数据库
package sg.edu.rp.c346.todolist;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
/**
* Created by User on 26/12/2017.
*/
public class DatabaseHelper extends SQLiteOpenHelper {
// final is a constant
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 DatabaseHelper(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 EXITS "+ TABLE_NAME);
onCreate(db);
}
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 date as instered incorrectly it will return -1
if (result == -1) {
return false;
} else {
return true;
}
}
/**
* Return all the data from database
* @return
*/
//cursor is know indirect subclass
public Cursor getListContent() {
SQLiteDatabase db = this.getWritableDatabase();
Cursor data =db.rawQuery("SELECT * FROM " + TABLE_NAME,null);
return data;
}
/**
* Returns only the ID that matches the name passed in
* @param name
* @return
*/
public Cursor getItemID(String name){
SQLiteDatabase db=this.getWritableDatabase();
String query = "SELECT "+ COL1 +" FROM "+TABLE_NAME+
" WHERE "+ COL2 +" = '"+ name +"'";
Cursor data = db.rawQuery(query,null);
return data;
}
/**
* Delete from database
* @param id
* @param name
*/
public void deleteName(int id, String name){
SQLiteDatabase db=this.getWritableDatabase();
String query= "DELETE FROM "+ TABLE_NAME +" WHERE " + COL1 + " = '"
+ id + "'"+" AND " + COL2 + "= '" + name + "'";
db.execSQL(query);
}
}
package sg.edu.rp.c346.todolist;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
/**
* Created by User on 26/12/2017.
*/
public class ListDataActivity extends AppCompatActivity {
DatabaseHelper myDB;
ListView listView;
ArrayAdapter<String> listAdapter;
Button button;
Button btnRefresh;
String selectedName;
int selectedID;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.list_layout);
listView = (ListView) findViewById(R.id.listView);
button = (Button) findViewById(R.id.add);
btnRefresh = (Button) findViewById(R.id.refresh);
myDB = new DatabaseHelper(this);
// get the intent extra from the ListDataActivity
Intent receivedIntent=getIntent();
// now get the itemID we passed as an extra
selectedID=receivedIntent.getIntExtra("id",-1);//NOTE -1 it just a default values
// now get the name we passed as an extra
selectedName=receivedIntent.getStringExtra("name");
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(ListDataActivity.this, MainActivity.class);
startActivity(intent);
}
});
btnRefresh.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(ListDataActivity.this, ListDataActivity.class);
startActivity(intent);
}
});
//populate an ArrayList<String> from the databases and then view it
final ArrayList<String> theList = new ArrayList<>();
Cursor data = myDB.getListContent();
if (data.getCount() == 0) {
Toast.makeText(ListDataActivity.this, "The database was empty", Toast.LENGTH_LONG).show();
} else {
while (data.moveToNext()) {
// get the value from the database in column 1
// then add it to the ArrayList
theList.add(data.getString(1));
// create the list adapter and set the adapter
listAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, theList);
listView.setAdapter(listAdapter);
// set an onItemClickListen to the listView
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
String name = adapterView.getItemAtPosition(i).toString();
Cursor data = myDB.getItemID(name); //get the id assosicated with the name
int itemID = 1;
while (data.moveToNext()) {
itemID = data.getInt(0);
}
if (itemID > -1) {
Intent editScreenIntent = new Intent(ListDataActivity.this, EditDataActivity.class);
editScreenIntent.putExtra("id", itemID);
editScreenIntent.putExtra("name", name);
startActivity(editScreenIntent);
} else {
Toast.makeText(ListDataActivity.this, "No ID assosciated", Toast.LENGTH_SHORT).show();
}
}
});
}
}
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
myDB.deleteName(selectedID,selectedName);
theList.remove(i);
listAdapter.notifyDataSetChanged(); //change to your adapter instance here
Toast.makeText(ListDataActivity.this, "item removed", Toast.LENGTH_SHORT).show();
return true;
}
});
}
}
如何使用函数setOnItemLongClickListener从数据库删除/删除我的代码似乎不删除。
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
myDB.deleteName(selectedID,selectedName);
Toast.makeText(ListDataActivity.this, "item removed", Toast.LENGTH_SHORT).show();
return true;
}
});
此代码是数据库Activity
public void deleteName(int id, String name){
SQLiteDatabase db=this.getWritableDatabase();
String query= "DELETE FROM "+ TABLE_NAME +" WHERE " + COL1 + " = '"
+ id + "'"+" AND " + COL2 + "= '" + name + "'";
db.execSQL(query);
}
}
当您从数据库中删除数据但附加到适配器的列表仍保留数据时，您必须从该位置删除并通知您的适配器。 试试这段代码：
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
myDB.deleteName(theList.get(i));
theList.remove(i);
listAdapter.notifyDataSetChanged();
Toast.makeText(ListDataActivity.this, "item removed", Toast.LENGTH_SHORT).show();
return true;
}
});
如果要删除所选项目，可以使用：
public void deleteName(String name){
SQLiteDatabase db=this.getWritableDatabase();
String query= "DELETE FROM "+ TABLE_NAME +" WHERE " + COL2 + "= '" + name + "'";
db.execSQL(query);
}
并将deleteName()称为：
myDB.deleteName(theList.get(i));
我认为问题出在你的删除查询中，
public void deleteName(int id, String name){
SQLiteDatabase db=this.getWritableDatabase();
String query= "DELETE FROM "+ TABLE_NAME +" WHERE " + COL1 + " = "
+ String.valueOf(id) +" AND " + COL2 + "= '" + name + "'";
db.execSQL(query);
}
COL1 +“='”+ id +“'” - >单引号用于文本，not for numbers.