Question

我有saveinSQL类（扩展SQLiteOpenHelper），我在其中定义了我的数据库访问方法。我在Create类中创建了一个数据库。我想在Home类中访问数据库。我能够在我的Home类中获取数据库中的行数，这意味着我可以访问数据库。但是我无法在游标的帮助下访问SQLite表的特定单元格中的数据条目。我的 getHeader 功能似乎有问题。有人请帮帮我。我正在处理的部分是 Home Class 的 onCreate 函数。我得到的错误是 android.database.CursorIndexOutOfBoundsException：请求索引1，大小为1

这是我的家庭班。我在 temp.header = mydb.getHeader（1）;

上收到错误

package com.example.yashubale.mypetitions;
import android.content.Context;
import android.content.Intent;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
    public class Home extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {
        ArrayList<Petition> ap;
        saveinSQL mydb;

        String a,b,c;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        setTitle("Dashboard");
        ap = new ArrayList<Petition>();
        mydb = saveinSQL.getInstance(this);
        int numPetitions = mydb.numberOfRows();
    Toast.makeText(this , Integer.toString(numPetitions) ,     Toast.LENGTH_LONG).show();
        Petition temp = new Petition();
    //        temp.header = mydb.getHeader(2);
        temp.header = mydb.getHeader(1);
    //        temp.header = mydb.getHeader(3);
    //        for(int i= 1 ; i <= numPetitions ; i++){
    //
    //           // temp.header = mydb.getHeader(i);
    //            temp.description = mydb.getDescription(i);
    //            temp.people = mydb.getPeople(i);
    //            //ap.add(temp);
    //        }
      //  ListView lv = (ListView) findViewById(R.id.listpetitions);
      //  customeAdapter ca = new customeAdapter(this,ap);


    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();



    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.home, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
//        if (id == R.id.action_settings) {
//            return true;
//        }

    return super.onOptionsItemSelected(item);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_create) {
        startCreate(this);

    } else if (id == R.id.nav_mypetitions) {

    } else if (id == R.id.nav_dashboard) {

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}
public void startCreate(Context c){
    Intent intent = new Intent(c , Create.class);
    intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    startActivity(intent);
}
}

这是我的 saveinSQL类

 package com.example.yashubale.mypetitions;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.ArrayList;
public class saveinSQL extends SQLiteOpenHelper {

String header = new String();
String descrip = new String();
String people = new String();
Cursor res;
private static saveinSQL mInstance = null;
private Context myctx;
private static final int DATABASE_VERSION = 2;
private static final String PETITIONS_TABLE_NAME = "Petitions";
private static final String DATABASE_NAME = "myDB.db";
public static final String PETITIONS_COLUMN_ID = "id";
public static final String PETITIONS_COLUMN_HEADING = "heading";
public static final String PETITIONS_COLUMN_DESCRIPTION = "description";
public static final String PETITIONS_COLUMN_PEOPLE = "people";

public saveinSQL(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    myctx = context;
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(
            "create table Petitions" +
                    "(id integer primary key, heading text, description text, people text)"
    );
}

public static synchronized saveinSQL getInstance(Context context) {
    if (mInstance == null) {
        mInstance = new saveinSQL(context.getApplicationContext());
    }
    return mInstance;
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS Petitions");
    onCreate(db);
}

public boolean insertPetition  (String heading, String description,String people)
{
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("heading", heading);
    contentValues.put("description", description);
    contentValues.put("people", people);
    db.insert("Petitions", null, contentValues);
    return true;
}

public Cursor getData(int id){
    SQLiteDatabase db = this.getReadableDatabase();
     res =  db.rawQuery( "select * from Petitions where id="+id+"", null );
    return res;
}




public  String getHeader(int id){
    SQLiteDatabase db = this.getReadableDatabase();
     res = db.rawQuery("select * from Petitions where id=" + id + "", null);
    res.moveToPosition(id);
//        for(int i = 1; i < id; i++){
//            res.moveToNext();
//        }
    header =    res.getString(res.getColumnIndex(saveinSQL.PETITIONS_COLUMN_HEADING));
    res.moveToFirst();
    return header;
}

public String getDescription(int id){
    SQLiteDatabase db = this.getReadableDatabase();
    res = db.rawQuery("select * from Petitions where id=" + id + "", null);
    res.moveToFirst();
    for(int i = 1; i < id; i++){
        res.moveToNext();
    }
     descrip = res.getString(res.getColumnIndex(saveinSQL.PETITIONS_COLUMN_DESCRIPTION));
    return descrip;
}

public String getPeople(int id){
    SQLiteDatabase db = this.getReadableDatabase();
     res = db.rawQuery("select * from Petitions where id=" + id + "", null);
    res.moveToFirst();
    for(int i = 1; i < id; i++){
        res.moveToNext();
    }
     people = res.getString(res.getColumnIndex(saveinSQL.PETITIONS_COLUMN_PEOPLE));
    return people;
}




public int numberOfRows(){
    SQLiteDatabase db = this.getReadableDatabase();
    int numRows = (int) DatabaseUtils.queryNumEntries(db, PETITIONS_TABLE_NAME);
    return numRows;
}

public boolean updatePetitiont (Integer id, String heading, String description, String people)
{
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("heading", heading);
    contentValues.put("description", description);
    contentValues.put("people", people);
    db.update("Petitions", contentValues, "id = ? ", new String[] { Integer.toString(id) } );
    return true;
}

public Integer deletePetition (Integer id)
{
    SQLiteDatabase db = this.getWritableDatabase();
    return db.delete("Petitions",
            "id = ? ",
            new String[] { Integer.toString(id) });
}

public ArrayList<String> getAllPetitions()
{
    ArrayList<String> array_list = new ArrayList<String>();

    //hp = new HashMap();
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select * from Petitions", null );
    res.moveToFirst();

    while(res.isAfterLast() == false){
        array_list.add(res.getString(res.getColumnIndex(PETITIONS_COLUMN_HEADING)));
        res.moveToNext();
    }
    return array_list;
}
}

这是我的创建班级

public class Create extends AppCompatActivity {
private EditText mHeadingView;
private EditText mDescriptionView;
saveinSQL mydb = new saveinSQL(this);
EditText headingGet;
EditText descriptionGet;
EditText peopleGet;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_create);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    Button mEmailSignInButton = (Button) findViewById(R.id.createpetition);
    mEmailSignInButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            createPetition();
        }
    });

}

public void createPetition(){
    boolean cancel = false;
    View focusView = null;
    mHeadingView = (EditText)findViewById(R.id.heading);
    mDescriptionView = (EditText)findViewById(R.id.description);
    mHeadingView.setError(null);
    mDescriptionView.setError(null);
    String heading = mHeadingView.getText().toString();
    String description = mDescriptionView.getText().toString();
    if(heading.isEmpty()) {
        mHeadingView.setError("Heading is too short");
        focusView = mHeadingView;
        cancel = true;
    }
    if(description.isEmpty()){
        mDescriptionView.setError("Description is too short");
        focusView = mDescriptionView;
        cancel  = true;
    }

    if (cancel) {
        focusView.requestFocus();

    }
    else{
        headingGet =(EditText)findViewById(R.id.heading);
        descriptionGet =(EditText)findViewById(R.id.description);
        peopleGet =(EditText)findViewById(R.id.members);
//            for(int i = 1; i < 5 ; i++){
//                mydb.deletePetition(i);
//            }
        if(mydb.insertPetition(headingGet.getText().toString(), descriptionGet.getText().toString(), peopleGet.getText().toString())){
            Toast.makeText(getApplicationContext(), "Petition Added" , Toast.LENGTH_LONG).show();
            finish();
        }
    }
}

}

Answer 1

public  String getHeader(int id){
    SQLiteDatabase db = this.getReadableDatabase();
    String header = "";
    res = db.rawQuery("select * from Petitions where id=" + id + "", null);
    if (res.moveToFirst()) {
        header = res.getString(res.getColumnIndex(saveinSQL.PETITIONS_COLUMN_HEADING));
    }
    return header;
}

Answer 2

res = db.rawQuery("select * from Petitions where id=" + id + "", null);
res.moveToPosition(id);

查询只返回一行（因为WHERE过滤器），所以你不能移动到除0之外的任何位置。

将moveToPosition替换为moveToFirst。并且不需要返回任何其他列，并且您还应该在没有找到具有该ID的行时处理该情况：

res = db.rawQuery("select "+saveinSQL.PETITIONS_COLUMN_HEADING+
                  " from Petitions"+
                  " where id=" + id + "", null);
if (res.moveToFirst())
    header = res.getString(0);
else
    header = "";

请注意，有helper function可以更轻松地从返回单行的查询中获取值：

header = DatabaseUtils.stringForQuery(db,
                "select "+saveinSQL.PETITIONS_COLUMN_HEADING+
                " from Petitions"+
                " where id=" + id + "", null);

Answer 3

＆＃34;创建表格请愿书＆＃34; + ＆＃34;（id整数主键，标题文本，描述文本，人物文本）＆＃34;

＆＃34;创建表格请求（id整数主键自动增量，标题文本，描述文本，人物文本）＆＃34;

无法访问Android中SQLite数据库中的单个数据条目

3 个答案: