我想在数据库中为用户输入的每个标签创建一个新表，该表将有两列测验和注释，但我不断收到错误。我还想知道是否有其他方法可以实现这一目标。
这些是我的代码：
package com.example.mybank;
public class SomeActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.select);
choose = (Button) findViewById(R.id.register);
save = (Button) findViewById(R.id.save);
inputcos = (EditText) findViewById(R.id.inputcos);
select = (Spinner) findViewById(R.id.spinner);
choose.setOnClickListener(this);
save.setOnClickListener(this);
select.setOnItemSelectedListener(this);
loadSpinnerData();
}
private void loadSpinnerData() {
// TODO Auto-generated method stub
DatabaseHandler db = new DatabaseHandler(getApplicationContext());
// Spinner Drop down elements
List<String> lables = db.getAllLabels();
// Creating adapter for spinner
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, lables);
// Drop down layout style - list view with radio button
dataAdapter
.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// attaching data adapter to spinner
select.setAdapter(dataAdapter);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Boolean testing = true;
switch (v.getId()) {
case R.id.register:
save.setVisibility(View.VISIBLE);
inputcos.setVisibility(View.VISIBLE);
break;
case R.id.save:
try {
label = inputcos.getText().toString();
if (label.trim().length() > 0) {
// database handler
DatabaseHandler db = new DatabaseHandler(getApplicationContext());
// inserting new label into database
db.insertLabel(label);
// making input filed text to blank
inputcos.setText("");
// Hiding the keyboard
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(inputcos.getWindowToken(), 0);
// loading spinner with newly added data
loadSpinnerData();
} else {
Toast.makeText(getApplicationContext(), "Please enter course",
Toast.LENGTH_SHORT).show();
}
} catch (Exception e) {
testing = false;
if (testing) {
if (testing) {
Dialog dd = new Dialog(this);
String error = e.toString();
dd.setTitle("Error");
TextView tv = new TextView(this);
tv.setText(error);
dd.setContentView(tv);
dd.show();
}
}
} finally {
if (testing) {
Dialog dd = new Dialog(this);
TextView tv = new TextView(this);
if (label.trim().length() > 0) {
dd.setTitle("Success");
tv.setText("course sucessfully added");
} else {
dd.setTitle("warning");
tv.setText("no course input");
}
dd.setContentView(tv);
dd.show();
}
}
break;
}
}
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position,
long id) {
//creating database table for each label of the list view
if (label.trim().length() > 0) {
DatabaseHandler db = new DatabaseHandler(getApplicationContext());
db.createnewtable(label);
}
Intent i = new Intent(this, choices.class);
startActivity(i);
// Showing selected spinner item
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
}
数据库类：
public class DatabaseHandler extends SQLiteOpenHelper {
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "spinnerExample";
// Labels table name
private static final String TABLE_LABELS = "labels";
static final String TABLE_SPINNER = "course";
// Labels Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_NAME = "name";
private static final String KEY_NOTE="note";
private static final String KEY_QUIZES="quiz";
public DatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
// Category table create query
String CREATE_CATEGORIES_TABLE = "CREATE TABLE " + TABLE_LABELS + "("
+ KEY_ID + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT NOT NULL)";
db.execSQL(CREATE_CATEGORIES_TABLE);
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_LABELS);
// Create tables again
onCreate(db);
}
// creating tables for labels
public void createnewtable(String course){
SQLiteDatabase db = this.getWritableDatabase();
String sql = "CREATE TABLE " + course + " (" + KEY_QUIZES
+ " text not null, " + KEY_NOTE + " text not null " + ");";
Log.i("createDB=", sql);
db.execSQL("DROP TABLE IF EXISTS TABLE_SPINNER");
db.execSQL(sql);
}
/**
* Inserting new labels into labels table
* */
public void insertLabel(String label){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, label);
// Inserting Row
int i = (int) db.insert(TABLE_LABELS, null, values);
db.close(); // Closing database connection
//Now create new table for this category
if (i > 0) {
createnewtable(label);}
}
public long insertquiz(String quiz){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_QUIZES, quiz);
// Inserting Row
return db.insert(TABLE_SPINNER,null, values);
}
public long insertnote(String note){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NOTE, note);
// Inserting Row
return db.insert(TABLE_SPINNER,null, values);
}
/**
* Getting all labels
* returns list of labels
* */
public List<String> getAllLabels(){
List<String> labels = new ArrayList<String>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_LABELS;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
labels.add(cursor.getString(1));
} while (cursor.moveToNext());
}
// closing connection
cursor.close();
db.close();
// returning labels
return labels;}
public List<String> getAllquestions(){
List<String> quiz = new ArrayList<String>();
// Select All Query
String selectQuery = "SELECT * FROM TABLE_SPINNER WHERE category =" + KEY_QUIZES;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
quiz.add(cursor.getString(1));
} while (cursor.moveToNext());
}
// closing connection
cursor.close();
db.close();
// returning labels
return quiz;
}
}
答案 0 :(得分：0)
这是我看到的错误列表。
每次删除并插入TABLE_SPINNER。从未在onCreate中创建。
您每次拨打createnewtable时都会丢弃该平板电脑，但从未创建它。
您在插入语句中使用TABLE_SPINNER作为正确的表名，但是它在DROP和SELECT语句中的字符串文字中，所以你要这样做很可能得到一个Table not found错误。您需要始终使用您的变量。
解决上述问题后，必须合并插入测验和插入注释。您将这些列定义为not null，因此如果在内容值中插入一个键，则另一个值将为null，并抛出错误。
小心 SQL注入 - "SELECT * FROM " + TABLE_LABELS;
可以由db.query(TABLE_LABELS, null, null,...
Ovrerall，你不应该根据任意字符串值创建表。你以后如何查询？您必须知道要执行此操作的表的名称。
将同一模式的任何数据划分为单个表并没有什么好处。您应该在表格中添加String course列，而不是仅为String course创建表格，然后使用WHERE course = ?