如何引用现有的 SQLite 数据库创建新数据库并插入数据？
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【中文标题】如何引用现有的 SQLite 数据库创建新数据库并插入数据？【英文标题】：How to reference existing SQLite db else create new DB and insert data? 【发布时间】：2014-01-15 15:45:50 【问题描述】：我正在尝试使用数据库创建条形码扫描仪。如果数据库存在，则添加数据，否则创建一个名为“quantityCalculator.db”的新数据库，表名为“quantityCalculator”。
有一些现有的代码，但它会抛出许多错误以试图修复/
错误：
01-15 15:44:26.600: E/Trace(24862): error opening trace file: No such file or directory (2)
01-15 15:44:27.350: I/Adreno200-EGL(24862): <qeglDrvAPI_eglInitialize:299>: EGL 1.4 QUALCOMM build: AU_LINUX_android_JB_REL_RB1.04.01.01.06.043_msm7627a_JB_REL_RB1.2_Merge_release_AU (Merge)
01-15 15:44:27.350: I/Adreno200-EGL(24862): Build Date: 01/18/13 Fri
01-15 15:44:27.350: I/Adreno200-EGL(24862): Local Branch:
01-15 15:44:27.350: I/Adreno200-EGL(24862): Remote Branch: m/jb_rel_rb1.2
01-15 15:44:27.350: I/Adreno200-EGL(24862): Local Patches: NONE
01-15 15:44:27.350: I/Adreno200-EGL(24862): Reconstruct Branch: NOTHING
01-15 15:44:31.910: E/SQLiteLog(24862): (14) cannot open file at line 30178 of [00bb9c9ce4]
01-15 15:44:31.910: E/SQLiteLog(24862): (14) os_unix.c:30178: (2) open(//foodcalculator.db) -
01-15 15:44:31.920: E/SQLiteDatabase(24862): Failed to open database 'foodcalculator.db'.
01-15 15:44:31.920: E/SQLiteDatabase(24862): android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:213)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:197)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:485)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at com.example.quantitycalculator.AddItem.checkDataBase(AddItem.java:50)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at com.example.quantitycalculator.AddItem.onClick(AddItem.java:82)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.view.View.performClick(View.java:4106)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.view.View$PerformClick.run(View.java:17150)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.os.Handler.handleCallback(Handler.java:615)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.os.Handler.dispatchMessage(Handler.java:92)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.os.Looper.loop(Looper.java:137)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at android.app.ActivityThread.main(ActivityThread.java:4792)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at java.lang.reflect.Method.invokeNative(Native Method)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at java.lang.reflect.Method.invoke(Method.java:511)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:808)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:575)
01-15 15:44:31.920: E/SQLiteDatabase(24862): at dalvik.system.NativeStart.main(Native Method)
01-15 15:44:31.920: W/dalvikvm(24862): threadid=1: thread exiting with uncaught exception (group=0x40c83498)
01-15 15:44:31.920: E/test(24862): Exception
01-15 15:44:31.940: E/AndroidRuntime(24862): FATAL EXCEPTION: main
01-15 15:44:31.940: E/AndroidRuntime(24862): java.lang.NullPointerException
01-15 15:44:31.940: E/AndroidRuntime(24862): at com.example.quantitycalculator.AddItem.checkDataBase(AddItem.java:55)
01-15 15:44:31.940: E/AndroidRuntime(24862): at com.example.quantitycalculator.AddItem.onClick(AddItem.java:82)
01-15 15:44:31.940: E/AndroidRuntime(24862): at android.view.View.performClick(View.java:4106)
01-15 15:44:31.940: E/AndroidRuntime(24862): at android.view.View$PerformClick.run(View.java:17150)
01-15 15:44:31.940: E/AndroidRuntime(24862): at android.os.Handler.handleCallback(Handler.java:615)
01-15 15:44:31.940: E/AndroidRuntime(24862): at android.os.Handler.dispatchMessage(Handler.java:92)
01-15 15:44:31.940: E/AndroidRuntime(24862): at android.os.Looper.loop(Looper.java:137)
01-15 15:44:31.940: E/AndroidRuntime(24862): at android.app.ActivityThread.main(ActivityThread.java:4792)
01-15 15:44:31.940: E/AndroidRuntime(24862): at java.lang.reflect.Method.invokeNative(Native Method)
01-15 15:44:31.940: E/AndroidRuntime(24862): at java.lang.reflect.Method.invoke(Method.java:511)
01-15 15:44:31.940: E/AndroidRuntime(24862): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:808)
01-15 15:44:31.940: E/AndroidRuntime(24862): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:575)
01-15 15:44:31.940: E/AndroidRuntime(24862): at dalvik.system.NativeStart.main(Native Method)
主页：
package com.example.quantitycalculator;
import com.example.quantitycalculator.R;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class Homepage extends Activity
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
super.onCreate(savedInstanceState);
setContentView(R.layout.homepage);
final Button addButton = (Button) findViewById(R.id.scanner);
final Button editInventoryButton = (Button) findViewById(R.id.editItem);
final Button currentInventoryButton = (Button) findViewById(R.id.currentItems);
final Button settingsButton = (Button) findViewById(R.id.settings);
addButton.setOnClickListener(new OnClickListener()
@Override
public void onClick(View view)
Intent intent = new Intent(view.getContext(), AddItem.class);
startActivity(intent);
);
currentInventoryButton.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
Intent intent = new Intent(view.getContext(), CurrentItems.class);
startActivity(intent);
);
editInventoryButton.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
// TODO Auto-generated method stub
Intent intent = new Intent(view.getContext(), EditItems.class);
startActivity(intent);
);
settingsButton.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
// TODO Auto-generated method stub
Intent intent = new Intent(view.getContext(), Settings.class);
startActivity(intent);
);
@Override
public boolean onCreateOptionsMenu(Menu menu)
// Inflate the menu; this adds items to the action bar if it is present.
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
static final class ProductData
String barcode;
String title;
Double quantity;
添加项目：
package com.example.quantitycalculator;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import com.example.quantitycalculator.R;
import com.example.quantitycalculator.Homepage.ProductData;
public class AddItem extends Activity implements OnClickListener
private static final int REQUEST_BARCODE = 0;
private static final ProductData mProductData = new ProductData();
EditText mBarcodeEdit;
EditText mTitleEdit;
EditText mQuantityEdit;
private Button mScanButton;
private Button mAddButton;
final String DATABASE_NAME = "quantitycalculator.db";
final String DATABASE_PATH = "/data/data/com.quantitycalculator.db";
private final String PRODUCT_TABLE = "foodItems";
@Override
protected void onCreate(Bundle savedInstanceState)
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.add_product);
mBarcodeEdit = (EditText) findViewById(R.id.barcodeEdit);
mTitleEdit = (EditText) findViewById(R.id.titleEdit);
mQuantityEdit = (EditText) findViewById(R.id.quantityEdit);
mScanButton = (Button) findViewById(R.id.scanButton);
mScanButton.setOnClickListener(this);
mAddButton = (Button) findViewById(R.id.addButton);
mAddButton.setOnClickListener(this);
private boolean checkDataBase()
SQLiteDatabase checkDB = null;
try
checkDB = SQLiteDatabase.openDatabase(DATABASE_NAME, null,
SQLiteDatabase.OPEN_READONLY);
checkDB.close();
catch (SQLiteException e)
// database doesn't exist yet.
checkDB.execSQL("CREATE TABLE IF NOT EXISTS " + PRODUCT_TABLE
+ " (barcode String, title String, quantity Double);");
return checkDB != null ? true : false;
public void onClick(View v)
// TODO Auto-generated method stub
switch (v.getId())
case R.id.scanButton:
Intent intent = new Intent("com.google.zxing.client.android.SCAN");
intent.putExtra("SCAN_MODE", "PRODUCT_MODE");
startActivityForResult(intent, REQUEST_BARCODE);
break;
case R.id.addButton:
String barcode = mBarcodeEdit.getText().toString();
String title = mTitleEdit.getText().toString();
String quantity = mQuantityEdit.getText().toString();
SQLiteDatabase checkDB = null;
String errors = validateFields(barcode, title, quantity);
if (errors.length() > 0)
showInfoDialog(this, "Please fix errors", errors);
if (checkDataBase() == false)
checkDB = SQLiteDatabase.openDatabase(DATABASE_NAME, null,
SQLiteDatabase.OPEN_READWRITE);
mProductData.barcode = barcode;
mProductData.title = title;
mProductData.quantity = Double.valueOf(quantity);
checkDB.execSQL("INSERT INTO " + PRODUCT_TABLE + " Values "
+ (mProductData));
checkDB.close();
showInfoDialog(this, "Success", "Product saved successfully");
resetForm();
else
checkDB = SQLiteDatabase.openDatabase(DATABASE_NAME, null,
SQLiteDatabase.OPEN_READWRITE);
mProductData.barcode = barcode;
mProductData.title = title;
mProductData.quantity = Double.valueOf(quantity);
checkDB.execSQL("INSERT INTO " + PRODUCT_TABLE + " Values "
+ (mProductData));
checkDB.close();
showInfoDialog(this, "Success", "Product saved successfully");
resetForm();
private void showInfoDialog(Context context, String title,
String information)
new AlertDialog.Builder(context).setMessage(information)
.setTitle(title)
.setPositiveButton("OK", new DialogInterface.OnClickListener()
public void onClick(DialogInterface dialog, int which)
dialog.dismiss();
).show();
private void resetForm()
// TODO Auto-generated method stub
mBarcodeEdit.getText().clear();
mTitleEdit.getText().clear();
mQuantityEdit.getText().clear();
public void onActivityResult(int requestCode, int resultCode, Intent intent)
if (requestCode == REQUEST_BARCODE)
if (resultCode == RESULT_OK)
String barcode = intent.getStringExtra("SCAN_RESULT");
mBarcodeEdit.setText(barcode);
else if (resultCode == RESULT_CANCELED)
finish();
private static String validateFields(String barcode, String title,
String quantity)
StringBuilder errors = new StringBuilder();
if (barcode.matches("^\\s*$"))
errors.append("Barcode required\n");
if (title.matches("^\\s*$"))
errors.append("Title required\n");
if (!quantity.matches("^-?\\d+(.\\d+)?$"))
errors.append("Need numeric quantity\n");
return errors.toString();
产品数据库：
package com.example.quantitycalculator;
import com.example.quantitycalculator.Homepage.ProductData;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class ProductDatabase
private static final String PRODUCT_TABLE = "foodItems";
private static final String DATABASE_NAME = "quantitycalculator.db";
private static final int DATABASE_VERSION = 1;
private SQLiteDatabase db;
private static class ProductDatabaseHelper extends SQLiteOpenHelper
private static final String TAG = null;
public ProductDatabaseHelper(Context context)
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
@Override
public void onCreate(SQLiteDatabase db)
StringBuilder sql = new StringBuilder();
sql.append("create table ").append(PRODUCT_TABLE).append("( ")
.append(" _id integer primary key,")
.append(" barcode text,").append(" title text,")
.append(" quantity number").append(") ");
db.execSQL(sql.toString());
Log.d(TAG, PRODUCT_TABLE + "table created");
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
db.execSQL("drop table if exists " + PRODUCT_TABLE);
onCreate(db);
public ProductDatabase(Context context)
ProductDatabaseHelper helper = new ProductDatabaseHelper(context);
db = helper.getWritableDatabase();
public boolean insert(ProductData product)
ContentValues vals = new ContentValues();
vals.put("barcode", product.barcode);
vals.put("title", product.title);
vals.put("quantity", product.quantity);
return db.insert(PRODUCT_TABLE, null, vals) != -1;
所有帮助将不胜感激！
【问题讨论】：
【参考方案1】：您的 DATABASE_PATH 中缺少数据库文件夹。您不应对数据库路径进行硬编码 将您的 DATABASE_PATH 更改为这一行：
DB_PATH="/data/data/" + context.getPackageName() + "/" + "databases/";
您的 logcat 显示 Failed to open database 'foodcalculator.db'.，但在代码中我可以看到您正在创建 quantitycalculator.db。请发布正确的 logcat。
【讨论】：
【参考方案2】：将数据库功能与活动混合起来并不是一个好主意。您应该创建新类来与数据库通信。您应该阅读本教程，它将帮助您了解如何在应用程序中设计和创建 APP DB 接口：https://developer.android.com/training/basics/data-storage/databases.html
【讨论】：
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