我把我的sqlite数据库文件放在“assets”文件夹中我编写了一个DataManager类来从数据库中获取数据，但是我得到运行时错误..我使用调试工具查看我在{{ {1}}错误提升..请帮助我Sombody解决问题
这是我的Datamanager类。我正在为android预创建数据库，但我得到的文件未找到异常请帮助我..我已经在下面显示了我的Logcat。
（DATAMANAGER班）
CreateDataBase()logcat的：
package com.example.applicationdatabase;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class DataBaseManager extends SQLiteOpenHelper {
// The Android's default system path of your application database.
//data/data/ and /databases remain the same always. The one that must be changed is com.example which represents
//the MAIN package of your project
private static String DB_PATH = "/data/data/com.example.applicationdatabase/databases";
//the name of your database
private static String DB_NAME = "database";
private static SQLiteDatabase mDataBase;
private static DataBaseManager sInstance = null;
// database version
private static final int DATABASE_VERSION = 1;
/**
* Constructor Takes and keeps a reference of the passed context in order to
* access to the application assets and resources.
*/
private DataBaseManager() {
super(ApplicationContextProvider.getContext(), DB_NAME, null, DATABASE_VERSION);
try {
createDataBase();
openDataBase();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* Singleton for DataBase
*
* @return singleton instance
*/
public static DataBaseManager instance() {
if (sInstance == null) {
sInstance = new DataBaseManager();
}
return sInstance;
}
/**
* Creates a empty database on the system and rewrites it with your own
* database.
*
* @throws java.io.IOException io exception
*/
private void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// do nothing - database already exist
} else {
// By calling this method an empty database will be created into
// the default system path
// of your application so we are gonna be able to overwrite that
// database with our database.
this.getReadableDatabase();
try { copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each
* time you open the application.
*
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
// database doesn't exist yet.
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null;
}
/**
* Copies your database from your local assets-folder to the just created
* empty database in the system folder, from where it can be accessed and
* handled. This is done by transfering bytestream.
*
* @throws java.io.IOException io exception
*/
public void copyDataBase() throws IOException {
// Open your local db as the input stream
InputStream myInput =ApplicationContextProvider.getContext().getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
private void openDataBase() throws SQLException {
// Open the database
String myPath = DB_PATH + DB_NAME;
mDataBase = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READWRITE);
}
/**
* Select method
*
* @param query select query
* @return - Cursor with the results
* @throws android.database.SQLException sql exception
*/
public Cursor select(String query) throws SQLException {
return mDataBase.rawQuery(query, null);
}
/**
* Insert method
*
* @param table - name of the table
* @param values values to insert
* @throws android.database.SQLException sql exception
*/
public void insert(String table, ContentValues values) throws SQLException {
mDataBase.insert(table, null, values);
}
/**
* Delete method
*
* @param table - table name
* @param where WHERE clause, if pass null, all the rows will be deleted
* @throws android.database.SQLException sql exception
*/
public void delete(String table, String where) throws SQLException {
mDataBase.delete(table, where, null);
}
/**
* Update method
*
* @param table - table name
* @param values - values to update
* @param where - WHERE clause, if pass null, all rows will be updated
*/
public void update(String table, ContentValues values, String where) {
mDataBase.update(table, values, where, null);
}
/**
* Let you make a raw query
*
* @param command - the sql comand you want to run
*/
public void sqlCommand(String command) {
mDataBase.execSQL(command);
}
@Override
public synchronized void close() {
if (mDataBase != null)
mDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
答案 0 :(得分：2)
这是从Assest Folder读取数据库的工作代码。唯一的问题是PATH无法找到。
我希望它可以帮到某人，如果有任何疑问请告诉我......
package net.learn2develop.Databases;
import java.io.IOException;
import android.app.Activity;
import android.database.Cursor;
import android.database.SQLException;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class DatabasesActivity extends Activity {
protected static final String TAG = null;
private Button insertButton;
private Button updateButton;
private Button deleteButton;
private Button displayButton;
boolean status = false;
private EditText name;
private EditText email;
protected int value1;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
DBAdapter myDbHelper = new DBAdapter(null);
myDbHelper = new DBAdapter(this);
insertButton = (Button) findViewById(R.id.btnInsert);
updateButton = (Button) findViewById(R.id.btnUpdate);
deleteButton = (Button) findViewById(R.id.btnDelete);
displayButton = (Button) findViewById(R.id.btnDisplay);
name = (EditText) findViewById(R.id.edit_name);
email = (EditText) findViewById(R.id.edit_email);
// --- inserting ------
insertButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (name.getText().toString().trim().length() == 0)
{
Toast msg = Toast.makeText(getBaseContext(),
"Please Enter Name ", Toast.LENGTH_LONG);
msg.show();
}
else if (email.getText().toString().trim().length() == 0)
{
Toast msg = Toast.makeText(getBaseContext(),
"Please Enter Email", Toast.LENGTH_LONG);
msg.show();
}
else
insertRecord();
}
});
// --------Deleting the Records -----------
deleteButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
deleteRecord();
}
});
// --- Displaying the Records -------
displayButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
DisplayRecord();
}
});
updateButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (name.getText().toString().trim().length() == 0)
{
Toast msg = Toast.makeText(getBaseContext(),
"Please Enter Name ", Toast.LENGTH_LONG);
msg.show();
}
else if (email.getText().toString().trim().length() == 0)
{
Toast msg = Toast.makeText(getBaseContext(),
"Please Enter Email", Toast.LENGTH_LONG);
msg.show();
}
else
{
updateRecord();
}
}
});
try {
myDbHelper.createDataBase();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
try {
myDbHelper.openDataBase();
} catch (SQLException sqle) {
throw sqle;
}
}
protected void DisplayRecord() {
DBAdapter myDbHelper1 = new DBAdapter(null);
myDbHelper1.openDataBase();
Cursor c = myDbHelper1.getAllContacts();
if (c.moveToFirst()) {
do {
DisplayContact(c);
} while (c.moveToNext());
}
myDbHelper1.close();
}
protected void updateRecord() {
String Name = fetchName();
String Email = fetchEmail();
DBAdapter myDbHelper1 = new DBAdapter(null);
myDbHelper1.openDataBase();
if (myDbHelper1.updateContact(1, Name, Email))
{
Toast msg = Toast.makeText(getBaseContext(),
"Update Successfully ", Toast.LENGTH_LONG);
msg.show();
}
else
{
Toast msg = Toast.makeText(getBaseContext(),
"Update Failed ", Toast.LENGTH_LONG);
msg.show();
}
myDbHelper1.close();
}
protected void deleteRecord() {
DBAdapter myDbHelper1 = new DBAdapter(null);
myDbHelper1.openDataBase();
if (myDbHelper1.deleteContact(27))
{
Toast msg = Toast.makeText(getBaseContext(),
"Delete Successfully ", Toast.LENGTH_LONG);
msg.show();
}
else
{
Toast msg = Toast.makeText(getBaseContext(),
"Delete Failed ", Toast.LENGTH_LONG);
msg.show();
}
myDbHelper1.close();
}
protected void insertRecord() {
String Name = fetchName();
String Email = fetchEmail();
DBAdapter myDbHelper1 = new DBAdapter(null);
myDbHelper1.openDataBase();
long id = myDbHelper1.insertContact(Name, Email);
myDbHelper1.close();
Toast msg = Toast.makeText(getBaseContext(),
"Record: " + id + " Successfully inserted", Toast.LENGTH_LONG);
msg.show();
name.setText("");
email.setText("");
}
public void DisplayContact(Cursor c) {
Toast.makeText(
this,
"id: " + c.getString(0) + "\n" + "Name: " + c.getString(1)
+ "\n" + "Email: " + c.getString(2), Toast.LENGTH_LONG)
.show();
}
public String fetchName()
{
String Name = name.getText().trim().toString();
if (Name.contentEquals(name.getHint()))
{
return " ";
}
else
{
return Name;
}
}
public String fetchEmail()
{
String Email = email.getText().trim().toString();
if (Email.contentEquals(email.getHint()))
{
return " ";
}
else
{
return Email;
}
}
}
答案 1 :(得分：0)
我认为这个问题来自HoneyComb，对于早期版本我们没有问题。将代码从onCreate（）方法移动到onResume（）方法，并使用AsyncTasck进行数据库操作。我希望这能解决问题。 或者只是在DataBaseManager中编写数据库创建语句（SQL staements）或将sql查询放在任何xml（原始文件夹内）文件中并处理xml文件以创建数据库。
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "mydb.sqlite";
protected Context context;
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, 1);
this.context = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
String sqlStatement;
try {
InputStream in = context.getResources().openRawResource(R.raw.mydbqueries);
DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document doc = builder.parse(in, null);
NodeList statements = doc.getElementsByTagName("statement");
for (int i=0; i<statements.getLength(); i++) {
sqlStatement = statements.item(i).getChildNodes().item(0).getNodeValue();
db.execSQL(sqlStatement);
}
} catch (Throwable t) {
}
}
SQLiteDatabase sqliteDB = null;
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
onCreate(db);
}
public SQLiteDatabase open() throws SQLException
{
sqliteDB = this.getWritableDatabase();
return sqliteDB;
}
}
<?xml version="1.0" encoding="UTF-8"?><!-- <?xml version="1.0" encoding="utf-8"?> -->
<!-- database queries -->
<sql>
<!-- Meta data table -->
<!-- <statement> CREATE TABLE "android_metadata" ("locale" TEXT DEFAULT
'en_US') </statement> Meta data table <statement> INSERT INTO "android_metadata"
VALUES('en_US') </statement> -->
<statement>
sql statement
</statement>
</sql>
答案 2 :(得分：0)
我遇到了同样的问题，我知道这个错误导致的操作。因为你没有添加writte权限，你需要在manifest.xml中添加句子“”“
答案 3 :(得分：0)
如果要在“/ data / data / YOUR-PACKAGE / databases / YOUR-DATABASE”中访问数据库，但在访问之前没有任何数据库，则会引发此异常。所以你必须创建你的数据库。但是怎么样？在任何访问之前，您必须使用以下代码：
SQLiteDatabase db;
db = getWritableDatabase();
if (db != null) {
b.close();
}
copyDatabase();