我是Android编程的新手。 在这里，我想制作一个可以记录我们所有现金流的应用程序。 但是当我想制作一个具有数据库价值的Spinner时，我遇到了一些问题。 当我运行该程序时，Android Studio中的报告部分会给我一个报告＆＃34; android.database.sqlite.SQLiteCantOpenDatabaseException：未知错误（代码14）：无法打开数据库＆＃34;， 我对这个错误有点沮丧。我谷歌搜索它，但仍然无法找到解决方法，或者因为我不明白教程说的内容。请高手帮我解决一下这个错误。 非常感谢。
NB。这是Main_Activity（创建微调器的位置）的源代码
public class MainActivity extends ActionBarActivity {
private static Button BtnINewTrans;
private static Button BtnIViewCash;
private static Button BtnIAddCateg;
DatabaseHelper dbHelper = new DatabaseHelper(this);
Spinner selectCategory;
//ArrayAdapter<String> adapterCategory;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
onButtonClickButtonListener();
select_spinner_Category();
}
/*ArrayList<String> my_array = new ArrayList<String>();
my_array = getTableValues();
Spinner My_spinner = (Spinner) findViewById(R.id.spinner1);
ArrayAdapter my_Adapter = new ArrayAdapter(this, R.layout.spinner_row, my_array);
My_spinner.setAdapter(my_Adapter);*/
public void select_spinner_Category (){
ArrayList<String> arrayCategory = new ArrayList<String>();
arrayCategory = dbHelper.getAllCategory();
selectCategory = (Spinner) findViewById(R.id.spnCategSelect);
ArrayAdapter adapterCategory = new ArrayAdapter(this, android.R.layout.simple_spinner_item, arrayCategory);
// adapterCategory = new ArrayList<String>(this, android.R.layout.simple_spinner_item, R.id.spnCategSelect, AllCategoryList);
adapterCategory.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
selectCategory.setAdapter(adapterCategory);
selectCategory.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(getBaseContext(), parent.getItemAtPosition(position) + " selected", Toast.LENGTH_LONG).show();
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
public void onButtonClickButtonListener(){
BtnINewTrans = (Button)findViewById(R.id.btnNewTrans);
BtnINewTrans.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intentNewTrans = new Intent ("com.example.ever_ncn.cashflow.NewTransaction");
startActivity(intentNewTrans);
}
}
);
BtnIViewCash = (Button)findViewById(R.id.btnViewCashflow);
BtnIViewCash.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intentViewCash = new Intent ("com.example.ever_ncn.cashflow.ViewCashflow");
startActivity(intentViewCash);
}
}
);
BtnIAddCateg = (Button)findViewById(R.id.btnAddCateg);
BtnIAddCateg.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intentAddCateg = new Intent ("com.example.ever_ncn.cashflow.AddCategory");
startActivity(intentAddCateg);
}
}
);
}
@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_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
这个是Database_Helper
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String MyVillageSoftware = "MyVillageSoftware";
public static final String DATABASE_NAME = "Cashflow.db";
public static final String TABLE_Categ_NAME = "category_table";
public static final String COL1 = "CategId";
public static final String COL2 = "CategName";
public static final String COL3 = "Note";
public static final String COL4 = "Currency";
SQLiteDatabase db;
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, 2);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("Create table " + TABLE_Categ_NAME +
" (CategID Integer PRIMARY KEY AUTOINCREMENT, " +
"CategName Text," +
" Note Text," +
" Currency Text)");
}
public boolean insertCategData(String categname, String note, String currency){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(COL2, categname);
contentValues.put(COL3, note);
contentValues.put(COL4, currency);
long result = db.insert(TABLE_Categ_NAME, null, contentValues);
if (result == 1)
return true;
else
return false;
}
public ArrayList<String> getAllCategory() {
ArrayList<String> AllCategoryList = new ArrayList<String>();
try {
db = SQLiteDatabase.openOrCreateDatabase(DATABASE_NAME, null, null);
Cursor allrows = db.rawQuery("SELECT * FROM " + TABLE_Categ_NAME, null);
System.out.println("COUNT : " + allrows.getCount());
if (allrows.moveToFirst()) {
do {
String ID = allrows.getString(0);
String Categ = allrows.getString(1);
String Note = allrows.getString(2);
String Curr = allrows.getString(3);
AllCategoryList.add(Categ);
} while (allrows.moveToNext());
}
allrows.close();
db.close();
} catch (Exception e) {
}
return AllCategoryList;
}
/*public ArrayList<String>getAllCategory(){
ArrayList<String> AllCategoryList = new ArrayList<String>();
SQLiteDatabase db = this.getReadableDatabase();
String selectCateg="Select * FROM " +TABLE_Categ_NAME;
Cursor cursor = db.rawQuery(selectCateg, null);
if(cursor.getCount()>0){
while (cursor.moveToNext()){
String categname1=cursor.getString(cursor.getColumnIndex(COL2));
AllCategoryList.add(COL2);
}return AllCategoryList;
}
return AllCategoryList;
}*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " +TABLE_Categ_NAME);
onCreate(db);
}
}
答案 0 :(得分：0)
首先创建DBHelper类。
public class DBAdapter { 私有DBHelper dbHelper; 私有上下文; 私有SQLiteDatabase db;
public DBAdapter(Context context) {
this.context = context;
dbHelper = new DBHelper(context);
}
public void open() {
db = dbHelper.getWritableDatabase();
}
public void close() {
db.close();
}
public long insertBook(Book book) {
ContentValues values = new ContentValues();
values.put(DBHelper.TITLE, book.getTitle());
values.put(DBHelper.AUTHOR, book.getAuthor());
values.put(DBHelper.CATEGORY, book.getCategory());
values.put(DBHelper.ISBN, book.getISBN());
values.put(DBHelper.PRICE, book.getPrice());
long inserted = db.insert(DBHelper.TABLE_NAME, null, values);
return inserted;
}
public ArrayList<Book> getAllBooks() {
ArrayList<Book> allBooks = null;
String[] columns = { DBHelper.TITLE, DBHelper.AUTHOR };
Cursor cursor = db.query(DBHelper.TABLE_NAME, null, null, null, null,
null, null);
// select * from books;
if (cursor != null && cursor.getCount() > 0) {
int size = cursor.getCount();
cursor.moveToFirst();
allBooks = new ArrayList<Book>();
for (int i = 0; i < size; i++) {
String title = cursor.getString(cursor
.getColumnIndex(DBHelper.TITLE));
String author = cursor.getString(cursor
.getColumnIndex(DBHelper.AUTHOR));
String category = cursor.getString(cursor
.getColumnIndex(DBHelper.CATEGORY));
String ISBN = cursor.getString(cursor
.getColumnIndex(DBHelper.ISBN));
double price = cursor.getDouble(cursor
.getColumnIndex(DBHelper.PRICE));
allBooks.add(new Book(title, author, category, ISBN, price));
cursor.moveToNext();
}
}
cursor.close();
return allBooks;
}
}
然后创建DBAdapter
public class DBAdapter {
private DBHelper dbHelper;
private Context context;
private SQLiteDatabase db;
public DBAdapter(Context context) {
this.context = context;
dbHelper = new DBHelper(context);
}
public void open() {
db = dbHelper.getWritableDatabase();
}
public void close() {
db.close();
}
public long insertBook(Book book) {
ContentValues values = new ContentValues();
values.put(DBHelper.TITLE, book.getTitle());
values.put(DBHelper.AUTHOR, book.getAuthor());
values.put(DBHelper.CATEGORY, book.getCategory());
values.put(DBHelper.ISBN, book.getISBN());
values.put(DBHelper.PRICE, book.getPrice());
long inserted = db.insert(DBHelper.TABLE_NAME, null, values);
return inserted;
}
public ArrayList<Book> getAllBooks() {
ArrayList<Book> allBooks = null;
String[] columns = { DBHelper.TITLE, DBHelper.AUTHOR };
Cursor cursor = db.query(DBHelper.TABLE_NAME, null, null, null, null,
null, null);
// select * from books;
if (cursor != null && cursor.getCount() > 0) {
int size = cursor.getCount();
cursor.moveToFirst();
allBooks = new ArrayList<Book>();
for (int i = 0; i < size; i++) {
String title = cursor.getString(cursor
.getColumnIndex(DBHelper.TITLE));
String author = cursor.getString(cursor
.getColumnIndex(DBHelper.AUTHOR));
String category = cursor.getString(cursor
.getColumnIndex(DBHelper.CATEGORY));
String ISBN = cursor.getString(cursor
.getColumnIndex(DBHelper.ISBN));
double price = cursor.getDouble(cursor
.getColumnIndex(DBHelper.PRICE));
allBooks.add(new Book(title, author, category, ISBN, price));
cursor.moveToNext();
}
}
cursor.close();
return allBooks;
}
}
DBAdapter类在DBhelper类中创建一个对象并打开exit数据库，否则会创建一个新的数据库。
最终可以通过这种方式获取数据表单数据库
public class MainActivity extends Activity implements OnClickListener {
private EditText etTitle, etAuthor, etCategory, etISBN, etPrice;
private Button btnSave, btnView;
private DBAdapter dbAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbAdapter = new DBAdapter(this);
etTitle = (EditText) findViewById(R.id.etTitle);
etAuthor = (EditText) findViewById(R.id.etAuthor);
etCategory = (EditText) findViewById(R.id.etCategory);
etISBN = (EditText) findViewById(R.id.etISBN);
etPrice = (EditText) findViewById(R.id.etPrice);
btnSave = (Button) findViewById(R.id.btnSave);
btnView = (Button) findViewById(R.id.btnView);
btnSave.setOnClickListener(this);
btnView.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btnSave:
String title = etTitle.getText().toString();
String author = etAuthor.getText().toString();
String category = etCategory.getText().toString();
String ISBN = etISBN.getText().toString();
double price = Double.parseDouble(etPrice.getText().toString());
dbAdapter.open();
long inserted = dbAdapter.insertBook(new Book(title, author,
category, ISBN, price));
dbAdapter.close();
if (inserted >= 0) {
Toast.makeText(getApplicationContext(), "Insert Successful",
Toast.LENGTH_LONG).show();
}
break;
case R.id.btnView:
// retrieve a list of books
dbAdapter.open();
ArrayList<Book> books = dbAdapter.getAllBooks();
dbAdapter.close();
for (Book book : books) {
Toast.makeText(getApplicationContext(), book.toString(),
Toast.LENGTH_LONG).show();
}
// view
break;
default:
break;
}
}
}
////////////////////////
public class Book {
private String title;
private String author;
private String category;
private String ISBN;
private double price;
public Book(String title, String author, String category, String iSBN,
double price) {
super();
this.title = title;
this.author = author;
this.category = category;
ISBN = iSBN;
this.price = price;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public String getCategory() {
return category;
}
public void setCategory(String category) {
this.category = category;
}
public String getISBN() {
return ISBN;
}
public void setISBN(String iSBN) {
ISBN = iSBN;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public String toString() {
return "[" + title + " " + author + " " + category + " " + ISBN + " "
+ price + "]";
}
}