如何从 SQLite 数据库 (android) 中检索特定值并显示在可编辑的文本视图中

Question

I am currently building a small android application. On my MainActivity I have a spinner which is populated with data from the "device_names" table of my SQLite database.

When the user selects the desired device, they then have the option to update its information or delete it.

When they select update, they open a new activity with three text views, device name, device number and device password. This is where my problem arises.

I am very new to Java, and I can't figure out how to retrieve the corresponding values from the spinner on the previous page to populate the three different TextView so that the user can update the information.

Here is my main activity code:

package ben.findmyflock;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.inputmethod.InputMethodManager;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;


public class DeviceManager extends Activity implements AdapterView.OnItemSelectedListener{

    Spinner spinner;
    private Button newActivity;
    public final static String SELECTED_DEVICE = "ben.findmyflock.DEVICE";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_device_manager);

        spinner= (Spinner) findViewById(R.id.device_spinner);

        /*ArrayAdapter adapter=ArrayAdapter.createFromResource(this,R.array.device_array,android.R.layout.simple_spinner_item);
        spinner.setAdapter(adapter);*/

        spinner.setOnItemSelectedListener(this);
        loadSpinnerData();

    }

    /**
     * Function to load the spinner data from SQLite database
     * */
    private void loadSpinnerData() {
        // database handler
        DeviceOperations db = new DeviceOperations(getApplicationContext());

        // Spinner Drop down elements
        List<String> labels = db.getAllLabels();

        // Creating adapter for spinner
        ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item, labels);

        // Drop down layout style - list view with radio button
        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        // attaching data adapter to spinner
        spinner.setAdapter(dataAdapter);
    }

    public void addNewDevice(View v) {
        //do something when a button is clicked
        Button adddevicebutton=(Button) v;
        startActivity(new Intent(getApplicationContext(), AddDevice.class));
    }

    public void updateSelectedDevice(View v) {
        Intent intent = new Intent(this, UpdateDevice.class);
        Spinner spinner = (Spinner) findViewById(R.id.device_spinner);
        String selecteddevice = spinner.getSelectedItem().toString();
        intent.putExtra(SELECTED_DEVICE, selecteddevice);
        startActivity(intent);
    }



    public void deleteSelectedDevice(View v) {
        //delete selected spinner value from database


    }


    @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_device_manager, 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);
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        TextView myText= (TextView) view;
        Toast.makeText(this,myText.getText() + " Selected", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onNothingSelected(AdapterView<?> arg0) {

    }

}

Here my Update Device code:

package ben.findmyflock;

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;

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


public class UpdateDevice extends Activity {

    ListView listview;
    SQLiteDatabase sqLiteDatabse;
    DeviceOperations deviceOperations;
    Cursor cursor;

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

        Intent intent = getIntent();
        String selecteddevice = intent.getStringExtra(DeviceManager.SELECTED_DEVICE);
        EditText devname = (EditText)findViewById(R.id.update_device_name);
        devname.setText(selecteddevice, TextView.BufferType.EDITABLE);





        EditText devnum = (EditText)findViewById(R.id.update_device_number);

        deviceOperations = new DeviceOperations(getApplicationContext());
        sqLiteDatabse =deviceOperations.getReadableDatabase();
        cursor = deviceOperations.getInformation(sqLiteDatabse);
        if(cursor.moveToFirst())
        {
            do {

                String name,num,pass;
                name = cursor.getString(0);
                num = cursor.getString(1);
                pass = cursor.getString(2);

            }while (cursor.moveToNext());
        }

        devnum.setText(selecteddevicenumber, TextView.BufferType.EDITABLE);

        EditText devpass = (EditText)findViewById(R.id.update_device_password);
        devpass.setText(selecteddevicepassword, TextView.BufferType.EDITABLE);


    }

    @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_update_device, 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);
    }
}

And here is my Device Operations File

package ben.findmyflock;

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

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

/**
 * Created by Ben on 03/05/2015.
 */
public class DeviceOperations extends SQLiteOpenHelper{
    // Database Version
    public static final int database_version = 1;

    // Database Name
    public static final String DATABASE_NAME = "device_database";
    // Labels table name
    public static final String TABLE_NAME = "device_info";

    // Labels Table Columns names
    public static final String DEVICE_NAME = "device_name";
    public static final String DEVICE_NUMBER = "device_number";
    public static final String DEVICE_PASSWORD = "device_password";

    private static final String[] COLUMNS = {DEVICE_NAME,DEVICE_NUMBER,DEVICE_PASSWORD};

    public DeviceOperations(Context context) {
        super(context, DATABASE_NAME, null, database_version);
    }


    // Creating Tables
    @Override
    public void onCreate(SQLiteDatabase db) {
        // Category table create query
        String CREATE_DEVICE_TABLE = "CREATE TABLE " + TABLE_NAME + "(" + DEVICE_NAME + " TEXT," + DEVICE_NUMBER + " INTEGER" + DEVICE_PASSWORD + " TEXT)";
        db.execSQL(CREATE_DEVICE_TABLE);
    }


    // Upgrading database
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);

        // Create tables again
        onCreate(db);
    }

    //Inserting values
    public void putInformation(DeviceOperations dop,String name,String number,String pass)
    {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(DEVICE_PASSWORD, pass);
        values.put(DEVICE_NUMBER, number);
        values.put(DEVICE_NAME, name);

        db.insert(TABLE_NAME, null, values);
        db.close();
    }


    public Cursor getInformation(SQLiteDatabase db)
    {
        Cursor cursor;
        String[] projections = {DEVICE_NAME, DEVICE_NUMBER, DEVICE_PASSWORD};
        cursor = db.query(TABLE_NAME,projections,null,null,null,null,null);
        return cursor;
    }


    public List<String> getAllLabels(){
        List<String> labels = new ArrayList<String>();

        // Select All Query
        String selectQuery = "SELECT * FROM " + TABLE_NAME;

        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(selectQuery,null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                labels.add(cursor.getString(0));
            } while (cursor.moveToNext());
        }

        // closing connection
        cursor.close();
        db.close();

        // returning labels
        return labels;
    }
}

I hope this makes sense to someone. I really cant get it to work.

I think a simple search within the database to extract all the values that match the device name would work best and then convert the device number attribute to a string and the device password to another string, i just cant work that bit out.

Many Thanks Ben

Answer 1

If i understood well, your problem is "how can i pass to the activity the old data so the user can read them and update?". You can send the old data with the putExtra() . With your intent.putExtra(SELECTED_DEVICE, selecteddevice); you send only the type of device, if you put other information you can take them back from the UpdateDevice and you can SetText() of your EditText with the old data! Like that you don't need the Database for take back information. Have you try this?

Try to Start activity with StartActivityForResult , and take back new information with:

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if(requestCode == 1) {
        if (resultCode == RESULT_OK) {


            String result1 = data.getStringExtra("result1"); 
            String result2 = data.getStringExtra("result2");
            String result3 = data.getStringExtra("result3");

            //Update the database with new data
        }

        if (resultCode == RESULT_CANCELED) {
            //No change
        }
    }
}//onActivityResult

If you need the DataBase for take back information follow this link that is very helpfull Guide for SqliteHelper

So, you need a class that manage the devices with the getter and setter method. In the same time you need to save data in your DataBase for the "future maintenace". As you can see in the link with the method

getContact()
// Getting single contact
public Contact getContact(int id) {
SQLiteDatabase db = this.getReadableDatabase();

Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
        KEY_NAME, KEY_PH_NO }, KEY_ID + "=?",
        new String[] { String.valueOf(id) }, null, null, null, null);
if (cursor != null)
    cursor.moveToFirst();

Contact contact = new Contact(Integer.parseInt(cursor.getString(0)),
        cursor.getString(1), cursor.getString(2));
// return contact
return contact;
}

You can take back all information for a single Contact (for you device) searching it by id. Or the second method that can help you is

getAllContacts()
// Getting All Contacts
public List<Contact> getAllContacts() {
List<Contact> contactList = new ArrayList<Contact>();
// Select All Query
String selectQuery = "SELECT  * FROM " + TABLE_CONTACTS;

SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);

// looping through all rows and adding to list
if (cursor.moveToFirst()) {
    do {
        Contact contact = new Contact();
        contact.setID(Integer.parseInt(cursor.getString(0)));
        contact.setName(cursor.getString(1));
        contact.setPhoneNumber(cursor.getString(2));
        // Adding contact to list
        contactList.add(contact);
    } while (cursor.moveToNext());
}

// return contact list
return contactList;
}

That return a list of all items inside the table, so you can check something like that (put that code where you need to read all data from database):

DatabaseHandler db = new DatabaseHandler(this);

    // Reading all device
    List<Device> devices = db.getAllContacts();       

    for (Device dev : devices) {

          if(dev.getNameDevice() == DeviceToUpadeName){
            //do the get of all information
            device_number = dev.getDeviceNumber();//This getmethod is from you Device Class
            device_password = dev.getDevicePassword();
          }
}

All the information that i post here are from the link that i post. I write some explanation for more help. I hope it's all that you need! PS:Remeber the Device class fot the method get and set!