SQLite Android 问题
我正在使用 SQLite 为我的 Android 应用程序 (Java) 制作本地高分表。
由于某种原因，应用程序在尝试向表中添加新的高分时崩溃。这是相关代码：
private static String HIGHSCORES_TABLE_NAME = "SCORES_TABLE";
private SQLiteDatabase highScoresDB = null;
private Cursor cursor = null;
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
try
{
highScoresDB = openOrCreateDatabase("ScoresDatabase", MODE_PRIVATE, null);
createTable();
lookupData();
}
catch (SQLiteException se)
{
Log.e(getClass().getSimpleName(), "Could not create or Open the database");
}
finally
{
if (highScoresDB != null)
highScoresDB.execSQL("DELETE FROM " + HIGHSCORES_TABLE_NAME);
highScoresDB.close();
}
}
private void createTable() {
highScoresDB.execSQL("CREATE TABLE IF NOT EXISTS " + HIGHSCORES_TABLE_NAME + " (SCORE INT(3));");
}
private void insertData() {
highScoresDB.execSQL("INSERT INTO " + HIGHSCORES_TABLE_NAME + " Values ("+ highscore +");");
}
private void lookupData() {
cursor = highScoresDB.rawQuery("SELECT SCORE FROM " + HIGHSCORES_TABLE_NAME, null);
if (cursor.moveToLast()) {
highscore = cursor.getInt(cursor.getColumnIndex("SCORE"));
}
cursor.close();
}
public void restart() {
insertData();
}
当我查找高分时，我只想要最近的分数，所以我使用 moveToLast()。
I am making a local high scores table using SQLite for my Android application (Java).
For some reason, the application crashes while trying to add a new high score to the table. Here is the relevant code:
private static String HIGHSCORES_TABLE_NAME = "SCORES_TABLE";
private SQLiteDatabase highScoresDB = null;
private Cursor cursor = null;
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
try
{
highScoresDB = openOrCreateDatabase("ScoresDatabase", MODE_PRIVATE, null);
createTable();
lookupData();
}
catch (SQLiteException se)
{
Log.e(getClass().getSimpleName(), "Could not create or Open the database");
}
finally
{
if (highScoresDB != null)
highScoresDB.execSQL("DELETE FROM " + HIGHSCORES_TABLE_NAME);
highScoresDB.close();
}
}
private void createTable() {
highScoresDB.execSQL("CREATE TABLE IF NOT EXISTS " + HIGHSCORES_TABLE_NAME + " (SCORE INT(3));");
}
private void insertData() {
highScoresDB.execSQL("INSERT INTO " + HIGHSCORES_TABLE_NAME + " Values ("+ highscore +");");
}
private void lookupData() {
cursor = highScoresDB.rawQuery("SELECT SCORE FROM " + HIGHSCORES_TABLE_NAME, null);
if (cursor.moveToLast()) {
highscore = cursor.getInt(cursor.getColumnIndex("SCORE"));
}
cursor.close();
}
public void restart() {
insertData();
}
When I look up the high score, I only want the most recent one so I use moveToLast().
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我发现“cursor.moveToLast()”似乎无法正常工作。它确实移动了光标中的位置，但当您尝试读取该记录时会引发异常。
这有效：
cursor.moveToPosition(cursor.getCount()-1)
I found that "cursor.moveToLast()" does not seem to work correctly. It does move the position in the cursor, but throws an exception when you attempt to read that record.
This works:
cursor.moveToPosition(cursor.getCount()-1)
导致其崩溃的异常是什么，您何时插入新行？您是否在插入行之前打开数据库，因为在 create 方法的finally 块中调用了 Close() 。
如果这是您要存储在数据库中的唯一信息，请考虑使用共享首选项。
这个链接有一个如何使用它的演示 -
共享偏好设置演示
What is the exception that causes it to crash, When are you inserting a new row ? Are you opening the database before inserting a row , as Close() is being called on in the finally block of the create method.
If this is the only information you are going to store in the database , consider using Shared Preferences.
This link has a demo of how to use it -
Shared preferences demo
不要像您那样执行语句，而是使用 SQLite 对象类中包含的一些提供的方法：
http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html
这使得您的代码不易出现 SQL 打字错误或小错误。
另请发布您的 logcat。
Instead of doing statements like you are doing use some of the provided methods that are included in the SQLite Object class:
http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html
This makes your code less error prone to SQL Typos or small errors.
Also please post your logcat.