Question

我想从SQLITE数据库中获取数据并将其显示在LIST中。

我的数据库名称是AppDB.db，表名是Scrip，其中包含3列_id（主键）和符号＆amp; company_name，它们是文本。

我想只获取第2和第3列。我在Assets文件夹中复制了数据库。

当我执行下面的代码时，我会强行关闭，但我不知道可能是什么原因。请帮忙..

我绝对是Android的初学者，所以任何帮助都值得赞赏......

内容：

1。）DataAttach.java

2。）DbManager.java

3。）LogCat

4。）。xml简要说明

5.）AVD问题

6.。）数据库快照

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。） Main.xml

它包含在RelativeLayout中有3个TextView的RelativeLayout。

5。）我总是得到这个错误

即使重新打开eclipse，重新启动系统，重新创建AVD，尝试，kill_server和start_server，我收到此消息。

Failed to install DataAttach.apk on device 'emulator-5554': device not found
com.android.ddmlib.InstallException: device not found
Launch canceled!

6。）屏幕显示数据库：

Screenshot

整个DOC编辑最新代码和ACC。根据您的建议，但仍然无法使用应用程序。

Answer 1

我不知道你要用这个功能做什么。您正在尝试读取.db文件并说该数据库已创建。第一次尝试运行时，数据库路径中不会有.db文件。这就是为什么抛出'No such File or Directory'错误的原因。

11-25 12:06:13.398: E/Netd(31): Unable to bind netlink socket: No such file or directory

在DBManager构造函数中调用SQLiteOpenHelper的getReadableDatabase（），如果没有db，则会创建一个db。 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...");
                }
            }

Answer 2

SimpleCursorAdapter需要_id中的Cursor字段传递给它。因此，请尝试更改您的查询：

return mDb.query(DATABASE_TABLE, new String[] { KEY_ROWID, KEY_SYMBOL, KEY_COMPANY_NAME }, null, null, null, null, null);

你也得到了：

android.database.sqlite.DatabaseObjectNotClosedException：应用程序没有关闭在这里打开的游标或数据库对象

请确保在完成后使用的所有close()个对象上致电Cursor。

Answer 3

我认为，您需要将布局文件设置为：

SimpleCursorAdapter sca=new SimpleCursorAdapter(context, android.R.layout.simple_list_item_1, c, from, to);

因为您正在传递R.layout.main，这会在重新加载相同的布局文件时出错。

我不确定，但这可能是问题所在。还要在传递给适配器的游标中添加_id。

无法从Sqlite数据库中获取数据

3 个答案: