我正在尝试使用下拉式微调器来更新数据库中唯一行的当前信用列，该微调器从arraylist获取值。非常不确定如何进行此操作。感谢您提前提供的任何帮助。
我的数据库代码：
package com.example.parkangel;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class UDbHelper extends SQLiteOpenHelper
{
public static final String KEY_ROWID = "_id";
public static final String KEY_PFNAME = "payeeFname";
public static final String KEY_PSNAME = "payeeSname";
public static final String KEY_CARD = "card";
public static final String KEY_CREDITS = "credits";
private static final String DATABASE_NAME = "UserData.db";
private static final String DATABASE_TABLE = "UserTable";
private static final int DATABASE_VERSION = 1;
//private UDbHelper dbHelper;
//private final Context ourContext;
private static UDbHelper instance;
private SQLiteDatabase ourDatabase;
public UDbHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public static UDbHelper getInstance(Context context)
{
if (instance == null)
{
instance = new UDbHelper(context);
}
return instance;
}
@Override
public void onCreate(SQLiteDatabase db)
{
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" +
KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
KEY_PFNAME + " TEXT NOT NULL, " + KEY_PSNAME + "
TEXT NOT NULL, " +
KEY_CARD + " TEXT NOT NULL, " + KEY_CREDITS + " TEXT
NOT NULL);");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
public synchronized UDbHelper open() throws SQLException
{
System.out.println ("running open");
if(ourDatabase == null || !ourDatabase.isOpen())
ourDatabase = getWritableDatabase();
return this;
}
public String getData()
{
// TODO Auto-generated method stub
String[] columns = new String[] {KEY_ROWID, KEY_PFNAME, KEY_PSNAME,
KEY_CARD, KEY_CREDITS};
Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null,
null, null, null);
String result = " ";
int iRow = c.getColumnIndexOrThrow(KEY_ROWID);
int iPFname = c.getColumnIndexOrThrow(KEY_PFNAME);
int iPSname = c.getColumnIndexOrThrow(KEY_PSNAME);
int iCard = c.getColumnIndexOrThrow(KEY_CARD);
int iCredits = c.getColumnIndexOrThrow(KEY_CREDITS);
for(c.moveToFirst(); !c.isAfterLast(); c.moveToNext()){
result = result + c.getString(iRow) + " " +
c.getString(iPFname) + " " +
c.getString(iPSname)
+ " " + c.getString(iCard) + " " +
c.getString(iCredits) + "\n";
}
return result;
}
}
我的主要活动代码我将通过以下方式进行操作：
package com.example.parkangel;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
public class Balance extends Activity{
Button add;
TextView display;
Spinner spinner3;
String[] money = {"Select amount", "£1", "£2", "£5", "£10"};
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.balance_layout);
TextView tv = (TextView) findViewById(R.id.firstn);
UDbHelper db = new UDbHelper(this);
db.open();
String data = db.getData();
db.close();
tv.setText(data);
ArrayAdapter<String> adapter3 = new ArrayAdapter<String>(Balance.this,
android.R.layout.simple_spinner_item, money);
spinner3 = (Spinner) findViewById (R.id.moneytoadd);
spinner3.setAdapter(adapter3);
add = (Button) findViewById(R.id.topup);
}
public void onClick(View arg0)
{
}
public void updateActivity(View view){
Intent book = new Intent(Balance.this, BookTicket.class);
startActivity(book);
}
public void addBalance(View view){
Intent addB = new Intent(Balance.this, Balance.class);
startActivity(addB);
}
public void doUpdate(View view){
Intent upd = new Intent(Balance.this, UpdateTicket.class);
startActivity(upd);
}
}
答案 0 :(得分：0)
我没有发现问题，但我可以告诉你，你的代码非常不实用。您正在使用String在getData方法中构建结果。每次尝试将新数据（行）附加到旧数据时，您都要创建一个新的string来保存新数据。如果要从数据库中检索1000行，这意味着您要创建1000 string来构建最后一行。我建议使用StringBuilder代替：
StringBuilder strBuilder= new StringBuilder();
for(c.moveToFirst(); !c.isAfterLast(); c.moveToNext()){
strBuilder.append( c.getString(iRow) + " " +
c.getString(iPFname) + " " +
c.getString(iPSname)
+ " " + c.getString(iCard) + " " +
c.getString(iCredits) + "\n");
}
return str= strBuilder.toString();
以下是如何插入数据库的示例：
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_PFNAME , editText1.getText().toString());
values.put(KEY_PSNAME , stringArrayList.get(position));
values.put(KEY_CARD , "12345677");
values.put(KEY_CREDITS , "55");
// Inserting Row
db.insert(DATABASE_TABLE, null, values);
db.close(); // Closing database connection
答案 1 :(得分：0)
您的问题相当复杂，从微调器获取选定字段，更新数据库......我不打算提供完整的答案，但这应该可以让您开始：
这是您从微调器获取所选字段的方法，然后您可以使用它来更新数据库。一句警告，我相信setOnItemSelectedListener在最初设置时会被调用，因此您可能需要忽略第一次调用。
Spinner spinner;
spinner.setOnItemSelectedListener( new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> arg0, View view, int arg2,
long arg3) {
if(! (view instanceof TextView)){
// view is probably a textview, but record type if not.
System.out.println("incorrect view type " + view.getClass().getSimpleName());
return;
}
EditText et = (EditText) view;
String fieldName = et.getText().toString().trim();
//Now we got selected name, send name
//to a function that updates our database.
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
});