Question

我已经搜遍了所有但我的案例中没有答案，我正在开发一个我需要的应用程序：

数据库
将csv文件导入该数据库并显示的活动它在ListView
和onClick按钮的另一个活动在游标上运行游标该数据库中一列的值，并将其与字符串和结果返回一个表示已找到匹配的祝酒词。

我有一个扩展SQLiteOpenHelper的DBController类，当我在其他活动中调用此类时，它在第一个活动中完美连接，它导入csv文件并在listview中显示它，但在第二个活动中它不是做任何事情，我不知道问题是它没有连接，还是它正在返回一个空表。

这是我的代码：

DBController类：

package org.opencv.javacv.facerecognition;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.util.ArrayList;
import java.util.HashMap;
public class DBController extends SQLiteOpenHelper {
    private static final String LOGCAT = null;
    public DBController(Context applicationcontext) {
        super(applicationcontext, "classes.db", null, 1);  // creating DATABASE
        Log.d(LOGCAT, "Created");
    }
    @Override
    public void onCreate(SQLiteDatabase database) {
        String query;
        query = "CREATE TABLE IF NOT EXISTS course1 ( Id INTEGER PRIMARY KEY, student_number TEXT UNIQUE, student_fn TEXT, student_ln TEXT, attended INTEGER DEFAULT 0, time_attended TEXT)";
        database.execSQL(query);
    }
    @Override
    public void onUpgrade(SQLiteDatabase database, int version_old,
                          int current_version) {
        String query;
        query = "DROP TABLE IF EXISTS course1";
        database.execSQL(query);
        onCreate(database);
    }


    public ArrayList<HashMap<String, String>> getAllProducts() {
        ArrayList<HashMap<String, String>> studentList;
        studentList = new ArrayList<HashMap<String, String>>();
        String selectQuery = "SELECT  * FROM course1";
        SQLiteDatabase database = this.getWritableDatabase();
        Cursor cursor = database.rawQuery(selectQuery, null);
        if (cursor.moveToFirst()) {
            do {
                //Id, Company,Name,Price
                HashMap<String, String> map = new HashMap<String, String>();
                map.put("Id", cursor.getString(0));
                map.put("student_number", cursor.getString(1));
                map.put("student_fn", cursor.getString(2));
                map.put("student_ln", cursor.getString(3));
                map.put("attended", cursor.getString(4));
                map.put("time_attended", cursor.getString(5));
                studentList.add(map);
            } while (cursor.moveToNext());
        }
        return studentList;
    }
}

导入csv文件并在listview中显示它的DBActivity：

package org.opencv.javacv.facerecognition;

import android.app.Dialog;
import android.app.ListActivity;
import android.content.ActivityNotFoundException;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
public class DBActivity extends ListActivity {
    TextView lbl;
    DBController controller = new DBController(this);
    Button btnimport;
    ListView lv;
    final Context context = this;
    ListAdapter adapter;
    ArrayList<HashMap<String, String>> myList;
    public static final int requestcode = 1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.database_view);
        lbl = (TextView) findViewById(R.id.txtresulttext);
        btnimport = (Button) findViewById(R.id.btnupload);
        lv = getListView();
        btnimport.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent fileintent = new Intent(Intent.ACTION_GET_CONTENT);
                fileintent.setType("gagt/sdf");
                try {
                    startActivityForResult(fileintent, requestcode);
                } catch (ActivityNotFoundException e) {
                    lbl.setText("No activity can handle picking a file. Showing alternatives.");
                }
            }
        });
        myList= controller.getAllProducts();
        if (myList.size() != 0) {
            ListView lv = getListView();
            ListAdapter adapter = new SimpleAdapter(DBActivity.this, myList,
                    R.layout.v, new String[]{"student_number", "student_fn", "student_ln" , "attended" , "time_attended"}, new int[]{
                    R.id.studentnumber, R.id.studentfn, R.id.studentln, R.id.attended, R.id.timeattended});
            setListAdapter(adapter);
            lbl.setText("");
        }
    }
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (data == null)
            return;
        switch (requestCode) {
            case requestcode:
                String filepath = data.getData().getPath();
                controller = new DBController(getApplicationContext());
                SQLiteDatabase db = controller.getWritableDatabase();
                String tableName = "course1";
                db.execSQL("delete from " + tableName);
                try {
                    if (resultCode == RESULT_OK) {
                        try {
                            FileReader file = new FileReader(filepath);
                            BufferedReader buffer = new BufferedReader(file);
                            ContentValues contentValues = new ContentValues();
                            String line = "";
                            db.beginTransactionNonExclusive();
                            while ((line = buffer.readLine()) != null) {
                                String[] str = line.split(",", 5);  // defining 3 columns with null or blank field //values acceptance
                                //Id, Company,Name,Price
                                String student_number = str[0].toString();
                                String student_fn = str[1].toString();
                                String student_ln = str[2].toString();
                                String attended = str[3].toString();
                                String time_attended = str[4].toString();
                                contentValues.put("student_number", student_number);
                                contentValues.put("student_fn", student_fn);
                                contentValues.put("student_ln", student_ln);
                                contentValues.put("attended", attended);
                                contentValues.put("time_attended", time_attended);
                                db.insert(tableName, null, contentValues);
                                lbl.setText("Successfully Updated Database.");
                            }
                            db.setTransactionSuccessful();
                            db.endTransaction();

                        } catch (IOException e) {
                            if (db.inTransaction())
                                db.endTransaction();
                            Dialog d = new Dialog(this);
                            d.setTitle(e.getMessage().toString() + "first");
                            d.show();

                            // db.endTransaction();
                        }
                    } else {
                        if (db.inTransaction())
                            db.endTransaction();
                        Dialog d = new Dialog(this);
                        d.setTitle("Only CSV files allowed");
                        d.show();
                    }
                } catch (Exception ex) {
                    if (db.inTransaction())
                        db.endTransaction();
                    Dialog d = new Dialog(this);
                    d.setTitle(ex.getMessage().toString() + "second");
                    d.show();
                    // db.endTransaction();
                }
            db.close();
        }
        myList= controller.getAllProducts();
        if (myList.size() != 0) {
            ListView lv = getListView();
            ListAdapter adapter = new SimpleAdapter(DBActivity.this, myList,
                    R.layout.v, new String[]{"student_number", "student_fn", "student_ln" , "attended" , "time_attended"}, new int[]{
                    R.id.studentnumber, R.id.studentfn, R.id.studentln, R.id.attended, R.id.timeattended});
            setListAdapter(adapter);
            lbl.setText("Data Imported");
        }
    }
}

以下是如何将字符串与第二个类中的表中的列进行比较（这只是活动的一部分）：首先我在顶部添加了这个：

DBController controller = new DBController(this);
String number = "200910772";

，这是onCreate方法中的onClick代码：

buttonSearch.setOnClickListener(new View.OnClickListener() {
   public void onClick(View v) {
     controller = new DBController(getApplicationContext());
                            SQLiteDatabase db = controller.getWritableDatabase();
     String query = "SELECT * FROM course1 WHERE student_number=" + number;
     Cursor cursor = db.rawQuery(query, null);

     if(cursor.getCount() > 0) {
       cursor.moveToFirst();
       while(!cursor.isAfterLast()) {
             Toast.makeText(getApplicationContext(), "match found!", Toast.LENGTH_LONG).show();
             cursor.moveToNext();
          }
       }
   }

});

我无法弄清楚问题可能是什么.. 我是Android的新手，所以任何帮助都会受到高度赞赏。

Answer 1

我解决了它，真的是一个愚蠢的错误，导入时的csv文件在文本周围加了双引号，因此从未找到匹配，因为它正在考虑将双引号作为字符串的一部分。一旦删除，就会发现匹配。

android studio中的SQLite数据库，第二个活动是返回一个空表

1 个答案: