问题描述
package com.example.shift.adapter;
import android.graphics.Color;
import android.os.Handler;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.constraintlayout.widget.ConstraintLayout;
import androidx.recyclerview.widget.linearlayoutmanager;
import androidx.recyclerview.widget.RecyclerView;
import androidx.viewpager.widget.ViewPager;
import com.example.shift.R;
import com.example.shift.modal.HomePageModal;
import com.example.shift.modal.HorizontalProductScrollModel;
import com.example.shift.modal.sliderModel;
import org.jetbrains.annotations.NotNull;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
public class HomePageAdapter extends RecyclerView.Adapter {
private List<HomePageModal> homePageModalList;
public HomePageAdapter(List<HomePageModal> homePageModalList) {
this.homePageModalList = homePageModalList;
}
@Override
public int getItemViewType(int position) {
switch (homePageModalList.get(position).getType()) {
case 0:
return HomePageModal.BANNER_SLIDER;
case 1:
return HomePageModal.STRIP_AD_BANNER;
case 2:
return HomePageModal.HORIZONTAL_PRODUCT_VIEW;
case 3:
return HomePageModal.GRID_PRODUCT_VIEW;
default:
return -1;
}
}
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent,int viewType) {
switch (viewType) {
case HomePageModal.BANNER_SLIDER:
View bannerSliderview = LayoutInflater.from(parent.getContext()).inflate(R.layout.slider_layout,parent,false);
return new BannerSliderViewHolder(bannerSliderview);
case HomePageModal.STRIP_AD_BANNER:
View stripAdview = LayoutInflater.from(parent.getContext()).inflate(R.layout.strip_ad_layout,false);
return new StripAdBannerViewHolder(stripAdview);
case HomePageModal.HORIZONTAL_PRODUCT_VIEW:
View horizontalProductView = LayoutInflater.from(parent.getContext()).inflate(R.layout.horizontal_scroll_layout,false);
return new HorizontalProductViewholder (horizontalProductView);
case HomePageModal.GRID_PRODUCT_VIEW:
View gridProductView = LayoutInflater.from(parent.getContext()).inflate(R.layout.grid_product_layout,false);
return new GridProductViewholder(gridProductView);
default:
return null;
}
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder,int position) {
switch (homePageModalList.get(position).getType()) {
case HomePageModal.BANNER_SLIDER:
List<sliderModel> sliderModelList = homePageModalList.get(position).getSliderModelList();
((BannerSliderViewHolder) holder).setBannersliderViewpager(sliderModelList);
break;
case HomePageModal.STRIP_AD_BANNER:
int resource = homePageModalList.get(position).getResource();
String color = homePageModalList.get(position).getBackgroundColor();
((StripAdBannerViewHolder) holder).setStripAd(resource,color);
break;
case HomePageModal.HORIZONTAL_PRODUCT_VIEW:
String HorizontalLayouttitle =homePageModalList.get(position).getTitle();
List<HorizontalProductScrollModel>horizontalProductScrollModelList =homePageModalList.get(position).getHorizontalProductScrollModelList();
((HorizontalProductViewholder) holder).setHorizontalProductLayout(horizontalProductScrollModelList,HorizontalLayouttitle);
break;
case HomePageModal.GRID_PRODUCT_VIEW:
String GridLayouttitle =homePageModalList.get(position).getTitle();
List<HorizontalProductScrollModel>gridProductScrollModelList =homePageModalList.get(position).getHorizontalProductScrollModelList();
((GridProductViewholder) holder).setGridLayout(gridProductScrollModelList,GridLayouttitle);
break;
default:
return;
}
}
@Override
public int getItemCount() {
return homePageModalList.size();
}
/// Slider List
public class BannerSliderViewHolder extends RecyclerView.ViewHolder {
private ViewPager bannersliderViewpager;
private int currentpage = 2;
private Timer timer;
private final long DELAY_TIME = 3000;
private final long PERIOD_TIME = 3000;
public BannerSliderViewHolder(@NonNull View itemView) {
super(itemView);
bannersliderViewpager = itemView.findViewById(R.id.banner_slider_viewpager);
}
private void setBannersliderViewpager(final List<sliderModel>sliderModelList){
SliderAdapter sliderAdapter = new SliderAdapter(sliderModelList);
bannersliderViewpager.setAdapter(sliderAdapter); **I am getting error at this line **
bannersliderViewpager.setClipToPadding(false);
bannersliderViewpager.setPageMargin(20);
bannersliderViewpager.setCurrentItem(currentpage);
ViewPager.OnPagechangelistener onPagechangelistener = new ViewPager.OnPagechangelistener() {
@Override
public void onPageScrolled(int position,float positionOffset,int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
currentpage = position;
}
@Override
public void onPageScrollStateChanged(int state) {
if(state == ViewPager.SCROLL_STATE_IDLE){
PageLooper(sliderModelList);
}
}
};
bannersliderViewpager.addOnPagechangelistener(onPagechangelistener);
startBannerSlideshow(sliderModelList);
bannersliderViewpager.setonTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v,MotionEvent event) {
PageLooper(sliderModelList);
stopBannerSlideshow();
if(event.getAction()==MotionEvent.ACTION_UP){
startBannerSlideshow(sliderModelList);
}
return false;
}
});
}
private void PageLooper(@NotNull List<sliderModel> sliderModelList) {
if (currentpage == sliderModelList.size() - 2) {
currentpage = 2;
bannersliderViewpager.setCurrentItem(currentpage,false);
}
if (currentpage == 1) {
currentpage = sliderModelList.size() - 3;
bannersliderViewpager.setCurrentItem(currentpage,false);
}
}
private void startBannerSlideshow(List<sliderModel> sliderModelList) {
Handler handler = new Handler();
Runnable update = new Runnable() {
@Override
public void run() {
if (currentpage >= sliderModelList.size()) {
currentpage = 1;
}
bannersliderViewpager.setCurrentItem(currentpage++,true);
}
};
timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
handler.post(update);
}
},DELAY_TIME,PERIOD_TIME);
}
private void stopBannerSlideshow() {
timer.cancel();
}
}
/// Strip Ad
public class StripAdBannerViewHolder extends RecyclerView.ViewHolder {
private ImageView stripAdImage;
private ConstraintLayout stripAdContainer;
public StripAdBannerViewHolder(@NonNull View itemView) {
super(itemView);
stripAdImage = itemView.findViewById(R.id.strip_ad_image);
stripAdContainer = itemView.findViewById(R.id.strip_ad_container);
}
private void setStripAd(int resource,String color) {
stripAdImage.setimageResource(resource);
stripAdContainer.setBackgroundColor(Color.parseColor(color));
}
}
/// Horizontal
public class HorizontalProductViewholder extends RecyclerView.ViewHolder{
private TextView horizontalLayoutTitle;
private Button horizontalviewAllbtn;
private RecyclerView horizontalrecyclerview;
public HorizontalProductViewholder(@NonNull View itemView) {
super(itemView);
horizontalLayoutTitle = itemView.findViewById(R.id.h_s_product_titile);
horizontalviewAllbtn = itemView.findViewById(R.id.horizontal_scroll_lt_viewAllbtn);
horizontalrecyclerview = itemView.findViewById(R.id.horizontal_scroll_lt_recyclerview);
}
private void setHorizontalProductLayout(@NotNull List<HorizontalProductScrollModel> horizontalProductScrollModelList,String title){
horizontalLayoutTitle.setText(title);
if(horizontalProductScrollModelList.size() >8 ){
horizontalviewAllbtn.setVisibility(View.VISIBLE);
}else{
horizontalviewAllbtn.setVisibility(View.INVISIBLE);
}
HorizontalProductScrollAdapter horizontalProductScrollAdapter = new HorizontalProductScrollAdapter(horizontalProductScrollModelList);
linearlayoutmanager linearlayoutmanagerhorizontal = new linearlayoutmanager(itemView.getContext());
linearlayoutmanagerhorizontal.setorientation(linearlayoutmanager.HORIZONTAL);
horizontalrecyclerview.setLayoutManager(linearlayoutmanagerhorizontal);
horizontalrecyclerview.setAdapter(horizontalProductScrollAdapter);
horizontalProductScrollAdapter.notifyDataSetChanged();
}
}
/// Grid Layout
public class GridProductViewholder extends RecyclerView.ViewHolder{
private TextView gridLayoutTitle;
private Button gridLayoutViewAllbtn;
private GridView gridView;
public GridProductViewholder(@NonNull View itemView) {
super(itemView);
TextView gridLayoutTitle = itemView.findViewById(R.id.grid_product_layout_titile);
Button gridLayoutViewAllbtn = itemView.findViewById(R.id.grid_product_layout_viewAlbtn);
GridView gridView = itemView.findViewById(R.id.grid_product_layout_gridView);
}
private void setGridLayout(List<HorizontalProductScrollModel>horizontalProductScrollAdapterList,String title){
gridLayoutTitle.setText(title);
gridView.setAdapter(new gridProductLayoutAdapter(horizontalProductScrollAdapterList));
}
}
}
[Null object Exception][1]**我收到此错误 java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.viewpager.widget.ViewPager.setAdapter(androidx.viewpager.widget.PagerAdapter)'在空对象引用上 在 com.example.shift.adapter.HomePageAdapter$BannerSliderViewHolder.setBannersliderViewpager(HomePageAdapter.java:124) **
解决方法
bannersliderViewpager
是使用 itemView.findViewById(R.id.banner_slider_viewpager);
初始化的,当没有给定 ID 的视图时,它返回 null
。这会导致您的 NullPointerException
,因为您正在对 null
对象引用调用方法。