Android 以编程方式滑动时更改 ViewPager 动画持续时间
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Change ViewPager animation duration when sliding programmatically
提问by Ixx
I'm changing slide with the following code:
我正在使用以下代码更改幻灯片：
viewPager.setCurrentItem(index++, true);
But it changes too fast. Is there a way to set manually the animation speed?
但是变化太快了。有没有办法手动设置动画速度？
回答by Oleg Vaskevich
I've wanted to do myself and have achieved a solution (using reflection, however). I haven't tested it yet but it shouldwork or need minimal modification.Tested on Galaxy Nexus JB 4.2.1. You need to use a ViewPagerCustomDurationin your XML instead of ViewPager, and then you can do this:
我想自己做并且已经实现了一个解决方案（但是使用反射）。我还没有测试过，但它应该可以工作或需要最少的修改。在 Galaxy Nexus JB 4.2.1 上测试。您需要ViewPagerCustomDuration在 XML 中使用 a而不是ViewPager，然后您可以这样做：
ViewPagerCustomDuration vp = (ViewPagerCustomDuration) findViewById(R.id.myPager);
vp.setScrollDurationFactor(2); // make the animation twice as slow
ViewPagerCustomDuration.java:
ViewPagerCustomDuration.java：
import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.animation.Interpolator;
import java.lang.reflect.Field;
public class ViewPagerCustomDuration extends ViewPager {
public ViewPagerCustomDuration(Context context) {
super(context);
postInitViewPager();
}
public ViewPagerCustomDuration(Context context, AttributeSet attrs) {
super(context, attrs);
postInitViewPager();
}
private ScrollerCustomDuration mScroller = null;
/**
* Override the Scroller instance with our own class so we can change the
* duration
*/
private void postInitViewPager() {
try {
Field scroller = ViewPager.class.getDeclaredField("mScroller");
scroller.setAccessible(true);
Field interpolator = ViewPager.class.getDeclaredField("sInterpolator");
interpolator.setAccessible(true);
mScroller = new ScrollerCustomDuration(getContext(),
(Interpolator) interpolator.get(null));
scroller.set(this, mScroller);
} catch (Exception e) {
}
}
/**
* Set the factor by which the duration will change
*/
public void setScrollDurationFactor(double scrollFactor) {
mScroller.setScrollDurationFactor(scrollFactor);
}
}
ScrollerCustomDuration.java:
ScrollerCustomDuration.java：
import android.annotation.SuppressLint;
import android.content.Context;
import android.view.animation.Interpolator;
import android.widget.Scroller;
public class ScrollerCustomDuration extends Scroller {
private double mScrollFactor = 1;
public ScrollerCustomDuration(Context context) {
super(context);
}
public ScrollerCustomDuration(Context context, Interpolator interpolator) {
super(context, interpolator);
}
@SuppressLint("NewApi")
public ScrollerCustomDuration(Context context, Interpolator interpolator, boolean flywheel) {
super(context, interpolator, flywheel);
}
/**
* Set the factor by which the duration will change
*/
public void setScrollDurationFactor(double scrollFactor) {
mScrollFactor = scrollFactor;
}
@Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, (int) (duration * mScrollFactor));
}
}
Hope this helps someone!
希望这可以帮助某人！
回答by lobzik
I have found better solution, based on @df778899's answerand the Android ValueAnimator API. It works fine without reflection and is very flexible. Also there is no need for making custom ViewPager and putting it into android.support.v4.view package. Here is an example:
我找到了更好的解决方案，基于@df778899 的答案和 Android ValueAnimator API。它无需反射即可正常工作，并且非常灵活。也不需要制作自定义 ViewPager 并将其放入 android.support.v4.view 包中。下面是一个例子：
private void animatePagerTransition(final boolean forward) {
ValueAnimator animator = ValueAnimator.ofInt(0, viewPager.getWidth());
animator.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
viewPager.endFakeDrag();
}
@Override
public void onAnimationCancel(Animator animation) {
viewPager.endFakeDrag();
}
@Override
public void onAnimationRepeat(Animator animation) {
}
});
animator.setInterpolator(new AccelerateInterpolator());
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
private int oldDragPosition = 0;
@Override
public void onAnimationUpdate(ValueAnimator animation) {
int dragPosition = (Integer) animation.getAnimatedValue();
int dragOffset = dragPosition - oldDragPosition;
oldDragPosition = dragPosition;
viewPager.fakeDragBy(dragOffset * (forward ? -1 : 1));
}
});
animator.setDuration(AppConstants.PAGER_TRANSITION_DURATION_MS);
if (viewPager.beginFakeDrag()) {
animator.start();
}
}
UPDATE:
更新：
Just checked if this solution can be used to swipe several pages at once (for example if first page should be showed after the last one). This is slightly modified code to handle specified page count:
刚刚检查了此解决方案是否可用于一次滑动几页（例如，如果第一页应该在最后一页之后显示）。这是稍微修改的代码来处理指定的页数：
private int oldDragPosition = 0;
private void animatePagerTransition(final boolean forward, int pageCount) {
// if previous animation have not finished we can get exception
if (pagerAnimation != null) {
pagerAnimation.cancel();
}
pagerAnimation = getPagerTransitionAnimation(forward, pageCount);
if (viewPager.beginFakeDrag()) { // checking that started drag correctly
pagerAnimation.start();
}
}
private Animator getPagerTransitionAnimation(final boolean forward, int pageCount) {
ValueAnimator animator = ValueAnimator.ofInt(0, viewPager.getWidth() - 1);
animator.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
viewPager.endFakeDrag();
}
@Override
public void onAnimationCancel(Animator animation) {
viewPager.endFakeDrag();
}
@Override
public void onAnimationRepeat(Animator animation) {
viewPager.endFakeDrag();
oldDragPosition = 0;
viewPager.beginFakeDrag();
}
});
animator.setInterpolator(new AccelerateInterpolator());
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
int dragPosition = (Integer) animation.getAnimatedValue();
int dragOffset = dragPosition - oldDragPosition;
oldDragPosition = dragPosition;
viewPager.fakeDragBy(dragOffset * (forward ? -1 : 1));
}
});
animator.setDuration(AppConstants.PAGER_TRANSITION_DURATION_MS / pageCount); // remove divider if you want to make each transition have the same speed as single page transition
animator.setRepeatCount(pageCount);
return animator;
}
回答by Cícero Moura
public class PresentationViewPager extends ViewPager {
public static final int DEFAULT_SCROLL_DURATION = 250;
public static final int PRESENTATION_MODE_SCROLL_DURATION = 1000;
public PresentationViewPager (Context context) {
super(context);
}
public PresentationViewPager (Context context, AttributeSet attrs) {
super(context, attrs);
}
public void setDurationScroll(int millis) {
try {
Class<?> viewpager = ViewPager.class;
Field scroller = viewpager.getDeclaredField("mScroller");
scroller.setAccessible(true);
scroller.set(this, new OwnScroller(getContext(), millis));
} catch (Exception e) {
e.printStackTrace();
}
}
public class OwnScroller extends Scroller {
private int durationScrollMillis = 1;
public OwnScroller(Context context, int durationScroll) {
super(context, new DecelerateInterpolator());
this.durationScrollMillis = durationScroll;
}
@Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, durationScrollMillis);
}
}
}
回答by Paul Burke
Better solution is to simply access the private fields by creating the class in the support package. EDITThis is bound to the MAX_SETTLE_DURATIONof 600ms, set by the ViewPagerclass.
更好的解决方案是通过在支持包中创建类来简单地访问私有字段。编辑这绑定到MAX_SETTLE_DURATION600 毫秒，由ViewPager类设置。
package android.support.v4.view;
import android.content.Context;
import android.util.AttributeSet;
public class SlowViewPager extends ViewPager {
// The speed of the scroll used by setCurrentItem()
private static final int VELOCITY = 200;
public SlowViewPager(Context context) {
super(context);
}
public SlowViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) {
setCurrentItemInternal(item, smoothScroll, always, VELOCITY);
}
}
You can, of course, then add a custom attribute so this can be set via XML.
当然，您可以添加自定义属性，以便通过 XML 进行设置。
回答by Eugene Kartoyev
I used Cicero Moura's version to make a Kotlin class that still works perfectly as of Android 10.
我使用 Cicero Moura 的版本制作了一个 Kotlin 类，该类从 Android 10 开始仍然可以完美运行。
import android.content.Context
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.animation.DecelerateInterpolator
import android.widget.Scroller
import androidx.viewpager.widget.ViewPager
class CustomViewPager(context: Context, attrs: AttributeSet) :
ViewPager(context, attrs) {
private companion object {
const val DEFAULT_SPEED = 1000
}
init {
setScrollerSpeed(DEFAULT_SPEED)
}
var scrollDuration = DEFAULT_SPEED
set(millis) {
setScrollerSpeed(millis)
}
private fun setScrollerSpeed(millis: Int) {
try {
ViewPager::class.java.getDeclaredField("mScroller")
.apply {
isAccessible = true
set(this@CustomViewPager, OwnScroller(millis))
}
} catch (e: Exception) {
e.printStackTrace()
}
}
inner class OwnScroller(private val durationScrollMillis: Int) : Scroller(context, AccelerateDecelerateInterpolator()) {
override fun startScroll(startX: Int, startY: Int, dx: Int, dy: Int, duration: Int) {
super.startScroll(startX, startY, dx, dy, durationScrollMillis)
}
}
}
Initializing from the activity class:
从活动类初始化：
viewPager.apply {
scrollDuration = 2000
adapter = pagerAdapter
}
回答by Foobnix
Here is my code used in Librera Reader
这是我在Librera Reader 中使用的代码
public class MyViewPager extends ViewPager {
public MyViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
initMyScroller();
}
private void initMyScroller() {
try {
Class<?> viewpager = ViewPager.class;
Field scroller = viewpager.getDeclaredField("mScroller");
scroller.setAccessible(true);
scroller.set(this, new MyScroller(getContext())); // my liner scroller
Field mFlingDistance = viewpager.getDeclaredField("mFlingDistance");
mFlingDistance.setAccessible(true);
mFlingDistance.set(this, Dips.DP_10);//10 dip
Field mMinimumVelocity = viewpager.getDeclaredField("mMinimumVelocity");
mMinimumVelocity.setAccessible(true);
mMinimumVelocity.set(this, 0); //0 velocity
} catch (Exception e) {
LOG.e(e);
}
}
public class MyScroller extends Scroller {
public MyScroller(Context context) {
super(context, new LinearInterpolator()); // my LinearInterpolator
}
@Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, 175);//175 duration
}
}
}
回答by Anil Jaiswal
After wasting my whole day I found a solution set offscreenPageLimit to total no. of the page.
在浪费了我一整天之后，我找到了一个解决方案，将 offscreenPageLimit 设置为 no。页面的。
In order to keep a constant length ViewPager scrolls smooth, setOffScreenLimit(page.length) will keep all the views in memory. However, this poses a problem for any animations that involves calling View.requestLayout function (e.g. any animation that involves making changes to the margin or bounds). It makes them really slow (as per Romain Guy) because the all of the views that's in memory will be invalidated as well. So I tried a few different ways to make things smooth but overriding requestLayout and other invalidate methods will cause many other problems.
为了保持恒定长度的 ViewPager 滚动平滑， setOffScreenLimit(page.length) 会将所有视图保留在内存中。但是，这对于任何涉及调用 View.requestLayout 函数的动画（例如，涉及更改边距或边界的任何动画）都会带来问题。这让它们变得非常慢（按照 Romain Guy 的说法），因为内存中的所有视图也将失效。所以我尝试了几种不同的方法来使事情顺利，但覆盖 requestLayout 和其他无效方法会导致许多其他问题。
A good compromise is to dynamically modify the off screen limit so that most of the scrolls between pages will be very smooth while making sure that all of the in page animations smooth by removing the views when the user. This works really well when you only have 1 or 2 views that will have to make other views off memory.
一个很好的折衷方案是动态修改屏幕外限制，以便页面之间的大多数滚动将非常平滑，同时通过删除用户时的视图来确保所有页面内动画平滑。当您只有 1 或 2 个视图必须使其他视图脱离内存时，这非常有效。
***Use this when no any solution works because by setting offeset limit u will load all the fragments at the same time
***当没有任何解决方案时使用此方法，因为通过设置偏移限制，您将同时加载所有片段
