Java SQLite游标崩溃
我的SQLite类有问题。事实上,我正在学习如何在android上建立(更新和读取)一个数据库,并成功地在数据库上编写了代码,但当我试图读取信息并在屏幕上显示时,我的应用程序就崩溃了。Java SQLite游标崩溃,java,android,sqlite,cursor,Java,Android,Sqlite,Cursor,我的SQLite类有问题。事实上,我正在学习如何在android上建立(更新和读取)一个数据库,并成功地在数据库上编写了代码,但当我试图读取信息并在屏幕上显示时,我的应用程序就崩溃了。 我搜索了这个问题,发现崩溃的原因是光标。我评论了游标的方法,所以如果有人能帮我,我将不胜感激 这是我的数据库类 package com.example.sqlprogramming; import android.content.ContentValues; import android
我搜索了这个问题,发现崩溃的原因是光标。我评论了游标的方法,所以如果有人能帮我,我将不胜感激 这是我的数据库类
package com.example.sqlprogramming;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseClass {
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "person_name";
public static final String KEY_RATE = "person_rate";
private static final String DATABASE_NAME = "HotOrNotdb";
private static final String DATABASE_TABLE = "peopleTable";
private static final int DATABASE_VERSION = 2;
private Dhelper ourHelperdb;
private final Context ourContext;
private SQLiteDatabase ourDatabase;
private static class Dhelper extends SQLiteOpenHelper{
public Dhelper(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
db.execSQL("create table if not exists " + DATABASE_TABLE + " (" +
KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
KEY_NAME + "VARCHAR NOT NULL, " +
KEY_RATE + "VARCHAR 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 DatabaseClass(Context c){
ourContext = c;
}
public DatabaseClass open() throws SQLException{
ourHelperdb = new Dhelper(ourContext);
ourDatabase = ourHelperdb.getWritableDatabase();
return this;
}
public void close(){
ourHelperdb.close();
}
public long addEntry(String personName, String personHotness) {
// TODO Auto-generated method stub
ContentValues cv = new ContentValues();
cv.put(KEY_NAME, personName);
cv.put(KEY_RATE, personHotness);
return ourDatabase.insert(DATABASE_TABLE, null, cv);
}
//HERE IS MY PROBLEM WITH THE CURSOR
public String getData() {
// TODO Auto-generated method stub
String[] columns = new String[]{KEY_ROWID, KEY_NAME, KEY_RATE};
String result = "hello";
Cursor c = ourDatabase.query(true, DATABASE_TABLE, columns, null, null, null, null, null, null);
int iRowId = c.getColumnIndex(KEY_ROWID);
int iName = c.getColumnIndex(KEY_NAME);
int iRate = c.getColumnIndex(KEY_RATE);
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()){
result = result + c.getString(iRowId) + " " + c.getString(iName) +" " + c.getString(iRate) + "\n";
}
c.close();
return result;
}
}
这个类调用数据库类,应该从数据库中获取信息,并将其显示在屏幕上
package com.example.sqlprogramming;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class SQLview extends Activity{
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_sqlview);
TextView textInfo = (TextView) findViewById (R.id.tvSQLinfo);
DatabaseClass info = new DatabaseClass(this);
info.open();
String _data = info.getData();
info.close();
textInfo.setText(_data);
}
}
再次感谢你。
我很快会发布stacktrace和logcat
这是我的Logcat/Stacktrace
02-24 20:08:12.378: E/Curosr!(1221): I got an error here :
02-24 20:08:12.378: E/Curosr!(1221): android.database.sqlite.SQLiteException: no such column: person_name (code 1): , while compiling: SELECT _id AS _id, person_name, person_rate FROM peopleTable
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1161)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1032)
02-24 20:08:12.378: E/Curosr!(1221): at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1200)
02-24 20:08:12.378: E/Curosr!(1221): at com.example.sqlprogramming.DatabaseClass.getData(DatabaseClass.java:75)
02-24 20:08:12.378: E/Curosr!(1221): at com.example.sqlprogramming.SQLview.onCreate(SQLview.java:14)
02-24 20:08:12.378: E/Curosr!(1221): at android.app.Activity.performCreate(Activity.java:5104)
02-24 20:08:12.378: E/Curosr!(1221): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-24 20:08:12.378: E/Curosr!(1221): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
02-24 20:08:12.378: E/Curosr!(1221): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
02-24 20:08:12.378: E/Curosr!(1221): at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-24 20:08:12.378: E/Curosr!(1221): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
02-24 20:08:12.378: E/Curosr!(1221): at android.os.Handler.dispatchMessage(Handler.java:99)
02-24 20:08:12.378: E/Curosr!(1221): at android.os.Looper.loop(Looper.java:137)
02-24 20:08:12.378: E/Curosr!(1221): at android.app.ActivityThread.main(ActivityThread.java:5039)
02-24 20:08:12.378: E/Curosr!(1221): at java.lang.reflect.Method.invokeNative(Native Method)
02-24 20:08:12.378: E/Curosr!(1221): at java.lang.reflect.Method.invoke(Method.java:511)
02-24 20:08:12.378: E/Curosr!(1221): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-24 20:08:12.378: E/Curosr!(1221): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-24 20:08:12.378: E/Curosr!(1221): at dalvik.system.NativeStart.main(Native Method)
02-2420:08:12.378:E/Curosr!(1221):我这里有个错误:
02-24 20:08:12.378:E/Curosr!(1221):android.database.sqlite.SQLiteException:没有这样的列:person\u name(代码1):,编译时:从peopleTable中选择_id作为_id,person\u name,person\u rate
02-24 20:08:12.378:E/Curosr!(1221):在android.database.sqlite.SQLiteConnection.nativePrepareStatement(本机方法)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteProgram.(SQLiteProgram.java:58)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteQuery.(SQLiteQuery.java:37)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1161)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1032)
02-24 20:08:12.378:E/Curosr!(1221):位于android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1200)
02-24 20:08:12.378:E/Curosr!(1221):位于com.example.sqlprogramming.DatabaseClass.getData(DatabaseClass.java:75)
02-24 20:08:12.378:E/Curosr!(1221):位于com.example.sqlprogramming.SQLview.onCreate(SQLview.java:14)
02-24 20:08:12.378:E/Curosr!(1221):位于android.app.Activity.performCreate(Activity.java:5104)
02-24 20:08:12.378:E/Curosr!(1221):位于android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-24 20:08:12.378:E/Curosr!(1221):位于android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
02-24 20:08:12.378:E/Curosr!(1221):位于android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
02-24 20:08:12.378:E/Curosr!(1221):位于android.app.ActivityThread.access$600(ActivityThread.java:141)
02-24 20:08:12.378:E/Curosr!(1221):位于android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
02-24 20:08:12.378:E/Curosr!(1221):位于android.os.Handler.dispatchMessage(Handler.java:99)
02-24 20:08:12.378:E/Curosr!(1221):位于android.os.Looper.loop(Looper.java:137)
02-24 20:08:12.378:E/Curosr!(1221):位于android.app.ActivityThread.main(ActivityThread.java:5039)
02-24 20:08:12.378:E/Curosr!(1221):位于java.lang.reflect.Method.Invokenactive(本机方法)
02-24 20:08:12.378:E/Curosr!(1221):位于java.lang.reflect.Method.invoke(Method.java:511)
02-24 20:08:12.378:E/Curosr!(1221):位于com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-24 20:08:12.378:E/Curosr!(1221):位于com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-24 20:08:12.378:E/Curosr!(1221):在dalvik.system.NativeStart.main(本机方法)
如果您正在阅读,您需要使用:
ourDatabase = ourHelperdb.getReadableDatabase();
打开数据库时,将其设置为写入
(这是我的第一个猜测,堆栈后跟踪)
下面是我的一些代码中关于如何读取光标的工作示例:
mDb = mDbHelper.getReadableDatabase();
Cursor c = mDb.query("Timesheets", new String[] {
KEY_TIMESHEETS_ROWID + " AS _id", KEY_TIMESHEETS_DESCRIPTION,
KEY_TIMESHEETS_TITLE, KEY_TIMESHEETS_DATE_START,
KEY_TIMESHEETS_DATE_END, KEY_TIMESHEETS_INVOICED,
KEY_TIMESHEETS_PROJECTID }, "timesheet_id = ?",
new String[] { String.valueOf(timesheetId) }, null, null, null);
c.moveToFirst();
SimpleDateFormat dateFormat = new SimpleDateFormat(
"yyyy-MM-dd HH:mm:ss");
Timesheet timesheet = new Timesheet();
while (c.isAfterLast() == false) {
timesheet.setTimesheetId(c.getInt(0));
// ...
c.moveToNext();
}
c.close();
create语句缺少一些空格。尝试使用:
db.execSQL("create table if not exists " + DATABASE_TABLE + " (" +
KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
KEY_NAME + " VARCHAR NOT NULL, " +
KEY_RATE + " VARCHAR NOT NULL);");
根据您当前的声明,您的最后两个列名将成为
person\u nameVARCHAR
和person\u rateVARCHAR
始终发布带有崩溃错误的完整堆栈跟踪。请在此处添加logcat。感谢您的评论,我添加了getReadableDatabase();nethod找到DBHelper并使用光标作为示例,但这不起作用,当我尝试读取数据时,它仍然会崩溃。数据库返回getWritableDatabase()
也可以从中读取。使用getReadableDatabase()
不是必需的。这是我尝试过的,但不起作用,logcat消息也是一样的,谢谢。@R00t您必须卸载并重新安装应用程序,新的create语句才能生效。