我一直试图从数据库中获取价格值并尝试获得总计。我使用了rawQuery，但总是崩溃。我认为我的rawQuery中有一个问题..我仍然无法在多次尝试之后获得总数...
这是代码：
将对DBAdapter
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;
// ------------------------------------ DBAdapter.java ---------------------------------------------
// TO USE:
// Change the package (at top) to match your project.
// Search for "TODO", and make the appropriate changes.
public class DBAdapter {
/////////////////////////////////////////////////////////////////////
// Constants & Data
/////////////////////////////////////////////////////////////////////
// For logging:
private static final String TAG = "DBAdapter";
// DB Fields
public static final String KEY_ROWID = "_id";
public static final int COL_ROWID = 0;
/*
* CHANGE 1:
*/
// TODO: Setup your fields here:
public static final String KEY_NAME = "name";
public static final String KEY_QUANTITY = "studentnum";
public static final String KEY_PRICE = "favcolour";
// TODO: Setup your field numbers here (0 = KEY_ROWID, 1=...)
public static final int COL_NAME = 1;
public static final int COL_QUANTITY = 2;
public static final int COL_PRICE = 3;
public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_NAME, KEY_QUANTITY, KEY_PRICE};
// DB info: it's name, and the table we are using (just one).
public static final String DATABASE_NAME = "MyDb";
public static final String DATABASE_TABLE = "mainTable";
// Track DB version if a new version of your app changes the format.
public static final int DATABASE_VERSION = 2;
private static final String DATABASE_CREATE_SQL =
"create table " + DATABASE_TABLE
+ " (" + KEY_ROWID + " integer primary key autoincrement, "
/*
* CHANGE 2:
*/
// TODO: Place your fields here!
// + KEY_{...} + " {type} not null"
// - Key is the column name you created above.
// - {type} is one of: text, integer, real, blob
// (http://www.sqlite.org/datatype3.html)
// - "not null" means it is a required field (must be given a value).
// NOTE: All must be comma separated (end of line!) Last one must have NO comma!!
+ KEY_NAME + " text not null, "
+ KEY_QUANTITY + " integer not null, "
+ KEY_PRICE + " string not null"
// Rest of creation:
+ ");";
// Context of application who uses us.
private final Context context;
private DatabaseHelper myDBHelper;
private SQLiteDatabase db;
/////////////////////////////////////////////////////////////////////
// Public methods:
/////////////////////////////////////////////////////////////////////
public DBAdapter(Context ctx) {
this.context = ctx;
myDBHelper = new DatabaseHelper(context);
}
// Open the database connection.
public DBAdapter open() {
db = myDBHelper.getWritableDatabase();
return this;
}
// Close the database connection.
public void close() {
myDBHelper.close();
}
// Add a new set of values to the database.
public long insertRow(String name, String studentNum, String favColour) {
/*
* CHANGE 3:
*/
// TODO: Update data in the row with new fields.
// TODO: Also change the function's arguments to be what you need!
// Create row's data:
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
initialValues.put(KEY_QUANTITY, studentNum);
initialValues.put(KEY_PRICE, favColour);
// Insert it into the database.
return db.insert(DATABASE_TABLE, null, initialValues);
}
// Delete a row from the database, by rowId (primary key)
public boolean deleteRow(long rowId) {
String where = KEY_ROWID + "=" + rowId;
return db.delete(DATABASE_TABLE, where, null) != 0;
}
public Cursor getTotalPrice() {
Cursor c = db.rawQuery("SELECT SUM("+ KEY_PRICE +")from " + DATABASE_TABLE, null);
return c;
}
public void deleteAll() {
Cursor c = getAllRows();
long rowId = c.getColumnIndexOrThrow(KEY_ROWID);
if (c.moveToFirst()) {
do {
deleteRow(c.getLong((int) rowId));
} while (c.moveToNext());
}
c.close();
}
// Return all data in the database.
public Cursor getAllRows() {
String where = null;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS,
where, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
// Get a specific row (by rowId)
public Cursor getRow(long rowId) {
String where = KEY_ROWID + "=" + rowId;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS,
where, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
// Change an existing row to be equal to new data.
public boolean updateRow(long rowId, String name, int studentNum, String favColour) {
String where = KEY_ROWID + "=" + rowId;
/*
* CHANGE 4:
*/
// TODO: Update data in the row with new fields.
// TODO: Also change the function's arguments to be what you need!
// Create row's data:
ContentValues newValues = new ContentValues();
newValues.put(KEY_NAME, name);
newValues.put(KEY_QUANTITY, studentNum);
newValues.put(KEY_PRICE, favColour);
// Insert it into the database.
return db.update(DATABASE_TABLE, newValues, where, null) != 0;
}
/////////////////////////////////////////////////////////////////////
// Private Helper Classes:
/////////////////////////////////////////////////////////////////////
/**
* Private class which handles database creation and upgrading.
* Used to handle low-level database access.
*/
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase _db) {
_db.execSQL(DATABASE_CREATE_SQL);
}
@Override
public void onUpgrade(SQLiteDatabase _db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading application's database from version " + oldVersion
+ " to " + newVersion + ", which will destroy all old data!");
// Destroy old database:
_db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
// Recreate new database:
onCreate(_db);
}
}
}
Listprice：
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.*;
/**
* Created by User on 6/2/2015.
*/
public class Listprice extends ActionBarActivity {
DBAdapter myDb;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listprice);
openDB();
TextView textView = (TextView) findViewById(R.id.order90);
TextView textView1 = (TextView) findViewById(R.id.quan90);
TextView textView2 = (TextView) findViewById(R.id.price90);
TextView textView3 = (TextView) findViewById(R.id.totalprice);
Bundle extras = getIntent().getExtras();
if (extras != null) {
String newText = extras.getString("firstmessage");
String newText1 = extras.getString("secondmessage");
String newText2 = extras.getString("thirdmessage");
if (newText != null) {
textView.setText(newText);
}
if (newText1 != null) {
textView1.setText(newText1);
}
if (newText2 != null) {
textView2.setText(newText2);
}
}
String num1 = textView.getText().toString().trim();
int num2 = Integer.parseInt(textView1.getText().toString());
int num3 = Integer.parseInt(textView2.getText().toString());
int num4 = num2 * num3;
registerListClickCallBack();
myDb.insertRow(num1, "Quantity = " + num2, ""+num4);
populateListViewFromDB();
Cursor sum=myDb.getTotalPrice();
textView3.setText(""+sum);
}
private void populateListViewFromDB() {
Cursor cursor = myDb.getAllRows();
//Query for the record we just added.
//Use the ID:
startManagingCursor(cursor);
String[] fromFieldNames = new String[]
{DBAdapter.KEY_NAME, DBAdapter.KEY_QUANTITY, DBAdapter.KEY_PRICE};
int[] toViewIDs = new int[]
{R.id.item_name, R.id.quantities, R.id.pricest};
SimpleCursorAdapter myCursorAdapter =
new SimpleCursorAdapter(
this,
R.layout.item_layout,
cursor,
fromFieldNames,
toViewIDs
);
// Set the adapter for the list view
ListView myList = (ListView) findViewById(R.id.listViewFromDB);
myList.setAdapter(myCursorAdapter);
}
private void openDB(){
myDb = new DBAdapter(this);
myDb.open();
}
@Override
protected void onDestroy() {
super.onDestroy();
closeDB();
}
private void closeDB() {
myDb.close();
}
private void registerListClickCallBack() {
ListView myList = (ListView) findViewById(R.id.listViewFromDB);
myList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View viewClicked,
int position, long idInDB) {
updateItemForId(idInDB);
}
});
}
private void updateItemForId(final long idInDB) {
final Cursor cursor = myDb.getRow(idInDB);
if (cursor.moveToFirst()) {
AlertDialog.Builder alertDialog = new AlertDialog.Builder(Listprice.this);
// Setting Dialog Title
alertDialog.setTitle("Confirm Delete...");
// Setting Dialog Message
alertDialog.setMessage("Are you sure you want delete this?");
// Setting Positive "Yes" Button
alertDialog.setPositiveButton("YES", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int which) {
// Write your code here to invoke YES event
Toast.makeText(getApplicationContext(), "You clicked on YES", Toast.LENGTH_SHORT).show();
myDb.deleteRow(idInDB);
populateListViewFromDB();
}
});
// Setting Negative "NO" Button
alertDialog.setNegativeButton("NO", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// Write your code here to invoke NO event
Toast.makeText(getApplicationContext(), "You clicked on NO", Toast.LENGTH_SHORT).show();
dialog.cancel();
}
});
// Showing Alert Message
alertDialog.show();
}
cursor.close();
populateListViewFromDB();
}
public void clear(View view) {
myDb.deleteAll();
populateListViewFromDB();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public void addFood(View view) {
Intent gotofood = new Intent(this, food.class);
startActivity(gotofood);
}
public void addDrinks(View view) {
Intent gotodrinks = new Intent(this, drink.class);
startActivity(gotodrinks);
}
public void gotomainmaenu(View view) {
Intent gotomain = new Intent(this, MainActivity.class);
startActivity(gotomain);
}
}
答案 0 :(得分：0)
听起来您希望每件商品的价格总和乘以该商品的数量。如果是这样，这应该有效：
public double getTotalPrice() {
String sql = "select sum(" + KEY_QUANTITY + " * " + KEY_PRICE + ") from "
+ DATABASE_TABLE;
Cursor cursor = db.rawQuery(sql, null);
if (cursor.moveToFirst()) {
return cursor.getDouble(0);
}
return 0;
}