如何通过数据库中的信息过滤listView

Question

我编写了一个能够在数据库中保存主题和标记的应用程序。我必须解决的最后一个问题是，如何从Marks类中过滤ListView，以便它只显示相应的主题。

该应用程序由三个类组成。

主：

package maturaarbeit.nicola_pfister.marks;

import maturaarbeit.nicola_pfister.marks.database.DBAdapter;
import android.app.AlertDialog.Builder;
import android.app.ListActivity;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v4.widget.SimpleCursorAdapter;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.EditText;
import android.widget.ListView;

public class Main extends ListActivity {

    DBAdapter db = new DBAdapter(this);

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.subjects);
    }

    @Override
    protected void onPause() {
        super.onPause();
        db.close();
    }

    @Override
    protected void onResume() {
        super.onResume();
        db.open();
        getData();
    }

    @SuppressWarnings("deprecation")
    private void getData() {
        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
                android.R.layout.simple_list_item_1, 
                db.getAllSubjects(), 
                new String[] { "subject" }, 
                new int[] { android.R.id.text1 });

        ListView listView = (ListView) findViewById(android.R.id.list);
        listView.setAdapter(adapter);
        listView.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long id) {

            Cursor cursor = db.getSubject(id);
            String subject = null;
            try {
                subject = cursor.getString(cursor.getColumnIndex("subject"));
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            Intent intent = new Intent(Main.this, Marks.class);
            intent.putExtra("selected", subject);
            startActivity(intent);
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.subjects, menu);
        return true;
    }

    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case R.id.menu_add:
            Builder builder = new Builder(this);
            final EditText input = new EditText(this);
            builder
                .setTitle(R.string.dialog_addsubject)
                .setView(input)
                .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {

                    public void onClick(DialogInterface dialog, int which) {
                        String value = input.getText().toString();
                        db.insertSubject(value);
                        getData();
                    }
                })
                .setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {

                    public void onClick(DialogInterface dialog, int which) {
                    }

                })
                .show();
            break;
        case R.id.menu_delete:
//          getData();
            break;
        }
        return super.onOptionsItemSelected(item);
    }
}

商标：

package maturaarbeit.nicola_pfister.marks;

import java.util.Calendar;

import maturaarbeit.nicola_pfister.marks.database.DBAdapter;
import android.app.AlertDialog.Builder;
import android.app.ListActivity;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v4.widget.SimpleCursorAdapter;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.ListView;


public class Marks extends ListActivity {

    DBAdapter db = new DBAdapter(this);


    String selection = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.marks);

        final Bundle extras = getIntent().getExtras();
        selection = extras.getString("selected");

        if (extras!= null) {
            setTitle(selection);
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        db.close();
    }

    @Override
    protected void onResume() {
        super.onResume();
        db.open();
        getData();

    }

    @SuppressWarnings("deprecation")
    private void getData() {
        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
                android.R.layout.simple_list_item_1, 
                db.getAllMarks(), 
                new String[] { "value" }, 
                new int[] { android.R.id.text1 });


        ListView listView = (ListView) findViewById(android.R.id.list);
        listView.setAdapter(adapter);
    }

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

    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case R.id.menu_add:
            Builder builder = new Builder(this);
            final EditText input = new EditText(this);
            builder
                .setTitle(R.string.dialog_addmark)
                .setView(input)
                .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {

                    public void onClick(DialogInterface dialog, int which) {
                        String value = input.getText().toString();

                        Calendar cal = Calendar.getInstance();
                        int day = cal.get(Calendar.DAY_OF_MONTH);
                        int month = cal.get(Calendar.MONTH) + 1;
                        final String date = day + "." + month + ".";

                        db.insertMark(date, selection, value);
                        getData();
                    }
                })
                .setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {

                    public void onClick(DialogInterface dialog, int which) {
                    }

                })
                .show();
            break;
        case R.id.menu_delete:
            break;
        }
        return super.onOptionsItemSelected(item);
    }
}

和DBAdapter：

package maturaarbeit.nicola_pfister.marks.database;

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 DBAdapter {

    int id = 0;
    public static final String KEY_ROWID = "_id";
    public static final String KEY_DATE = "date";
    public static final String KEY_SUBJECT = "subject";
    public static final String KEY_VALUE = "value";
    public static final String TAG = "DBAdapter";

    private static final String DATABASE_NAME = "database";
    private static final String DATABASE_TABLE_MARKS = "marks";
    private static final String DATABASE_TABLE_SUBJECTS = "subjects";
    private static final int DATABASE_VERSION = 1;

    private static final String DATABASE_CREATE_MARKS =
            "create table " + DATABASE_TABLE_MARKS + " (" + KEY_ROWID + " integer primary key autoincrement, " +
                    KEY_DATE +" text not null, " +
                    KEY_SUBJECT +" text not null, " +
                    KEY_VALUE +" text not null" +  ");";

    private static final String DATABASE_CREATE_SUBJECTS =
            "create table " + DATABASE_TABLE_SUBJECTS + " (" + KEY_ROWID + " integer primary key autoincrement, " +
                    KEY_SUBJECT +" text not null " + ");";

    @SuppressWarnings("unused")
    private final Context context;

    private DatabaseHelper DBHelper;
    private SQLiteDatabase db;

    public DBAdapter(Context context) {
        this.context = context;
        DBHelper = new DatabaseHelper(context);
    }

    private static class DatabaseHelper extends SQLiteOpenHelper {

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

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL(DATABASE_CREATE_MARKS);
            db.execSQL(DATABASE_CREATE_SUBJECTS);
        }

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

    public DBAdapter open() throws SQLException {
        db = DBHelper.getWritableDatabase();
        return this;
    }

    public void close() {
        DBHelper.close();
    }

    public long insertMark (String date, String subject, String value) {
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_DATE, date);
        initialValues.put(KEY_SUBJECT, subject);
        initialValues.put(KEY_VALUE, value);
        return db.insert(DATABASE_TABLE_MARKS, null, initialValues);
    }

    public boolean deleteMark(long rowId) {
        return db.delete(DATABASE_TABLE_MARKS, KEY_ROWID + "=" + rowId, null) > 0;
    }

    public Cursor getAllMarks() {
        return db.query(DATABASE_TABLE_MARKS, new String[] {
                KEY_ROWID,
                KEY_DATE,
                KEY_SUBJECT,
                KEY_VALUE
        }, null, null, null, null, null);
    }

    public Cursor getMark(long rowId) throws SQLException {
        Cursor mCursor =
                db.query(true, DATABASE_TABLE_MARKS, new String[] {
                        KEY_ROWID,
                        KEY_DATE,
                        KEY_SUBJECT,
                        KEY_VALUE
                },
                KEY_ROWID + "=" + rowId,
                null, null, null, null, null);
        if (mCursor != null) {
            mCursor.moveToFirst();
        }
        return mCursor;
    }

    public boolean updateMark(long rowId, String date, String subject, String value) {
        ContentValues args = new ContentValues();
        args.put(KEY_DATE, date);
        args.put(KEY_SUBJECT, subject);
        args.put(KEY_VALUE, value);
        return db.update(DATABASE_TABLE_MARKS, args, KEY_ROWID + "=" + rowId, null) >0;
    }

    public void deleteMark() {
        db.delete(DATABASE_TABLE_MARKS, null, null);
    }

    public long insertSubject (String subject) {
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_SUBJECT, subject);
        return db.insert(DATABASE_TABLE_SUBJECTS, null, initialValues);
    }

    public boolean updateSubject(long rowId, String subject) {
        ContentValues args = new ContentValues();
        args.put(KEY_SUBJECT, subject);
        return db.update(DATABASE_TABLE_MARKS, args, KEY_ROWID + "=" + rowId, null) >0;
    }

    public Cursor getSubject(long rowId) throws SQLException {
        Cursor mCursor =
                db.query(true, DATABASE_TABLE_SUBJECTS, new String[] {
                        KEY_ROWID,
                        KEY_SUBJECT
                },
                KEY_ROWID + "=" + rowId,
                null, null, null, null, null);
        if (mCursor != null) {
            mCursor.moveToFirst();
        }
        return mCursor;
    }

    public Cursor getAllSubjects() {
        return db.query(DATABASE_TABLE_SUBJECTS, new String[] {
                KEY_ROWID,
                KEY_SUBJECT
        }, null, null, null, null, null);
    }
}

就像现在一样，标记活动显示任何主题的所有标记，即使标题说明了其他内容。我想使用我的数据库的“主题”列过滤ListView，以便只显示数据库的项目，这些项目与标题所说的主题相同。我开始被互联网上找到的所有不同解决方案所震撼，我无法将其中的任何一个适应我的问题......

提前谢谢

Answer 1

也许在DBAdapter中创建这样的方法，并在SimpleCursorAdapter中使用它而不是db.getAllMarks（），并传入选择。

public Cursor getMarks(String subject) {
    return db.query(DATABASE_TABLE_MARKS, new String[] {
            KEY_ROWID,
            KEY_DATE,
            KEY_SUBJECT,
            KEY_VALUE
    }, KEY_SUBJECT + " = ?", subject, null, null, null);
}