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我有片段类使用按钮，该按钮必须登录用户，如果存在或必须显示文本用户无效。我有使用sqlite数据库。但问题是当我点击登录按钮我的应用程序崩溃。 以下是破片按钮被点击的应用程序得到崩溃在Android片段
public class FirstFragment extends Fragment {
LoginDataBaseAdapter loginDataBaseAdapter;
String userName;
EditText testUser;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.firstfragment,container,false);
// create a instance of SQLite Database
loginDataBaseAdapter = new LoginDataBaseAdapter(getActivity());
loginDataBaseAdapter = loginDataBaseAdapter.open();
//get the reference of the design
final testUser = (EditText) view.findViewById(R.id.editTextUserNameToLogin);
final EditText testPassword = (EditText) view.findViewById(R.id.editTextPasswordToLogin);
final Button btnLogin = (Button) view.findViewById(R.id.buttonSignIn);
final Button btnCreate=(Button)view.findViewById(R.id.buttonCreateAccount);
//set OnClick Listener on login button
btnLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
userName=testUser.getText().toString();
EditText testPassword = (EditText) getActivity().findViewById(R.id.editTextPasswordToLogin);
String password = testPassword.getText().toString();
//fetch the password from the database for respective user name
String storedPassword = loginDataBaseAdapter.getSinlgeEntry(userName);
Toast.makeText(getActivity(),storedPassword,1).show();
// check if the Stored password matches with Password entered by user
if (password.equals(storedPassword)) {
Toast.makeText(getActivity(), "Congrats:Login Sucessfull", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getActivity(), "User Name or Password does not match", Toast.LENGTH_LONG).show();
}
}
});
return view;
}
我的DB类“LoginDataBaseAdapter”的附加代码我有一个功能检查的地方，我们已经通过的用户名密码。这里是代码
public String getSinlgeEntry(String userName) {
Cursor cursor = db.query("LOGIN", null, " USERNAME=?", new String[]{userName}, null, null, null);
if (cursor.getCount() < 1) // UserName Not Exist
{
cursor.close();
return "NOT EXIST";
}
cursor.moveToFirst();
String password = cursor.getString(cursor.getColumnIndex("PASSWORD"));
cursor.close();
return password;
}
现在我无法弄清楚，我失踪了。当我点击登录按钮时，我的应用程序会崩溃。 预先感谢您。
我的logcat：
java.lang.NullPointerException
at com.example.betatestregister.LoginDataBaseAdapter.getSinlgeEntry(LoginDataBaseAdapter.java:68)
at com.example.betatestregister.FirstFragment$1.onClick(FirstFragment.java:52)
at android.view.View.performClick(View.java:4204)
at android.view.View$PerformClick.run(View.java:17355)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
我LoginDataBaseAdapter类代码：
package com.example.betatestregister;
/** * 通过创建罗汉上24/05/13。 */
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.widget.Toast;
public class LoginDataBaseAdapter {
static final String DATABASE_NAME = "login.db";
static final int DATABASE_VERSION = 1;
public static final int NAME_COLUMN = 1;
// TODO: Create public field for each column in your table.
// SQL Statement to create a new database.
static final String DATABASE_CREATE = "create table " + "LOGIN" +
"(" + "ID" + " integer primary key autoincrement," + "USERNAME text,PASSWORD
text); ";
// Variable to hold the database instance
public SQLiteDatabase db;
// Context of the application using the database.
private final Context context;
// Database open/upgrade helper
private DataBaseHelper dbHelper;
public LoginDataBaseAdapter(Context _context) {
context = _context;
dbHelper = new DataBaseHelper(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public LoginDataBaseAdapter open() throws SQLException {
// db = dbHelper.getWritableDatabase();
return this;
}
public void close() {
db.close();
}
public SQLiteDatabase getDatabaseInstance() {
return db;
}
public void insertEntry(String userName, String password) {
ContentValues newValues = new ContentValues();
// Assign values for each row.
newValues.put("USERNAME", userName);
newValues.put("PASSWORD", password);
// Insert the row into your table
db.insert("LOGIN", null, newValues);
///Toast.makeText(context, "Reminder Is Successfully Saved",
Toast.LENGTH_LONG).show();
}
public int deleteEntry(String UserName) {
//String id=String.valueOf(ID);
String where = "USERNAME=?";
int numberOFEntriesDeleted = db.delete("LOGIN", where, new String[]{UserName});
// Toast.makeText(context, "Number fo Entry Deleted Successfully :
"+numberOFEntriesDeleted, Toast.LENGTH_LONG).show();
return numberOFEntriesDeleted;
}
public String getSinlgeEntry(String userName) {
Cursor cursor = db.query("LOGIN", null, " USERNAME=?", new String[]{userName},
null, null, null);
if (cursor.getCount() < 1) // UserName Not Exist
{
cursor.close();
// Toast.makeText(context, "Number fo Entry Deleted Successfully :
"+numberOFEntriesDeleted, Toast.LENGTH_LONG).show();
return "NOT EXIST";
}
cursor.moveToFirst();
String password = cursor.getString(cursor.getColumnIndex("PASSWORD"));
cursor.close();
return password;
}
public void updateEntry(String userName, String password) {
// Define the updated row content.
ContentValues updatedValues = new ContentValues();
// Assign values for each row.
updatedValues.put("USERNAME", userName);
updatedValues.put("PASSWORD", password);
String where = "USERNAME = ?";
db.update("LOGIN", updatedValues, where, new String[]{userName});
}
}
请发布您的错误日志 –
@Rohan Ale后用你的logcat输出行号..并显示它所在的行号例外。 – TheFlash
请发布您的logcat ...你的数据库是空的，它似乎 – Pragnani