Accessing SQLite database from fragment
Question
My app contains MainActivity class and several fragments. One of the is the registration fragment which I want it to be able tho interact with my database which should contain only one table named USERS to whom I will CRUD. I've opened the MySQLiteOpenHelper class that extends SQLiteOpenHelper and created a User class as well. I've declared:
MySQLiteOpenHelper db = new MySQLiteOpenHelper(this);
in the activity's onCreate method. My question is how do I interact with this db from the fragments? I've tried the following code but it didn't work:
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
public class registration extends Fragment {
public registration() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.registration, container,
false);
return rootView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
final EditText etFirstName = (EditText) getActivity().findViewById(
R.id.etFirstName);
final EditText etLastName = (EditText) getActivity().findViewById(
R.id.etLastName);
final EditText etEmail = (EditText) getActivity().findViewById(
R.id.etEmail);
final EditText etUsername = (EditText) getActivity().findViewById(
R.id.etUsername);
final EditText etPassword = (EditText) getActivity().findViewById(
R.id.etPassword);
Button bDone = (Button) getActivity().findViewById(R.id.bDone);
bDone.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
MySQLiteOpenHelper db = new MySQLiteOpenHelper(null);//do I need this??
db.addUser(new User(etFirstName.getText().toString(),
etLastName.getText().toString(), etEmail.getText()
.toString(), etUsername.getText().toString(),
etPassword.getText().toString()));
}
});
}
}
What happens now is that the moment I click the DONE button the app crushes... Thank's!!
MySQLiteOpenHelper looks like this:
import java.util.LinkedList;
import java.util.List;
import android.R.string;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class MySQLiteOpenHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION=1;
private static final String DATABASE_NAME="MyDB";
private static final String TABLE_USERS="USERS";
private static final String FIRST_NAME="First_name";
private static final String LAST_NAME="Last_name";
private static final String EMAIL="Email";
private static final String USERNAME="Username";
private static final String PASSWORD="Password";
private static final String COLUMNS[]={FIRST_NAME, LAST_NAME, EMAIL, USERNAME, PASSWORD};
public MySQLiteOpenHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
String CREATE_MyDB_TABLE = "CREATE TABLE USERS ( " +
"First_name TEXT, " +
"Last_name TEXT, "+
"Email KEY TEXT NOT NULL, "+
"Username TEXT NOT NULL, "+
"Password TEXT NOT NULL)";
db.execSQL(CREATE_MyDB_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS USERS");
this.onCreate(db);
}
public void addUser(User user){
Log.d("addUser", user.toString());
SQLiteDatabase db=this.getWritableDatabase();
ContentValues values=new ContentValues();
values.put(FIRST_NAME, user.getFirstName());
values.put(LAST_NAME, user.getLastName());
values.put(EMAIL, user.getEmail());
values.put(USERNAME, user.getUsername());
values.put(PASSWORD, user.getPassword());
db.insert(TABLE_USERS, null, values);
db.close();
}
public User getUser(String Email){
SQLiteDatabase db=this.getReadableDatabase();
Cursor cursor=
db.query(TABLE_USERS, COLUMNS, "Email =?", new String[] {String.valueOf(Email)}, null, null, null);
if (cursor != null)
cursor.moveToFirst();
User user=new User();
user.setFirstName(cursor.getString(0));
user.setLastName(cursor.getString(1));
user.setEmail(cursor.getString(2));
user.setUsername(cursor.getString(3));
user.setPassword(cursor.getString(4));
Log.d("getUser ("+Email+")", user.toString());
return user;
}
public List<User> getAllUsers(){
List<User> users=new LinkedList<User>();
String query="SELECT * FROM "+TABLE_USERS;
SQLiteDatabase db=this.getWritableDatabase();
Cursor cursor= db.rawQuery(query, null);
User user=null;
if (cursor.moveToFirst()){
do{
user=new User();
user.setFirstName(cursor.getString(0));
user.setLastName(cursor.getString(1));
user.setEmail(cursor.getString(2));
user.setUsername(cursor.getString(3));
user.setPassword(cursor.getString(4));
users.add(user);
} while (cursor.moveToNext());
}
Log.d("getAllUsers", users.toString());
return users;
}
public int updateUser(User user){
SQLiteDatabase db=this.getWritableDatabase();
ContentValues values=new ContentValues();
values.put(FIRST_NAME, user.getFirstName());
values.put(LAST_NAME, user.getLastName());
values.put(EMAIL, user.getEmail());
values.put(USERNAME, user.getUsername());
values.put(PASSWORD, user.getPassword());
int i=db.update(TABLE_USERS, values, "Email =?", new String[]{String.valueOf(user.getEmail())});
db.close();
return i;
}
public void deleteUser(User user){
SQLiteDatabase db=this.getWritableDatabase();
db.delete(TABLE_USERS, "Email =?", new String[]{String.valueOf(user.getEmail())});
db.close();
Log.d("deleteUser", user.toString());
}
}
LogCat:
04-18 12:16:09.132: E/Trace(1051): error opening trace file: No such file or directory (2)
04-18 12:16:09.404: D/libEGL(1051): loaded /system/lib/egl/libEGL_emulation.so
04-18 12:16:09.416: D/(1051): HostConnection::get() New Host Connection established 0xb9324060, tid 1051
04-18 12:16:09.492: D/libEGL(1051): loaded /system/lib/egl/libGLESv1_CM_emulation.so
04-18 12:16:09.492: D/libEGL(1051): loaded /system/lib/egl/libGLESv2_emulation.so
04-18 12:16:09.672: W/EGL_emulation(1051): eglSurfaceAttrib not implemented
04-18 12:16:09.708: D/OpenGLRenderer(1051): Enabling debug mode 0
04-18 12:16:09.800: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb931a8e0): name, size, mSize = 1, 1048576, 1048576
04-18 12:16:09.960: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9331d10): name, size, mSize = 2, 5184, 1053760
04-18 12:16:10.068: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9309b60): name, size, mSize = 4, 20736, 1074496
04-18 12:16:10.072: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb932d4b8): name, size, mSize = 5, 9216, 1083712
04-18 12:16:10.140: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9312810): name, size, mSize = 7, 7488, 1091200
04-18 12:16:10.152: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9325d70): name, size, mSize = 8, 100, 1091300
04-18 12:16:10.212: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb93176a0): name, size, mSize = 10, 7488, 1098788
04-18 12:16:10.252: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9373798): name, size, mSize = 11, 7488, 1106276
04-18 12:16:10.336: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9315840): name, size, mSize = 12, 2304, 1108580
04-18 12:16:42.528: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9378b38): name, size, mSize = 78, 7488, 1116068
04-18 12:16:42.800: D/dalvikvm(1051): GC_CONCURRENT freed 142K, 3% free 8216K/8391K, paused 14ms+0ms, total 25ms
04-18 12:16:44.200: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9308998): name, size, mSize = 85, 7488, 1123556
04-18 12:16:44.216: D/OpenGLRenderer(1051): TextureCache::get: create texture(0xb9316848): name, size, mSize = 86, 7488, 1131044
04-18 12:16:53.192: D/addUser(1051): First name: dsfLast name: dsfdsfEmail: dsfdsfUsername: Password:
04-18 12:16:53.196: D/AndroidRuntime(1051): Shutting down VM
04-18 12:16:53.196: W/dalvikvm(1051): threadid=1: thread exiting with uncaught exception (group=0xa627b288)
04-18 12:16:53.200: E/AndroidRuntime(1051): FATAL EXCEPTION: main
04-18 12:16:53.200: E/AndroidRuntime(1051): java.lang.NullPointerException
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
04-18 12:16:53.200: E/AndroidRuntime(1051): at com.craftyonhand.www.MySQLiteOpenHelper.addUser(MySQLiteOpenHelper.java:60)
04-18 12:16:53.200: E/AndroidRuntime(1051): at com.craftyonhand.www.registration$1.onClick(registration.java:47)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.view.View.performClick(View.java:4084)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.view.View$PerformClick.run(View.java:16966)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.os.Handler.handleCallback(Handler.java:615)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.os.Handler.dispatchMessage(Handler.java:92)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.os.Looper.loop(Looper.java:137)
04-18 12:16:53.200: E/AndroidRuntime(1051): at android.app.ActivityThread.main(ActivityThread.java:4745)
04-18 12:16:53.200: E/AndroidRuntime(1051): at java.lang.reflect.Method.invokeNative(Native Method)
04-18 12:16:53.200: E/AndroidRuntime(1051): at java.lang.reflect.Method.invoke(Method.java:511)
04-18 12:16:53.200: E/AndroidRuntime(1051): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
04-18 12:16:53.200: E/AndroidRuntime(1051): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-18 12:16:53.200: E/AndroidRuntime(1051): at dalvik.system.NativeStart.main(Native Method)
04-18 12:16:55.792: I/Process(1051): Sending signal. PID: 1051 SIG: 9
3 answers
solution1
3 2014-04-18 12:28:01
MySQLiteOpenHelper db = new MySQLiteOpenHelper(null);//do I need this??
Yes you need it and you also need to pass a non- null valid Context as an argument. In a fragment, you can use getActivity() to get the activity to use as a Context once the fragment is attached to its host activity.
Okay so it does show on logcat but for some reason it says that there is no such table USERS... As far as I know it should open it if it does not exsits. Am I wrong?
Possibly you have an older version of the database file around. Clear app data or uninstall it to remove it and make the database helper onCreate() create set up the tables for you. See When is SQLiteOpenHelper onCreate() / onUpgrade() run? for more.
solution2
1 2014-04-18 12:28:45
You should change this
MySQLiteOpenHelper db = new MySQLiteOpenHelper(null);//do I need this??
With
MySQLiteOpenHelper db = new MySQLiteOpenHelper(getActivity());//do I need this??
solution3
1 2014-04-18 12:28:46
Replace
MySQLiteOpenHelper db = new MySQLiteOpenHelper(null);
with
MySQLiteOpenHelper db = new MySQLiteOpenHelper(getActivity());
Update onUpgrade() method
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String CREATE_MyDB_TABLE = "CREATE TABLE IF NOT EXISTS USERS ( " +
"First_name TEXT, " +
"Last_name TEXT, "+
"Email KEY TEXT NOT NULL, "+
"Username TEXT NOT NULL, "+
"Password TEXT NOT NULL)";
db.execSQL(CREATE_MyDB_TABLE);
this.onCreate(db);
}
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