android-从本地文件读取数据库
我通过文章阅读和练习 这是我的样品 有人可以检查一下，让我知道为什么城市表找不到？谢谢 我已经用表创建了一个数据库android-从本地文件读取数据库,android,Android,我通过文章阅读和练习 这是我的样品 有人可以检查一下，让我知道为什么城市表找不到？谢谢 我已经用表创建了一个数据库 city : _id ; name 1 ; abc 2 ; def 在DataNaseHelper.openDataBase中，我尝试 Cursor result = myDataBase.rawQuery("SELECT * FROM city", null); Log.d("trung", result.getExtras().toString
city : _id ; name
1 ; abc
2 ; def
Cursor result = myDataBase.rawQuery("SELECT * FROM city", null);
Log.d("trung", result.getExtras().toString());
11-25 22:24:13.393: E/AndroidRuntime(337): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.joomavatar.phonebook/com.joomavatar.phonebook.NumberSearch}: android.database.sqlite.SQLiteException: no such table: city: , while compiling: SELECT * FROM city
public class DataBaseHelper extends SQLiteOpenHelper{
//The Android's default system path of your application database.
private static final String DB_PATH = "/data/data/com.joomavatar.phonebook/databases/";
private static final String DB_NAME = "hanoi";
private SQLiteDatabase myDataBase;
private final Context myContext;
/**
* Constructor
* Takes and keeps a reference of the passed context in order to access to the application assets and resources.
* @param context
*/
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
//do nothing - database already exist
}else{
//By calling this method and 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 {
Log.d("trung", "create table");
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 does't exist yet.
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* 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.
* */
private void copyDataBase() throws IOException{
//Open your local db as the input stream
InputStream myInput = myContext.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();
}
public void openDataBase() throws SQLException{
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
Cursor result = myDataBase.rawQuery("SELECT * FROM city", null);
Log.d("trung", result.getExtras().toString());
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.
}
找不到表城市。在我看来，学习使用SQlite的最佳资源是 是
是的，我试过那个教程。但在我的例子中，我有一个数据库文件，我想加载它。在我的数据库中，我有城市表。但是我得到了上面的错误，不知道为什么：（只是为了确保数据库被正确复制-你能从data/data文件夹导出数据库文件并用一些工具查看它吗？）Huhhmmm..它没有在emulator上运行。我在我的htc设备上试过，它工作正常：d检查前一篇文章：你能验证db文件是否正确复制到内存中吗？
/data/data/com.joomavatar.phonebook/databases/hanoi