从SQLite数据库检索数据时获取错误 [英] Getting error, when retrieving data from SQLite database

问题描述

我已经使用SQLite数据库浏览器创建了数据库。我必须遵循此。

解决方案

不要定义 DatabaseHelper 作为您的Android清单中的活动，不 活动。

与任何其他类一样，在活动中创建并使用 DatabaseHelper 。

I have created database by using SQLite Database browser . I have to follow this example.

Name of the database is : jokesdatabase.sql,which has one table jokes i places this in assets folder like this: assets folder

Now, My code is:

DatabaseHelper.java

public class DatabaseHelper extends SQLiteOpenHelper {
private Context mycontext;

private String DB_PATH = "/data/data/a.b.c/databases/";
private static String DB_NAME = "jokesdatabase.sql"; //I have aslo tru .db extenstion
private static String DB_TABLE = "jokes";

public SQLiteDatabase myDataBase;

public DatabaseHelper(Context context) throws IOException {
    super(context, DB_NAME, null, 1);
    this.mycontext = context;
    boolean dbexist = checkdatabase();
    if (dbexist) {
        // System.out.println("Database exists");
        opendatabase();
    } else {
        // System.out.println("Database doesn't exist");
        createdatabase();
    }
}

public void createdatabase() throws IOException {
    boolean dbexist = checkdatabase();
    if (dbexist) {
        System.out.println(" Database exists.");
    } else {
        this.getReadableDatabase();
        try {
            copydatabase();
        } catch (IOException e) {
            throw new Error("Error copying database");
        }
    }
}

private boolean checkdatabase() {
    // SQLiteDatabase checkdb = null;
    boolean checkdb = false;
    try {
        String myPath = DB_PATH + DB_NAME;
        File dbfile = new File(myPath);
        checkdb = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READWRITE) != null;
        checkdb = dbfile.exists();
    } catch (SQLiteException e) {
        System.out.println("Database doesn't exist");
    }

    return checkdb;
}

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 byte to inputfile to 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);

}

public synchronized void close() {
    if (myDataBase != null) {
        myDataBase.close();
    }
    super.close();
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

// This will return a cursor containing database records
public Cursor data() {

    Cursor c;
    c = myDataBase.query(DB_TABLE, null, null, null, null, null, null);
    return c;
}

@Override
public void onCreate(SQLiteDatabase arg0) {
    // TODO Auto-generated method stub

}

}

Result.java

Now Androidmanifest.xml

<application android:icon="@drawable/icon" android:label="@string/app_name">
    <activity android:name=".DatabaseHelper"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name=".Result" android:label="@string/app_name"></activity>
 </application>

And finally I get following error message on logcat.

Give me, what is the error in my code. I have only want to create database using sqlite browser. please dont give the via coding solution.Correct this problem only. which is link.

解决方案

Don't define your DatabaseHelper as activity in your Android manifest, it is not an Activity.

Create and use your DatabaseHelper from within a Activity, just like any other class.

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