我正试图从我的国家数据库中选择一个国家，并将其返回到要在文本视图中显示的光标。但是每次我运行此活动时，我的应用程序都会崩溃。这是我的代码：
数据库类：
package com.mypackage.msdassignment;
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;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
public class DBManager
{
public static final String KEY_ID = "_id";
public static final String KEY_CONTENT = "country";
public static final String KEY_YEAR = "year";
public static final String KEY_MONTH = "month";
public static final String KEY_DESC = "description";
public static final String DATABASE_NAME = "Countries database";
public static final String DATABASE_TABLE = "Country";
public static final int DATABASE_VERSION = 1;
//create table MY_DATABASE (ID integer primary key, Content text not null);
private static final String SCRIPT_CREATE_DATABASE =
"create table " + DATABASE_TABLE + " ("
+ KEY_ID + " integer primary key autoincrement, "
+ KEY_CONTENT + " text ,"
+ KEY_YEAR + " integer ,"
+ KEY_MONTH + " month ,"
+ KEY_DESC + " text);";
private Context context;
private DBHelper DBHelper;
private SQLiteDatabase db;
public DBManager(Context ctx)
{
context = ctx;
}
//beginning of helper class
public class DBHelper extends SQLiteOpenHelper
{
public DBHelper(Context context, String name, CursorFactory factory, int version)
{
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(SCRIPT_CREATE_DATABASE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
// TODO Auto-generated method stub
}
}
public DBManager openToRead() throws SQLException
{
DBHelper = new DBHelper(context, DATABASE_NAME, null, DATABASE_VERSION);
db = DBHelper.getReadableDatabase();
return this;
}
public DBManager openToWrite() throws SQLException
{
DBHelper = new DBHelper(context, DATABASE_NAME, null, DATABASE_VERSION);
db = DBHelper.getWritableDatabase();
return this;
}
public void close()
{
DBHelper.close();
}
public long insert(String content, int year, String month, String description)
{
ContentValues contentValues = new ContentValues();
contentValues.put(KEY_CONTENT, content);
contentValues.put(KEY_YEAR, year);
contentValues.put(KEY_MONTH, month);
contentValues.put(KEY_DESC, description);
return db.insert(DATABASE_TABLE, null, contentValues);
}
public int deleteAll()
{
return db.delete(DATABASE_TABLE, null, null);
}
public void deleteDatabase()
{
context.deleteDatabase(DATABASE_NAME);
}
public Cursor queueAll()
{
String[] columns = new String[]{
KEY_ID,
KEY_CONTENT,
KEY_YEAR,
KEY_MONTH,
KEY_DESC};
Cursor cursor = db.query(DATABASE_TABLE, columns,
null, null, null, null, null);
return cursor;
}
//this is the method with the problem
public Cursor getCountry()
{
Cursor cursor = db.query(DATABASE_TABLE, new String[] {"country", "month"},
"country like " + "'%Ireland%'", null, null, null, null);
return cursor;
}
}
我想了解这个国家的活动：
package com.mypackage.msdassignment;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
public class CountryInfo extends Activity
{
private DBManager db;
Cursor cursor;
String passedValue;
TextView mytextView;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.country_layout);
//intent passed data
passedValue = getIntent().getStringExtra(MainActivity.ID_EXTRA);
int num = Integer.parseInt(passedValue);
mytextView = (TextView)findViewById(R.id.country);
db = new DBManager(this);
db.openToRead();
cursor = db.getCountry();
String s = cursor.getString(1);
mytextView.setText(s);
}
}
Logcat错误：
04-02 22:29:30.980: D/AndroidRuntime(17632): procName from cmdline: com.mypackage.msdassignment
04-02 22:29:30.980: E/AndroidRuntime(17632): in writeCrashedAppName, pkgName :com.mypackage.msdassignment
04-02 22:29:30.980: D/AndroidRuntime(17632): file written successfully with content: com.mypackage.msdassignment StringBuffer : ;com.mypackage.msdassignment
04-02 22:29:30.980: E/AndroidRuntime(17632): FATAL EXCEPTION: main
04-02 22:29:30.980: E/AndroidRuntime(17632): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mypackage.msdassignment/com.mypackage.msdassignment.CountryInfo}: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.os.Handler.dispatchMessage(Handler.java:99)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.os.Looper.loop(Looper.java:130)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.app.ActivityThread.main(ActivityThread.java:3683)
04-02 22:29:30.980: E/AndroidRuntime(17632): at java.lang.reflect.Method.invokeNative(Native Method)
04-02 22:29:30.980: E/AndroidRuntime(17632): at java.lang.reflect.Method.invoke(Method.java:507)
04-02 22:29:30.980: E/AndroidRuntime(17632): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:880)
04-02 22:29:30.980: E/AndroidRuntime(17632): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:638)
04-02 22:29:30.980: E/AndroidRuntime(17632): at dalvik.system.NativeStart.main(Native Method)
04-02 22:29:30.980: E/AndroidRuntime(17632): Caused by: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.database.AbstractCursor.checkPosition(AbstractCursor.java:580)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:214)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:41)
04-02 22:29:30.980: E/AndroidRuntime(17632): at com.mypackage.msdassignment.CountryInfo.onCreate(CountryInfo.java:31)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
04-02 22:29:30.980: E/AndroidRuntime(17632): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
04-02 22:29:30.980: E/AndroidRuntime(17632): ... 11 more
04-02 22:29:31.330: W/ResourceType(17644): Skipping entry 0x7f060002 in package table 0 because it is not complex!
04-02 22:29:31.330: W/ResourceType(17644): Skipping entry 0x7f060002 in package table 0 because it is not complex!
04-02 22:29:31.330: W/ResourceType(17644): Skipping entry 0x7f060002 in package table 0 because it is not complex!
04-02 22:29:31.330: W/ResourceType(17644): Skipping entry 0x7f060002 in package table 0 because it is not complex!
04-02 22:29:31.330: W/ResourceType(17644): Skipping entry 0x7f060002 in package table 0 because it is not complex!
最佳答案
我似乎找不到游标上的.moveToFirst()方法调用，它将游标移动到结果集的第一行。我相信这很可能是你问题的原因。
所以，试试
cursor = db.getCountry();
if(cursor.moveToFirst()) {
String s = cursor.getString(1);
mytextView.setText(s);
}
另外，记住getstring方法是基于零的（正如其他人在他们的答案中指出的那样）。使用1将为您提供列“month”，因为您的textfields id的名称我怀疑这不是您要查找的：）
关于android - SQLite Android选择查询问题，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/15775673/