我正在尝试创建一个名为Reminder的表，其中包含用户名作为名为User的表中的外键。但我得到表提醒在运行时没有名为Username 的列。
添加用户代码。
package com.example.champ.remindme;
import android.app.AlertDialog;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class SignUp extends AppCompatActivity {
EditText editUsername,editPassword,editEmail,editMobileNumber;
Button btnSignUpButton;
SQLiteDatabase db;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sign_up);
editUsername = (EditText)findViewById(R.id.editUsername);
editPassword = (EditText)findViewById(R.id.editPassword);
editEmail = (EditText)findViewById(R.id.editEmail);
editMobileNumber = (EditText)findViewById(R.id.editMobileNumber);
btnSignUpButton = (Button)findViewById(R.id.btnSiginUpButton);
db=openOrCreateDatabase("RemindMe", Context.MODE_PRIVATE, null);
db.execSQL("create table IF NOT EXISTS User (Username TEXT PRIMARY KEY ,Password TEXT, Email TEXT, Contact_No INTEGER)");
}
public void AddUser(View v){
if(editUsername.length()==0||
editPassword.length()==0||
editEmail.length()==0||
editMobileNumber.length()==0)
{
showMessage("Error", "Please enter all values");
return;
}
db.execSQL("INSERT INTO User VALUES('"+editUsername.getText().toString()+"'," +
"'"+editPassword.getText().toString()+ "'," +
"'"+editEmail.getText().toString()+"',"+
"'"+Integer.parseInt(editMobileNumber.getText().toString())+"');");
showMessage("Success", "Record added");
}
public void showMessage(String title,String message)
{
AlertDialog.Builder builder=new AlertDialog.Builder(this);
builder.setCancelable(true);
builder.setTitle(title);
builder.setMessage(message);
builder.show();
}
}
添加提醒代码。
package com.example.champ.remindme;
import android.Manifest;
import android.app.AlertDialog.Builder;
import android.content.Context;
import android.content.pm.PackageManager;
import android.database.sqlite.SQLiteDatabase;
import android.location.Address;
import android.location.Geocoder;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import android.widget.EditText;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.List;
public class AddEventPlace extends FragmentActivity implements OnMapReadyCallback {
private GoogleMap mMap;
Double Latitude=0.0;
Double Longitude=0.0;
EditText edtAddress;
String username,item;
SQLiteDatabase db;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_event_place);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
edtAddress=(EditText)findViewById(R.id.Address);
db=openOrCreateDatabase("RemindMe", Context.MODE_PRIVATE, null);
db.execSQL("create table IF NOT EXISTS Reminder (" +
"ID INTEGER PRIMARY KEY AUTOINCREMENT," +
"item TEXT not NULL," +
"Time TIMESTAMP DEFAULT CURRENT_TIMESTAMP not NULL," +
"Date DATETIME DEFAULT CURRENT_TIMESTAMP not NULL," +
"x_coordinates REAL," +
"y_coordinates REAL," +
"Username TEXT," +
"FOREIGN KEY(Username) REFERENCES User(Username));");
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
// Add a marker in Sydney and move the camera
LatLng sydney = new LatLng(-34, 151);
mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
mMap.setMyLocationEnabled(true);
}
public void onSearch(View view)
{
EditText location_tf = (EditText)findViewById(R.id.Address);
String location = location_tf.getText().toString();
List<Address> addressList = null;
if(location != null || !location.equals(""))
{
Geocoder geocoder = new Geocoder(this);
try {
addressList = geocoder.getFromLocationName(location , 1);
} catch (IOException e) {
e.printStackTrace();
}
Address address = addressList.get(0);
LatLng latLng = new LatLng(address.getLatitude() , address.getLongitude());
Latitude=address.getLatitude();
Longitude=address.getLongitude();
//Latitude=0.0;
//Longitude=0.0;
mMap.addMarker(new MarkerOptions().position(latLng).title("Marker"));
mMap.animateCamera(CameraUpdateFactory.newLatLng(latLng));
}
}
public void Done(View view){
username = getIntent().getStringExtra("Username");
item = getIntent().getStringExtra("item");
DateFormat timeFormat = new SimpleDateFormat("h:mm a");
String time = timeFormat.format(Calendar.getInstance().getTime());
DateFormat dateFormat = new SimpleDateFormat("EEE, MMM d, yy");
String date = dateFormat.format(Calendar.getInstance().getTime());
if(item.trim().length()==0||
date.trim().length()==0||
Longitude ==0.0||
Latitude==0.0||
username.trim().length()==0)
{
showMessage("Error", "Please enter all values");
return;
}
db.execSQL("INSERT INTO Reminder (item, Time, Date, x_coordinates, y_coordinates, Username) VALUES(" +
"'"+item+"'," +
"'"+time+"'," +
"'"+date+"',"+
"'"+Longitude+"',"+
"'"+Latitude+"',"+
"'"+username+"'"+
");");
showMessage("Success", "Record added");
}
public void showMessage(String title,String message)
{
Builder builder=new Builder(this);
builder.setCancelable(true);
builder.setTitle(title);
builder.setMessage(message);
builder.show();
}
}
答案 0 :(得分：1)
让我猜一下，首先你在Reminder中没有Username列，并且你试图将它添加到表中？
问题可能是由于以前版本的代码已经创建了没有Username列的表，并且由于它已经存在而无法重新创建表。
您应该通过扩展SQLiteOpenHelper创建DBHelper，然后覆盖onUpgrade方法
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
}
更多代码可以帮助您 -
public class DBHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "dpname.db";
public static final String TABLE_NAME = "table1";
public static final String COL1 = "col1";
// More columns and tables ....
private static final int DATABASE_VERSION = 2;
//You should update database_version everytime you are trying to update the database, Note - data saved will be lost
private static DBHelper mDbHelper;
public void onCreate(SQLiteDatabase db) {
String CREATE_FIRST_TABLE = "CREATE TABLE " + TABLE_NAME +
"(" +
COL1 + " INTEGER PRIMARY KEY ," +
COL2 + " TEXT," +
//... More columns
")";
db.execSQL(CREATE_FIRST_TABLE);
//.. Create More tables
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
@Override
public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
private DBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// More functions to select, insert, delete, update records
// Example a function to insert Post given below
// Better make a class to hold your data structure for different tables
public void insertDetail(String s1, String s2, Integer i1...){
SQLiteDatabase db = this.getWritableDatabase();
db.beginTransaction();
try {
ContentValues values = new ContentValues();
values.put(COL1,i1);
values.put(COL2,s1);
//....
db.insertOrThrow(TABLE_NAME, null, values);
db.setTransactionSuccessful();
} catch(SQLException e){
//....
} finally{
db.endTransaction();
}
}
public static synchronized DBHelper getInstance(Context context) {
// Use the application context, which will ensure that you
// don't accidentally leak an Activity's context.
if (mDbHelper == null) {
mDbHelper = new DBHelper(context.getApplicationContext());
}
return mDbHelper;
}
}
在你的活动中使用这个 -
db = DBHelper.getInstance(getApplicationContext());
db.insertDetail(String1,String2,Integer1);