我是安卓工作室开发的新手，大部分都是直接开发的。这些概念似乎是相当新的，谷歌的文档要么写得很差，要么让我非常困惑。即使在这里看其他问题也不足以为我澄清这一点。
到目前为止，在我的应用程序中，用户要么注册，要么登录，用户的角色会被保存到数据库中，或者从数据库中检索到。在当前状态下，登录和注册与数据库一起工作，插入和检索它们的字符会相应地更新UI。
我有一些片段改变了角色的统计数据，并且在使用ViewModel对角色使用观察者进行更改后，UI不会得到更新。此外，数据库也不会随更改而更新。
我可能错过了一些简单的事情来让它发挥作用。请让我知道我应该对当前代码进行的任何更改，以及今后的任何建议。
我尝试做的主要目标是将字符更改保存到数据库中，并使用新的更改更新UI。
编辑：我已经从数据库中删除了回调逻辑，重构了一些Dao查询，并相应地更新了repo和viewmodel，并添加了findById查询。我已经使用我的字符类将数据绑定添加到我的home片段的xml中。
我的数据库：
@Database(entities = {Character.class}, version = 1)
public abstract class MyDatabase extends RoomDatabase {
public abstract UserDao userDao();
private static MyDatabase INSTANCE;
public static MyDatabase getDatabase(final Context context) {
if (INSTANCE == null) {
synchronized (MyDatabase.class) {
if (INSTANCE == null) {
INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
MyDatabase.class, "character_database")
.build();
}
}
}
return INSTANCE;
}
}
我的DAO:
@Dao //Data Access Object
public interface UserDao {
@Query("SELECT * FROM character_table")
LiveData<List<Character>> getAllCharacters();
@Query("SELECT * FROM character_table WHERE email LIKE :email LIMIT 1")
LiveData<Character> findByEmail(String email);
@Query("SELECT * FROM character_table WHERE name")
LiveData<List<Character>> sortByName();
@Query("SELECT * FROM character_table WHERE id LIKE :id LIMIT 1")
LiveData<Character> findById(int id);
@Query("SELECT * FROM character_table WHERE rank")
LiveData<List<Character>> sortByRank();
@Query("SELECT * FROM character_table WHERE total_exp")
LiveData<List<Character>> sortByExp();
@Query("SELECT * FROM character_table WHERE village")
LiveData<List<Character>> sortByVillage();
@Query("SELECT * FROM character_table WHERE email LIKE :email AND password LIKE :password")
LiveData<Character> login(String email, String password);
@Delete
void deleteCharacter(Character player);
@Query("DELETE FROM character_table")
void deleteAll();
@Insert(onConflict = OnConflictStrategy.REPLACE)
void save(Character player);
@Update
void update(Character player);
我的存储库：EDIT：我添加了要更新和删除的异步任务。
public class CharacterRepository {
private final UserDao userDao;
private LiveData<List<Character>> allCharacters;
private LiveData<List<Character>> sortByName;
private LiveData<List<Character>> sortByExp;
private LiveData<List<Character>> sortByRank;
private LiveData<List<Character>> sortByVillage;
CharacterRepository(Application application){
MyDatabase db = MyDatabase.getDatabase(application);
userDao = db.userDao();
allCharacters = userDao.getAllCharacters();
sortByName = userDao.sortByName();
sortByExp = userDao.sortByExp();
sortByRank = userDao.sortByRank();
sortByVillage = userDao.sortByVillage();
}
public LiveData<Character> login(String email, String password){
return userDao.login(email, password);
}
LiveData<List<Character>> sortByName(){
return sortByName;
}
LiveData<Character> findByEmail(String email){
return userDao.findByEmail(email);
}
LiveData<List<Character>> sortByName(){
return sortByName;
}
LiveData<List<Character>> sortByExp(){
return sortByExp;
}
LiveData<List<Character>> sortByRank(){
return sortByRank;
}
LiveData<List<Character>> sortByVillage(){
return sortByVillage;
}
LiveData<List<Character>> getAll(){
return allCharacters;
}
public void insert(Character player){
new insertAsyncTask(userDao).execute(player);
}
public void update(Character player){
new updateAsyncTask(userDao).execute(player);
}
public void delete(Character player){
new deleteAsyncTask(userDao).execute(player);
}
public LiveData<Character> getPlayer(String id){
return userDao.findByEmail(id);
}
private static class insertAsyncTask extends AsyncTask<Character, Void, Void> {
private UserDao mAsyncTaskDao;
insertAsyncTask(UserDao dao) {
mAsyncTaskDao = dao;
}
@Override
protected Void doInBackground(Character... characters) {
mAsyncTaskDao.save(characters[0]);
return null;
}
}
private static class updateAsyncTask extends AsyncTask<Character, Void, Void> {
private UserDao mAsyncTaskDao;
updateAsyncTask(UserDao dao) {
mAsyncTaskDao = dao;
}
@Override
protected Void doInBackground(Character... characters) {
mAsyncTaskDao.update(characters[0]);
return null;
}
}
private static class deleteAsyncTask extends AsyncTask<Character, Void, Void> {
private UserDao mAsyncTaskDao;
deleteAsyncTask(UserDao dao) {
mAsyncTaskDao = dao;
}
@Override
protected Void doInBackground(Character... characters) {
mAsyncTaskDao.deleteCharacter(characters[0]);
return null;
}
}
}
我的ViewModel:EDIT:getPlayer是通过id而不是电子邮件找到的。
public class MyViewModel extends AndroidViewModel {
private CharacterRepository cRepository;
private LiveData<List<Character>> allCharacters;
public MyViewModel(Application application){
super(application);
cRepository = new CharacterRepository(application);
allCharacters = cRepository.getAll();
}
LiveData<List<Character>> getAllCharacters() {return allCharacters;}
public void insert(Character player){
cRepository.insert(player);
}
public void deletePlayer(Character player){
cRepository.delete(player);
}
public void updatePlayer(Character player){
cRepository.update(player);
}
public LiveData<Character> getPlayer(int id){
return cRepository.getPlayer(id);
}
public LiveData<Character> findByEmail(String email){
return cRepository.findByEmail(email);
}
public LiveData<Character> login(String email, String password){
return cRepository.login(email, password);
}
}
这段代码是我添加了数据绑定的主页片段：EDIT：使用getArguments从我的活动中获取Id，称为binding。onChanged((中的setPlayer(播放器(使一切正常工作，更新数据库和UI。在我为玩家设置了一些东西之后，我更新了玩家
private MyViewModel viewModel;
private FragmentHomeBinding binding;
private View rootView;
private Character player;
private int id;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater,
@Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
binding = DataBindingUtil.inflate(inflater, R.layout.fragment_home, container, false);
rootView = binding.getRoot();
viewModel = ViewModelProviders.of(this).get(MyViewModel.class);
id = getArguments().getInt("id");
return rootView;
}
@Override
public void onStart() {
super.onStart();
// Home fragment buttons.
final Button sleepButton = getView().findViewById(R.id.sleepButton);
final Button bankButton = getView().findViewById(R.id.bankButton);
final Button infoButton = getView().findViewById(R.id.infoButton);
// The view that shows the players pool ratio.
info = getView().findViewById(R.id.poolAmount);
layout = getView().findViewById(R.id.poolInfo);
// The players status bars.
healthBar = getView().findViewById(R.id.healthBar);
chakraBar = getView().findViewById(R.id.chakraBar);
staminaBar = getView().findViewById(R.id.staminaBar);
//Observe LiveData Character.
viewModel.getPlayer(id).observe(this, new Observer<Character>() {
@Override
public void onChanged(@Nullable final Character character) {
player = character;
player.setRank(updateRank());
binding.setPlayer(player);
//Setting the progress and max for each user pool.
healthBar.setProgress((int)player.getHealth());
healthBar.setMax((int)player.getHealthMax());
chakraBar.setProgress((int)player.getChakra());
chakraBar.setMax((int)player.getChakraMax());
staminaBar.setProgress((int)player.getStamina());
staminaBar.setMax((int)player.getStaminaMax());
}
});
sleepButton.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
if (player.isAwake()) {
player.setAwake(false);
sleepButton.setText("Wake Up");
Toast.makeText(getContext(), "You went to sleep...", Toast.LENGTH_SHORT).show();
} else {
player.setAwake(true);
sleepButton.setText("Sleep");
Toast.makeText(getContext(), "You woke up!", Toast.LENGTH_SHORT).show();
}
}
});
bankButton.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
final AlertDialog.Builder builder = new AlertDialog.Builder(getContext());
final View bankPrompt = getLayoutInflater().inflate(R.layout.bank_prompt, null);
builder.setView(bankPrompt);
final AlertDialog dialog = builder.create();
dialog.show();
TextView bankMoney = bankPrompt.findViewById(R.id.bankAmount);
TextView pocketMoney = bankPrompt.findViewById(R.id.pocketAmount);
Button depositButton = bankPrompt.findViewById(R.id.depositButton);
Button withdrawButton = bankPrompt.findViewById(R.id.withdrawButton);
ImageButton closeBankPrompt = bankPrompt.findViewById(R.id.closeBank);
pocketMoney.setText(String.valueOf(player.getPocketMoney()));
bankMoney.setText(String.valueOf(player.getBankMoney()));
depositButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final View transactionPrompt = getLayoutInflater()
.inflate(R.layout.bank_transaction, null);
builder.setView(transactionPrompt);
TextView transactionText = transactionPrompt.findViewById(R.id.bankTransactionText);
transactionText.setText(R.string.bank_deposit);
final AlertDialog dialog = builder.create();
dialog.show();
Button confirmDeposit = transactionPrompt.findViewById(R.id.confirmTransaction);
ImageButton closePrompt = transactionPrompt.findViewById(R.id.cancelTransaction);
confirmDeposit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
bankTransaction(player,0, transactionPrompt, bankPrompt);
dialog.hide();
}
});
closePrompt.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.hide();
}
});
}
});
withdrawButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final View transactionPrompt = getLayoutInflater()
.inflate(R.layout.bank_transaction, null);
builder.setView(transactionPrompt);
TextView transactionText = transactionPrompt.findViewById(R.id.bankTransactionText);
transactionText.setText(R.string.bank_withdraw);
final AlertDialog dialog = builder.create();
dialog.show();
Button confirmWithdraw = transactionPrompt.findViewById(R.id.confirmTransaction);
ImageButton closePrompt = transactionPrompt.findViewById(R.id.cancelTransaction);
confirmWithdraw.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
bankTransaction(player,1, transactionPrompt, bankPrompt);
dialog.hide();
}
});
closePrompt.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.hide();
}
});
}
});
closeBankPrompt.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.hide();
}
});
}
});
infoButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ScrollView info = getView().findViewById(R.id.infoView);
if (info.getVisibility() == View.VISIBLE)
info.setVisibility(View.GONE);
else
info.setVisibility(View.VISIBLE);
}
});
}
在我的第二个片段中，我有相同的观察线，具有与此类似的动作。它们运行正常，只是用户界面在第一次之后没有更新。我觉得我对观察者以及它应该如何被称为观察者有错误的看法。编辑：我现在在我的第二个片段中也做了同样的事情，它也起作用了。
我现在已经了解了它的工作原理，并将相应地更新代码。也许有人会觉得它有用。