LogCat error:
FATAL EXCEPTION: main
Process: com.sam.shoppingcart, PID: 31773
android.database.sqlite.SQLiteException: near "Beef": syntax error (code 1): , while compiling: SELECT KEY_NAME FROM shop WHERE KEY_NAME=Corned Beef
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:893)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:504)
at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1339)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1278)
at com.sam.shoppingcart.SQLiteHandler.ifExists(SQLiteHandler.java:63)
at com.sam.shoppingcart.CustomListAdapter$1.onClick(CustomListAdapter.java:77)
我使用带有“添加”和“删除”按钮的自定义适配器的列表视图。当单击“添加”按钮时，LV项的名称和价格获取将添加到DB。如果LV项目已经存在于DB中，我想在添加时进行检查。为此，我在DBHandler中创建了ifExists（模型模型）函数。但现在点击添加按钮，它给了我错误。我做错了什么？ PS：我从here获得了这个功能。
public class MainActivity extends AppCompatActivity {
private ListView listView;
private ArrayList<Model> mListData;
private CustomListAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView)findViewById(R.id.list);
mListData = new ArrayList<>();
mListData.add(new Model("Beef Manhattan", "50"));
mListData.add(new Model("Chicken Fried Steak", "90"));
mListData.add(new Model("Corned Beef", "100"));
mListData.add(new Model("Domesticated Turkey", "80"));
mListData.add(new Model("Eggs Benedict", "10"));
mListData.add(new Model("French Dip", "20"));
mListData.add(new Model("Green Bean Casserole", "30"));
mListData.add(new Model("Potato Salad", "40"));
mListData.add(new Model("Pumpkin Pie", "60"));
mListData.add(new Model("Salisbury Steak", "70"));
adapter = new CustomListAdapter(this, R.layout.listrow, mListData);
listView.setAdapter(adapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action) {
startActivity(new Intent(MainActivity.this, NextActivity.class));
return true;
}
return super.onOptionsItemSelected(item);
}
}public class CustomListAdapter extends ArrayAdapter<Model> {
private Context mContext;
int resource;
private ArrayList<Model> mListData = new ArrayList<Model>();
public CustomListAdapter(Context mContext, int resource, ArrayList<Model> mListData) {
super(mContext, resource, mListData);
this.resource = resource;
this.mContext = mContext;
this.mListData = mListData;
}
public void setListData(ArrayList<Model> mListData) {
this.mListData = mListData;
notifyDataSetChanged();
}
@Override
public int getCount() {
return super.getCount();
}
@Override
public View getView(final int position, View convertView, final ViewGroup parent) {
View v = convertView;
final ViewHolder holder;
if (v == null) {
holder = new ViewHolder();
LayoutInflater inflater = ((Activity) mContext).getLayoutInflater();
v = inflater.inflate(resource, parent, false);
holder.name = (TextView) v.findViewById(R.id.name);
holder.rate = (TextView) v.findViewById(R.id.rate);
holder.add = (Button) v.findViewById(R.id.add);
holder.remove = (Button) v.findViewById(R.id.remove);
v.setTag(holder);
} else {
holder = (ViewHolder) v.getTag();
}
final Model item = mListData.get(position);
holder.name.setText(item.getName());
holder.rate.setText(item.getRate());
holder.add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteHandler db = new SQLiteHandler(getContext());
if(db.ifExists(item)){
Toast.makeText(getContext(), "Already Present", Toast.LENGTH_SHORT).show();
}else{
db.addItems(holder.name.getText().toString(), holder.rate.getText().toString());
Toast.makeText(getContext(), "Added", Toast.LENGTH_SHORT).show();
}
}
});
holder.remove.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteHandler db = new SQLiteHandler(getContext());
db.deleteItem(item);
Toast.makeText(getContext(), "Removed", Toast.LENGTH_SHORT).show();
}
});
return v;
}
class ViewHolder {
TextView name;
TextView rate;
Button add;
Button remove;
}
}public class SQLiteHandler extends SQLiteOpenHelper {
private static final String TAG = SQLiteHandler.class.getSimpleName();
// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "android_api";
// Profile Settings table name
private static final String TABLE_SHOP = "shop";
// Profile Settings information names
private static final String KEY_ID = "id";
private static final String KEY_NAME = "name";
private static final String KEY_PRICE = "price";
public SQLiteHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_PROF_TABLE = "CREATE TABLE " + TABLE_SHOP + "("+KEY_ID+" INTEGER PRIMARY KEY, "+KEY_NAME+" TEXT, "+KEY_PRICE+" TEXT" + ")";
db.execSQL(CREATE_PROF_TABLE);
Log.d(TAG, "Database tables created");
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_SHOP);
// Create tables again
onCreate(db);
}
// Check before adding item if item already exist
SQLiteDatabase db = this.getWritableDatabase();
public boolean ifExists(Model model) {
Cursor cursor = null;
String checkQuery = "SELECT KEY_NAME FROM "+TABLE_SHOP+" WHERE KEY_NAME="+model.getName();
cursor= db.rawQuery(checkQuery,null);
boolean exists = (cursor.getCount() > 0);
cursor.close();
return exists;
}
// Add items to db
public void addItems(String name, String mobile){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, name);
values.put(KEY_PRICE, mobile);
long id = db.insert(TABLE_SHOP, null, values); // insert to 1st row
db.close(); // Closing database connection
Log.d(TAG, "New products inserted into sqlite: " + id);
}
// Fetch all data
public ArrayList<HashMap<String, String>> getProfDetails()
{
ArrayList<HashMap<String, String>> array_list = new ArrayList<HashMap<String, String>>();
SQLiteDatabase db = this.getReadableDatabase();
String selectQuery = "SELECT * FROM " + TABLE_SHOP;
Cursor res = db.rawQuery(selectQuery, null);
res.moveToFirst();
while (res.isAfterLast() == false)
{
HashMap<String, String> hashmap= new HashMap<String, String>();
hashmap.put("name", res.getString(res.getColumnIndex(KEY_NAME)));
hashmap.put("price", res.getString(res.getColumnIndex(KEY_PRICE)));
array_list.add(hashmap);
res.moveToNext();
}
return array_list;
}
// Getting Sum of "price"
public int sumofPrice(){
SQLiteDatabase db = this.getReadableDatabase();
String selectQuery = "SELECT SUM(price) FROM " + TABLE_SHOP;
Cursor cur = db.rawQuery(selectQuery, null);
int total=0;
if(cur.moveToFirst())
{
total = cur.getInt(0);
}
return total;
}
// Delete single row
public void deleteItem(Model model) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_SHOP, KEY_NAME + " = ?",new String[] { String.valueOf(model.getName()) });
db.close();
}
// Delete whole table
public void deleteTable() {
SQLiteDatabase db = this.getWritableDatabase();
// Delete All Rows
db.delete(TABLE_SHOP, null, null);
db.close();
Log.d(TAG, "Deleted all info from sqlite");
}
}
答案 0 :(得分：3)
检查下面更新的ifExists（）方法，
public boolean ifExists(Model model)
{
Cursor cursor = null;
String checkQuery = "SELECT " + KEY_NAME + " FROM " + TABLE_SHOP + " WHERE " + KEY_NAME + "= '"+model.getName() + "'";
cursor= db.rawQuery(checkQuery,null);
boolean exists = (cursor.getCount() > 0);
cursor.close();
return exists;
}
两件事，首先是你将变量作为列名的值传递，第二件事是你传递名称值和空格而没有引用它们所以它会使应用程序崩溃。
现在尝试上面的代码。
答案 1 :(得分：1)
String checkQuery = "SELECT KEY_NAME FROM "+TABLE_SHOP+" WHERE KEY_NAME="+model.getName();
将其更改为
String checkQuery = "SELECT "+KEY_NAME+" FROM "+TABLE_SHOP+" WHERE "+KEY_NAME+"="+model.getName();
答案 2 :(得分：1)
private boolean hasRow(String id) {
String selectString = "SELECT * FROM " + tablename + " WHERE " +
id + " =?";
sqliteDatabase = getReadableDatabase();
Cursor cursor = sqliteDatabase.rawQuery(selectString, new String[] {id});
boolean hasObject = false;
if(cursor.moveToFirst()){
hasObject = true;
}
cursor.close();
sqliteDatabase.close(); //Close the database
return hasObject; //return value.
}
这将找到第一次出现，并且会说是这行存在。 要获取有多少行，请使用
while(cursor.moveToNext()) {
count++;
}