我想允许用户仅从右向左滑动ViewPager
。因此,一旦他通过一个页面,他就无法回到它。怎么办呢?
我尝试了this解决方案:
public class CustomViewPager extends ViewPager {
float lastX = 0;
boolean lockScroll = false;
public CustomViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CustomViewPager(Context context) {
super(context);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
lastX = ev.getX();
lockScroll = false;
return super.onTouchEvent(ev);
case MotionEvent.ACTION_MOVE:
if (lastX > ev.getX()) {
lockScroll = false;
} else {
lockScroll = true;
}
lastX = ev.getX();
break;
}
lastX = ev.getX();
if(lockScroll) {
return false;
} else {
return super.onTouchEvent(ev);
}
}
}
但它仍然允许我向另一个方向轻扫。
答案 0 :(得分:68)
还有一件事你错过了:onInterceptTouchEvent。它必须包含与onTouchEvent相同的逻辑。
我的完整解决方案基于this回答。它允许您在任何需要的时间内启用/禁用任何方向的分页。
<强> 1。创建枚举
public enum SwipeDirection {
all, left, right, none ;
}
2.Extend ViewPager
public class CustomViewPager extends ViewPager {
private float initialXValue;
private SwipeDirection direction;
public CustomViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
this.direction = SwipeDirection.all;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if (this.IsSwipeAllowed(event)) {
return super.onTouchEvent(event);
}
return false;
}
@Override
public boolean onInterceptTouchEvent(MotionEvent event) {
if (this.IsSwipeAllowed(event)) {
return super.onInterceptTouchEvent(event);
}
return false;
}
private boolean IsSwipeAllowed(MotionEvent event) {
if(this.direction == SwipeDirection.all) return true;
if(direction == SwipeDirection.none )//disable any swipe
return false;
if(event.getAction()==MotionEvent.ACTION_DOWN) {
initialXValue = event.getX();
return true;
}
if(event.getAction()==MotionEvent.ACTION_MOVE) {
try {
float diffX = event.getX() - initialXValue;
if (diffX > 0 && direction == SwipeDirection.right ) {
// swipe from left to right detected
return false;
}else if (diffX < 0 && direction == SwipeDirection.left ) {
// swipe from right to left detected
return false;
}
} catch (Exception exception) {
exception.printStackTrace();
}
}
return true;
}
public void setAllowedSwipeDirection(SwipeDirection direction) {
this.direction = direction;
}
3.在布局中使用viewPager
<package_name.customviewpager
android:id="@+id/customViewPager"
android:layout_height="match_parent"
android:layout_width="match_parent" />
4.启用代码中的任何滑动方向。默认为全部(左右)
mViewPager.setAllowedSwipeDirection(SwipeDirection.right);
答案 1 :(得分:1)
package com.contacts_app.jamison.contacts__proprivacy4;
import android.content.Context;
import android.content.res.Resources;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
public class ViewPager_Settings extends ViewPager
{
private final String TAG = ViewPager_Settings.class.getSimpleName();
public float startX;
public ViewPager_Settings(Context context, AttributeSet attrs) {
super(context, attrs);
}
////////////////////////////////////////////////////////////////////////////////////////////////
public static int dpTOpx(double dp)
{
return (int) (dp * Resources.getSystem().getDisplayMetrics().density);
}
public static int pxTOdp(double px)
{
return (int) (px / Resources.getSystem().getDisplayMetrics().density);
}
////////////////////////////////////////////////////////////////////////////////////////////////
/*****DispatchTouchEvent for the View Pager to intercept and block swipes Right*****/
@Override
public boolean dispatchTouchEvent(MotionEvent ev)
{
final int actionMasked = ev.getActionMasked() & MotionEvent.ACTION_MASK;
//int movement_limit = pxTOdp(50);
switch (actionMasked)
{
case (MotionEvent.ACTION_DOWN):
{
startX = ev.getX();
Log.i(TAG, "startX: " + startX);
/*Should always be this below*/
return super.dispatchTouchEvent(ev);
}
case (MotionEvent.ACTION_MOVE):
{
Log.i(TAG, "ev.getX() - startX:" + (ev.getX() - startX));
/*Switching directional changes would be a matter of flipping the "<" sign in the line below.*/
if (ev.getX() - startX > 0)
{
/*The result is that the ViewPager will not swipe from left*/
ev.setAction(MotionEvent.ACTION_CANCEL);;
}
/*Should always be this below*/
super.dispatchTouchEvent(ev);
}
/**The ACTION_UP case statement is only needed if you don't want to pass down the touch event
* to buttons that may receive the click after the swipe is blocked.*/
/*case (MotionEvent.ACTION_UP):
{
//Log.i(TAG, "movement_limit: " + movement_limit);
//(-50) may need to be changed to something more broader in scope to accompany all screen densities
if ( (ev.getX() - startX) < (-50) )
{
ev.setAction(MotionEvent.ACTION_CANCEL);
}
//Should always be this below
super.dispatchTouchEvent(ev);
}*/
}
/*Should always be this below*/
return super.dispatchTouchEvent(ev);
}
////////////////////////////////////////////////////////////////////////////////////////////////
}/*****END OF FILE*****/
请勿忘记更改顶部的行以放置应用的包名称。 此外,大多数(如果不是全部)评论还可以让您深入了解代码在您决定修改内容时所执行的操作。
答案 2 :(得分:0)
像这样定义你的适配器
public class MyFragmentStatePagerAdapter extends FragmentStatePagerAdapter {
private final int totalPages = 10;
private int currentPage = 0;
public MyFragmentStatePagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// Use whatever logic you want here to
// to select a fragment based on
// currentPage instead of position
if (currentPage % 2 == 0) {
return new Fragment1();
} else {
return new Fragment2();
}
}
@Override
public int getCount() {
return currentPage == totalPages ? 1 : 2;
}
@Override
public int getItemPosition(Object object){
return PagerAdapter.POSITION_NONE;
}
public void nextPage() {
currentPage++;
notifyDataSetChanged();
}
}
在使用视图寻呼机的片段中,执行此操作
@Override
public void onPageSelected(int arg0) {
if (arg0 > 0) {
pagerAdapter.nextPage();
pager.setCurrentItem(0, false);
}
}
答案 3 :(得分:0)
尝试添加(与onTouchEvent相同的逻辑)
@Override
public boolean onInterceptTouchEvent(MotionEvent arg0) {
// allow/ not allow swiping to switch between pages
return !lockScroll ;
}