回答:请注意，我结合了这两种建议来生成以下代码:
DBAdapter.java:
String name = "";
public String getName(long l) {
Cursor result = myDBHelper.getReadableDatabase().query(
DBAdapter.DATABASE_TABLE_NAME, //Name of your table
new String[] { DBAdapter.KEY_NAME }, //List of columns to return, as a String array. Just one in your case.
DBAdapter.KEY_ROWID + "=?", //The row selection criteria. Equivalent to saying "Where the key id is equal to..."
new String[] { String.valueOf(l) }, //...this value
null, //This parameter deals with grouping results. No need here, hence null.
null, //Relates to the above. Also null.
null //Orders results. There should just be one, so it's null here, but can be useful.
);
if (result.moveToFirst()) {
name = result.getString(result.getColumnIndex(DBAdapter.KEY_NAME));
}
return name;
CharacterInfo.java(NavigationDrawer 父级):
DBAdapter myDb = new DBAdapter(this);
myDb.open();
String name = myDb.getName(1);
mTitle1 = name;
myDb.close();
虽然这产生了一个无错误的环境，但应用程序因 “No such table” 错误 (code 1) 而崩溃，我尚未解决。
结束答案
首先，我知道有很多此类问题。我已经看了至少一打，但似乎无法理解它，所以我发布了一个问题，希望有人能帮我一个忙，并在提供方法的同时更详细地向我解释.
我想创建一个方法来获取我指定的 KEY_ROWID 的 KEY_NAME。 (我认为这可以使用 DBAdapter 中已有的 getRow() 方法来完成)。然后，将其转换为字符串以将其显示为 TextView。
我需要知道如何填写 DBAdapter 底部名为 getName 的方法
一个完美的答案将允许我在设置标题的单独 Activity 中编写以下代码:mTitle1 = getName;
非常感谢大家的宝贵时间。
我有一个非常好的 DBAdapter，由我遵循的教程提供:
public class DBAdapter {
private static final String TAG = "DBAdapter"; //used for logging database version changes
// Field Names:
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_DATE = "date";
public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_NAME, KEY_DATE};
// Column Numbers for each Field Name:
public static final int COL_ROWID = 0;
public static final int COL_NAME = 1;
public static final int COL_DATE = 2;
// DataBase info:
public static final String DATABASE_NAME = "dbCharacters";
public static final String DATABASE_TABLE = "Character_Info";
// The version number must be incremented each time a change to DB structure occurs.
public static final int DATABASE_VERSION = 2;
//SQL statement to create database
private static final String DATABASE_CREATE_SQL =
"CREATE TABLE " + DATABASE_TABLE
+ " (" + KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ KEY_NAME + " TEXT NOT NULL, "
+ KEY_DATE + " TEXT"
+ ");";
private final Context context;
private DatabaseHelper myDBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx) {
this.context = ctx;
myDBHelper = new DatabaseHelper(context);
}
// Open the database connection.
public DBAdapter open() {
db = myDBHelper.getWritableDatabase();
return this;
}
// Close the database connection.
public void close() {
myDBHelper.close();
}
// Add a new set of values to be inserted into the database.
public long insertRow(String name, String date) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
initialValues.put(KEY_DATE, date);
// Insert the data into the database.
return db.insert(DATABASE_TABLE, null, initialValues);
}
// Delete a row from the database, by rowId (primary key)
public boolean deleteRow(long rowId) {
String where = KEY_ROWID + "=" + rowId;
return db.delete(DATABASE_TABLE, where, null) != 0;
}
public void deleteAll() {
Cursor c = getAllRows();
long rowId = c.getColumnIndexOrThrow(KEY_ROWID);
if (c.moveToFirst()) {
do {
deleteRow(c.getLong((int) rowId));
} while (c.moveToNext());
}
c.close();
}
// Return all data in the database.
public Cursor getAllRows() {
String where = null;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS, where, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
// Get a specific row (by rowId)
public Cursor getRow(long rowId) {
String where = KEY_ROWID + "=" + rowId;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS,
where, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
// Change an existing row to be equal to new data.
public boolean updateRow(long rowId, String name, String date) {
String where = KEY_ROWID + "=" + rowId;
ContentValues newValues = new ContentValues();
newValues.put(KEY_NAME, name);
newValues.put(KEY_DATE, date);
// Insert it into the database.
return db.update(DATABASE_TABLE, newValues, where, null) != 0;
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase _db) {
_db.execSQL(DATABASE_CREATE_SQL);
}
@Override
public void onUpgrade(SQLiteDatabase _db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading application's database from version " + oldVersion
+ " to " + newVersion + ", which will destroy all old data!");
// Destroy old database:
_db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
// Recreate new database:
onCreate(_db);
}
}
public void getName (long id) {
}
}
这是 PPartisan 的建议:
public String getName(long l) {
Cursor result = myDBHelper.getReadableDatabase().query(
DBAdapter.DATABASE_NAME, //Name of your database
new String[] { DBAdapter.KEY_NAME }, //List of columns to return, as a String array. Just one in your case.
DBAdapter.KEY_ROWID + "=?", //The row selection criteria. Equivalent to saying "Where the key id is equal to..."
new String[] { String.valueOf(1) }, //...this value
null, //This parameter deals with grouping results. No need here, hence null.
null, //Relates to the above. Also null.
null //Orders results. There should just be one, so it's null here, but can be useful.
);
if (result.moveToFirst()) {
name = result.getString(result.getColumnIndex(DBAdapter.KEY_NAME));
}
return name;
扎汉的建议:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.character_info);
mCharacterInfoDrawerFragment = (CharacterInfo_Drawer_Fragment)
getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
openDB();
String name = DBAdapter.getName(1);
mTitle1 = name;
closeDB();
mCharacterInfoDrawerFragment.setUp(
R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout));
}
最佳答案
从 Android 中的 SQLite 数据库检索数据涉及运行查询，理想情况下 (IMO) 使用 query()方法(您也可以使用 rawQuery())。
由于数据库操作很容易运行很长时间(几秒)，因此您希望查询数据库的次数尽可能少，使查询本身尽可能具体，并真正脱离 UI 线程执行。
例如，如果您确实只想访问数据库的一个“单元格”，那么您将构造一个 query()，如下所示:
Cursor result = myDbInstance.getReadableDatabase().query(
DBAdapter.DATABASE_TABLE, //Name of your table
new String[] { DBAdapter.KEY_NAME }, //List of columns to return, as a String array. Just one in your case.
DBAdapter.KEY_ID + "=?", //The row selection criteria. Equivalent to saying "Where the key id is equal to..."
new String[] { String.valueOf(idOfTheRowToQuery) }, //...this value
null, //This parameter deals with grouping results. No need here, hence null.
null, //Relates to the above. Also null.
null //Orders results. There should just be one, so it's null here, but can be useful.
)
所有这些都将返回一个 Cursor 对象。要访问存储的 String，您需要检查它是否有条目(它应该有)，移动到第一个(在本例中也是唯一的)条目，然后运行以下命令:
if (result.moveToFirst()) {
String name = result.getString(result.getColumnIndex(DBAdapter.KEY_NAME));
}
然后您只需将它分配给您的 TextView。
不过要记住几点:
关于android - 获取 SQLite 单个单元格并在单个 TextView 中显示，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33245713/