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How do I delay Android Room loading until after activity and prompts complete?

Problem: I'm receiving a null database name error. The Android Room database calls in my MainActiity.class proceed to execute though there is a prompt to let the user choose the database name.
What I'm trying to do: I'm still learning Android, but I'm trying to work out in a separate app, the use of a master Room database to manage the use of multiple Room databases used by the app (this is a sandbox type of app to play with this idea). This database management functionality is working well but things are hard coded. So, I'm at the step where I'm wanting the user to have the ability, through the use of sharedPreferences and a custom alert prompts, to have the option to create at install the first room database name and add others thereafter. The option to add them later is not an issue as something will be loaded. However, on the intial app launch, I would like the user to have the option to create and name the first DB rather than a default be created -- which is not really that big a deal, but why have a potential default DB the user never uses. I could even develop a method of renaming, which I will, but it seems to make sense to allow the user to do this.
What I have tried: I've tried to create some methods to encapsulate and separate out the DB calls from the prompts, but the code still blows through to the DB code. I did some searching on delaying Room but couldn't find anything specific to it. I'm open to the wisdom of others.
Code again, this is just one activity since I'm playing with the idea... and learning at the same time.
public class MainActivity extends AppCompatActivity {
private static final String TAG = "DB_INFO";
SharedPreferences sharedPreferences;
SharedPreferences.Editor settings;
String databaseName;
String prevDB;
Button button;
MasterDatabase masterDB;
List<MasterDatabaseList> mdbList;
ArrayList<BaseDatabase> bdbList = new ArrayList<>();
// Current Database
int currentBaseDBIndex = -1;
BaseDatabase currentDB = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = findViewById(R.id.button);
sharedPreferences = getSharedPreferences("AppSettings", MODE_PRIVATE);
settings = sharedPreferences.edit();
setupOnClickActions();
startChecks();
Toast.makeText(this, "database: " + databaseName + "\r\n" + "prevDB: " + prevDB, Toast.LENGTH_LONG).show();
}
private void startChecks(){
if(isFirstTime()) {
databaseName = PopupDialog.AlertInputBox(this, "Enter Research Project Name",
"Without spaces or special characters, enter a name for your research project.");
settings.putString("database", databaseName);
settings.commit();
settings.apply();
startDBs();
}else{
databaseName = PopupDialog.AlertInputBox(this, "Enter Research Project Name",
"Without spaces or special characters, enter a new or existing name for your research project.");
settings.putString("prevDB", sharedPreferences.getString("database", ""));
settings.putString("database", databaseName);
settings.commit();
settings.apply();
prevDB = sharedPreferences.getString("prevDB", "");
startDBs();
}
}
private void startDBs(){
masterDB = MasterDatabase.getInstance(this);
mdbList = masterDB.getMasterDao().getAllDatabases();
// Add a DB if none exists
if(mdbList.size()<1){
addBaseDB("sample.db");
}
setCurrentIndexDBandDao(databaseName); /* Add some data to db1 IF it exists (it should) --------------------- */
if (currentBaseDBIndex > -1 && currentDB.getBaseDao().count() < 1) {
currentDB.getBaseDao().insert(new BaseTable("Added " + databaseName + " ... etc."));
}
/* Extract and Log Data for ALL the BaseDatabase databases i.e. db1 and db2 */
for(MasterDatabaseList masterdb: masterDB.getMasterDao().getAllDatabases()) {
Log.d(TAG,"Database is " + masterdb.getDatabaseName());
setCurrentIndexDBandDao(masterdb.getDatabaseName());
if (currentBaseDBIndex > -1) {
for(BaseTable bt: currentDB.getBaseDao().getAllBaseTables()) {
Log.d(TAG,"Extracted Base Table row where MyData is" + bt.getMydata());
}
}
}
}
// METHODS =========================================================================================================
// Attempt to clear and reset SharedPreferences to a user first execution
private void setupOnClickActions(){
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
settings.putBoolean("firstTime", false);
settings.clear();
settings.commit();
settings.apply();
}
});
}
/* Add a new Database
Note that it assumes that it will now be the current
so the current values are set */
private void addBaseDB(String baseDBName) {
masterDB.getMasterDao().insert(new MasterDatabaseList(baseDBName));
}
/* Build/ReBuild the 3 Lists according to the master database*/
private void buildBaseLists() {
bdbList.clear();
mdbList = masterDB.getMasterDao().getAllDatabases();
// Loop through the databases defined in the master database adding the database and dao to the respective lists
for (MasterDatabaseList masterDB: masterDB.getMasterDao().getAllDatabases()) {
BaseDatabase baseDB = BaseDatabase.getInstance(this, masterDB.getDatabaseName());
bdbList.add(baseDB);
}
}
/* Set the currentDB according to the database name*/
private void setCurrentIndexDBandDao(String baseDBName) {
currentBaseDBIndex = getListIndexByBaseDBName(baseDBName);
if(currentBaseDBIndex == -1) {
addBaseDB(baseDBName);
buildBaseLists();
currentBaseDBIndex = getListIndexByBaseDBName(baseDBName);
}
if (currentBaseDBIndex > -1) {
buildBaseLists();
}
currentDB = bdbList.get(currentBaseDBIndex);
}
/* Get the index according to the database name passed*/
private int getListIndexByBaseDBName(String baseDBName) {
if(mdbList==null)
mdbList = masterDB.getMasterDao().getAllDatabases();
int rv = -1; // default to not found
for(int i=0; i < mdbList.size();i++) {
if (mdbList.get(i).getDatabaseName().equals(baseDBName)) {
rv = i;
break;
}
}
return rv;
}
/* Output all rows from the BaseTable for data extracted by the BaseDaos getAllBaseTables */
private void logBaseData(List<BaseTable> baseTableList) {
Log.d(TAG,"Current Database Index is " + currentBaseDBIndex + " DB name is " + mdbList.get(currentBaseDBIndex).getDatabaseName());
for(BaseTable bt: baseTableList) {
Log.d(TAG,"\tMyData value is " + bt.getMydata());
}
}
private boolean isFirstTime(){
if (sharedPreferences.getBoolean("firstTime", true)) {
settings.putBoolean("firstTime", false);
settings.commit();
settings.apply();
return true;
} else {
return false;
}
}
}
The BaseDatabase - databaseName is where the error occurs because of the empty variable
#Database(
entities = {BaseTable.class},
version = 1
)
public abstract class BaseDatabase extends RoomDatabase {
public abstract BaseDao getBaseDao();
private static final int NUMBER_OF_THREADS = 4;
public static final ExecutorService databaseWriteExecutor =
Executors.newFixedThreadPool(NUMBER_OF_THREADS);
public static BaseDatabase getInstance(Context context, String databaseName) {
BaseDatabase instance = null;
if (databaseName != null) {
return Room.databaseBuilder(context, BaseDatabase.class, databaseName)
.allowMainThreadQueries()
.build();
}
return instance;
}
}

Here's an example with 2 activities. The first MainActivity that
displays a list of the available databases (none at first)
clicking on a database allows it to be selected (it is not accessed or created (if new))
allows a database to be added, by entering it's name in the EditText, to the available databases (it is not created or accessed).
allows a second activity to be passed the database name where the activity can then open the database (creating it if it doesn't exist).
note that the database isn't accessed.
So first the MasterDatabaseList class (entity) :-
#Entity(tableName = MasterDatabaseList.TABLE_NAME,
indices = { #Index(value = MasterDatabaseList.COL_DATABASE_NAME, unique = true)
}
)
class MasterDatabaseList {
public static final String TABLE_NAME = "masterdatabaselist";
public static final String COl_ID = "id";
public static final String COL_DATABASE_NAME = "databasename";
public static final String[] ALL_COLUMNS = new String[]{
COl_ID, COL_DATABASE_NAME
};
#PrimaryKey
#ColumnInfo(name = COl_ID)
Long id;
#ColumnInfo(name = COL_DATABASE_NAME)
String databaseName;
public MasterDatabaseList() {}
#Ignore
public MasterDatabaseList(String databaseName) {
this.databaseName = databaseName;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getDatabaseName() {
return databaseName;
}
public void setDatabaseName(String databaseName) {
this.databaseName = databaseName;
}
}
similar to previous answer (but note some added constants)
MasterDatabaseDao
#Dao
abstract class MasterDao {
#Insert(onConflict = OnConflictStrategy.IGNORE)
abstract long insert(MasterDatabaseList masterDatabaseList);
#Query("SELECT * FROM masterdatabaselist")
abstract List<MasterDatabaseList> getAllDatabases();
Cursor getAllDatabasesAsCursor() {
MatrixCursor matrixCursor = new MatrixCursor(
new String[]{
BaseColumns._ID, /* Cursor Adapter must use _id column for id) */
MasterDatabaseList.COL_DATABASE_NAME
},
0
);
for(MasterDatabaseList m: getAllDatabases()) {
matrixCursor.addRow(new Object[]{m.id,m.databaseName});
}
return matrixCursor;
}
}
Note the new method that gets the list of available databases as a Cursor (for the ListView)
MasterDatabase
#Database(
entities = {MasterDatabaseList.class},
version = 1
)
abstract class MasterDatabase extends RoomDatabase {
abstract MasterDao getMasterDao();
static volatile MasterDatabase instance = null;
public static MasterDatabase getInstance(Context context) {
if (instance == null) {
instance = Room.databaseBuilder(context,MasterDatabase.class,"master.db")
.allowMainThreadQueries()
.build();
}
return instance;
}
}
unchanged from previous answer
2nd Activity UseSelectedDatabase
public class UseSelectedDatabase extends AppCompatActivity {
public static final String INTENT_EXTRA_DATABASEID = "database_id";
public static final String INTENT_EXTRA_DATABASENAME = "database_name";
long mDatabaseId;
String mDatabaseName;
TextView mDatabaseBeingUsed;
Button mDoneButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_use_selected_database);
mDatabaseBeingUsed = this.findViewById(R.id.database_name);
mDoneButton = this.findViewById(R.id.done);
mDatabaseId = this.getIntent().getLongExtra(INTENT_EXTRA_DATABASEID,-1);
mDatabaseName = this.getIntent().getStringExtra(INTENT_EXTRA_DATABASENAME);
mDatabaseBeingUsed.setText(mDatabaseName);
setDoneButton();
/*
can now get an instance of the database
*/
}
private void setDoneButton() {
mDoneButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
finish();
}
});
}
}
This doesn't access the database but just receives the database name and id in the master database. i.e. just shows that you can pass all the information required to access the database.
2nd Activities layout activity_use_selected_database.xml :-
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".UseSelectedDatabase">
<TextView
android:id="#+id/database_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="No Database Set?"
>
</TextView>
<Button
android:id="#+id/done"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="DONE">
</Button>
</LinearLayout>
Initial Activity MainActivity :-
public class MainActivity extends AppCompatActivity {
MasterDatabase mMasterDB;
MasterDao mMasterDBDao;
EditText mDBToAdd;
Button mAddDB,mUseSelectedDatabase;
ListView mDatabaseList;
SimpleCursorAdapter mSCA;
Cursor mCsr;
long mSelectedDatabaseId = 0;
String mSelectedDatabaseName = "";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mDBToAdd = this.findViewById(R.id.database_name);
mAddDB = this.findViewById(R.id.addDatabase);
mUseSelectedDatabase = this.findViewById(R.id.useSelectedDatabase);
mDatabaseList = this.findViewById(R.id.database_list);
mMasterDB = MasterDatabase.getInstance(this);
mMasterDBDao = mMasterDB.getMasterDao();
setUpAddDBButton();
setUpUseSelectedDatabaseButton();
setOrRefreshDatabaseList();
}
private void setUpAddDBButton() {
mAddDB.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (mDBToAdd.getText().toString().length() > 0) {
if (mMasterDBDao.insert(new MasterDatabaseList(mDBToAdd.getText().toString())) > 0) {
mDBToAdd.setText("");
setOrRefreshDatabaseList();
}
}
}
});
}
private void setUpUseSelectedDatabaseButton() {
mUseSelectedDatabase.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (mSelectedDatabaseId > 0) {
Intent intent = new Intent(view.getContext(),UseSelectedDatabase.class);
intent.putExtra(UseSelectedDatabase.INTENT_EXTRA_DATABASEID, mSelectedDatabaseId);
intent.putExtra(UseSelectedDatabase.INTENT_EXTRA_DATABASENAME,mSelectedDatabaseName);
startActivity(intent);
}
}
});
}
private void setOrRefreshDatabaseList() {
mCsr = mMasterDBDao.getAllDatabasesAsCursor();
if (mSCA == null) {
mSCA = new SimpleCursorAdapter(
this.getApplicationContext(),
android.R.layout.simple_list_item_1,
mCsr,
new String[]{MasterDatabaseList.COL_DATABASE_NAME},
new int[]{android.R.id.text1},
0
);
mDatabaseList.setAdapter(mSCA);
mDatabaseList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
/* Handle Clicking on an Item (i.e. prepare UseSelected Button) */
#SuppressLint("Range")
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
mSelectedDatabaseId = l;
if (l > 0) {
mSelectedDatabaseName = mCsr.getString(mCsr.getColumnIndex(MasterDatabaseList.COL_DATABASE_NAME));
mUseSelectedDatabase.setText(mSelectedDatabaseName);
mUseSelectedDatabase.setClickable(true);
} else {
mUseSelectedDatabase.setText("NO DATEBASE SELECTED");
mUseSelectedDatabase.setClickable(false);
}
}
});
} else {
mSCA.swapCursor(mCsr);
}
}
#Override
protected void onResume() {
super.onResume();
setOrRefreshDatabaseList();
}
#Override
protected void onDestroy() {
super.onDestroy();
mCsr.close();
}
}
Initial Activity's layout activity_main.xml :-
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!" />
<EditText
android:id="#+id/database_name"
android:layout_width="500dp"
android:layout_height="wrap_content"
android:text="">
</EditText>
<Button
android:id="#+id/addDatabase"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Add Database"
>
</Button>
<ListView
android:id="#+id/database_list"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</ListView>
<Button
android:id="#+id/useSelectedDatabase"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="NO SELECTED DATABASE"
android:clickable="false"
>
</Button>
</LinearLayout>
Demo
When first run MainActivity displays :-
i.e. no available databases (clicking buttons does nothing).
Database Test001 entered into Edit Text and then Add Database clicked :-
at this stage the Test001 database has not been created. However the MasterDatabase has been created and the Test001 row has been added (i.e. at some time the database could be opened and created if it doesn't already exist) :-
Test001 is clicked :-
The Use Selected button has been changed to Test001 (perhaps should be Use Test001).
Still the Test001 database hasn't been accessed at all, as there is no need.
Database Test002 is entered into the Edit Text (cleared after adding) and Add Database is clicked :-
Note if an existing database is entered into the Edit Text it will NOT be added and the Text Box will not be cleared.
Test002 is clicked, the button changes to Test002 and the button is clicked, starting the 2nd activity :-
The database isn't opened or accessed (i.e. further demonstrating waiting and doing things)
The DONE button is clicked returning to the first activity. Still the database has not been opened/accessed BUT with the other code (Base???? clases etc) could be (probably in the UseSelectedDatabase activity).
Extra As proof of concept the the BaseTable??? classes from the previous question were added, as were some new User??? classes with BaseDatabase being :-
#Database(
entities = {BaseTable.class,User.class},
version = 1
)
abstract class BaseDatabase extends RoomDatabase {
abstract BaseDao getBaseDao();
abstract UserDao getUserDao();
public static BaseDatabase getInstance(Context context, String databaseName) {
BaseDatabase db = Room.databaseBuilder(context, BaseDatabase.class, databaseName)
.allowMainThreadQueries()
.build();
db.getOpenHelper().getWritableDatabase();
return db;
}
}
With the following added to the UseSelectedDatabase activity:-
....
/*
can now get an instance of the database
*/
db = BaseDatabase.getInstance(this,mDatabaseName);
baseDao = db.getBaseDao();
userDao = db.getUserDao();
baseDao.insert(new BaseTable("X"));
userDao.insert(new User("Snowman","Fred","Wlibur","Bloggs","password",0));
List<BaseTable> baseTableList = baseDao.getAllBaseTables();
List<User> userList = userDao.getAllUsers();
Restarting the App selecting Test001 and then Test002 results in the database being shown as :-
i.e. Test001, albeit it closed, has obviously been created as has Test002.

Need Help Refreshing my database ListView in my app

My app layout apparently isn't a normal layout so I a having trouble setting my List Adapter to auto updated when an edit is made.
I make my edits to my database in this Java File which is controlled in its own activity and layout.
public void onClick(View view){
if (view == findViewById(R.id.addsave)) {
RecipeRepo repo = new RecipeRepo(this);
Recipe recipe = new Recipe();
if (editTextName.getText().toString().equals("")) {
editTextName.setError("Recipe name required!");
return;
} else {
recipe.name = editTextName.getText().toString();
}
if (textImagePath.getText().toString().equals("") ) {
recipe.image = ("");
}else{
recipe.image = textImagePath.getText().toString();
}
recipe.category = staticSpinner.getSelectedItem().toString();
if (editTextIngredients.getText().toString().equals("")) {
editTextIngredients.setError("Ingredient required!");
return;
} else {
recipe.ingredients = editTextIngredients.getText().toString();
}
if (editTextInstruct.getText().toString().equals("")) {
editTextIngredients.setError("Instruction required!");
return;
} else {
recipe.instructions = editTextInstruct.getText().toString();
}
recipe.cooktemp = editTextCookTemp.getText().toString();
recipe.cooktime = editTextCookTime.getText().toString();
recipe.serves = editTextServings.getText().toString();
recipe.recipe_Id = _Recipe_Id;
if (_Recipe_Id == 0) {
_Recipe_Id = repo.insert(recipe);
Toast.makeText(this, "New Recipe Added", Toast.LENGTH_SHORT).show();
finish();
it actually inserts and updates in this java file
int insert(Recipe recipe){
//Open connection to write data
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(Recipe.KEY_SERVES, recipe.serves);
values.put(Recipe.KEY_COOKTIME, recipe.cooktime);
values.put(Recipe.KEY_COOKTEMP, recipe.cooktemp);
values.put(Recipe.KEY_INSTRUCT, recipe.instructions);
values.put(Recipe.KEY_INGREDIENTS, recipe.ingredients);
values.put(Recipe.KEY_CATEGORY, recipe.category);
values.put(Recipe.KEY_IMAGE, recipe.image);
values.put(Recipe.KEY_NAME, recipe.name);
//Inserting Row
long recipe_Id = db.insert(Recipe.TABLE, null, values);
db.close();// Closing database connection
return (int) recipe_Id;
}
void delete(int recipe_Id){
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.delete(Recipe.TABLE, Recipe.KEY_ID + "=?", new String[] {String.valueOf(recipe_Id)});
db.close();
}
void update(Recipe recipe){
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(Recipe.KEY_SERVES, recipe.serves);
values.put(Recipe.KEY_COOKTIME, recipe.cooktime);
values.put(Recipe.KEY_COOKTEMP, recipe.cooktemp);
values.put(Recipe.KEY_INSTRUCT, recipe.instructions);
values.put(Recipe.KEY_INGREDIENTS, recipe.ingredients);
values.put(Recipe.KEY_CATEGORY, recipe.category);
values.put(Recipe.KEY_IMAGE, recipe.image);
values.put(Recipe.KEY_NAME, recipe.name);
db.update(Recipe.TABLE, values, Recipe.KEY_ID + "=?", new String[]{String.valueOf(recipe.recipe_Id)});
db.close();
}
and lastly it gets put into the list view from this Java file and separate layout. Which is where my adapters are but i cannot get the notifyDataSetChanged() to work here at all... as in it wont even come up.
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
RecipeRepo repo = new RecipeRepo(this);
if (id == R.id.nav_meat) {
final ArrayList<HashMap<String, String>> recipeList = repo.getRecipeMeat();
if(recipeList.size()!=0) {
ListView lv = (ListView) findViewById(R.id.list);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
recipe_Id = (TextView) view.findViewById(R.id.recipe_Id);
String recipeId = recipe_Id.getText().toString();
Intent objIndent = new Intent(getApplicationContext(), RecipeDetail.class);
objIndent.putExtra("recipe_Id", Integer.parseInt(recipeId));
startActivity(objIndent);
}
});
ListAdapter adapter = new SimpleAdapter(SousChef.this, recipeList, R.layout.view_recipe_entry, new String[]{"id", "category", "name"}, new int[]{R.id.recipe_Id, R.id.recipe_list_category, R.id.recipe_list_name});
lv.setAdapter(adapter);
}else {
Toast.makeText(this, "No recipe!", Toast.LENGTH_SHORT).show();
}
} else if (id == R.id.nav_veg) {
final ArrayList<HashMap<String, String>> recipeList = repo.getRecipeVeg();
if(recipeList.size()!=0) {
ListView lv = (ListView) findViewById(R.id.list);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
recipe_Id = (TextView) view.findViewById(R.id.recipe_Id);
String recipeId = recipe_Id.getText().toString();
Intent objIndent = new Intent(getApplicationContext(), RecipeDetail.class);
objIndent.putExtra("recipe_Id", Integer.parseInt(recipeId));
startActivity(objIndent);
}
});
ListAdapter adapter = new SimpleAdapter(SousChef.this, recipeList, R.layout.view_recipe_entry, new String[]{"id", "category", "name"}, new int[]{R.id.recipe_Id, R.id.recipe_list_category, R.id.recipe_list_name});
lv.setAdapter(adapter);
}else {
Toast.makeText(this, "No recipe!", Toast.LENGTH_SHORT).show();
}
So any advise on setting this up to automatically update would be a huge help. I have been racking my brain over this for a couple days now looking at different examples and what not, but no setup is quite like this one which doesnt allow me to have everything in one file.
And thank you in advance.
category picking image:
Category picking Image

There are for sure more answers but this is one that might help,
Quick Example for the proposed solution
SHORT EXPLANATION
inside MainActivity
//create a public static adapter
public static ListAdapter adapter
inside onCreateView()
//Create your adapter and set it to the right ListView
ListView lv = findViewById(R.id.listView_in_xml);
adapter = new SimpleAdapter(...)
lv.setAdapter(adapter)
inside CustomAdapter which in your case I assume is SimpleAdapter
//add a public method to be called so that the Adapter updates and displays the new data
public void updateMethod(){
//update your List<Recipe> that I would guess you have calling the database again
//if needed update your getCount() return value so that it returns the number of childs in your ListView which most of the cases is just the List<Recipe>.size()
//notifyDataSetChanged()
}
inside your DB HANDLER CLASS
//in every update, add, delete or any method that requires the ListView to Update just call the created method,
MainActivity.CustomAdapter.updateMethod();
PROBLEMS
You will have to make sure the public static adapter has been initialized and is not null, or simply check whether the adapter is not null and update, because if the adapter is null that activity has not launched yet thus no need to trigger the updateMethod().
OTHER SOLUTIONS
Instead of creating a public static adapter create a public static boolean, then whenever data changes set that boolean to true from the database.
Finally, whenever you resume your activity check against that boolean and update your ListViewAdapter if needed.
MORE COMPLICATED SOLUTIONS WHICH I KNOW WORK CAUSE I USE IT
Use TaskAsyncTaskLoader which utilizes a Loader in your MainActivity and implements LoaderManager.LoaderCallbacks.
Optionally, you can make the Loader be, public static Loaderand inside your DBHandler you trigger the loader to load the data again or use any other logic you want.
Proofs of Working suggested solution,

You can Broadcast Intent from the change database file after you get the response in the onCreate() of adapter loading class
Intent intent = new Intent("key_to_identify_the_broadcast");
Bundle bundle = new Bundle();
bundle.putString("edttext", "changed");
intent.putExtra("bundle_key_for_intent", bundle);
context.sendBroadcast(intent);
and then you can receive the bundle in your fragment by using the BroadcastReceiver class
private final BroadcastReceiver mHandleMessageReceiver = new
BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
Bundle bundle =
intent.getExtras().getBundle("bundle_key_for_intent");
if(bundle!=null){
String edttext = bundle.getString("edttext");
}
//you can call any of your methods for using this bundle for your use case
}
};
in onCreate() of your adapter adding class you need to register the broadcast receiver first otherwise this broadcast receiver will not be triggered
IntentFilter filter = new IntentFilter("key_to_identify_the_broadcast");
getActivity().getApplicationContext().
registerReceiver(mHandleMessageReceiver, filter);
Finally you can unregister the receiver to avoid any exceptions
#Override
public void onDestroy() {
try {
getActivity().getApplicationContext().
unregisterReceiver(mHandleMessageReceiver);
} catch (Exception e) {
Log.e("UnRegister Error", "> " + e.getMessage());
}
super.onDestroy();
}

Customize intent in share button with splitting string or how to split string and replace odd commas

Description: I want to use share button. With share button user sending a list as a message. In the list each item has Title + Description
The problem: System get all items from a list and put it in the line one after another by using a comma.
I have: TitleItemOne,DescriptionItemOne,TitleItemTwo,DescriptionItemTwo
I need:
TitleItemOne - DescriptionItemOne
TitleItemTwo - DescriptionItemTwo
Or:
Maybe it is easier to replace all ODD comma "," with "-" so it will that style which i am looking for.
That's the code (needed code in Sharebutton method)
/**
* Displays list of list that were entered and stored in the app.
*/
public class CatalogActivity extends AppCompatActivity implements
LoaderManager.LoaderCallbacks<Cursor> {
private static final String TAG = "myLogs";
/** Identifier for the pet data loader */
private static final int LIST_LOADER = 0;
/** Adapter for the ListView */
ListCursorAdapter mCursorAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_catalog);
Log.v(TAG, "Зашли в catalog activity oncreate");
// Setup FAB to open EditorActivity
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(CatalogActivity.this, EditorActivity.class);
startActivity(intent);
}
});
// Find the ListView which will be populated with the list data
ListView listListView = (ListView) findViewById(R.id.list);
// Find and set empty view on the ListView, so that it only shows when the list has 0 items.
View emptyView = findViewById(R.id.empty_view);
listListView.setEmptyView(emptyView);
// Setup an Adapter to create a list item for each row of list data in the Cursor.
// There is no items data yet (until the loader finishes) so pass in null for the Cursor.
mCursorAdapter = new ListCursorAdapter(this, null);
listListView.setAdapter(mCursorAdapter);
// Setup the item click listener
listListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
ShoppingListBdHelper helper = new ShoppingListBdHelper(view.getContext());
if (helper.setCompleted(id)) {
mCursorAdapter.setCompleted(view);
}
}
});
// Kick off the loader
getSupportLoaderManager().initLoader(LIST_LOADER, null, this);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu options from the res/menu/menu_catalog.xml file.
// This adds menu items to the app bar.
getMenuInflater().inflate(R.menu.menu_catalog, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// User clicked on a menu option in the app bar overflow menu
switch (item.getItemId()) {
// Respond to a click on the "Insert dummy data" menu option
case R.id.action_share_button:
shareButton(mCursorAdapter.getCursor());
return true;
// Respond to a click on the "Delete all entries" menu option
case R.id.action_delete_all_entries:
deleteAllItems();
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* Share button
*/
private void shareButton(Cursor cursor) {
Log.v(TAG, "--- WE ARE IN SHARE BUTTON METHOD ---");
List<String> test;
test = new ArrayList<String>();
cursor.moveToFirst();
while(!cursor.isAfterLast()) {
Log.d(TAG, "field: " + cursor.getString(cursor.getColumnIndex(ListContract.ListEntry.COLUMN_ITEM_NAME)));
test.add(cursor.getString(cursor.getColumnIndex(ListContract.ListEntry.COLUMN_ITEM_NAME))); //add the item
test.add(cursor.getString(cursor.getColumnIndex(ListContract.ListEntry.COLUMN_ITEM_DESCRIPTION))); //add the item
cursor.moveToNext();
}
cursor.moveToFirst();
Log.v(TAG, "--- OUR LIST INCLUDES: " + test.toString());
Intent myIntent = new Intent();
myIntent.setAction(Intent.ACTION_SEND);
myIntent.putStringArrayListExtra("test", (ArrayList<String>) test);
myIntent.putExtra(android.content.Intent.EXTRA_TEXT, test.toString());
Log.v(TAG, "--- INTENT EXTRAS ARE: " + myIntent.getExtras());
myIntent.setType("text/plain");
startActivity(Intent.createChooser(myIntent, "Share using"));
}
/**
* Helper method to delete all list in the database.
*/
private void deleteAllItems() {
Log.v(TAG, "Сработал метод удаления всех данных");
long rowsDeleted = getContentResolver().delete(ListContract.ListEntry.CONTENT_URI, null, null);
Log.v("CatalogActivity", rowsDeleted + " rows deleted from list database");
}
#Override
public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
Log.v(TAG, "Начал работать loader cursor");
// Define a projection that specifies the columns from the table we care about.
String[] projection = {
ListContract.ListEntry._ID,
ListContract.ListEntry.COLUMN_ITEM_NAME,
ListContract.ListEntry.COLUMN_ITEM_DESCRIPTION,
ListContract.ListEntry.COLUMN_ITEM_COMPLETED
};
// This loader will execute the ContentProvider's query method on a background thread
return new CursorLoader(this, // Parent activity context
ListContract.ListEntry.CONTENT_URI, // Provider content URI to query
projection, // Columns to include in the resulting Cursor
null, // No selection clause
null, // No selection arguments
null); // Default sort order
}
#Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
// Update {#link ListCursorAdapter} with this new cursor containing updated pet data
mCursorAdapter.swapCursor(data);
Log.v(TAG, "Cursor adapter загрузился");
}
#Override
public void onLoaderReset(Loader<Cursor> loader) {
// Callback called when the data needs to be deleted
mCursorAdapter.swapCursor(null);
}
}

you can format your strings to html or using "\n"
string to html :
you can use Html.fromHtml() to use HTML tag in your string :
Html.fromHtml("<h2>Title</h2><br><p>Description here</p>"));
for using "\n" you can use System.getProperty("line.separator") wich is OS dependent line separator

Change
test.add(cursor.getString(cursor.getColumnIndex(ListContract.ListEntry.COLUMN_ITEM_NAME))); //add the item test.add(cursor.getString(cursor.getColumnIndex(ListContract.ListEntry.COLUMN_ITEM_DESCRIPTION)));
To
test.add(cursor.getString(cursor.getColumnIndex(ListContract.ListEntry.COLUMN_ITEM_NAME)) + "-" + (cursor.getString(cursor.getColumnIndex(ListContract.ListEntry.COLUMN_ITEM_DESCRIPTION)));
Note:
I may not have all the parenthesis correctly closed, but you get the idea

Permanently save intent from other activity (with two values) to listview

I'm trying to save two values from an activity (where the user can put in two different values, one String value and one integer value) in the listview from another activity. In the first activity, it shows a list with a course and the amount of points for that course in one listview, like this:
Course: English
Points: 4
Now, the problem is, everytime I want to put in another value using the add_course_actitivty, it overwrites the previous value. I've looked at different solutions, like with sharedpreferences (Add items to listview from other activity), but this uses only one value and if I try to work with sharedpreferences, it overwrites the other value in the sharedpreferences, but I want users to add multiple courses and corresponding points. Also on restart, it deletes the values in the listview (I read to prevent this you need to store it in sharedpreferences, but this doesn't work the way I need it to be)
KeuzeActivity.class (shows the listview):
public class KeuzeActivity extends AppCompatActivity {
private FloatingActionButton fab_add;
private String student_naam;
private ListView keuze_list;
boolean wantDelete;
private ArrayAdapter adapter;
private String vak;
private int ec;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_keuze);
// setting title
student_naam = getIntent().getStringExtra("student");
setTitle("Keuzevakken en projecten van " + student_naam);
//initialzing elements
fab_add = (FloatingActionButton)findViewById(R.id.fab_add);
keuze_list = (ListView) findViewById(R.id.keuze_list);
//initializing list
final ArrayList<Course> courseItems = new ArrayList<Course>();
adapter = new ArrayAdapter<Course>(this, android.R.layout.simple_list_item_1, courseItems);
keuze_list.setAdapter(adapter);
// checks if intent has required values, put it in listview
if (getIntent().hasExtra("vak") && getIntent().hasExtra("ec")) {
vak = getIntent().getStringExtra("vak");
ec = getIntent().getIntExtra("ec", ec);
courseItems.add(new Course(vak, ec));
adapter.notifyDataSetChanged();
}
// make fab go to other activity
fab_add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(KeuzeActivity.this, add_course_activity.class));
}
});
// long press deletes item
keuze_list.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
#Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
showDeleteDialog();
if (wantDelete) {
courseItems.remove(position);
adapter.notifyDataSetChanged();
}
return true;
}
});
}
private void showDeleteDialog() {
AlertDialog.Builder infobuilder = new AlertDialog.Builder(this);
infobuilder.setCancelable(false);
infobuilder.setTitle("Vak/project verwijderen");
infobuilder.setMessage("Weet je zeker dat je het vak of project wilt verwijderen?");
final TextView text = new TextView(this);
// action when pressed OK
infobuilder.setPositiveButton("Ja", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
wantDelete = true;
dialog.cancel();
}
});
infobuilder.setNegativeButton("Nee", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
wantDelete = false;
dialog.cancel();
}
});
infobuilder.show();
}
}
add_course_activity.class (let's users input course and points)
public class add_course_activity extends AppCompatActivity {
private EditText course_edit;
private EditText ec_edit;
private Button save_btn;
private String student_name;
private int ec;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_course);
setTitle("Voeg vak of project toe");
final Context context = getApplicationContext();
// initializing elements
course_edit = (EditText) findViewById(R.id.edit_vak);
ec_edit = (EditText) findViewById(R.id.edit_ec);
save_btn = (Button) findViewById(R.id.save_button);
// action on savebutton
save_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (course_edit.getText().toString().trim().length() > 0 && ec_edit.getText().toString().trim().length() > 0 ) {
ec = Integer.parseInt(ec_edit.getText().toString());
Intent goBack = new Intent(add_course_activity.this, KeuzeActivity.class);
goBack.putExtra("vak", course_edit.getText().toString());
goBack.putExtra("ec", ec);
goBack.putExtra("student", PreferenceManager.getDefaultSharedPreferences(context).getString("student_name", student_name));
startActivity(goBack);
}
else {
Toast.makeText(context, "Voer juiste informatie in!", Toast.LENGTH_SHORT).show();
}
}
});
}
}
Course.java class (getters and setters + with toString method)
public class Course {
private String vak;
private int ec;
public Course(String vak, int ec) {
this.vak = vak;
this.ec = ec;
}
public String getVak() {
return vak;
}
public void setVak(String vak) {
this.vak = vak;
}
public int getEc() {
return ec;
}
public void setEc(int ec) {
this.ec = ec;
}
#Override
public String toString() {
return ("Vak: " + vak + "\n" + "Punten: " + ec);
}
}
Note that my code isn't clean or done, but to get further I need to fix this problem.

You have several way to do it. As other replies have suggested you can use an SQLLite database and add data to a course table and retrieve data from it.
If you find Db approach to complicated/heavy
You could also use SharedPreferences what you need to do is figure a way to store a string that represent a list of course. It is not the best way to approach it but it will work.
Lets say you choose to serialize your Course object with "vac-ec"
Then you just store a serialized list of course. Example "vac1-ec1,vac2-ec2"
When you need to add a course you juste grab the previous string split it to list, append the new course to the list and re-serialize the list to a string to encode it.
Other solution could be to use Realm.

You should used SQLiteDatabase and create a table with valid attributes and insert your new values into them

Okay, now things are clearer. As answered by #Dwijraj, when storing what potentially will be a large set of data, for maximum control it is best to use SQLite.
You can read more about the different Saving Data methods here:
https://developer.android.com/training/basics/data-storage/index.html
SharedPreferences are best used to store small amounts of information, like storing the settings of an application. [Mute] for example. Or a highscore in case of a game.
A Database is a better option when it comes to storing large pieces of data that you will potentially manipulate.
Your data structure can be something like this, Courses table containing Unique_ID , Course Name, Course Level, Course summary.
A table for English for example which will contain
Exams, Scores, Duration.
There are a lot of things you can do.

Try by storing the records in SQLite, and get it when you want to show.
By this, You can have a track of all added items. And you can show the items you want.

Android - Wanting to alternate icon images in a listview using cursorLoader

I have an application that displays a listView of contacts sorted by Last, then first names. Beside each contact is an image (icon). There are 3 kinds of contacts for which I'd like to display 3 different images (customers/suppliers/other) I have a default image now that is set to customer. I'm wondering if there's a way using the cusorLoader shown below to alternate images on the fly, or whether it would just be best to add a method involving a cursor in my onResume. (onResume is called each time I need to display the images). I believe simpleCursorAdapter can only take textViews as args, so if it's possible, maybe a compound textview/image would work. My icons are not stored in the database, just in the drawables.
Thanks in advance for any replies.
#Override
protected void onResume() {
super.onResume();
//Starts a new or restarts an existing Loader in this manager
getLoaderManager().restartLoader(0, null, this);
}
/*
* The fillData method binds the simpleCursorAadapter to the listView.
*/
private void fillData() {
String[] from = new String[] { ContactsDB.COLUMN_LAST_NAME, ContactsDB.COLUMN_FIRST_NAME };
//The XML views that the data will be bound to:
int[] to = new int[] {R.id.label2, R.id.label};
getLoaderManager().initLoader(0, null, this);
adapter = new SimpleCursorAdapter(this, R.layout.contact_row, null, from,
to, 0);
setListAdapter(adapter);
}
// Sort the names by last name, then by first name
String orderBy = ContactsDB.COLUMN_LAST_NAME + " COLLATE NOCASE ASC"
+ "," + ContactsDB.COLUMN_FIRST_NAME + " COLLATE NOCASE ASC" ;
// Creates a new loader after the initLoader () call
#Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
String[] projection = { ContactsDB.ROW_ID, ContactsDB.COLUMN_LAST_NAME, ContactsDB.COLUMN_FIRST_NAME };
CursorLoader cursorLoader = new CursorLoader(this,
SomeContentProvider.CONTENT_URI, projection, null, null, orderBy);
return cursorLoader;
}
#Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
// Swap the new cursor in.
// (The framework will take care of closing the old cursor once we return.)
adapter.swapCursor(data); //Call requires Min API 11
}
#Override
public void onLoaderReset(Loader<Cursor> loader) {
// This is called when the last Cursor provided to onLoadFinished()
// above is about to be closed.
// Data is no longer available, delete the reference
adapter.swapCursor(null);
}
}

Here is the code I use to dynamically show a drawable on a ListView, you have to use the function setViewBinder on your adapter:
mAdapter.setViewBinder(new ViewBinder() {
public boolean setViewValue(View aView, Cursor aCursor, int aColumnIndex) {
//Modification of the icon to display in the list
if (aColumnIndex == aCursor.getColumnIndex(DatabaseHandler.RATE_EMOTION)) {
int emotionID = aCursor.getInt(aColumnIndex);
Drawable emotionDrawable = resources.getDrawable(R.drawable.ic_unknown_rate);
//if emotion is set
if(emotionID > 0){
String emotionDrawablePath = "ic_smi" + emotionID;
int emotionDrawableID = resources.getIdentifier(emotionDrawablePath,"drawable", getPackageName());
//if a drawable is found
if(emotionDrawableID > 0){
emotionDrawable = resources.getDrawable(emotionDrawableID);
}
}
ImageView emotionImage = (ImageView) aView;
emotionImage.setImageDrawable(emotionDrawable);
return true;
}
return false;
}
});
You can see in this example that I change the drawable according to the data I get from the cursor for every row.