请帮助我，我正在尝试使用本地数据库文件预填充我的自动完成文本视图 这是我的代码 这是我不断收到的错误
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.saud.app.autocompletesample/com.saud.app.autocompletesample.MainActivity}: android.database.sqlite.SQLiteException: near "drugstable": syntax error (code 1 SQLITE_ERROR): , while compiling: drugstable
DatabaseHelper.java
package com.saud.app.autocompletesample;
import android.annotation.SuppressLint;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import com.google.android.material.shape.CutCornerTreatment;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.SQLException;
import java.util.ArrayList;
public class DrugsDataBase extends SQLiteOpenHelper {
private static String DB_PATH = "";
private final Context myContext;
private static final String database_name = "aaa.db";
private static final int version = 1;
public static final String table_name = "drugstable";
public static final String column_id = "id";
public static final String column_name = "drug";
private SQLiteDatabase db;
public DrugsDataBase(Context context) {
super(context, database_name, null, version);
this.myContext = context;
DB_PATH = myContext.getDatabasePath(database_name)
.toString();
}
public void createDataBase()
throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// do nothing - database already exist
} else {
// By calling this method and
// the empty database will be
// created into the default system
// path of your application
// so we are gonna be able
// to overwrite that database
// with our database.
this.getWritableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error(
"Error copying database");
}
}
}
// Check if the database already exist
// to avoid re-copying the file each
// time you open the application
// return true if it exists
// false if it doesn't.
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH;
checkDB
= SQLiteDatabase
.openDatabase(
myPath, null,
SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
// database doesn't exist yet.
Log.e("message", "" + e);
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null;
}
/**
* Copies your database from your
* local assets-folder to the just
* created empty database in the
* system folder, from where it
* can be accessed and handled.
* This is done by transferring bytestream.
*/
private void copyDataBase()
throws IOException {
// Open your local db as the input stream
InputStream myInput
= myContext.getAssets()
.open(database_name);
// Path to the just created empty db
String outFileName = DB_PATH;
// 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);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase()
throws SQLException {
// Open the database
String myPath = DB_PATH;
db = SQLiteDatabase
.openDatabase(
myPath, null,
SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close() {
// close the database.
if (db != null)
db.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
SQLiteDatabase db = this.getReadableDatabase();
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase,
int oldVersion,
int newVersion) {
// It is an abstract method which is
// used to perform different task
// based on the version of database.
}
public ArrayList<String> getNames() {
SQLiteDatabase db = this.getReadableDatabase();
ArrayList<String> names = new ArrayList<>();
Cursor cursor = db.rawQuery(table_name, null);
cursor.moveToNext();
while (!cursor.isAfterLast()) {
names.add(cursor.getString(1));
cursor.moveToNext();
}
cursor.close();
return names;
}
}
MainActivity.java
package com.saud.app.autocompletesample;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
import androidx.appcompat.app.AppCompatActivity;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
private AutoCompleteTextView autoCompleteTextView;
private ArrayList<String> names;
private DrugsDataBase dataBase;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
autoCompleteTextView = findViewById(R.id.autoCompleteTextView);
dataBase = new DrugsDataBase(this);
names = dataBase.getNames();
ArrayAdapter<String> autoCompleteAdapter = new ArrayAdapter<>(this, android.R.layout.simple_dropdown_item_1line, names);
autoCompleteTextView.setAdapter(autoCompleteAdapter);
}
}
我一次又一次地重新创建了数据库文件，我确信现在一切都好了 经过 2 天的谷歌搜索和教程导致更多错误后，我现在出现了心理障碍！
在 DrugsDataBase 类的 getNames 方法中，您应该使用 query 方法构造正确的 SQL 查询。该查询应从 drugtable 表中检索特定列。查询应如下所示：
public ArrayList<String> getNames() {
SQLiteDatabase db = this.getReadableDatabase();
ArrayList<String> names = new ArrayList<>();
// Define the columns you want to retrieve
String[] columns = { column_name }; // Only retrieve the "drug" column
// Query the table to retrieve the names
Cursor cursor = db.query(table_name, columns, null, null, null, null, null);
if (cursor != null && cursor.moveToFirst()) {
do {
names.add(cursor.getString(cursor.getColumnIndex(column_name)));
} while (cursor.moveToNext());
cursor.close();
}
return names;
}
此查询使用查询方法从 drugtable 表的“drug”列中检索值。生成的 Cursor 将仅包含“药物”列值，并且您可以迭代 Cursor 以使用药物名称填充 ArrayList。
确保您已正确声明 column_name 常量，并且它与数据库表定义中的实际列名称匹配。