android - 数据库删除功能不起作用

Question

大家好，我在从数据库中删除项目时遇到了一些问题。我在一项 Activity 中有一个学校列表。这是我的屏幕截图[![Schools.java][1]][1]

在 schooldetails.class 的顶部，我有一个星形图标来为学校添加书签。单击书签图标后，图标变为实心图标，相应的学校将保存到我的书签类中。直到一切正常。现在我正在尝试通过重新单击填充的星形图标来删除书签。我希望从书签类中删除带有书签的学校。这就是我在 Schooldetails 类中所做的

package com.example.user.educationhunt;

import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.Toast;

import com.example.user.educationhunt.database.DatabaseHelper;
import com.example.user.educationhunt.fragment.About;
import com.example.user.educationhunt.fragment.Admission;
import com.example.user.educationhunt.fragment.FeeStructure;
import com.example.user.educationhunt.listner.DatabaseUpdatedListener;
import com.example.user.educationhunt.pojos.Bookmarkitem;
import com.example.user.educationhunt.pojos.OurSchool;

import java.util.ArrayList;
import java.util.List;

public class SchoolDetails extends AppCompatActivity implements DatabaseUpdatedListener {

    private Toolbar toolbar;
    private TabLayout tabLayout;
    private ViewPager viewPager;
    Boolean isStarFilled = false;
    DatabaseHelper db;
    OurSchool ourSchool;
    private Menu menu;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_school_details);

        ourSchool = (OurSchool) getIntent().getSerializableExtra("school");

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setTitle(ourSchool.getSchoolName());


        db = new DatabaseHelper(this);
        db.databaseUpdatedListener = this;

        Toast.makeText(this, ourSchool.getSchoolName(), Toast.LENGTH_SHORT).show();

        viewPager = (ViewPager) findViewById(R.id.viewpager);
        setupViewPager(viewPager);

        tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(viewPager);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.fav_school, menu);
        this.menu = menu;
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.star_School:
                Bookmarkitem bookmarkitem = new Bookmarkitem();
                bookmarkitem.setBookmarkID(ourSchool.getSchoolId());
                bookmarkitem.setName(ourSchool.getSchoolName());
                bookmarkitem.setLogo(ourSchool.getSchoolLogo());
                bookmarkitem.setAddress(ourSchool.getSchoolAddress());
                db.addSchoolBookmark(bookmarkitem, item);
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        List<Bookmarkitem> bookmarkitems = db.getAllSchoolBookmark();
        if (bookmarkitems.size() != 0) {
            for (Bookmarkitem bookmarkitem : bookmarkitems) {
                if (bookmarkitem.getBookmarkID() == ourSchool.getSchoolId()) {
                    isStarFilled = true;
                    break;
                }
                else isStarFilled=false;
            }
            if (isStarFilled) {
                menu.getItem(0).setIcon(getResources().getDrawable(R.mipmap.starfilled));
            }else if (isStarFilled.booleanValue()==true){
                delete();
                menu.getItem(0).setIcon(getResources().getDrawable(R.mipmap.star));
            }
        }
        return true;
    }

    public void delete(){
        List<Bookmarkitem> bookmarkitems = db.getAllSchoolBookmark();
        db.removeBookmarkItem(ourSchool.getSchoolId());    }

    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFragment(new About(), "ABOUT US");
        adapter.addFragment(new Admission(), "ADMISSION");
        adapter.addFragment(new FeeStructure(), "FEE");
        viewPager.setAdapter(adapter);
    }


    @Override
    public void setDatabaseSuccess(String schoolName, MenuItem item) {
        Toast.makeText(this, schoolName + "successfully added as bookmark", Toast.LENGTH_SHORT).show();
        item.setIcon(R.mipmap.starfilled);
    }

    @Override
    public void setDatabaseError(String failureMessage) {
        Toast.makeText(this, failureMessage, Toast.LENGTH_SHORT).show();
    }

    class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

        public ViewPagerAdapter(FragmentManager manager) {
            super(manager);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

        public void addFragment(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }
}

这是我的数据库类

package com.example.user.educationhunt.database;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.view.MenuItem;

import com.example.user.educationhunt.listner.DatabaseUpdatedListener;
import com.example.user.educationhunt.pojos.Bookmarkitem;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by user on 11/22/2016.
 */
public class DatabaseHelper extends SQLiteOpenHelper {

    public DatabaseUpdatedListener databaseUpdatedListener;
    static final String DATABASE_NAME = "BookmarkDatabase";
    private static final int DATABASE_VERSION = 1;
    private static final String TABLE_NAME_BOOKMARK = "bookmark";

    //    Contact table columns name
    private static final String ID = "Id";
    private static final String NAME = "Name";
    private static final String LOGO = "Logo";
    private static final String LOCATION = "Location";

    String createTableBookmark = "Create table if not exists `Bookmark` ("
            + "`name`   TEXT," + "`location`    TEXT," + "`logo`    TEXT);";

    String CREATE_SCHOOL_BOOKMARK_TABLE = "CREATE TABLE " + TABLE_NAME_BOOKMARK + "("
            + ID + " INTEGER PRIMARY KEY, "
            + NAME + " TEXT, "
            + LOGO + " TEXT, "
            + LOCATION + " TEXT " + ")";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    public void insertBookmarkData(Bookmarkitem bookmarkitem) {
        SQLiteDatabase db = getWritableDatabase();
        ContentValues content = new ContentValues();
        content.put("name", bookmarkitem.name);
        content.put("location", bookmarkitem.address);
        content.put("logo", bookmarkitem.logo);

        db.insert("Bookmark", null, content);
    }

    public ArrayList<Bookmarkitem> getBookmarkist() {
        String sql = "select * from Bookmark ";
        ArrayList<Bookmarkitem> bookmarklist = new ArrayList<Bookmarkitem>();

        Cursor c = getWritableDatabase().rawQuery(sql, null);
        while (c.moveToNext()) {
            Bookmarkitem info = new Bookmarkitem();
            info.name = c.getString(c.getColumnIndex("name"));
            info.address = c.getString(c.getColumnIndex("location"));
            info.logo = c.getString(c.getColumnIndex("logo"));
            bookmarklist.add(info);
        }
        c.close();
        return bookmarklist;
    }

    public Bookmarkitem getBookmarkData(String bookmarkName) {
        String sql = "select * from Bookmark  where id='" + bookmarkName + "'";

        Cursor c = getWritableDatabase().rawQuery(sql, null);
        while (c.moveToNext()) {
            Bookmarkitem info = new Bookmarkitem();
            info.name = c.getString(c.getColumnIndex("name"));
            info.address = c.getString(c.getColumnIndex("location"));
            info.logo = c.getString(c.getColumnIndex("logo"));
        }
        c.close();
        Bookmarkitem info = null;
        return info;
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        // TODO Auto-generated method stub
        sqLiteDatabase.execSQL(CREATE_SCHOOL_BOOKMARK_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int arg1, int arg2) {
        // TODO Auto-generated method stub
        sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME_BOOKMARK);
        onCreate(sqLiteDatabase);
    }

    public void addSchoolBookmark(Bookmarkitem bookmarkitem, MenuItem menuItem) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(ID, bookmarkitem.getBookmarkID());
        values.put(NAME, bookmarkitem.getName());
        values.put(LOGO, bookmarkitem.getLogo());
        values.put(LOCATION, bookmarkitem.getAddress());

        //inserting row
        if (db.insert(TABLE_NAME_BOOKMARK, null, values) != -1) {
            databaseUpdatedListener.setDatabaseSuccess(bookmarkitem.getName(), menuItem);
        } else {
            databaseUpdatedListener.setDatabaseError("Failed to insert");
        }
        db.close();
    }

    public List<Bookmarkitem> getAllSchoolBookmark() {
        SQLiteDatabase db = this.getWritableDatabase();
        String selectQuery = "SELECT * FROM " + TABLE_NAME_BOOKMARK;
        List<Bookmarkitem> bookmarkitems = new ArrayList<>();
        Cursor cursor = db.rawQuery(selectQuery, null);

        if (cursor.moveToFirst()) {
            do {
                Bookmarkitem bookmarkitem = new Bookmarkitem();
                bookmarkitem.setBookmarkID(Integer.parseInt(cursor.getString(0)));
                bookmarkitem.setName(cursor.getString(1));
                bookmarkitem.setLogo(cursor.getString(2));
                bookmarkitem.setAddress(cursor.getString(3));
                bookmarkitems.add(bookmarkitem);
            } while (cursor.moveToNext());
        }
        return bookmarkitems;
    }

    public void removeBookmarkItem(int sID) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.execSQL("DELETE FROM " + TABLE_NAME_BOOKMARK + " WHERE " + ID + "= '" + sID + "'");
        db.close();
    }
}

除此之外，点击书签类项目中的列表。我希望加载相应类的详细信息。这是我的书签类

package com.example.user.educationhunt;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.Toast;

import com.example.user.educationhunt.adapter.BookmarkAdapter;
import com.example.user.educationhunt.database.DatabaseHelper;
import com.example.user.educationhunt.pojos.Bookmarkitem;

import java.util.ArrayList;
import java.util.List;

public class Bookmark extends AppCompatActivity {
    private List<Bookmarkitem> ourBookmarkListItems = new ArrayList<Bookmarkitem>();
    private ListView listView;
    private BookmarkAdapter adapter;
    DatabaseHelper dbhelper;
    private Toolbar toolbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_bookmark);
        dbhelper = new DatabaseHelper(this);

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        toolbar.setPadding(0, getStatusBarHeight(), 0, 0);

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setTitle("Bookmark");

        List<Bookmarkitem> bookmarkedSchools = dbhelper.getAllSchoolBookmark();

        listView = (ListView) findViewById(R.id.list_bookmarked);
        if (bookmarkedSchools.size() != 0) {
            adapter = new BookmarkAdapter(this, bookmarkedSchools);
            listView.setAdapter(adapter);
        } else {
            Toast.makeText(this, "You have no bookmark yet.", Toast.LENGTH_SHORT).show();
        }

        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                startActivity(new Intent(Bookmark.this,SchoolDetails.class));
            }
        });

          }

    public int getStatusBarHeight() {
        int result = 0;
        int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android");
        if (resourceId > 0) {
            result = getResources().getDimensionPixelSize(resourceId);
        }
        return result;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                onBackPressed();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

我既没有得到任何错误也没有得到正确的结果。请有人帮忙

Answer 1

在你的助手类中使用它 :D

public boolean removeBookmarkItem(String id) {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.delete(TABLE_NAME_BOOKMARK, ID + "=" + id, null) > 0;
    }