无法获取来自SQLite数据库数据 [英] Not able to fetch data from Sqlite Database
问题描述
我想从SQLite数据库提取数据，并在列表中显示出来。
I want to fetch data from SQLITE database and display it in a LIST.
我的数据库名称是AppDB.db和表名是代息，其中包含3列_id（主键）和符号放; COMPANY_NAME这是文本。
My database name is AppDB.db and table name is Scrip which contains 3 columns _id(primary key) and symbol&company_name which are text.
我想只获取第二和第三列。我在Assets文件夹复制的数据库。
I want to fetch only 2nd and 3rd column. I have copied database in Assets folder.
我得到强制关闭当我执行以下code，但我不知道可能是什么原因。请帮助..
I get force close when I execute following code but I don't know what might be the reason. Please help..
我绝对初学者到Android，所以任何帮助AP preciated ...
内容：
1）DataAttach.java
1.) DataAttach.java
2）DbManager.java
2.) DbManager.java
3）LogCat中
4）在短暂的.xml
4.) .xml in brief
5）AVD问题
6）数据库的快照
1）DataAttach.java
public class DataAttach extends Activity {
private DbManager dbM;
private Cursor c;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
try {
dbM = new DbManager(this);
dbM.createDataBase();
dbM.openDB();
try {
c = dbM.fetchAllData();
} catch (Exception e) {
throw new Error("\n\nERROR Fetchin data\n\n");
}
if (c != null) {
SimpleCursorAdapter adapter = new SimpleCursorAdapter(
this,
android.R.layout.simple_list_item_1,
c,
new String[] { c.getString(c.getColumnIndex("_id")),
c.getString(c.getColumnIndex("symbol")),
c.getString(c.getColumnIndex("company_name")) },
new int[] { R.id._id, R.id.symbol, R.id.company_name });
ListView list = (ListView) findViewById(R.id.MainLayout);
list.setAdapter(adapter);
}
}
catch (Exception e) {
throw new Error("\n\nERROR DB failure\n\n");
}
finally {
c.close();
dbM.close();
}
}
}
2）DbManager.java
public class DbManager extends SQLiteOpenHelper {
private static final String KEY_ROWID = "_id";
private static final String KEY_SYMBOL = "symbol";
private static final String KEY_COMPANY_NAME = "company_name";
private static final String DATABASE_NAME = "AppDB";
private static final String DATABASE_PATH = "/data/data/com.dbexample/databases/";
private static final Integer DATABASE_VERSION = 3;
private static final String DATABASE_TABLE = "Scrip";
// private static final String TAG = "DbManager";
private final Context ctx;
private SQLiteDatabase mDb;
public DbManager(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
this.ctx = context;
}
/*
* Creates a empty database on the system and rewrites it with your own
* database.
*/
public void createDataBase() {
if (checkDataBase()) {
// 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 can overwrite
* that database with our database.
*/
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("\n\nERROR copying database\n\n");
}
}
}
/*
* Check if the database already exist to avoid re-copying the file each
* time you open the application.
*/
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
String myPath = DATABASE_PATH + DATABASE_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
throw new Error("\n\nERROR database does't exist yet\n\n");
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null ? true : false;
}
/*
* Copies your DB from your local assets-folder to the just created empty DB
* in the system folder, from where it can be accessed and handled.
*/
private void copyDataBase() throws IOException {
/* Open your local db as the input stream */
InputStream myInput = ctx.getAssets().open(DATABASE_NAME);
/* Path to the just created empty db */
String outFileName = DATABASE_PATH + DATABASE_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);
}
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDB() throws SQLException {
String myPath = DATABASE_PATH + DATABASE_NAME;
mDb = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY);
}
@Override
public void close() {
mDb.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public Cursor fetchAllData() {
return mDb.query(DATABASE_TABLE, new String[] { KEY_ROWID, KEY_SYMBOL,
KEY_COMPANY_NAME }, null, null, null, null, null);
// return mDb.rawQuery("select _id,symbol,company_name from Scrip",
// new String[] { KEY_ROWID,KEY_SYMBOL, KEY_COMPANY_NAME });
}
}
3）。LOG CAT
sqlite3_open_v2("/data/data/com.dbexample/databases/AppDB", &handle, 1, NULL) failed
Failed to open the database. closing it.
android.database.sqlite.SQLiteCantOpenDatabaseException: unable to open database file
at android.database.sqlite.SQLiteDatabase.dbopen(Native Method)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:1017)
4。）的main.xml
它含有3 TextViews RelativeLayout的内RelativeLayout的。
It contains RelativeLayout having 3 TextViews within RelativeLayout.
5）的我总是得到这个错误的
5.) I ALWAYS GET THIS ERROR
即使重开食，重新启动系统，重新创建AVD，努力，kill_server和START_SERVER后，我得到这个消息。
Even after reopening the eclipse, restarting the system, recreating the AVD, trying, kill_server and start_server, I get this message.
Failed to install DataAttach.apk on device 'emulator-5554': device not found
com.android.ddmlib.InstallException: device not found
Launch canceled!
DB的 6）截图：
全DOC编辑，以最新code和ACC。您的建议，但还是应用程序无法正常工作。的
WHOLE DOC EDITED TO LATEST CODE AND ACC. TO YOUR SUGGESTIONS, but still app doesn't work.
推荐答案
我不知道你是想用这个函数来完成。你想读一个.db文件，说数据库被创建。当您尝试运行第一次不会有数据库路径的.db文件。这就是为什么没有这样的文件或目录引发错误。
I don't know what you are trying to do with this function. You're trying to read a .db file and say the DB is created. First time when you try to run there won't be a .db file in the database path. That is why the 'No such File or Directory' error is thrown.
11-25 12:06:13.398: E/Netd(31): Unable to bind netlink socket: No such file or directory
在DBManager构造函数调用SQLiteOpenHelper的getReadableDatabase（）如果没有一个这将创建一个数据库。 <一href=\"http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html#getReadableDatabase%28%29\"相对=nofollow> SQLiteOpenHelper
In the DBManager Constructor call the SQLiteOpenHelper's getReadableDatabase() which will create a db if there is not one. SQLiteOpenHelper
public void createNewDatabase() {
InputStream assetsDB = null;
try {
assetsDB = context.getAssets().open(DATABASE_NAME);
OutputStream dbOut = new FileOutputStream(DATABASE_PATH
+ DATABASE_NAME);
byte[] buffer = new byte[1024];
int length;
while ((length = assetsDB.read(buffer)) > 0) {
dbOut.write(buffer, 0, length);
}
dbOut.flush();
dbOut.close();
assetsDB.close();
Log.i(TAG, "New database created...");
} catch (IOException e) {
Log.e(TAG, "Could not create new database...");
}
}
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