I created a ListView for which I implemented a custom adapter. Additionally I connected it to a SQLite database, which contains the content for the ListView.
I have one ListView with several items. Every item consists of a TextView and an ImageView which functions as a button. When the user clicks the ImageView, I want to delete the item from the database and automatically update the ListView.
Unluckily, I just know how to delete the item from the database. I can't think of a way to automatically update the ListView in my program, after the item got deleted from the database.
In the version below, I added an onItemClickListener for the ListView in the MainActivity - but it doesn't function for when the user clicks the ImageView (even though the ImageView is part of the ListView).
MainActivity
public class MainActivity extends AppCompatActivity {
//References to buttons and other controls on the layout
private Button btn_add;
private EditText et_todo;
private Switch sw;
private static ListView lv;
private static DataAdapter todoAdapter;
private DataBaseHelper dbHelper;
/**
* Initialization Method
*
* @param savedInstanceState
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new DataBaseHelper(MainActivity.this);
assignVariables();
registerClick();
showAllToDos(dbHelper);
}
private void assignVariables() {
//assign values to variables
btn_add = (Button) findViewById(R.id.btn_add);
et_todo = (EditText) findViewById(R.id.et_todo);
lv = (ListView) findViewById(R.id.lv);
}
public void showAllToDos(DataBaseHelper dbHelper) {
todoAdapter = new DataAdapter(MainActivity.this, R.layout.list_item, dbHelper.getAllAsList(), dbHelper);
lv.setAdapter(todoAdapter);
}
private void registerClick() {
btn_add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String toDoTitle = et_todo.getText().toString();
if(Pattern.matches("s*", toDoTitle)) {
Toast.makeText(MainActivity.this, "Title is missing", Toast.LENGTH_SHORT).show();
} else if(dbHelper.existsInDB(new DataModel(toDoTitle))) {
Toast.makeText(MainActivity.this, "Already added as ToDo", Toast.LENGTH_SHORT).show();
} else {
DataModel dModel = new DataModel(toDoTitle);
dbHelper.addOne(dModel);
showAllToDos(dbHelper);
}
//empty input field
et_todo.setText("");
}
});
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
DataModel clickedItem = (DataModel) adapterView.getItemAtPosition(position);
dbHelper.deleteOne(clickedItem);
showAllToDos(dbHelper);
}
});
}
}
DataModel
public class DataModel {
//Attributes
private int id;
private String title;
//Constructors
public DataModel(String title) {
this.title = title;
}
public DataModel() {
}
//toString
@Override
public String toString() {
return "DataModel{" +
"id=" + id +
", title='" + title + '\'' +
'}';
}
//Getters and Setters
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
DataAdapter
public class DataAdapter extends ArrayAdapter<DataModel> {
/**
* Attributes
*/
private Context mContext;
private int mResource;
private ArrayList<DataModel> mList;
private DataBaseHelper mDbHelper;
public DataAdapter(Context context, int resource, ArrayList<DataModel> list, DataBaseHelper dbHelper) {
super(context, resource, list);
mContext = context;
mResource = resource;
mList = list;
mDbHelper = dbHelper;
}
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
//get the objects information
String title = getItem(position).getTitle();
//create object with the information
DataModel model = new DataModel(title);
LayoutInflater inflater = LayoutInflater.from(mContext);
convertView = inflater.inflate(mResource, parent, false);
//get TextViews
TextView tvTitle = (TextView) convertView.findViewById(R.id.task);
//set information to TextViews
tvTitle.setText(title);
//delete function
ImageView delView = (ImageView) convertView.findViewById(R.id.delView);
delView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
mDbHelper.deleteOne(model);
}
});
return convertView;
}
}
DataBaseHelper
public class DataBaseHelper extends SQLiteOpenHelper {
public static final String TODO_TABLE = "TODO_TABLE";
public static final String COLUMN_ID = "ID";
public static final String COLUMN_TODO_TITLE = "TODO_TITLE";
private Context mContext;
public DataBaseHelper(@Nullable Context context) {
super(context, "todo.db", null, 1);
mContext = context;
}
/**
* Is called when the app requests or inputs new data.
*
* @param db
*/
@Override
public void onCreate(SQLiteDatabase db) {
String createTableStatement = "CREATE TABLE " + TODO_TABLE
+ " (" + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
+ COLUMN_TODO_TITLE + " TEXT)";
db.execSQL(createTableStatement);
//create new Table
}
/**
* Called whenever the database version number changes.
* Prevents the previous apps from crashing.
*
* @param sqLiteDatabase
* @param i
* @param i1
*/
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
}
/**
* method to add new database entry
*
* @param dModel
* @return
*/
public boolean addOne(DataModel dModel) {
SQLiteDatabase db = this.getWritableDatabase(); //for insert actions
ContentValues cv = new ContentValues(); //Content values stores data in pairs
cv.put(COLUMN_TODO_TITLE, dModel.getTitle());
long insert = db.insert(TODO_TABLE, null, cv);
//clean up, close connection to database and cursor
db.close();
if(insert == -1) { //if insert is negative number than insert went wrong
return false;
} else { //if insert is positive number than insert succeeded
return true;
}
}
public boolean deleteOne(DataModel dModel) {
//if DataModel is found in the database, delete it and return true
//if it is not found, return false
SQLiteDatabase db = this.getWritableDatabase();
String queryString = "DELETE FROM " + TODO_TABLE
+ " WHERE " + COLUMN_TODO_TITLE + " = " + "\"" + dModel.getTitle() + "\"";;
Cursor cursor = db.rawQuery(queryString, null);
if(cursor.moveToFirst()) {
return true;
} else {
return false;
}
}
public ArrayList<DataModel> getAllAsList() {
//create empty list
ArrayList<DataModel> returnList = new ArrayList<>();
//get data from the database
String queryString = "SELECT * FROM " + TODO_TABLE;
SQLiteDatabase db = this.getReadableDatabase(); //get data from database
Cursor cursor = db.rawQuery(queryString, null);
if(cursor.moveToFirst()) { //returns a true if there were items selected
//loop through results, create new todo objects, put them into return list
do {
String todoTitle = cursor.getString(1);
DataModel newTodo = new DataModel(todoTitle);
returnList.add(newTodo);
} while(cursor.moveToNext());
} else { //returns a false if no items were selected
//failure, to not add anything to the list
}
//clean up, close connection to database and cursor
cursor.close();
db.close();
return returnList;
}
public boolean existsInDB(DataModel dModel) {
SQLiteDatabase db = this.getWritableDatabase(); //for insert actions
String queryString = "SELECT * FROM " + TODO_TABLE
+ " WHERE " + COLUMN_TODO_TITLE + " = " + "\"" + dModel.getTitle() + "\"";
Cursor cursor = db.rawQuery(queryString, null);
if(cursor.moveToFirst()) {
return true;
} else {
return false;
}
}
}
I appreciate any kind of help or suggestion. Let me know, if you need further explanation.
Nicole
