在Android 中,像常用的控件:TextView \ EditText \ Button\ImageView\ViewPager\RadioGroup\RadioButton\Switch\CheckBox等等
这些大多数都是很有历史的控件了,我们接下来将一下一个全新的控件:
ViewPager2
在没推出androidx之前,android生态有些混乱,自从Google官方开始重视这一问题以后 就有了后续的jetpack和一系列的控件
viewpager 我们一般是exends PageAdapter或者其他的适配器,完成不通类型之间页面滑动 A--->B---->C 默认会缓存2个页面的数据,有个缓存设计,也就是当前在B页面---C页面的数据会初始化,所以才有了懒加载(Fragment)
懒加载原理请移步---------> https://blog.csdn.net/qq_29769851/article/details/90712756
先看看ViewPager2的源码:
继承自ViewGroup
setAdapter
/*** <p>Set a new adapter to provide page views on demand.</p>** <p>If you're planning to use {@link androidx.fragment.app.Fragment Fragments} as pages,* implement {@link androidx.viewpager2.adapter.FragmentStateAdapter FragmentStateAdapter}. If* your pages are Views, implement {@link RecyclerView.Adapter} as usual.</p>** <p>If your pages contain LayoutTransitions, then those LayoutTransitions <em>must</em> have* {@code animateParentHierarchy} set to {@code false}. Note that if you have a ViewGroup with* {@code animateLayoutChanges="true"} in your layout xml file, a LayoutTransition is added* automatically to that ViewGroup. You will need to manually call {@link* android.animation.LayoutTransition#setAnimateParentHierarchy(boolean)* getLayoutTransition().setAnimateParentHierarchy(false)} on that ViewGroup after you inflated* the xml layout, like this:</p>** <pre>* View view = layoutInflater.inflate(R.layout.page, parent, false);* ViewGroup viewGroup = view.findViewById(R.id.animated_viewgroup);* viewGroup.getLayoutTransition().setAnimateParentHierarchy(false);* </pre>** @param adapter The adapter to use, or {@code null} to remove the current adapter* @see androidx.viewpager2.adapter.FragmentStateAdapter* @see RecyclerView#setAdapter(Adapter)*/
public void setAdapter(@Nullable @SuppressWarnings("rawtypes") Adapter adapter) {final Adapter<?> currentAdapter = mRecyclerView.getAdapter();mAccessibilityProvider.onDetachAdapter(currentAdapter);unregisterCurrentItemDataSetTracker(currentAdapter);mRecyclerView.setAdapter(adapter);mCurrentItem = 0;restorePendingState();mAccessibilityProvider.onAttachAdapter(adapter);registerCurrentItemDataSetTracker(adapter);
}
描述的意思 大概是使用RecyclerView 的 dapter,在了解了使用方法以后,于是就开始体验一下吧!
@FindView(R.id.splash_viewpage2)
ViewPager2 viewPager2;
设置滑动方向 ---> 左右或者上下
viewPager2.setOrientation(ViewPager2.ORIENTATION_HORIZONTAL);
ViewPager2的Adapter
public class SplashAdapter extends RecyclerView.Adapter<SplashAdapter.SplashVH> {private List<SplashImageBean> list;public SplashAdapter(List<SplashImageBean> list) {this.list = list;}@NonNull@Overridepublic SplashVH onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {View view = ((LayoutInflater)parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.item_splash_wellcome,parent,false);return new SplashVH(view);}@Overridepublic void onBindViewHolder(@NonNull SplashVH holder, int position) {holder.iv_splash_image_center.setBackgroundResource(list.get(position).getIcon());
// holder.imageView.startCountDown();}@Overridepublic int getItemCount() {return list == null ? 0 : list.size();}static class SplashVH extends RecyclerView.ViewHolder{private ImageView iv_splash_image_center;private CountDownView countDownView;public SplashVH(@NonNull View itemView) {super(itemView);this.iv_splash_image_center = itemView.findViewById(R.id.iv_splash_image_center);countDownView = itemView.findViewById(R.id.cdv_splash_number);}}
那么 跟之前的 ViewPager有些API变更 比如 addOnPageChange 现已经更换为:
registerOnPageChangeCallback
Code:
viewPager2.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {@Overridepublic void onPageSelected(int position) {if (position == list.size()-1){btn_splash_start.setVisibility(View.VISIBLE);btn_splash_start.startAnimation(animation);}else{btn_splash_start.setVisibility(View.GONE);}}@Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {super.onPageScrolled(position, positionOffset, positionOffsetPixels);}@Overridepublic void onPageScrollStateChanged(int state) {super.onPageScrollStateChanged(state);}});
