Question

我的SQLite类有问题。事实上，我正在学习如何在android上设置（更新和读取）数据库并且我在数据库上成功写入，但是当我尝试读取信息并在屏幕上显示它们时，我的应用程序就崩溃了。
我搜索了问题，发现崩溃的原因是Cursor。我评论了光标的方法，所以如果有人可以帮助我，我会很感激。

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;
}
    }

此类调用数据库类，并应从数据库中获取信息以在屏幕上显示它。

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。我很快就会发布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)

Answer 1

如果您正在阅读，则需要使用：

ourDatabase = ourHelperdb.getReadableDatabase();

当您打开数据库时，您将其设置为写入。

（这是我的第一个猜测，后堆栈跟踪）。

以下是我的一些代码中有关如何读取游标的工作示例：

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();

Answer 2

您的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);");

根据您当前的陈述，您的最后两个列名称变为person_nameVARCHAR和person_rateVARCHAR

SQLite Cursor崩溃了

2 个答案: