java如何缓存firebase中的json数据以使其脱机可用？
我有一个json数据，它成功地显示在recycler视图中，现在我想让它离线。“我的回收器”视图“显示列表”和“单击列表”打开一个新的子活动以显示详细信息，并具有一个imageslider，因此我希望使其脱机可用。我的代码在下面
这是我的主要活动页面：
public class
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_picnic);
reference= FirebaseDatabase.getInstance().getReference().child("picnic");
recyclerView=(RecyclerView)findViewById(R.id.recyclerpicniclist2);
search=findViewById(R.id.picnic_search2);
search.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
@Override
public boolean onQueryTextSubmit(String s) {
return false;
}
@Override
public boolean onQueryTextChange(String s) {
adapter.getFilter().filter(s);
return true;
}
});
recyclerView.setLayoutManager(new LinearLayoutManager(this));
picniclist=new ArrayList<newpicnic>();
reference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot dataSnapshot1:dataSnapshot.getChildren()){
newpicnic n=dataSnapshot1.getValue(newpicnic.class);
picniclist.add(n);
}
adapter=new PicnicAdapter(picnic.this,picniclist);
recyclerView.setAdapter(adapter);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Toast.makeText(picnic.this,"Page is not found",Toast.LENGTH_SHORT).show();
}
});
}
}
这是我编写set和get方法的类：
public newpicnic() {
}
public String getSpotName() {
return SpotName;
}
public void setSpotName(String spotName) {
SpotName = spotName;
}
public String getDescription() {
return Description;
}
public void setDescription(String description) {
Description = description;
}
public String getAddress() {
return Address;
}
public void setAddress(String address) {
Address = address;
}
public List<String> getImg_url() {
return img_url;
}
public void setImg_url(List<String> img_url) {
this.img_url = img_url;
}
}
这是我的适配器：
public PicnicAdapter(Context c,ArrayList<newpicnic>n){
context=c;
picnic=n;
picnic2=new ArrayList<>();
picnic2.addAll(picnic);
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
LayoutInflater inflater=LayoutInflater.from(context);
View view=inflater.inflate(R.layout.activity_picnic_list_item,parent,false);
//new holder for picnic details
final MyViewHolder viewHolder=new MyViewHolder(view);
viewHolder.view_picnic.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent p = new Intent(context,picnic_details.class);
p.putExtra("spot_name",picnic.get(viewHolder.getAdapterPosition()).getSpotName());
p.putExtra("Description",picnic.get(viewHolder.getAdapterPosition()).getDescription());
p.putExtra("Address",picnic.get(viewHolder.getAdapterPosition()).getAddress());
context.startActivity(p);
}
});
return viewHolder;
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
holder.SpotName.setText(picnic.get(position).getSpotName());
}
@Override
public int getItemCount() {
return picnic.size();
}
@Override
public Filter getFilter() {
return picnicDataFilter;
}
private Filter picnicDataFilter=new Filter() {
@Override
protected FilterResults performFiltering(CharSequence charSequence) {
ArrayList<newpicnic> filteredList=new ArrayList<>();
if (charSequence == null || charSequence.length()==0){
filteredList.addAll(picnic2);
}
else {
String filter=charSequence.toString().toLowerCase().trim();
for(newpicnic dataItem:picnic2){
if(dataItem.getSpotName().toLowerCase().contains(filter)){
filteredList.add(dataItem);
}
}
}
FilterResults results=new FilterResults();
results.values=filteredList;
return results;
}
@Override
protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
picnic.clear();
picnic.addAll((Collection<? extends newpicnic>) filterResults.values);
notifyDataSetChanged();
}
};
class MyViewHolder extends RecyclerView.ViewHolder{
TextView SpotName;
LinearLayout view_picnic;
TextView Description;
TextView Address;
public MyViewHolder( View itemView) {
super(itemView);
SpotName=itemView.findViewById(R.id.SpotName);
view_picnic=itemView.findViewById(R.id.list_root);
Description=itemView.findViewById(R.id.picnic_description);
Address=itemView.findViewById(R.id.picnic_address);
}
}
}
这是我的子活动：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_picnic_details);
Bundle r=getIntent().getExtras();
pname=r.getString("spot_name");
imgurl=new ArrayList<>();
reference= FirebaseDatabase.getInstance().getReference("picnic");
reference.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot list:dataSnapshot.getChildren()){
if (list.child("SpotName").getValue().toString().equals(pname)){
imgurl.addAll((List)list.child("img_url").getValue());
}
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
//Recieve data
String placname2=getIntent().getExtras().getString("spot_name");
String placename=getIntent().getExtras().getString("spot_name");
String description=getIntent().getExtras().getString("Description");
String address=getIntent().getExtras().getString("Address");
//in views
CollapsingToolbarLayout collapsingToolbarLayout=findViewById(R.id.collapsingbar);
collapsingToolbarLayout.setTitleEnabled(true);
TextView picnicplacename=findViewById(R.id.place_name2);
TextView picnicdescription=findViewById(R.id.picnic_description);
TextView picnicaddress=findViewById(R.id.picnic_address);
//setting vlaues
picnicdescription.setText(description);
picnicaddress.setText(address);
picnicplacename.setText(placname2);
//img_url
carouselView=findViewById(R.id.picnic_carousel);
loadcarousel();
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
loadcarousel();
}
},5000);
}
public void loadcarousel(){
carouselView.setPageCount(imgurl.size());
//setting image carousel
carouselView.setImageListener(new ImageListener() {
@Override
public void setImageForPosition(int position, final ImageView imageView) {
Glide.with(getApplicationContext()).asBitmap().load(imgurl.get(position)).into(new CustomTarget<Bitmap>() {
@Override
public void onResourceReady(@NonNull Bitmap resource, @Nullable Transition<? super Bitmap> transition) {
imageView.setImageBitmap(resource);
}
@Override
public void onLoadCleared(@Nullable Drawable placeholder) {
}
});
}
});
//end of the slider
}
}
# 1 楼答案
只需使用firebase数据库离线设施，只需一行：
更多参考：https://firebase.google.com/docs/database/android/offline-capabilities
希望这会有帮助