowInMid=false;
private ScrollBar mScrollBar;
private int headViewWidth=0;//頭視圖寬度
private int footViewWidth=0;//尾視圖寬度
private boolean canShowScrollBar=true;//是否需要顯示滾動條
private boolean canPullUp=true;//可以左拉
private boolean canPullDown=true;//可以右拉
public HorizontalListView5(Context context) {
super(context);
init(context);
}
public HorizontalListView5(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public HorizontalListView5(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context);
}
@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
public HorizontalListView5(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init(context);
}
private void init(Context context){
mGesture = new GestureDetector(getContext(), mOnGesture);
mScroller=new Scroller(context);
mScrollBar=new ScrollBar(context);
}
private void initParams(){
mScroller.forceFinished(true);//避免在滑動過程中變換視圖內容時,出現列表無法滾動的情況
removeAllViewsInLayout();
if(adapter!=null&&lastItemIndex<adapter.getCount())
hasToScrollValue=scrollValue;//保持顯示位置不變
else hasToScrollValue=0;//滾動到列表頭
scrollValue=0;//列表已經發生有效滾動的位移值
firstItemIndex = 0;//顯示的第一個子項的下標
lastItemIndex = -1;//顯示的最後的一個子項的下標
maxScrollValue=Integer.MAX_VALUE;//列表發生滾動所能達到的最大位移值(這個由最後顯示的列表項決定)
// 列表發生滾動所能達到的最小位移值(值爲0表示不能發生類似下拉刷新的操作,負值表示可以)
if(!isCanPullLeft()) minScrollValue = 0;
else minScrollValue = Integer.MIN_VALUE;
displayOffset=0;//列表顯示的偏移值(用於矯正列表顯示的所有子項的顯示位置)
firstItemLeftEdge=0;//第一個子項的左邊界
lastItemRightEdge=0;//最後一個子項的右邊界
if(hasHeadView||hasFootView) {
if (hasHeadView) {
scrollValue = headView.getMeasuredWidth();
headView.layout(0, 0, 0, 0);
setHeadView(headView);
}
if (hasFootView) {
footView.layout(0, 0, 0, 0);
setFootView(footView);
}
}else requestLayout();
}
private DataSetObserver mDataObserver = new DataSetObserver() {
@Override
public void onChanged() {
//執行Adapter數據改變時的邏輯
initParams();
}
@Override
public void onInvalidated() {
//執行Adapter數據失效時的邏輯
initParams();
}
};
@Override
public ListAdapter getAdapter() {
return adapter;
}
@Override
public void setAdapter(ListAdapter adapter) {
if(adapter!=null){
adapter.registerDataSetObserver(mDataObserver);
}
if(this.adapter!=null){
this.adapter.unregisterDataSetObserver(mDataObserver);
}
this.adapter=adapter;
requestLayout();
}
@Override
public View getSelectedView() {
return null;
}
@Override
public void setSelection(int i) {
}
private void addAndMeasureChild(View child, int viewIndex) {
LayoutParams params = child.getLayoutParams();
params = params==null ? new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT):params;
addViewInLayout(child, viewIndex, params, true);
child.measure(MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.UNSPECIFIED),
MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.UNSPECIFIED));
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
//在執行佈局之前需要先移除滾動條,以免影響其它視圖的顯示運算
mScrollBar.remove(this);
//需要先佈局列表項再根據餘下的空間佈局列表頭尾
//佈局列表項
/*
1.計算這一次整體滾動偏移量
2.根據偏移量提取需要緩存視圖
3.根據偏移量顯示新的列表項
4.根據整體偏移值整頓所有列表項位置
5.計算最大滾動位移值,記錄已經發生有效滾動的位移值
6.根據顯示的最終效果,判斷是否要居中顯示
*/
int dx=calculateScrollValue();
removeNonVisibleItems(dx);
showListItem(dx);
adjustItems();
//佈局列表頭、尾
adjustHeadAndFootView(dx);
calculateMaxScrollValue();
adjustShow();
if(canShowScrollBar) {
//佈局完所有的視圖之後添加上滾動條的顯示
addAndMeasureChild(mScrollBar, getChildCount());
if (adapter != null) {
mScrollBar.showHorizontal(this, firstItemIndex, lastItemIndex, adapter.getCount(), headViewWidth, footViewWidth);
} else {
mScrollBar.showHorizontal(this, 0, 0, 0, headViewWidth, footViewWidth);
}
}
//繼續滾動
if(!mScroller.isFinished()){
//在onLayout中requestLayout()方法必須按以下形式調用,否則沒有效果
post(new Runnable(){
@Override
public void run() {
requestLayout();
}
});
}else if(isRemoveFootView){//表示所有的計算都已經完成
isRemoveFootView=false;
//這是修補因移除尾視圖而出現列表頭空白的bug
int startIndex=0;
if(canShowScrollBar) startIndex=1;
if(getChildCount()>startIndex){
if(getChildAt(0).getLeft()>getShowStartEdge()){
//表示列表頭有出現空白
hasToScrollValue += getChildAt(0).getLeft()-getShowStartEdge();
//在onLayout中requestLayout()方法必須按以下形式調用,否則沒有效果
post(new Runnable(){
@Override
public void run() {
requestLayout();
}
});
}
}
}
}
/**
* 計算這一次整體滾動偏移量
* @return
*/
private int calculateScrollValue(){
int dx=0;
if(mScroller.computeScrollOffset()){
hasToScrollValue = mScroller.getCurrX();
}
if(hasToScrollValue <= minScrollValue){
hasToScrollValue = minScrollValue;
mScroller.forceFinished(true);
}
if(hasToScrollValue >= maxScrollValue) {
hasToScrollValue = maxScrollValue;
mScroller.forceFinished(true);
}
dx=hasToScrollValue-scrollValue;
scrollValue=hasToScrollValue;
return -dx;
}
/**
* 計算最大滾動值
*/
private void calculateMaxScrollValue(){
if(getListItemCount()>0) {
if(lastItemIndex==adapter.getCount()-1) {//已經顯示了最後一項
if(getChildAt(getChildCount() - 1).getRight()>=getShowEndEdge()) {
setMaxScrollValue(scrollValue + getChildAt(getChildCount() - 1).getRight() - getShowEndEdge());
}else{
setMaxScrollValue(0);
}
}else{
setMaxScrollValue(Integer.MAX_VALUE);
}
}else{
if(adapter!=null&&adapter.getCount()>0){
// 修補bug:當尾視圖足夠寬能夠佔據所有可視區域時,
// maxScrollValue的值沒有改變,而導致滾動出現空白區域
setMaxScrollValue(scrollValue + getChildAt(getChildCount() - 1).getRight() - getShowEndEdge());
}else {
if (getChildCount() > 0
&& getChildAt(getChildCount() - 1).getRight() >= getShowEndEdge()) {
setMaxScrollValue(scrollValue + getChildAt(getChildCount() - 1).getRight() - getShowEndEdge());
}else{
setMaxScrollValue(0);
}
}
}
}
/**
* 根據偏移量提取需要緩存視圖
* @param dx
*/
private void removeNonVisibleItems(int dx) {
if(getListItemCount()>0) {
//移除列表頭
View child = getChildAt(getStartItemIndex());
while (getListItemCount()>0&&child != null && child.getRight() + dx <= getShowStartEdge()) {
displayOffset += child.getMeasuredWidth();
cacheView.offer(child);
removeViewInLayout(child);
firstItemIndex++;
child = getChildAt(getStartItemIndex());
}
//移除列表尾
child = getChildAt(getEndItemIndex());
while (getListItemCount()>0&&child != null && child.getLeft() + dx >= getShowEndEdge()) {
cacheView.offer(child);
removeViewInLayout(child);
lastItemIndex--;
child = getChildAt(getEndItemIndex());
}
}
}
/**
* 根據偏移量顯示新的列表項
* @param dx
*/
private void showListItem(int dx) {
if(adapter==null)return;
int firstItemEdge = getFirstItemLeftEdge()+dx;
int lastItemEdge = getLastItemRightEdge()+dx;
displayOffset+=dx;//計算偏移量
//顯示列表頭視圖
while(firstItemEdge > getShowStartEdge() && firstItemIndex-1 >= 0) {
firstItemIndex--;//往前顯示一個列表項
View child = adapter.getView(firstItemIndex, cacheView.poll(), this);
addAndMeasureChild(child, getStartItemIndex());
firstItemEdge -= child.getMeasuredWidth();
displayOffset -= child.getMeasuredWidth();
}
//顯示列表未視圖
while(lastItemEdge < getShowEndEdge() && lastItemIndex+1 < adapter.getCount()) {
lastItemIndex++;//往後顯示一個列表項
View child = adapter.getView(lastItemIndex, cacheView.poll(), this);
addAndMeasureChild(child, getEndItemIndex()+1);
lastItemEdge += child.getMeasuredWidth();
}
}
/**
* 調整各個item的位置
*/
private void adjustItems() {
if(getListItemCount() > 0){
int left = displayOffset+getShowStartEdge();
int top = getPaddingTop();
int endIndex = getEndItemIndex();
int startIndex = getStartItemIndex();
int childWidth,childHeight;
for(int i=startIndex;i<=endIndex;i++){
View child = getChildAt(i);
childWidth = child.getMeasuredWidth();
childHeight = child.getMeasuredHeight();
child.layout(left, top, left + childWidth, top + childHeight);
left += childWidth;
}
firstItemLeftEdge=getChildAt(getStartItemIndex()).getLeft();
lastItemRightEdge=getChildAt(getEndItemIndex()).getRight();
}
}
/**
* 調整列表頭、尾
*/
private void adjustHeadAndFootView(int dx){
headViewWidth=footViewWidth=0;
if(hasHeadView){
int left,right;
if(getListItemCount()>0){
right=firstItemLeftEdge;
}else{
right=headView.getRight()+dx;
}
left=right-headView.getMeasuredWidth();
headView.layout(left, getPaddingTop(), right, headView.getMeasuredHeight()+getPaddingTop());
headViewWidth=headView.getMeasuredWidth();
}
if(hasFootView){
int left,right;
if(getListItemCount()>0){
left=getChildAt(getEndItemIndex()).getRight();
}else{
//添加headView.getRight()>=getShowStartEdge()條件用於修補原先的bug
if(hasHeadView&&headView.getRight()>=getShowStartEdge())
left=headView.getRight();
else {
if(footView.getLeft()==0&&dx==0){//第一次賦值
left=getShowStartEdge();
}else{
left=footView.getLeft()+dx;
}
//調整以修補顯示bug
if(hasHeadView) {//重新調整headView的位置
headView.layout(left-headView.getMeasuredWidth(), getPaddingTop(), left, headView.getMeasuredHeight() + getPaddingTop());
}
}
}
right=left+footView.getMeasuredWidth();
footView.layout(left, getPaddingTop(), right, footView.getMeasuredHeight()+getPaddingTop());
footViewWidth=footView.getMeasuredWidth();
}
}
private void adjustShow(){
if(isCanShowInMid()){//可以居中顯示
int endEdge=getShowEndEdge();
boolean canAdjust=false;
if(hasFootView){
if(footView.getRight()<endEdge) canAdjust=true;
}else if(getListItemCount()>0){
if(getChildAt(getEndItemIndex()).getRight()<endEdge) canAdjust=true;
}else if(hasHeadView){
if(headView.getRight()<endEdge) canAdjust=true;
}
if(canAdjust){
//居中顯示
int itemsWidth=getChildAt(getChildCount()-1).getRight()-getShowStartEdge();
int left=(getShowWidth()-itemsWidth)/2+getShowStartEdge();
int right;
View child;
for(int i=0;i<getChildCount();i++){
child= getChildAt(i);
right=left+child.getMeasuredWidth();
child.layout(left,child.getTop(),right,child.getBottom());
left=right;
}
}
}
}
//以下八個方法爲概念性封裝方法,有助於往後的擴展和維護
/**
* 獲得列表視圖中item View的總數
* @return
*/
private int getListItemCount(){
int itemCount=getChildCount();
if(hasHeadView)itemCount-=1;
if(hasFootView)itemCount-=1;
return itemCount;
}
/**
* 獲得列表視圖中第一個item View下標
* @return
*/
private int getStartItemIndex(){
if(hasHeadView) return 1;
return 0;
}
/**
* 獲得列表視圖中最後一個item View下標
* @return
*/
private int getEndItemIndex(){
if(hasFootView) return getChildCount()-2;
return getChildCount()-1;
}
/**
* 獲得列表視圖中第一個item View左邊界值
* @return
*/
private int getFirstItemLeftEdge(){
if(getListItemCount()>0) {
return firstItemLeftEdge;
}else{
if(hasHeadView) return headView.getRight();
else return getShowStartEdge();
}
}
/**
* 獲得列表視圖中最後一個item View右邊界值
* @return
*/
private int getLastItemRightEdge(){
if(getListItemCount()>0) {
return lastItemRightEdge;
}else{
if(hasFootView) return footView.getLeft();
else return getShowStartEdge();
}
}
/**
* 取得視圖可見區域的左邊界
* @return
*/
private int getShowStartEdge(){
return getPaddingLeft();
}
/**
* 取得視圖可見區域的右邊界
* @return
*/
private int getShowEndEdge(){
return getWidth()-getPaddingRight();
}
/**
* 取得視圖可見區域的寬度
* @return
*/
private int getShowWidth(){
return getWidth()-getPaddingLeft()-getPaddingRight();
}
public void setMaxScrollValue(int maxScrollValue) {
if(isCanPullRight()&&maxScrollValue!=Integer.MAX_VALUE) {
if(isSpringBack){//在執行回彈操作
this.maxScrollValue = Integer.MAX_VALUE;
}else if(mScroller.isFinished()){//手動執行滾動操作
this.maxScrollValue = Integer.MAX_VALUE;
}else{
if(maxScrollValue<0)this.maxScrollValue=0;
else this.maxScrollValue = maxScrollValue;
}
}else{
if(maxScrollValue<0)this.maxScrollValue=0;
else this.maxScrollValue = maxScrollValue;
}
}
public void setHeadView(View view){
if(view!=null) {
int headRight=-1;
int width=0;
if (hasHeadView&&headView!=null) {
headRight=headView.getRight();
width=headView.getWidth();
removeViewInLayout(headView);
}
hasHeadView = true;
headView=view;
addAndMeasureChild(headView, 0);
if(getListItemCount()>0) {//有列表內容
if (headRight == -1) {
//新增列表頭
if (firstItemIndex == 0) {//第一個顯示的是第一個列表項
//滾動整個列表,讓其顯示完整列表頭(讓列表往回滾)
scrollValue = headView.getMeasuredWidth()
+ getShowStartEdge() - firstItemLeftEdge;
hasToScrollValue=0;
} else {//不是顯示第一個列表項
//不滾動列表項,增加歷史滾動值
hasToScrollValue += headView.getMeasuredWidth();
scrollValue = hasToScrollValue;
}
} else {
//替換列表頭
hasToScrollValue += headView.getMeasuredWidth()-width;
}
}
setMaxScrollValue(Integer.MAX_VALUE);
requestLayout();
}
}
public void removeHeadView(){
if(hasHeadView&&headView!=null){
hasHeadView=false;
int left=headView.getLeft();
int width=headView.getMeasuredWidth();
removeViewInLayout(headView);
if(headView.getRight()>=getShowStartEdge()) {//列表頭有顯示
scrollValue = -(width+left-getShowStartEdge());
hasToScrollValue=0;
}else{
scrollValue-=width;
hasToScrollValue-=width;
}
requestLayout();
}else{
hasHeadView=false;
}
}
public void setFootView(View view){
if(view!=null) {
if (hasFootView&&footView!=null) {
removeViewInLayout(footView);
}
hasFootView=true;
footView=view;
addAndMeasureChild(footView, -1);
requestLayout();
}
}
private boolean isRemoveFootView=false;
public void removeFootView(){
if(hasFootView&&footView!=null){
hasFootView=false;
int left=footView.getLeft();
mScroller.forceFinished(true);//用於修補由於快速華東的過程中移除尾視圖而出現bug
removeViewInLayout(footView);
if(left<getShowEndEdge()) {//表示需要回退
hasToScrollValue -= getShowEndEdge()-left;
isRemoveFootView=true;
}
requestLayout();
}else{
hasFootView=false;
}
}
/**
* 在onTouchEvent處理事件,讓子視圖優先消費事件
* @param event
* @return
*/
@Override
public boolean onTouchEvent(MotionEvent event) {
if(dealTouchEvent(event)) return true;
return mGesture.onTouchEvent(event);
}
private GestureDetector.OnGestureListener mOnGesture = new GestureDetector.SimpleOnGestureListener() {
@Override
public boolean onDown(MotionEvent e) {
mScroller.forceFinished(true);//點擊時停止滾動
return true;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
minScrollValue=0;//在快速滑動時,不能出現類似下拉刷新的操作
mScroller.fling(scrollValue, 0, (int)-velocityX, 0, 0, maxScrollValue, 0, 0);
requestLayout();
return true;
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
if(isCanPullLeft()) {
minScrollValue = Integer.MIN_VALUE;//手動滑動時可以出現類似下拉刷新的操作
}else{
minScrollValue = 0;
}
synchronized(HorizontalListView5.this){
hasToScrollValue += (int)calDistanceVal(distanceX);
}
requestLayout();
return true;
}
@Override
public boolean onSingleTapConfirmed(MotionEvent e) {
int startIndex=0;
if(canShowScrollBar) startIndex=1;
for(int i=0;i<getChildCount();i++){
View child = getChildAt(i);
if(child==mScrollBar) break;
if (isEventWithinView(e, child)) {
if(hasHeadView&&i==0){
//點擊列表頭
if(OnHeadViewClickListener!=null)
OnHeadViewClickListener.onClick(child);
}else if(hasFootView&&i==getChildCount()-(1+startIndex)){
//點擊列表尾
if(OnFootViewClickListener!=null)
OnFootViewClickListener.onClick(child);
}else {
int position=firstItemIndex + i;
if(hasHeadView) position--;
if (getOnItemClickListener() != null) {
getOnItemClickListener().onItemClick(HorizontalListView5.this, child, position, adapter.getItemId(position));
}
if (getOnItemSelectedListener() != null) {
getOnItemSelectedListener().onItemSelected(HorizontalListView5.this, child, position, adapter.getItemId(position));
}
}
break;
}
}
return true;
}
@Override
public void onLongPress(MotionEvent e) {
int startIndex=0;//這個值用於處理滾動條的影響
if(canShowScrollBar) startIndex=1;
int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
View child = getChildAt(i);
if(child==mScrollBar) return;
if (isEventWithinView(e, child)) {
if(hasHeadView&&i==0){
//長按列表頭
if(OnHeadViewLongClickListener!=null)
OnHeadViewLongClickListener.onLongClick(child);
}else if(hasFootView&&i==getChildCount()-(1+startIndex)){
//長按列表尾
if(OnFootViewLongClickListener!=null)
OnFootViewLongClickListener.onLongClick(child);
} else {
int position=firstItemIndex + i;
if(hasHeadView) position--;
if (getOnItemLongClickListener() != null) {
getOnItemLongClickListener().onItemLongClick(HorizontalListView5.this, child, position, adapter.getItemId(position));
}
}
break;
}
}
}
private boolean isEventWithinView(MotionEvent e, View child) {
Rect viewRect = new Rect();
int[] childPosition = new int[2];
child.getLocationOnScreen(childPosition);
int left = childPosition[0];
int right = left + child.getWidth();
int top = childPosition[1];
int bottom = top + child.getHeight();
viewRect.set(left, top, right, bottom);
return viewRect.contains((int) e.getRawX(), (int) e.getRawY());
}
};
private boolean isEventDownIntercept=false;
private boolean isSpringBack=false;
private boolean isCanPullDownInthis=true;
/**
* 在手勢解析器之前攔截事件
* @param event
* @return
*/
private boolean dealTouchEvent(MotionEvent event){
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
isCanPullDownInthis=true;
int startIndex=0;
if(canShowScrollBar) startIndex=1;
if(getChildCount()==startIndex){
isCanPullDownInthis=false;
}else{
if(getChildAt(getChildCount()-(1+startIndex)).getRight()<getShowEndEdge()){
isCanPullDownInthis=false;
}
}
isEventDownIntercept=springBack();
if (isEventDownIntercept) return true;
break;
case MotionEvent.ACTION_MOVE:
return isEventDownIntercept;
case MotionEvent.ACTION_UP:
return springBack();
}
return false;
}
/**
* 採用阻尼式算法,重新提取移動值
* @param distanceVal
* @return
*/
private float calDistanceVal(float distanceVal){
if(!isCanPullDownInthis&&distanceVal>0){
return 0;
}
int startIndex=0;//這個值用於處理滾動條的影響
if(canShowScrollBar) startIndex=1;
if(getChildCount()>startIndex){
int dis=getChildAt(0).getLeft()-getShowStartEdge();
if(dis>0){//執行頭部拉伸阻尼式計算
if(distanceVal>=0) distanceVal = distanceVal/2;
else {
float sc = 1 - dis / (getShowWidth() * 0.4f);
sc = sc < 0 ? 0 : sc;
distanceVal = distanceVal * sc;
}
if(onPullLeftListener!=null)
onPullLeftListener.onScroll(distanceVal);
}else {
dis = getShowEndEdge() - getChildAt(getChildCount() - (1 + startIndex)).getRight();
if (dis > 0 && getFirstItemLeftEdge() < getShowStartEdge()) {
//執行尾部拉伸阻尼式計算
if (distanceVal <= 0) distanceVal = distanceVal / 2;
else {
float sc = 1 - dis / (getShowWidth() * 0.4f);
sc = sc < 0 ? 0 : sc;
distanceVal = distanceVal * sc;
}
if (onPullRightListener != null)
onPullRightListener.onScroll(distanceVal);
}
}
}
return distanceVal;
}
/**
* 執行回滾操作
* @return
*/
private boolean springBack(){
isSpringBack=false;
int startIndex=0;
if(canShowScrollBar) startIndex=1;
if(getChildCount()>startIndex){
int dis=getChildAt(0).getLeft()-getShowStartEdge();
if(dis>0){//執行頭部回滾操作
mScroller.startScroll(scrollValue, 0, dis, 0, 500);
isSpringBack=true;
requestLayout();
if(onPullLeftListener!=null
&&(dis>getShowWidth()/5||dis>120))
onPullLeftListener.onFullEvent();
return true;
}
dis=getShowEndEdge()-getChildAt(getChildCount()-(1+startIndex)).getRight();
if(dis>0&&getFirstItemLeftEdge()<getShowStartEdge()){
//執行尾部回滾操作
mScroller.startScroll(scrollValue, 0, -dis, 0, 500);
isSpringBack=true;
requestLayout();
if(onPullRightListener!=null
&&(dis>getShowWidth()/5||dis>120))
onPullRightListener.onFullEvent();
return true;
}
}
return false;
}
private OnPullListener onPullLeftListener = null;
private OnPullListener onPullRightListener = null;
private OnClickListener OnHeadViewClickListener;
private OnClickListener OnFootViewClickListener;
private OnLongClickListener OnHeadViewLongClickListener;
private OnLongClickListener OnFootViewLongClickListener;
public void setOnPullLeftListener(OnPullListener onPullLeftListener) {
this.onPullLeftListener = onPullLeftListener;
}
public void setOnPullRightListener(OnPullListener onPullRightListener) {
this.onPullRightListener = onPullRightListener;
}
public void setOnHeadViewClickListener(OnClickListener onHeadViewClickListener) {
OnHeadViewClickListener = onHeadViewClickListener;
}
public void setOnFootViewClickListener(OnClickListener onFootViewClickListener) {
OnFootViewClickListener = onFootViewClickListener;
}
public void setOnHeadViewLongClickListener(OnLongClickListener onHeadViewLongClickListener) {
OnHeadViewLongClickListener = onHeadViewLongClickListener;
}
public void setOnFootViewLongClickListener(OnLongClickListener onFootViewLongClickListener) {
OnFootViewLongClickListener = onFootViewLongClickListener;
}
public interface OnPullListener{
/**
* 滾動時執行
* @param dis 移動的位移值
*/
void onScroll(float dis);
/**
* 事件確認(類似下拉刷新事件觸發)
*/
void onFullEvent();
}
public synchronized void scrollTo(int x) {
mScroller.startScroll(hasToScrollValue, 0, x - hasToScrollValue, 0);
requestLayout();
}
public boolean isCanShowInMid() {
return canShowInMid;
}
/**
* 可以劇中顯示則不能使用左/右拉功能
* @param canShowInMid
*/
public void setCanShowInMid(boolean canShowInMid) {
this.canShowInMid = canShowInMid;
if(canShowInMid) {
setCanPullLeft(false);
setCanPullRight(false);
}
}
public boolean isCanShowScrollBar() {
return canShowScrollBar;
}
public void setCanShowScrollBar(boolean canShowScrollBar) {
this.canShowScrollBar = canShowScrollBar;
}
public boolean isCanPullRight() {
return canPullDown;
}
public void setCanPullRight(boolean canPullDown) {
this.canPullDown = canPullDown;
if (canPullDown) setCanShowInMid(false);
}
public boolean isCanPullLeft() {
return canPullUp;
}
public void setCanPullLeft(boolean canPullUp) {
this.canPullUp = canPullUp;
if (canPullUp) setCanShowInMid(false);
}
}
實現思路如下:
1.在原來的版本上擴展滾動的邊界值
在之前的版本代碼中,列表的滾動無法超出界面的可視區域,爲了實現左/右拉伸及回彈功能,必須擴展其滾動邊界值(在代碼中對應的屬性:maxScrollValue、minScrollValue);還必須考慮兼容以前的版本功能。
public void setMaxScrollValue(int maxScrollValue) {
if(isCanPullRight()&&maxScrollValue!=Integer.MAX_VALUE) {
if(isSpringBack){//在執行回彈操作
this.maxScrollValue = Integer.MAX_VALUE;
}else if(mScroller.isFinished()){//手動執行滾動操作
this.maxScrollValue = Integer.MAX_VALUE;
}else{
if(maxScrollValue<0)this.maxScrollValue=0;
else this.maxScrollValue = maxScrollValue;
}
}else{
if(maxScrollValue<0)this.maxScrollValue=0;
else this.maxScrollValue = maxScrollValue;
}
}
private GestureDetector.OnGestureListener mOnGesture = new GestureDetector.SimpleOnGestureListener() {
......
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
minScrollValue=0;//在快速滑動時,不能出現類似下拉刷新的操作
mScroller.fling(scrollValue, 0, (int)-velocityX, 0, 0, maxScrollValue, 0, 0);
requestLayout();
return true;
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
if(isCanPullLeft()) {
minScrollValue = Integer.MIN_VALUE;//手動滑動時可以出現類似下拉刷新的操作
}else{
minScrollValue = 0;
}
synchronized(HorizontalListView5.this){
hasToScrollValue += (int)calDistanceVal(distanceX);
}
requestLayout();
return true;
}
......
}
2.在OnGestureListener.onScroll()方法中採用阻尼算法重新計算滾動值
/**
* 採用阻尼式算法,重新提取移動值
* @param distanceVal
* @return
*/
private float calDistanceVal(float distanceVal){
if(!isCanPullDownInthis&&distanceVal>0){
return 0;
}
int startIndex=0;//這個值用於處理滾動條的影響
if(canShowScrollBar) startIndex=1;
if(getChildCount()>startIndex){
int dis=getChildAt(0).getLeft()-getShowStartEdge();
if(dis>0){//執行頭部拉伸阻尼式計算
if(distanceVal>=0) distanceVal = distanceVal/2;
else {
float sc = 1 - dis / (getShowWidth() * 0.4f);
sc = sc < 0 ? 0 : sc;
distanceVal = distanceVal * sc;
}
if(onPullLeftListener!=null)
onPullLeftListener.onScroll(distanceVal);
}else {
dis = getShowEndEdge() - getChildAt(getChildCount() - (1 + startIndex)).getRight();
if (dis > 0 && getFirstItemLeftEdge() < getShowStartEdge()) {
//執行尾部拉伸阻尼式計算
if (distanceVal <= 0) distanceVal = distanceVal / 2;
else {
float sc = 1 - dis / (getShowWidth() * 0.4f);
sc = sc < 0 ? 0 : sc;
distanceVal = distanceVal * sc;
}
if (onPullRightListener != null)
onPullRightListener.onScroll(distanceVal);
}
}
}
return distanceVal;
}
private GestureDetector.OnGestureListener mOnGesture = new GestureDetector.SimpleOnGestureListener() {
......
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
if(isCanPullLeft()) {
minScrollValue = Integer.MIN_VALUE;//手動滑動時可以出現類似下拉刷新的操作
}else{
minScrollValue = 0;
}
synchronized(HorizontalListView5.this){
hasToScrollValue += (int)calDistanceVal(distanceX);
}
requestLayout();
return true;
}
......
}
3.onTouchEvent()中採用事件攔截,實現回彈功能
/**
* 在手勢解析器之前攔截事件
* @param event
* @return
*/
private boolean dealTouchEvent(MotionEvent event){
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
isCanPullDownInthis=true;
int startIndex=0;
if(canShowScrollBar) startIndex=1;
if(getChildCount()==startIndex){
isCanPullDownInthis=false;
}else{
if(getChildAt(getChildCount()-(1+startIndex)).getRight()<getShowEndEdge()){
isCanPullDownInthis=false;
}
}
isEventDownIntercept=springBack();
if (isEventDownIntercept) return true;
break;
case MotionEvent.ACTION_MOVE:
return isEventDownIntercept;
case MotionEvent.ACTION_UP:
return springBack();
}
return false;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if(dealTouchEvent(event)) return true;
return mGesture.onTouchEvent(event);
}
4.居中顯示功能和左/右拉伸功能不兼容,做好排異處理
/**
* 可以劇中顯示則不能使用左/右拉功能
* @param canShowInMid
*/
public void setCanShowInMid(boolean canShowInMid) {
this.canShowInMid = canShowInMid;
if(canShowInMid) {
setCanPullLeft(false);
setCanPullRight(false);
}
}
public void setCanPullRight(boolean canPullDown) {
this.canPullDown = canPullDown;
if (canPullDown) setCanShowInMid(false);
}
public void setCanPullLeft(boolean canPullUp) {
this.canPullUp = canPullUp;
if (canPullUp) setCanShowInMid(false);
}
5.爲左/右拉伸功能添加回調事件,同時設置啓動開關
private OnPullListener onPullLeftListener = null;
private OnPullListener onPullRightListener = null;
public void setOnPullLeftListener(OnPullListener onPullLeftListener) {
this.onPullLeftListener = onPullLeftListener;
}
public void setOnPullRightListener(OnPullListener onPullRightListener) {
this.onPullRightListener = onPullRightListener;
}
public interface OnPullListener{
/**
* 滾動時執行
* @param dis 移動的位移值
*/
void onScroll(float dis);
/**
* 事件確認(類似下拉刷新事件觸發)
*/
void onFullEvent();
}