我正在使用ViewPager(支持庫)。每次ViewPager改變可見頁面時,我都想知道它是向左還是向右滾動。如何知道viewpager是向左還是向右滾動?
請給我一個解決方案。任何推薦也歡迎。
謝謝
我正在使用ViewPager(支持庫)。每次ViewPager改變可見頁面時,我都想知道它是向左還是向右滾動。如何知道viewpager是向左還是向右滾動?
請給我一個解決方案。任何推薦也歡迎。
謝謝
設置setOnPageChangeListener
您ViewPager
和
@Override
public void onPageSelected(int arg0) {
if(lastPage>arg0)
{//User Move to left}
else(lastPage<arg0)
{//User Move to right}
lastPage=arg0
}
使用ViewPager.OnPageChangeListener
接口。您可以使用傳遞給onPageSelected
的位置參數,並將其與前一個值進行比較,以確定ViewPager
滾動的方式。
你可以把類的成員變量到最後保存訪問
頁private int mLastVisitedPageIndex = 0;
然後用下面的函數來檢查方向
@Override
public void onPageSelected(int i) {
boolean isMovingForward = mLastVisitedPageIndex < i?true:false;
//Use isMovingForward variable anywhere now
mLastVisitedPageIndex = i;
}
這不是一個完美的解決方案,但這裏的檢查刷卡方向,當你開始刷卡的方式:
new ViewPager.OnPageChangeListener() {
private static final float thresholdOffset = 0.5f;
private boolean scrollStarted, checkDirection;
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
if (checkDirection) {
if (thresholdOffset > positionOffset) {
Log.i(C.TAG, "going left");
} else {
Log.i(C.TAG, "going right");
}
checkDirection = false;
}
}
@Override
public void onPageSelected(int position) {}
@Override
public void onPageScrollStateChanged(int state) {
if (!scrollStarted && state == ViewPager.SCROLL_STATE_DRAGGING) {
scrollStarted = true;
checkDirection = true;
} else {
scrollStarted = false;
}
}
});
編輯:有一個更優雅的辦法,包括使用ViewPager.PageTransformer
並檢查它的位置間隔:
...
myViewPager.setPageTransformer(true, new PageTransformer());
...
public class PageTransformer implements ViewPager.PageTransformer {
public void transformPage(View view, float position) {
if (position < -1) {
// [-00,-1): the page is way off-screen to the left.
} else if (position <= 1) {
// [-1,1]: the page is "centered"
} else {
// (1,+00]: the page is way off-screen to the right.
}
}
}
您可以瞭解更多從:Using ViewPager for Screen Slides
使用該
@Override
public void onPageSelected(int position)
{
mCurrentFragmentPosition = position;
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
{
boolean isGoingToRightPage = position == mCurrentFragmentPosition;
if(isGoingToRightPage)
{
// user is going to the right page
}
else
{
// user is going to the left page
}
}
這是一個很好的解決方案,因爲它允許隨時監控滑動方向。另一個解決方案http://stackoverflow.com/a/34356483/231590在單張幻燈片中監視滾動方向。 – soshial
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
private int mCurrentSelectedScreen;
private int mNextSelectedScreen;
private static final float thresholdOffset = 0.5f;
private boolean scrollStarted=true, checkDirection=false;
ArrayList<Integer> comp_ary=new ArrayList<Integer>();
@Override
public void onPageSelected(int arg0) {
}
@Override
public void onPageScrolled(int position, float positionOffset,
int positionOffsetPixels) {
//Log.e("positionOffsetPixels : "+positionOffsetPixels, "positionOffset : "+positionOffset);
comp_ary.add(positionOffsetPixels);
if (checkDirection) {
if (comp_ary.get(2) < comp_ary.get(comp_ary.size()-1)) {
Log.e("going left", "going left");
} else
if (comp_ary.get(2) > comp_ary.get(comp_ary.size()-1))
{
Log.e("going right", "going right");
}
checkDirection = false;
comp_ary=new ArrayList<Integer>();
}
}
@Override
public void onPageScrollStateChanged(int arg0) {
if (!scrollStarted && arg0 == ViewPager.SCROLL_STATE_SETTLING) {
scrollStarted = true;
checkDirection = true;
} else {
scrollStarted = false;
}
}
});
pager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
if(position == pager.getCurrentItem()){
// Move Right
}
else{
// Move Left
}
}
我解決了問題,這個實現。希望能幫助到你。
public static final float EPSILON= 0.001f;
@Override
public void onPageScrolled(final int position, final float positionOffset, final int positionOffsetPixels) {
// initial position (positionOffset == 0)
if (positionOffset < EPSILON) {
mIsRight = positionOffset < 0.5;
return;
}
// code here
if (mIsRight) {
} else {
}
}
相同的溶液GuilhE與未成年修復以避免在第一頁上進行尋呼離開(向右滑動)時出現誤報(不再使用p年齡向左)在ViewPager中。 它只是做一個額外的檢查,看看是否滑動實際上已經移動。
new ViewPager.OnPageChangeListener() {
private static final float thresholdOffset = 0.5f;
private static final int thresholdOffsetPixels = 1;
private boolean scrollStarted, checkDirection;
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
if (checkDirection) {
if (thresholdOffset > positionOffset && positionOffsetPixels > thresholdOffsetPixels) {
Log.i(C.TAG, "going left");
} else {
Log.i(C.TAG, "going right");
}
checkDirection = false;
}
}
@Override
public void onPageSelected(int position) {}
@Override
public void onPageScrollStateChanged(int state) {
if (!scrollStarted && state == ViewPager.SCROLL_STATE_DRAGGING) {
scrollStarted = true;
checkDirection = true;
} else {
scrollStarted = false;
}
}
});
我們也可以做到這一點使用自定義Viewpager,它可以包含swipeLeft()和swipeRight()方法和它的onTouchEvent(MotionEvent事件)方法可以包含ACTION_MOVE和ACTION_CANCEL情況。
//如果有幫助,這可以是代碼。
public class SwiperViewPager extends ViewPager {
SwiperListener mSwiperListener;
private float downX;
private float downY;
private boolean isTouchCaptured;
private float upX1;
private float upY1;
private float upX2;
private float upY2;
public SwiperViewPager(Context context) {
super(context);
}
public SwiperViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
private float x1, x2;
static final int min_distance = 20;
boolean eventSent = false;
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_MOVE: {
downX = event.getX();
downY = event.getY();
if (!isTouchCaptured) {
upX1 = event.getX();
upY1 = event.getY();
isTouchCaptured = true;
} else {
upX2 = event.getX();
upY2 = event.getY();
float deltaX = upX1 - upX2;
float deltaY = upY1 - upY2;
//HORIZONTAL SCROLL
if (Math.abs(deltaX) > Math.abs(deltaY)) {
if (Math.abs(deltaX) > min_distance) {
// left or right
if (deltaX < 0) {
if(!eventSent && mSwiperListener!=null){
mSwiperListener.onLeftSwipe();
eventSent = true;
}
}
if (deltaX > 0) {
if(!eventSent && mSwiperListener!=null){
if(mSwiperListener.onRightSwipe()){
eventSent = true;
return false;
}
}
}
} else {
//not long enough swipe...
}
}
//VERTICAL SCROLL
else {
if (Math.abs(deltaY) > min_distance) {
// top or down
if (deltaY < 0) {
}
if (deltaY > 0) {
}
} else {
//not long enough swipe...
}
}
}
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:{
isTouchCaptured = false;
eventSent = false;
}
}
return super.onTouchEvent(event);
}
public void setmSwiperListener(SwiperListener mSwiperListener) {
this.mSwiperListener = mSwiperListener;
}
public static interface SwiperListener {
public boolean onLeftSwipe();
public boolean onRightSwipe();
}
}
private float sumPositionAndPositionOffset;
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
boolean isSwipeToLeft = position + positionOffset > sumPositionAndPositionOffset;
sumPositionAndPositionOffset = position + positionOffset;
}
但它給結果一旦得到屏幕滾動完全...有沒有什麼辦法來作爲開始滾動? – CoDe
檢查我的答案,它可能不是完美的解決方案,但它是一個開始;) – GuilhE
'setOnPageChangeListener'現在已被棄用,使用'ViewPager.addOnPageChangeListener'來代替。 –