我使用带有片段的RecyclerView来显示来自SQLite数据库的数据。
我在RecyclerView外部有两个按钮来更改从数据库检索数据的查询。第一个按钮显示（星期一至星期五）的数据，第二个按钮显示（星期六至星期日）的数据。我尝试了mAdapter.notifyDataSetChanged();，但是没有用，或者我写错了。
请帮助我准确地编写该代码
这是我的片段代码：
public class stationFragment extends BaseFragment {
private List<DatabaseModel> Times = new ArrayList<DatabaseModel>();
DatabaseHelper databaseHelper;
public View mView;
RecyclerView mRecyclerView;
public RecyclerView.Adapter mAdapter;
public int Position;
public static stationFragment instance(int position) {
stationFragment fragment = new stationFragment();
fragment.Position = position;
return fragment;
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
mView = inflater.inflate(R.layout.fragment_station, container, false);
showInRecyclerView();
return mView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
list();
}
public void list(){
ArrayList<DatabaseModel> LineList = new ArrayList<>();
LineList.clear();
mAdapter = new DataAdapter(LineList);
DatabaseHelper db = new DatabaseHelper(getContext());
final List<DatabaseModel> m = db.getAllUsers(Position);
if (m.size() > 0) {
for (int i = 0; i < m.size(); i++) {
LineList.add(m.get(i));
mAdapter.notifyDataSetChanged();
}
}
db.close();
}
public void showInRecyclerView(){
databaseHelper = new DatabaseHelper(getContext());
Times = databaseHelper.getAllUsers(Position);
mRecyclerView = mView.findViewById(R.id.myRecycler);
mAdapter = new DataAdapter(Times);
mRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
mRecyclerView.setAdapter(mAdapter);
}
}
这是我的活动代码（buttonOne和buttonTwo）：
public class station extends BaseActivity {
Toolbar mToolbar;
private TabLayout tbLayout;
private ViewPager vPager;
private ButtonCell backBtn;
Boolean btnOneOn = false;
Boolean btnTwoOn = false;
ButtonCell Button2;
ButtonCell Button1;
RecyclerView recyclerView=findViewById(R.id.myRecycler);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_station);
final DatabaseHelper helper = new DatabaseHelper(this);
try {
helper.importIfNotExist();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
mToolbar = findViewById(R.id.tlbr1);
setSupportActionBar(mToolbar);
initView();
setupWithViewPager();
tbLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
public void line1(View view) {
Intent line1 = new Intent(this, line1.class);
startActivity(line1);
}
private void setupWithViewPager() {
BasePagerAdapter basePagerAdapter = new BasePagerAdapter(this, getSupportFragmentManager());
vPager.setAdapter(basePagerAdapter);
tbLayout.setupWithViewPager(vPager);
}
private void initView() {
vPager = findViewById(R.id.view_pager);
tbLayout = findViewById(R.id.tab_layout);
backBtn = findViewById(R.id.backBtn);
}
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.backBtn:
line1(view);
return;
}
}
public void buttonOne(View view) {
Button1 = findViewById(R.id.tg_btn1);
Button2 = findViewById(R.id.tg_btn2);
//If the Button is off
if (!btnOneOn) {
Button2.setBackgroundColor(getResources().getColor(R.color.md_blue_grey_900));
Button1.setBackgroundColor(getResources().getColor((R.color.md_white_1000)));
Button1.setTextColor(getResources().getColor(R.color.md_blue_grey_900));
Button2.setTextColor(getResources().getColor(R.color.md_white_1000));
btnTwoOn = false;
btnOneOn = true;
C.whatDay = "6";
}
//If it is is clicked while on
else {
btnTwoOn = false;
Button2.setBackgroundColor(getResources().getColor((R.color.md_blue_grey_900)));
}
}
public void buttonTwo(View view) {
Button2 = findViewById(R.id.tg_btn2);
Button1 = findViewById(R.id.tg_btn1);
//If the Button is off
if (!btnTwoOn) {
Button1.setBackgroundColor(getResources().getColor(R.color.md_blue_grey_900));
Button2.setBackgroundColor(getResources().getColor((R.color.md_white_1000)));
Button2.setTextColor(getResources().getColor(R.color.md_blue_grey_900));
Button1.setTextColor(getResources().getColor(R.color.md_white_1000));
btnOneOn = false;
btnTwoOn = true;
C.whatDay = "7";
}
//If it is is clicked while on
else {
btnOneOn = false;
Button1.setBackgroundColor(getResources().getColor((R.color.md_blue_grey_900)));
}
}
}
这是我的DatabaseHelper：
public class DatabaseHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_NAME = "MetroDB";//name of the database
private static final String TABLE_NAME = "stationtime";//name for the table
static String db_path = "/data/data/ir.shirazmetro/databases/";
private static final String Station = "station";
private static final String Time = "time";
private static final String Line = "line";
private static final String Day = "day";
private final Context context;
private SQLiteDatabase database;
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
this.context = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
//Query to create table in databse
String CREATE_CONTACTS_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "(" + Station + " TEXT," + Time + " TEXT," + Line + " TEXT," + Day + " INTEGER)";
db.execSQL(CREATE_CONTACTS_TABLE);
}
//Executes once a database change is occurred
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
private boolean checkExist() {
SQLiteDatabase db = null;
try {
db = SQLiteDatabase.openDatabase(db_path + DATABASE_NAME, null, SQLiteDatabase.OPEN_READONLY);
} catch (SQLException e) {
}
return db != null;
}
private void copyDatabase() throws IOException {
OutputStream myOutput = new FileOutputStream(db_path + DATABASE_NAME);
byte[] buffer = new byte[1024];
int length;
InputStream myInput = context.getAssets().open(DATABASE_NAME + ".db");
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
myInput.close();
myOutput.flush();
myOutput.close();
}
public void importIfNotExist() throws IOException {
boolean dbExist = checkExist();
if (!dbExist) {
this.getReadableDatabase();
try {
copyDatabase();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void open() {
database = SQLiteDatabase.openDatabase(db_path + DATABASE_NAME, null, SQLiteDatabase.OPEN_READWRITE);
}
//method to list all details from table
public List<DatabaseModel> getAllUsers(int Position) {
List<DatabaseModel> contactList = new ArrayList<DatabaseModel>();
String whatStation = C.whatStation;
String whatLine = C.whatLine;
String selectQuery = null;
switch (Position){
case 0:
selectQuery = "SELECT " + Time + " FROM " + TABLE_NAME + " WHERE " + Station + " LIKE '%" + whatStation + "%' AND " + Line + " LIKE '%B%' AND " + Day +" LIKE '%" + C.whatDay +"%'" ;
break;
case 1:
selectQuery = "SELECT " + Time + " FROM " + TABLE_NAME + " WHERE " + Station + " LIKE '%" + whatStation + "%' AND " + Line + " LIKE '%A%' AND " + Day +" LIKE '%" + C.whatDay +"%'" ;
break;
}
;//retrieve data from the database
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
cursor.moveToFirst();
if (cursor.getCount() > 0) {
do {
DatabaseModel m = new DatabaseModel();
// m.setStation(cursor.getString(0));
m.setTime(cursor.getString(cursor.getColumnIndex(Time)));
// m.setLine(cursor.getString(2));
contactList.add(m);
} while (cursor.moveToNext());
}
cursor.close();
return contactList;
}
}
这是我的dataAdapter：
public class DataAdapter extends RecyclerView.Adapter<DataAdapter.MyViewHolder> {
List<DatabaseModel> Times;
public DataAdapter(List<DatabaseModel> times) {
Times = times;
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater .from(parent.getContext()).inflate(R.layout.time_view_row,parent,false);
return new MyViewHolder((view));
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
holder.textViewCell_time.setText(Times.get(position).getTime());
}
@Override
public int getItemCount() {
return Times.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
TextViewCell textViewCell_time;
public MyViewHolder(@NonNull View itemView) {
super(itemView);
textViewCell_time = itemView.findViewById(R.id.textView);
}
}
}
我应该怎么做才能正常工作？ 谢谢。
答案 0 :(得分：1)
阿里
根据您的代码：
public void list(){
ArrayList<DatabaseModel> LineList = new ArrayList<>();
LineList.clear();
mAdapter = new DataAdapter(LineList);
DatabaseHelper db = new DatabaseHelper(getContext());
final List<DatabaseModel> m = db.getAllUsers(Position);
if (m.size() > 0) {
for (int i = 0; i < m.size(); i++) {
LineList.add(m.get(i));
mAdapter.notifyDataSetChanged();
}
}
db.close();
}
public void showInRecyclerView(){
databaseHelper = new DatabaseHelper(getContext());
Times = databaseHelper.getAllUsers(Position);
mRecyclerView = mView.findViewById(R.id.myRecycler);
mAdapter = new DataAdapter(Times); //LINE 1
mRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
mRecyclerView.setAdapter(mAdapter);
}
在OnActivityCreated（）中，您调用了list（）；在onCreate（）中，您调用了showInRecyclerView（），而这两个函数都是您适配器的不同对象。所以，我认为，您的list（）对象被showInRecyclerView（）覆盖，这就是为什么看起来mAdapter.notifyDataSetChanged（）;的原因。不管用。 根据需要更改代码。
阿里， 将您的代码更改为：
public void list(){
ArrayList<DatabaseModel> LineList = new ArrayList<>();
LineList.clear();
DatabaseHelper db = new DatabaseHelper(getContext());
final List<DatabaseModel> m = db.getAllUsers(Position);
if (m.size() > 0) {
for (int i = 0; i < m.size(); i++) {
LineList.add(m.get(i));
}
}
db.close();
}