Android：数据库帮助-返回特定列中的所有项目

Question

我真的被困住了。我熟悉Java和Android开发，但没有任何数据库经验。这是我第一次。我已经阅读了多个教程，但我无法弄清楚如何从特定行返回所有值并将其设置为单个字符串。

下面是我的数据库控制台。我能够获取所有项目并将其显示在我的视图中，但我打算编写一个特定的函数来仅对 TITLE 列中的所有数据执行某些操作。任何人都可以阐明或提供一个小例程来将 TITLE 列中的所有项目放入单个字符串中吗？最后一个函数是我的 getTitleList，这是我想要收集数据的地方

这是函数：

public void getTitleList(){
cursor = db.rawQuery("SELECT TITLE FROM table", null);


cursor.close();

}

这是我的类

package edu.asu;

import java.util.ArrayList;

导入 android.content.ContentValues； 导入 android.content.Context； 导入 android.content.Intent; 导入 android.database.Cursor; 导入 android.database.sqlite.SQLiteDatabase; 导入 android.os.Bundle； 导入 android.view.Menu； 导入 android.view.MenuInflater; 导入 android.view.MenuItem; 导入 android.widget.AdapterView; 导入 android.widget.AdapterView.OnItemClickListener; 导入 android.widget.AdapterView.OnItemSelectedListener; 导入 android.widget.ListView; 导入 android.widget.SimpleCursorAdapter; 导入 android.widget.Toast; 导入 android.view.View； 导入 android.app.ListActivity;

导入静态 android.provider.BaseColumns._ID;

公共类 DbBookConsole 扩展 ListActivity {

private static String[] FROM = { _ID, DbConstants.TITLE, DbConstants.PRICE,
        DbConstants.ISBN, DbConstants.CHECKIN };
private DbCreate books;
private static SQLiteDatabase db;
private static int[] TO = { R.id.rowid, R.id.name, R.id.price, R.id.isbn, R.id.checkin};
private ListView lv1;
private static String itemId;
private static String titles;
private static String test;
private Cursor cursor;

static final int BOOK_CANCELED = 0;
static final int BOOK_ADDED = 1;
static final int BOOK_MODIFIED = 2;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    showDatabaseContent();


    lv1 = getListView();

    lv1.setTextFilterEnabled(true);

    lv1.setOnItemClickListener(new OnItemClickListener() {

        public void onItemClick(AdapterView<?> a, View v, int position,
                long id) {
            cursor = (Cursor) a.getItemAtPosition(position);
            itemId = cursor.getString(0);
            openOptionsMenu();


        }
    });

    lv1.setOnItemSelectedListener(new OnItemSelectedListener() {

        public void onItemSelected(AdapterView<?> parent, View view,
                int position, long id) {

        }

        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub

        }

    });
}

// selected item index from ListView
public void showDialogItemId(long itemId) {
    Toast.makeText(this,
            "Menu item selected index is" + Long.toString(itemId),
            Toast.LENGTH_LONG).show();

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, menu);

    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.modifyitem:
        if (null != itemId) {
            Bundle bookToModify = new Bundle();
            bookToModify.putString("cTitle", cursor.getString(1));
            bookToModify.putString("cPrice", cursor.getString(2));
            bookToModify.putString("cISBN", cursor.getString(3));
            bookToModify.putString("cCheckin", cursor.getString(4));

            bookToModify.putString("mod_type", "modifyBook");
            Intent intent = new Intent(this, BookDetails.class);
            intent.setClass(this, BookDetails.class);
            intent.putExtras(bookToModify);
            startActivityForResult(intent, BOOK_MODIFIED);
        } else {
            Toast
                    .makeText(this, "Select Book to modify",
                            Toast.LENGTH_LONG).show();
        }
        break;
    case R.id.additem:

        Intent i = new Intent(this, BookDetails.class);
        Bundle bun = new Bundle();
        bun.putString("mod_type", "addBook");
        i.setClass(this, BookDetails.class);
        i.putExtras(bun);
        startActivityForResult(i, BOOK_ADDED);
        break;
        case R.id.removeitem:
        if (null != itemId) {
            removeBook(itemId);
            showDatabaseContent();
        } else {
            Toast
                    .makeText(this, "Select Book to delete",
                            Toast.LENGTH_LONG).show();
        }
        break;
    }
    return true;
}

@Override
protected void onActivityResult(int requestCode, int resultCode,
        Intent intent) {
    // See which child activity is calling us back.
    switch (resultCode) {

    case BOOK_ADDED:
        // This is the standard resultCode that is sent back if the
        // activity crashed or didn't doesn't supply an explicit result.
        if (resultCode == RESULT_FIRST_USER) {
            Bundle bundle = new Bundle();
            bundle = intent.getBundleExtra("bookData");
            addBook(bundle);
            showDatabaseContent();
        } else {
            Toast.makeText(this, "CANCEL BOOK BUTTON PRESSED",
                    Toast.LENGTH_LONG).show();
        }
        break;
    case BOOK_MODIFIED:
        if (resultCode == 2) {
            Bundle bundle = new Bundle();
            bundle = intent.getBundleExtra("bookData");
            modifyBook(bundle);
            showDatabaseContent();
        } else {
            Toast.makeText(this, "MODIFY BOOK FAILED", Toast.LENGTH_LONG)
                    .show();
        }
        break;
    default:
        break;
    }
}

// method removes item from database
private void removeBook(String itemId) {
    db = books.getWritableDatabase();
    db.delete(DbConstants.TABLE_NAME, "_ID=" + itemId, null);

}

private void addBook(Bundle bundle) {
    // Insert a new record into the Events data source.
    // You would do something similar for delete and update.
    db = books.getWritableDatabase();
    ContentValues vals = new ContentValues();
    vals.put(DbConstants.TITLE, bundle.getString("bookTitle"));
    vals.put(DbConstants.PRICE, bundle.getString("bookPrice"));
    vals.put(DbConstants.ISBN, bundle.getString("bookISBN"));
    vals.put(DbConstants.CHECKIN, bundle.getString("bookCheck"));
    db.insertOrThrow(DbConstants.TABLE_NAME, null, vals);
}

// method should modify existing Contact
private void modifyBook(Bundle bundle) {
    db = books.getWritableDatabase();
    ContentValues vals = new ContentValues();
    vals.put(DbConstants.TITLE, bundle.getString("bookTitle"));
    vals.put(DbConstants.PRICE, bundle.getString("bookPrice"));
    vals.put(DbConstants.ISBN, bundle.getString("bookISBN"));
    vals.put(DbConstants.CHECKIN, bundle.getString("bookCheck"));
    db.update(DbConstants.TABLE_NAME, vals, _ID + "=" + itemId, null);
}

private Cursor getBooks() {
    db = books.getReadableDatabase();
    cursor = db.query(DbConstants.TABLE_NAME, FROM, null, null, null, null, null,
            null);
    startManagingCursor(cursor);
    return cursor;
}

public void showDatabaseContent() {
    books = new DbCreate(this);
    try {
        cursor = getBooks();


        showBooks(cursor);



    } finally {
        books.close();
        db.close();
    }
}

private void showBooks(Cursor cursor) {
    // set up data binding

    SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
            R.layout.item, cursor, FROM, TO);
    setListAdapter(adapter);



}

公共 void getTitleList(){ 游标 = db.rawQuery("从表中选择标题", null);

cursor.close();

} }

Answer 1

除非我误解了从游标中获取查询中的所有项目的问题，循环遍历所有项目并连接成一个字符串，否则您会执行如下操作：

//  constants of column indexes
int INDEX_ROWID = 0; 
int INDEX_TITLE = 1; 

...

db = new MyDBAdapter(this);
db.open();

Cursor c = db.getTitleList();
startManagingCursor(c);

String allTitles;

// loop through cursor 
while(c.moveToNext()) {
    allTitles += c.getString(INDEX_TITLE);
}

希望有帮助