如何将RecyclerView与数据库一起使用？
我有一个ListView，我使用mysql和json显示数据库中的数据，但通过一些研究，我发现RecyclerView小部件是ListView的更高级和更灵活的版本。这个小部件是一个用于显示大型数据集的容器，而RecyclerView我可以得到这样的结果。那我怎么能纠正我的代码呢？如何从数据库中提取图像并将其提取到RecyclerView
以下是我在ListView
private void showarticles(String json){
JSONObject jsonObject = null;
ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String, String>>();
try {
JSONArray result = new JSONArray(json);
for(int i = 0; i<result.length(); i++){
JSONObject jo = result.getJSONObject(i);
String name = jo.getString("Nom");
String ref = jo.getString("Description");
HashMap<String,String> articles= new HashMap<>();
articles.put("name",name);
articles.put("ref",ref);
list.add(articles);
}
} catch (JSONException e) {
e.printStackTrace();
}
adapter = new SimpleAdapter(
getActivity(), list, R.layout.list_row2,
new String[]{"name","ref"},
new int[]{R.id.name, R.id.description});
listView.setAdapter(adapter);
}
private void getJSON() {
class GetJSON extends AsyncTask<Void, Void, String> {
ProgressDialog loading;
@Override
protected void onPreExecute() {
super.onPreExecute();
loading = ProgressDialog.show(getActivity(), "Téléchargement", "Veuillez patientez...", false, false);
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
loading.dismiss();
JSON_STRING = s;
showarticles(s);
}
@Override
protected String doInBackground(Void... params) {
RequestHandler rh = new RequestHandler();
String s = rh.sendGetRequest(URL);
return s;
}
}
GetJSON gj = new GetJSON();
gj.execute();
}
更新
public class recyclerFragment extends Fragment {
private RecyclerView mRecyclerView;
ListAdapter adapter;
private String JSON_STRING;
public static final String URL = "http://aaaa.com/Back/getArticles.php";
private MyAdapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootview = inflater.inflate(R.layout.recycler_fragment, container, false);
mRecyclerView = (RecyclerView) rootview.findViewById(R.id.my_list);
mRecyclerView.addItemDecoration(new SpacesItemDecoration(10));
mLayoutManager = new GridLayoutManager(getActivity(), 2);
mRecyclerView.setLayoutManager(mLayoutManager);
mAdapter = new MyAdapter(null);
mRecyclerView.setAdapter(mAdapter);
getJSON();
return rootview;
}
private void showarticles(String json){
JSONObject jsonObject = null;
ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String, String>>();
try {
JSONArray result = new JSONArray(json);
for(int i = 0; i<result.length(); i++){
JSONObject jo = result.getJSONObject(i);
String name = jo.getString("Nom");
String ref = jo.getString("Description");
HashMap<String,String> articles= new HashMap<>();
articles.put("name",name);
articles.put("ref",ref);
list.add(articles);
}
} catch (JSONException e) {
e.printStackTrace();
}
mAdapter = new SimpleAdapter(
getActivity(), list, R.layout.list_row2,
new String[]{"name","ref"},
new int[]{R.id.nom, R.id.email2});
mRecyclerView.setAdapter(mAdapter);
}
private void getJSON() {
class GetJSON extends AsyncTask<Void, Void, String> {
ProgressDialog loading;
@Override
protected void onPreExecute() {
super.onPreExecute();
loading = ProgressDialog.show(getActivity(), "Téléchargement", "Veuillez patientez...", false, false);
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
loading.dismiss();
JSON_STRING = s;
showEmployee(s);
}
@Override
protected String doInBackground(Void... params) {
RequestHandler rh = new RequestHandler();
String s = rh.sendGetRequest(URL);
return s;
}
}
GetJSON gj = new GetJSON();
gj.execute();
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(getActivity().getApplicationContext(), ViewProduit.class);
HashMap<String, String> map = (HashMap) parent.getItemAtPosition(position);
String tid = map.get("ref").toString();
intent.putExtra("ref", tid);
startActivity(intent);
}
}
Error:(31, 27) error: cannot find symbol variable myArrayList
Error:(76, 13) error: cannot find symbol variable myArrayList
Error:(77, 20) error: cannot find symbol variable myArrayList
Error:(41, 45) error: cannot find symbol class SpacesItemDecoration
Error:(44, 20) error: constructor MyAdapter in class MyAdapter cannot be applied to given types;
required: no arguments
found: <null>
reason: actual and formal argument lists differ in length
Error:(74, 20) error: incompatible types: SimpleAdapter cannot be converted to MyAdapter
Error:(106, 5) error: method does not override or implement a method from a supertype
Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
> Compilation failed; see the compiler error output for details.
1 个答案:
答案 0 :(得分：0)
您需要先在布局中添加RecyclerView。
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:ads="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/black">
<android.support.v7.widget.RecyclerView
android:id="@+id/my_list"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
现在，如果您在Activity，请与RecyclerView一起初始化LayoutManager。在您的情况下，您需要GridLayoutManager
// Declare them first
private RecyclerView mRecyclerView;
private MyAdapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
初始化onCreate功能中的项目，并在此处设置Adapter。
mRecyclerView = (RecyclerView) findViewById(R.id.my_list);
mRecyclerView.addItemDecoration(new SpacesItemDecoration(10));
mLayoutManager = new GridLayoutManager(getActivity(), 2);
mRecyclerView.setLayoutManager(mLayoutManager);
mAdapter = new MyAdapter();
mRecyclerView.setAdapter(mAdapter);
现在让ArrayList准备好在Adapter中传递它，然后致电notifyDataSetChanged()以使用您要展示的项目填充RecyclerView。
所以，您可以使用自定义Adapter
public class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
public MyAdapter() {
}
public class ViewHolder extends RecyclerView.ViewHolder {
// Declare the items in each row
private TextView myTextView;
public ViewHolder(final View itemView) {
super(itemView);
// Initialize the items here
myTextView = (TextView) itemView.findViewById(R.id.my_textview);
}
public void bindView(int pos) {
// Set the items here with specific array elements you have
String text = myArrayList.get(pos);
myTextView.setText(text);
}
}
// Now define the viewholder for Normal list item
public class NormalViewHolder extends ViewHolder {
public NormalViewHolder(View itemView) {
super(itemView);
itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO: Here's what you want to do when your list item is clicked
}
});
}
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v;
v = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_layout, parent, false);
NormalViewHolder vh = new NormalViewHolder(v);
return vh;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
try {
if (holder instanceof NormalViewHolder) {
NormalViewHolder vh = (NormalViewHolder) holder;
vh.bindView(position);
}
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public int getItemCount() {
if (myArrayList != null)
return myArrayList.size();
else return 0;
}
@Override
public int getItemViewType(int position) {
return super.getItemViewType(position);
}
}
将myArrayList声明为全局，并使用您想要的元素填充myArrayList，并根据需要自定义bindView。完成myArrayList notifyDatasetChanged() Adapter mAdapter.notifyDataSetChanged()之后填写public class recyclerFragment extends Fragment {
private RecyclerView mRecyclerView;
private MyAdapter mAdapter;
private String JSON_STRING;
public static final String URL = "http://aaaa.com/Back/getArticles.php";
private RecyclerView.LayoutManager mLayoutManager;
// Declare the list globally
ArrayList<HashMap<String,String>> list;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootview = inflater.inflate(R.layout.recycler_fragment, container, false);
mRecyclerView = (RecyclerView) rootview.findViewById(R.id.my_list);
// Initialize the list here
list = new ArrayList<HashMap<String, String>>();
// Initialize other items
mRecyclerView.addItemDecoration(new SpacesItemDecoration(10));
mLayoutManager = new GridLayoutManager(getActivity(), 2);
mRecyclerView.setLayoutManager(mLayoutManager);
mAdapter = new MyAdapter();
mRecyclerView.setAdapter(mAdapter);
getJSON();
return rootview;
}
private void showarticles(String json){
JSONObject jsonObject = null;
try {
JSONArray result = new JSONArray(json);
for(int i = 0; i<result.length(); i++){
JSONObject jo = result.getJSONObject(i);
String name = jo.getString("Nom");
String ref = jo.getString("Description");
HashMap<String,String> articles= new HashMap<>();
articles.put("name",name);
articles.put("ref",ref);
list.add(articles);
}
} catch (JSONException e) {
e.printStackTrace();
}
// Here you can call notifyDataSetChanged in your Adapter. As you've the dataset ready now.
mAdapter.notifyDataSetChanged();
}
private void getJSON() {
class GetJSON extends AsyncTask<Void, Void, String> {
ProgressDialog loading;
@Override
protected void onPreExecute() {
super.onPreExecute();
loading = ProgressDialog.show(getActivity(), "Téléchargement", "Veuillez patientez...", false, false);
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
loading.dismiss();
JSON_STRING = s;
showEmployee(s);
}
@Override
protected String doInBackground(Void... params) {
RequestHandler rh = new RequestHandler();
String s = rh.sendGetRequest(URL);
return s;
}
}
GetJSON gj = new GetJSON();
gj.execute();
}
// Here you write your custom Adapter class
public class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
public MyAdapter() {
}
public class ViewHolder extends RecyclerView.ViewHolder {
// Declare the items in each row
private Button myButton;
public ViewHolder(final View itemView) {
super(itemView);
// Initialize the items here
myButton = (TextView) itemView.findViewById(R.id.my_button);
}
public void bindView(int pos) {
// Set the items here with specific array elements you have
myButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// Here's what you want to do when your list item is clicked
Intent intent = new Intent(getActivity().getApplicationContext(), ViewProduit.class);
HashMap<String, String> map = (HashMap) parent.getItemAtPosition(pos);
String tid = map.get("ref").toString();
intent.putExtra("ref", tid);
startActivity(intent);
}
});
}
}
// Now define the viewholder for Normal list item
public class NormalViewHolder extends ViewHolder {
public NormalViewHolder(View itemView) {
super(itemView);
}
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v;
v = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_layout, parent, false);
NormalViewHolder vh = new NormalViewHolder(v);
return vh;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
try {
if (holder instanceof NormalViewHolder) {
NormalViewHolder vh = (NormalViewHolder) holder;
vh.bindView(position);
}
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public int getItemCount() {
if (list != null)
return list.size();
else return 0;
}
@Override
public int getItemViewType(int position) {
return super.getItemViewType(position);
}
}
}
来电时{/ 1}}。
<强>更新
所以这是我正在使用您更新的代码并尽可能地修改。代码可能有错误，但我认为在你修改它之后你可以自己做其余的事情。
SELECT
SUM(T1.total) AS Total,
SUM(T1.received) AS Received,
T1.EventName,
T1.CurrencyType
FROM
(
SELECT
event_invoice.Id,
event_invoice.Amount AS total,
SUM(payments.recieved_amount + payments.adjust_amount) AS received,
event_invoice.EventName,
event_invoice.CurrencyType
FROM
event_invoice
LEFT JOIN payments ON event_invoice.Id = payments.invoice_id
GROUP BY
event_invoice.Id
ORDER BY
event_invoice.Id
) T1
GROUP BY
T1.EventName,
T1.CurrencyType
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