In my MainActivity i want my button to delete all items in my view list. Unfortunately all the solutions i found here won’t help me. If i click on the Button “Clear All” it deletes every item in my list, but the items are still saved in my Database.
I am totally new to Android Studio, so i don´t know how to write my code that it will work the way i want it.
This is my MainActivity:
package com.vorlesung.iubh.todo; import android.content.Context; import android.content.Intent; import android.database.Cursor; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.SparseBooleanArray; import android.view.View; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.ListView; import android.widget.Toast; import java.util.ArrayList; public class MainActivity extends AppCompatActivity { DatabaseHepler myDB; ArrayList<String> list; ListView myToDoList; ArrayAdapter<String> arrayAdapter; SparseBooleanArray selectedItem; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button addToDo = (Button) findViewById(R.id.addToDo); Button clearAll = (Button) findViewById(R.id.clearALL); Button editSelected = (Button) findViewById(R.id.editSelected); Button clearDone = (Button) findViewById(R.id.clearDone); myToDoList = (ListView) findViewById(R.id.myToDoList); myDB = new DatabaseHepler(this); list = new ArrayList<>(); Cursor data = myDB.getListContents(); if (data.getCount() == 0) Toast.makeText(this, "The Database was empty", Toast.LENGTH_LONG).show(); else { while (data.moveToNext()) { list.add(data.getString(1)); arrayAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_multiple_choice, list); myToDoList.setAdapter(arrayAdapter); } } } public void onClickaddToDo(View button) { Intent newToDo = new Intent(this, AddToDo.class); startActivity(newToDo); } // With this onClick i want to delete all Items from my List. public void onClickaclearALL(View button) { list.clear(); arrayAdapter.notifyDataSetChanged(); } } And this is my DataBase:
package com.vorlesung.iubh.todo; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class DatabaseHepler extends SQLiteOpenHelper { public static final String DATABASE_NAME = "myList.db"; public static final String TABLE_NAME = "myList_Data"; public static final String COL1 = "ID"; public static final String COL2 = "ITEM1"; public DatabaseHepler(Context context){super(context, DATABASE_NAME, null, 1);} @Override public void onCreate(SQLiteDatabase db) { String createTable = "CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " + "ITEM1 TEXT)"; db.execSQL(createTable); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){ db.execSQL("DROP IF TABLE EXISTS " + TABLE_NAME); } public boolean addData(String item1) { SQLiteDatabase db = this.getWritableDatabase(); ContentValues contentValues = new ContentValues(); contentValues.put(COL2, item1); long result = db.insert(TABLE_NAME, null, contentValues); if(result == -1) { return false; } else { return true; } } public Cursor getListContents() { SQLiteDatabase db = this.getWritableDatabase(); Cursor data = db.rawQuery("SELECT * FROM " + TABLE_NAME, null); return data; } public void deleteRow() { SQLiteDatabase db = this.getWritableDatabase(); db.execSQL("DELETE FROM " + TABLE_NAME+ " WHERE "+ COL2, null); db.close(); } } Hope someone can show me the way how to do that.