将SQLiteDatabase导出到CSV Android Studio

Question

Been working with this code for a few days now. I've don't have much experience in Java but I can piece together code I have found online and learn from that. I've been using this website as a template for my current activity. Android Export Sqlite Database I've changed a number of things on the code provided but it's one error after another. Right now with the code I have, I am getting sqldb (line 211 or so...) cannot resolve symbol . I just don't think I'm declaring sqldb correctly is my overall problem. You may notice other parts of the code from other places online too. Just trying to learn and then change the code to what I need when I'm done. Here is a few of the files. Thanks for any help! (If you see any other changes that would be great because all I have been doing is using the Android Studio suggestions). Not sure what files you need to see but here are a few. MyActivity is my main. When ' send ' is selected in MyActivity.java it should export the csv file.

MyActivity.java

package com.nate.nash.howtoloveme;
import android.app.ListActivity;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.os.Environment;
import android.support.annotation.Nullable;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatCallback;
import android.support.v7.app.AppCompatDelegate;
import android.support.v7.view.ActionMode;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;


public class MyActivity extends ListActivity implements AppCompatCallback {
private DBHelper dbHelper;


@Override
public void onBackPressed() {
    new AlertDialog.Builder(this)
            .setIcon(android.R.drawable.ic_dialog_alert)
            .setTitle("Closing Activity")
            .setMessage("Are you sure you want to close this activity?")
            .setPositiveButton("Yes", new DialogInterface.OnClickListener()
            {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    finish();
                }

            })
            .setNegativeButton("No", null)
            .show();
}
private AppCompatDelegate delegate;
TextView student_Id;

@Override
protected void onCreate(Bundle savedInstanceState) {

    // TODO remove comment code
    // TODO change wording from student to feeling
    // TODO change when list is removed or added, spinner changes
    // TODO start new activity after MainActivity.java

    //let's create the delegate, passing the activity at both arguments (Activity, AppCompatCallback)
    delegate = AppCompatDelegate.create(this, this);

    //we need to call the onCreate() of the AppCompatDelegate
    delegate.onCreate(savedInstanceState);

    //we use the delegate to inflate the layout
    delegate.setContentView(R.layout.activity_my);

    //TODO custom added

    //Finally, let's add the Toolbar
    Toolbar toolbar= (Toolbar) findViewById(R.id.my_awesome_toolbar);
    delegate.setSupportActionBar(toolbar);
    super.onCreate(savedInstanceState);

    StudentRepo repo = new StudentRepo(this);
    ArrayList<HashMap<String, String>> studentList = repo.getStudentList();
    if (studentList.size() != 0) {
        repo = new StudentRepo(this);

        studentList = repo.getStudentList();
        if(studentList.size()!=0) {
            ListView lv = getListView();
            lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
                    student_Id = (TextView) view.findViewById(R.id.student_Id);
                    String studentId = student_Id.getText().toString();
                    Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
                    objIndent.putExtra("student_Id", Integer.parseInt( studentId));
                    startActivity(objIndent);
                }
            });
            ListAdapter adapter = new SimpleAdapter( MyActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
            setListAdapter(adapter);
        }else{
            Toast.makeText(this, "No student!", Toast.LENGTH_SHORT).show();
        }

    } else {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_null);
        Button button = (Button) findViewById(R.id.angry_btn);
    }
    String versionName = "";
    try {
        versionName = getApplicationContext().getPackageManager().getPackageInfo(getApplicationContext().getPackageName(), 0).versionName;
    } catch (PackageManager.NameNotFoundException e) {
        e.printStackTrace();
    }
    TextView versionname = (TextView) findViewById(R.id.versionName);

}

public void onCheckboxClicked(View view) {
    // Is the view now checked?
    boolean checked = ((CheckBox) view).isChecked();

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_my, menu);
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, 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) {
        Intent intent = new Intent(MyActivity.this, SettingsActivity.class);
        startActivity(intent);
        //finish();
        return true;
    }

    if (id == R.id.action_add) {
        Intent intent = new Intent(MyActivity.this, MainActivity.class);
        startActivity(intent);
        return true;
    }

    if (id == R.id.test) {
        Intent intent = new Intent(MyActivity.this, HelloGridView.class);
        startActivity(intent);
        return true;
    }

    if (id == R.id.send) {

        //main code begins here
        try {
            SQLiteDatabase sqldb = dbHelper.getReadableDatabase();
            Cursor c = null;
            c = sqldb.rawQuery("select * from crud.db", null);
            int rowcount = 0;
            int colcount = 0;
            File sdCardDir = Environment.getExternalStorageDirectory();
            String filename = "MyBackUp.csv";
            // the name of the file to export with
            File saveFile = new File(sdCardDir, filename);
            FileWriter fw = new FileWriter(saveFile);
            BufferedWriter bw = new BufferedWriter(fw);
            rowcount = c.getCount();
            colcount = c.getColumnCount();
            if (rowcount > 0) {
                c.moveToFirst();
                for (int i = 0; i < colcount; i++) {
                    if (i != colcount - 1) {
                        bw.write(c.getColumnName(i) + ",");
                    } else {
                        bw.write(c.getColumnName(i));
                    }
                }
                bw.newLine();
                for (int i = 0; i < rowcount; i++) {
                    c.moveToPosition(i);
                    for (int j = 0; j < colcount; j++) {
                        if (j != colcount - 1)
                            bw.write(c.getString(j) + ",");
                        else
                            bw.write(c.getString(j));
                    }
                    bw.newLine();
                }
                bw.flush();
                Toast.makeText(this, "Exported Successfully.", Toast.LENGTH_SHORT).show();
                //infotext.setText("Exported Successfully.");
            }
        } catch (Exception ex) {
            if (sqldb.isOpen()) {
                try {
                    sqldb.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                Toast.makeText(this, ex.getMessage().toString(), Toast.LENGTH_SHORT).show();
                //infotext.setText(ex.getMessage().toString());
            }
        } finally {
        }



        return true;
    }

    if (id == R.id.array_add) {
        Intent intent = new Intent(MyActivity.this, ArraySave.class);
        startActivity(intent);
        return true;
    }

    if (id == R.id.action_quit) {
            new AlertDialog.Builder(this)
                    .setIcon(android.R.drawable.ic_dialog_alert)
                    .setTitle("Closing Activity")
                    .setMessage("Are you sure you want to close this activity?")
                    .setPositiveButton("Yes", new DialogInterface.OnClickListener()
                    {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            finish();
                        }

                    })
                    .setNegativeButton("No", null)
                    .show();

    }

    switch(item.getItemId())
    {
        case R.id.preferences:
        {
            Intent intent = new Intent();
            intent.setClassName(this, "MyPreferenceActivity");
            startActivity(intent);
            return true;
        }
    }

    return super.onOptionsItemSelected(item);
}



public void ButtonOnClick(View v) {
    switch (v.getId() /*to get clicked view id**/) {
        case R.id.angry_btn:
            Intent intent = new Intent(MyActivity.this, MainActivity.class);
            startActivity(intent);
            break;
        default:
            break;
    }
}


@Override
public void onSupportActionModeStarted(ActionMode mode) {

}

@Override
public void onSupportActionModeFinished(ActionMode mode) {

}

@Nullable
@Override
public ActionMode onWindowStartingSupportActionMode(ActionMode.Callback callback) {
    return null;
}
}

DBHelper.java

package com.nate.nash.howtoloveme;

/**
* Created by Nash on 1/13/2016.
*/
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DBHelper  extends SQLiteOpenHelper {
//version number to upgrade database version
//each time if you Add, Edit table, you need to change the
//version number.
private static final int DATABASE_VERSION = 4;

// Database Name
private static final String DATABASE_NAME = "crud.db";

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

@Override
public void onCreate(SQLiteDatabase db) {
    //All necessary tables you like to create will create here

    String CREATE_TABLE_STUDENT = "CREATE TABLE " + Student.TABLE  + "("
            + Student.KEY_ID  + " INTEGER PRIMARY KEY AUTOINCREMENT ,"
            + Student.KEY_name + " TEXT, "
           // + Student.KEY_age + " INTEGER, "
            + Student.KEY_info + " TEXT )";
           // + Student.KEY_email + " TEXT )";

    db.execSQL(CREATE_TABLE_STUDENT);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older table if existed, all data will be gone!!!
    db.execSQL("DROP TABLE IF EXISTS " + Student.TABLE);

    // Create tables again
    onCreate(db);

}

}

MainActivity.java

package com.nate.nash.howtoloveme;

/**
 * Created by Nash on 1/13/2016.
 */
import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.HashMap;

public class MainActivity extends ListActivity  implements android.view.View.OnClickListener{

    Button btnAdd,btnGetAll;
    TextView student_Id;

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if ((keyCode == KeyEvent.KEYCODE_BACK)) {
            Intent intent = new Intent(MainActivity.this, MyActivity.class);
            startActivity(intent);
            finish();
        }
        return super.onKeyDown(keyCode, event);
    }

    @Override
    public void onClick(View view) {
        if (view== findViewById(R.id.btnAdd)){

            Intent intent = new Intent(this,StudentDetail.class);
            intent.putExtra("student_Id",0);
            startActivity(intent);

        }else {

            StudentRepo repo = new StudentRepo(this);

            ArrayList<HashMap<String, String>> studentList =  repo.getStudentList();
            if(studentList.size()!=0) {
                ListView lv = getListView();
                lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
                        student_Id = (TextView) view.findViewById(R.id.student_Id);
                        String studentId = student_Id.getText().toString();
                        Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
                        objIndent.putExtra("student_Id", Integer.parseInt( studentId));
                        startActivity(objIndent);
                    }
                });
                ListAdapter adapter = new SimpleAdapter( MainActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
                setListAdapter(adapter);
            }else{
                Toast.makeText(this,"No student!",Toast.LENGTH_SHORT).show();
            }

        }
    }

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

        StudentRepo repo = new StudentRepo(this);

        ArrayList<HashMap<String, String>> studentList =  repo.getStudentList();
        if(studentList.size()!=0) {
            ListView lv = getListView();
            lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
                    student_Id = (TextView) view.findViewById(R.id.student_Id);
                    String studentId = student_Id.getText().toString();
                    Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
                    objIndent.putExtra("student_Id", Integer.parseInt( studentId));
                    startActivity(objIndent);
                }
            });
            ListAdapter adapter = new SimpleAdapter( MainActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
            setListAdapter(adapter);
        }else{
            Toast.makeText(this,"No student!",Toast.LENGTH_SHORT).show();
        }

        btnAdd = (Button) findViewById(R.id.btnAdd);
        btnAdd.setOnClickListener(this);

        btnGetAll = (Button) findViewById(R.id.btnGetAll);
        btnGetAll.setOnClickListener(this);

    }


}

Answer 1

try to use this function

private void exportDB() {

    File dbFile=getDatabasePath("MyDBName.db");
    DBHelper dbhelper = new DBHelper(getApplicationContext());
    File exportDir = new File(Environment.getExternalStorageDirectory(), "");
    if (!exportDir.exists())
    {
        exportDir.mkdirs();
    }

    File file = new File(exportDir, "csvname.csv");
    try
    {
        file.createNewFile();
        CSVWriter csvWrite = new CSVWriter(new FileWriter(file));
        SQLiteDatabase db = dbhelper.getReadableDatabase();
        Cursor curCSV = db.rawQuery("SELECT * FROM contacts",null);
        csvWrite.writeNext(curCSV.getColumnNames());
        while(curCSV.moveToNext())
        {
            //Which column you want to exprort
            String arrStr[] ={curCSV.getString(0),curCSV.getString(1), curCSV.getString(2)};
            csvWrite.writeNext(arrStr);
        }
        csvWrite.close();
        curCSV.close();
    }
    catch(Exception sqlEx)
    {
        Log.e("MainActivity", sqlEx.getMessage(), sqlEx);
    }
}

reference