Question

我正在实现一个SQLite数据库。在数据库中，我正在存储类型为Contact的对象，其定义如下。方法getContact()应该采用id并返回数据库中相应的Contact对象。但这不起作用。当我调试它时，控件就会卡在线上，然后应用程序崩溃了。

  Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
                    KEY_NAME_DEFAULT,KEY_NAME,KEY_IMAGE}, KEY_ID + "=?",
            new String[] { String.valueOf(id) }, null, null, null, null);

我对SQLite有一个非常基本的了解，无法弄清楚这里有什么问题。请帮忙。

联系班级

package com.example.nirvan.diary30;

import android.graphics.Bitmap;

public class Contact
{
String nameDefault;
public String name[];
public Bitmap image[];
public int id;

Contact(int id, String name,String arrName[],Bitmap arrImage[])
{
    this.id=id;
    this.nameDefault=name;
    this.name=arrName;
    this.image=arrImage;
}

}

在DatabaseHandler.java中

getContact（）

Contact getContact(int id)
{
    SQLiteDatabase db = this.getReadableDatabase();

    Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
                    KEY_NAME_DEFAULT,KEY_NAME,KEY_IMAGE}, KEY_ID + "=?",
            new String[] { String.valueOf(id) }, null, null, null, null);
    if (cursor != null)
        cursor.moveToFirst();


    Contact contact = new Contact(Integer.parseInt(cursor.getString(0)),
            cursor.getString(1) ,convertStringToArray(cursor.getString(2)) , backConverter(cursor.getString(3)));

    return contact;
}

更新的登录

 FATAL EXCEPTION: main
                                                                      Process: com.example.nirvan.diary30, PID: 6937
                                                                      android.database.sqlite.SQLiteException: no such column: image (code 1): , while compiling: SELECT id, nameDefault, name, image FROM contacts WHERE id=?
                                                                          at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
                                                                          at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
                                                                          at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
                                                                          at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
                                                                          at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
                                                                          at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
                                                                          at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
                                                                          at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
                                                                          at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1161)
                                                                          at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1032)
                                                                          at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1238)
                                                                          at com.example.nirvan.diary30.DatabaseHandler.getContact(DatabaseHandler.java:136)
                                                                          at com.example.nirvan.diary30.MainActivity$1.onPageSelected(MainActivity.java:87)
                                                                          at android.support.v4.view.ViewPager.dispatchOnPageSelected(ViewPager.java:1933)
                                                                          at android.support.v4.view.ViewPager.scrollToItem(ViewPager.java:685)
                                                                          at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:669)
                                                                          at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:630)
                                                                          at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:611)
                                                                          at android.support.design.widget.TabLayout$ViewPagerOnTabSelectedListener.onTabSelected(TabLayout.java:2156)
                                                                          at android.support.design.widget.TabLayout.dispatchTabSelected(TabLayout.java:1138)
                                                                          at android.support.design.widget.TabLayout.selectTab(TabLayout.java:1132)
                                                                          at android.support.design.widget.TabLayout.selectTab(TabLayout.java:1105)
                                                                          at android.support.design.widget.TabLayout$Tab.select(TabLayout.java:1396)
                                                                          at android.support.design.widget.TabLayout$TabView.performClick(TabLayout.java:1501)
                                                                          at android.view.View$PerformClick.run(View.java:18465)
                                                                          at android.os.Handler.handleCallback(Handler.java:733)
                                                                          at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                          at android.os.Looper.loop(Looper.java:136)
                                                                          at android.app.ActivityThread.main(ActivityThread.java:5086)
                                                                          at java.lang.reflect.Method.invokeNative(Native Method)
                                                                          at java.lang.reflect.Method.invoke(Method.java:515)
                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
                                                                          at dalvik.system.NativeStart.main(Native Method)

Answer 1

您的query()声明看起来不错。您需要检查cursor.moveToFirst()是否已返回true。如果false为空，则返回cursor。有关详细信息，请参阅here

试试这个：

if (cursor.moveToFirst())
{
   Contact contact = new Contact(Integer.parseInt(cursor.getString(0)),
            cursor.getString(1), 
            convertStringToArray(cursor.getString(2)),
            backConverter(cursor.getString(3)));
}
else
{
    // not found
}

如何为SQLite数据库编写查询语句？

1 个答案: