ViewPager2+TabLayout、会遇到底部tab点击 过度滚动问题、 比如tab一共有四页、当从第1页切换到第四页、会有动画滚动效果、如何去除动画效果?请往下看、若没有此问题就不用往下看了;
控制ViewPager2+TabLayout 滚动效果得核心TabLayoutMediator、具体用法不再阐述、展示其核心代码:
是的答案就在这里、
viewPager.setCurrentItem(tab.getPosition(), smoothScroll);
讨厌的动画就是smoothScroll==true 导致的、这个值可以在初始化TabLayoutMediator时设置、用来取消滚动动画;
如果有这样的需求、点击tab无动画、滑动有动画(类似微信)? 请继续往下看;
TabLayoutMediator 是final类 且smoothScroll字段时私有的、我们没法继承重写、但是可以copy源码修改、不会有问题、核心修改如图
已下是修改好的完整代码
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.recyclerview.widget.RecyclerView;
import androidx.viewpager2.widget.ViewPager2;
import com.google.android.material.tabs.TabLayout;
import java.lang.ref.WeakReference;
import static androidx.viewpager2.widget.ViewPager2.SCROLL_STATE_DRAGGING;
import static androidx.viewpager2.widget.ViewPager2.SCROLL_STATE_IDLE;
import static androidx.viewpager2.widget.ViewPager2.SCROLL_STATE_SETTLING;
public class TabLayoutMediators {
private TabLayout tabLayout;
private ViewPager2 viewPager;
private boolean autoRefresh;
private static boolean smoothScroll;
private TabConfigurationStrategy tabConfigurationStrategy;
@Nullable
private RecyclerView.Adapter> adapter;
private boolean attached;
@Nullable
private TabLayoutOnPageChangeCallback onPageChangeCallback;
@Nullable
private TabLayout.OnTabSelectedListener onTabSelectedListener;
@Nullable
private RecyclerView.AdapterDataObserver pagerAdapterObserver;
/**
* A callback interface that must be implemented to set the text and styling of newly created
* tabs.
*/
public interface TabConfigurationStrategy {
/**
* Called to configure the tab for the page at the specified position. Typically calls {@link
* TabLayout.Tab#setText(CharSequence)}, but any form of styling can be applied.
*
* @param tab The Tab which should be configured to represent the title of the item at the given
* position in the data set.
* @param position The position of the item within the adapter's data set.
*/
void onConfigureTab(@NonNull TabLayout.Tab tab, int position);
}
public TabLayoutMediators(
@NonNull TabLayout tabLayout,
@NonNull ViewPager2 viewPager,
@NonNull TabConfigurationStrategy tabConfigurationStrategy) {
this(tabLayout, viewPager, /* autoRefresh= */ true, tabConfigurationStrategy);
}
public TabLayoutMediators(
@NonNull TabLayout tabLayout,
@NonNull ViewPager2 viewPager,
boolean autoRefresh,
@NonNull TabConfigurationStrategy tabConfigurationStrategy) {
this(tabLayout, viewPager, autoRefresh, /* smoothScroll= */ false, tabConfigurationStrategy);
}
public TabLayoutMediators(
@NonNull TabLayout tabLayout,
@NonNull ViewPager2 viewPager,
boolean autoRefresh,
boolean smoothScroll,
@NonNull TabConfigurationStrategy tabConfigurationStrategy) {
this.tabLayout = tabLayout;
this.viewPager = viewPager;
this.autoRefresh = autoRefresh;
this.smoothScroll = smoothScroll;
this.tabConfigurationStrategy = tabConfigurationStrategy;
}
/**
* Link the TabLayout and the ViewPager2 together. Must be called after ViewPager2 has an adapter
* set. To be called on a new instance of TabLayoutMediator or if the ViewPager2's adapter
* changes.
*
* @throws IllegalStateException If the mediator is already attached, or the ViewPager2 has no
* adapter.
*/
public void attach() {
if (attached) {
throw new IllegalStateException("TabLayoutMediator is already attached");
}
adapter = viewPager.getAdapter();
if (adapter == null) {
throw new IllegalStateException(
"TabLayoutMediator attached before ViewPager2 has an " + "adapter");
}
attached = true;
// Add our custom OnPageChangeCallback to the ViewPager
onPageChangeCallback = new TabLayoutOnPageChangeCallback(tabLayout);
viewPager.registerOnPageChangeCallback(onPageChangeCallback);
// Now we'll add a tab selected listener to set ViewPager's current item
onTabSelectedListener = new ViewPagerOnTabSelectedListener(viewPager, smoothScroll);
tabLayout.addOnTabSelectedListener(onTabSelectedListener);
// Now we'll populate ourselves from the pager adapter, adding an observer if
// autoRefresh is enabled
if (autoRefresh) {
// Register our observer on the new adapter
pagerAdapterObserver = new PagerAdapterObserver();
adapter.registerAdapterDataObserver(pagerAdapterObserver);
}
populateTabsFromPagerAdapter();
// Now update the scroll position to match the ViewPager's current item
tabLayout.setScrollPosition(viewPager.getCurrentItem(), 0f, true);
}
/**
* Unlink the TabLayout and the ViewPager. To be called on a stale TabLayoutMediator if a new one
* is instantiated, to prevent holding on to a view that should be garbage collected. Also to be
* called before {@link #attach()} when a ViewPager2's adapter is changed.
*/
public void detach() {
if (autoRefresh && adapter != null) {
adapter.unregisterAdapterDataObserver(pagerAdapterObserver);
pagerAdapterObserver = null;
}
tabLayout.removeOnTabSelectedListener(onTabSelectedListener);
viewPager.unregisterOnPageChangeCallback(onPageChangeCallback);
onTabSelectedListener = null;
onPageChangeCallback = null;
adapter = null;
attached = false;
}
/**
* Returns whether the {@link TabLayout} and the {@link ViewPager2} are linked together.
*/
public boolean isAttached() {
return attached;
}
@SuppressWarnings("WeakerAccess")
void populateTabsFromPagerAdapter() {
tabLayout.removeAllTabs();
if (adapter != null) {
int adapterCount = adapter.getItemCount();
for (int i = 0; i < adapterCount; i++) {
TabLayout.Tab tab = tabLayout.newTab();
tabConfigurationStrategy.onConfigureTab(tab, i);
tabLayout.addTab(tab, false);
}
// Make sure we reflect the currently set ViewPager item
if (adapterCount > 0) {
int lastItem = tabLayout.getTabCount() - 1;
int currItem = Math.min(viewPager.getCurrentItem(), lastItem);
if (currItem != tabLayout.getSelectedTabPosition()) {
tabLayout.selectTab(tabLayout.getTabAt(currItem));
}
}
}
}
/**
* A {@link ViewPager2.OnPageChangeCallback} class which contains the necessary calls back to the
* provided {@link TabLayout} so that the tab position is kept in sync.
*
* This class stores the provided TabLayout weakly, meaning that you can use {@link
* ViewPager2#registerOnPageChangeCallback(ViewPager2.OnPageChangeCallback)} without removing the
* callback and not cause a leak.
*/
private static class TabLayoutOnPageChangeCallback extends ViewPager2.OnPageChangeCallback {
@NonNull
private final WeakReference tabLayoutRef;
private int previousScrollState;
private int scrollState;
TabLayoutOnPageChangeCallback(TabLayout tabLayout) {
tabLayoutRef = new WeakReference<>(tabLayout);
reset();
}
@Override
public void onPageScrollStateChanged(final int state) {
if (state == SCROLL_STATE_DRAGGING) {
smoothScroll = true;
} else if (state == SCROLL_STATE_IDLE) {
smoothScroll = false;
}
previousScrollState = scrollState;
scrollState = state;
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
TabLayout tabLayout = tabLayoutRef.get();
if (tabLayout != null) {
// Only update the text selection if we're not settling, or we are settling after
// being dragged
boolean updateText =
scrollState != SCROLL_STATE_SETTLING || previousScrollState == SCROLL_STATE_DRAGGING;
// Update the indicator if we're not settling after being idle. This is caused
// from a setCurrentItem() call and will be handled by an animation from
// onPageSelected() instead.
boolean updateIndicator =
!(scrollState == SCROLL_STATE_SETTLING && previousScrollState == SCROLL_STATE_IDLE);
tabLayout.setScrollPosition(position, positionOffset, updateText, updateIndicator);
}
}
@Override
public void onPageSelected(final int position) {
TabLayout tabLayout = tabLayoutRef.get();
if (tabLayout != null
&& tabLayout.getSelectedTabPosition() != position
&& position < tabLayout.getTabCount()) {
// Select the tab, only updating the indicator if we're not being dragged/settled
// (since onPageScrolled will handle that).
boolean updateIndicator =
scrollState == SCROLL_STATE_IDLE
|| (scrollState == SCROLL_STATE_SETTLING
&& previousScrollState == SCROLL_STATE_IDLE);
tabLayout.selectTab(tabLayout.getTabAt(position), updateIndicator);
}
}
void reset() {
previousScrollState = scrollState = SCROLL_STATE_IDLE;
}
}
/**
* A {@link TabLayout.OnTabSelectedListener} class which contains the necessary calls back to the
* provided {@link ViewPager2} so that the tab position is kept in sync.
*/
private static class ViewPagerOnTabSelectedListener implements TabLayout.OnTabSelectedListener {
private final ViewPager2 viewPager;
// private final boolean smoothScroll;
ViewPagerOnTabSelectedListener(ViewPager2 viewPager, boolean smoothScroll) {
this.viewPager = viewPager;
// this.smoothScroll = smoothScroll;
}
@Override
public void onTabSelected(@NonNull TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition(), smoothScroll);
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
// No-op
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
// No-op
}
}
private class PagerAdapterObserver extends RecyclerView.AdapterDataObserver {
PagerAdapterObserver() {
}
@Override
public void onChanged() {
populateTabsFromPagerAdapter();
}
@Override
public void onItemRangeChanged(int positionStart, int itemCount) {
populateTabsFromPagerAdapter();
}
@Override
public void onItemRangeChanged(int positionStart, int itemCount, @Nullable Object payload) {
populateTabsFromPagerAdapter();
}
@Override
public void onItemRangeInserted(int positionStart, int itemCount) {
populateTabsFromPagerAdapter();
}
@Override
public void onItemRangeRemoved(int positionStart, int itemCount) {
populateTabsFromPagerAdapter();
}
@Override
public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
populateTabsFromPagerAdapter();
}
}
}
将TabLayoutMediator替换为TabLayoutMediators 、
至此Over: