Working with SQLite database in Android

Trying to work with SQlite and Android. But inspite of the build success I am not getting any output on the Android emulator. Below is the code I have used.

DatabaseManager.java

package com.exampl开发者_如何学编程e.AndroidDatabase;

import java.util.ArrayList;

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;
import android.util.Log;

public class DatabaseManager
{
    // the Activity or Application that is creating an object from this class.
    Context context;

    // a reference to the database used by this application/object
    private SQLiteDatabase db;

    // These constants are specific to the database.  They should be 
    // changed to suit your needs.
    private final String DB_NAME = "database_name";
    private final int DB_VERSION = 1;

    // These constants are specific to the database table.  They should be
    // changed to suit your needs.
    private final String TABLE_NAME = "database_table";
    private final String TABLE_ROW_ID = "id";
    private final String TABLE_ROW_ONE = "table_row_one";
    private final String TABLE_ROW_TWO = "table_row_two";

    public DatabaseManager(Context context)
    {
        this.context = context;

        // create or open the database
        CustomSQLiteOpenHelper helper = new CustomSQLiteOpenHelper(context);
        this.db = helper.getWritableDatabase();
    }

    /**********************************************************************
     * ADDING A ROW TO THE DATABASE TABLE
     * 
     * This is an example of how to add a row to a database table
     * using this class.  You should edit this method to suit your
     * needs.
     * 
     * the key is automatically assigned by the database
     * @param rowStringOne the value for the row's first column
     * @param rowStringTwo the value for the row's second column 
     */
    public void addRow(String rowStringOne, String rowStringTwo)
    {
        // this is a key value pair holder used by android's SQLite functions
        ContentValues values = new ContentValues();
        values.put(TABLE_ROW_ONE, rowStringOne);
        values.put(TABLE_ROW_TWO, rowStringTwo);

        // ask the database object to insert the new data 
        try{db.insert(TABLE_NAME, null, values);}
        catch(Exception e)
        {
            Log.e("DB ERROR", e.toString());
            e.printStackTrace();
        }
    }



    /**********************************************************************
     * DELETING A ROW FROM THE DATABASE TABLE
     * 
     * This is an example of how to delete a row from a database table
     * using this class. In most cases, this method probably does
     * not need to be rewritten.
     * 
     * @param rowID the SQLite database identifier for the row to delete.
     */
    public void deleteRow(long rowID)
    {
        // ask the database manager to delete the row of given id
        try {db.delete(TABLE_NAME, TABLE_ROW_ID + "=" + rowID, null);}
        catch (Exception e)
        {
            Log.e("DB ERROR", e.toString());
            e.printStackTrace();
        }
    }

    /**********************************************************************
     * UPDATING A ROW IN THE DATABASE TABLE
     * 
     * This is an example of how to update a row in the database table
     * using this class.  You should edit this method to suit your needs.
     * 
     * @param rowID the SQLite database identifier for the row to update.
     * @param rowStringOne the new value for the row's first column
     * @param rowStringTwo the new value for the row's second column 
     */ 
    public void updateRow(long rowID, String rowStringOne, String rowStringTwo)
    {
        // this is a key value pair holder used by android's SQLite functions
        ContentValues values = new ContentValues();
        values.put(TABLE_ROW_ONE, rowStringOne);
        values.put(TABLE_ROW_TWO, rowStringTwo);

        // ask the database object to update the database row of given rowID
        try {db.update(TABLE_NAME, values, TABLE_ROW_ID + "=" + rowID, null);}
        catch (Exception e)
        {
            Log.e("DB Error", e.toString());
            e.printStackTrace();
        }
    }

    /**********************************************************************
     * RETRIEVING A ROW FROM THE DATABASE TABLE
     * 
     * This is an example of how to retrieve a row from a database table
     * using this class.  You should edit this method to suit your needs.
     * 
     * @param rowID the id of the row to retrieve
     * @return an array containing the data from the row
     */
    public ArrayList<Object> getRowAsArray(long rowID)
    {
        // create an array list to store data from the database row.
        // I would recommend creating a JavaBean compliant object 
        // to store this data instead.  That way you can ensure
        // data types are correct.
        ArrayList<Object> rowArray = new ArrayList<Object>();
        Cursor cursor;

        try
        {
            // this is a database call that creates a "cursor" object.
            // the cursor object store the information collected from the
            // database and is used to iterate through the data.
            cursor = db.query
            (
                    TABLE_NAME,
                    new String[] { TABLE_ROW_ID, TABLE_ROW_ONE, TABLE_ROW_TWO },
                    TABLE_ROW_ID + "=" + rowID,
                    null, null, null, null, null
            );

            // move the pointer to position zero in the cursor.
            cursor.moveToFirst();

            // if there is data available after the cursor's pointer, add
            // it to the ArrayList that will be returned by the method.
            if (!cursor.isAfterLast())
            {
                do
                {
                    rowArray.add(cursor.getLong(0));
                    rowArray.add(cursor.getString(1));
                    rowArray.add(cursor.getString(2));
                }
                while (cursor.moveToNext());
            }

            // let java know that you are through with the cursor.
            cursor.close();
        }
        catch (SQLException e) 
        {
            Log.e("DB ERROR", e.toString());
            e.printStackTrace();
        }

        // return the ArrayList containing the given row from the database.
        return rowArray;
    }




    /**********************************************************************
     * RETRIEVING ALL ROWS FROM THE DATABASE TABLE
     * 
     * This is an example of how to retrieve all data from a database
     * table using this class.  You should edit this method to suit your
     * needs.
     * 
     * the key is automatically assigned by the database
     */

    public ArrayList<ArrayList<Object>> getAllRowsAsArrays()
    {
        // create an ArrayList that will hold all of the data collected from
        // the database.
        ArrayList<ArrayList<Object>> dataArrays = new ArrayList<ArrayList<Object>>();

        // this is a database call that creates a "cursor" object.
        // the cursor object store the information collected from the
        // database and is used to iterate through the data.
        Cursor cursor;

        try
        {
            // ask the database object to create the cursor.
            cursor = db.query(
                    TABLE_NAME,
                    new String[]{TABLE_ROW_ID, TABLE_ROW_ONE, TABLE_ROW_TWO},
                    null, null, null, null, null
            );

            // move the cursor's pointer to position zero.
            cursor.moveToFirst();

            // if there is data after the current cursor position, add it
            // to the ArrayList.
            if (!cursor.isAfterLast())
            {
                do
                {
                    ArrayList<Object> dataList = new ArrayList<Object>();

                    dataList.add(cursor.getLong(0));
                    dataList.add(cursor.getString(1));
                    dataList.add(cursor.getString(2));

                    dataArrays.add(dataList);
                }
                // move the cursor's pointer up one position.
                while (cursor.moveToNext());
            }
        }
        catch (SQLException e)
        {
            Log.e("DB Error", e.toString());
            e.printStackTrace();
        }

        // return the ArrayList that holds the data collected from
        // the database.
        return dataArrays;
    }




    /**********************************************************************
     * THIS IS THE BEGINNING OF THE INTERNAL SQLiteOpenHelper SUBCLASS.
     * 
     * I MADE THIS CLASS INTERNAL SO I CAN COPY A SINGLE FILE TO NEW APPS 
     * AND MODIFYING IT - ACHIEVING DATABASE FUNCTIONALITY.  ALSO, THIS WAY 
     * I DO NOT HAVE TO SHARE CONSTANTS BETWEEN TWO FILES AND CAN
     * INSTEAD MAKE THEM PRIVATE AND/OR NON-STATIC.  HOWEVER, I THINK THE
     * INDUSTRY STANDARD IS TO KEEP THIS CLASS IN A SEPARATE FILE.
     *********************************************************************/

    /**
     * This class is designed to check if there is a database that currently
     * exists for the given program.  If the database does not exist, it creates
     * one.  After the class ensures that the database exists, this class
     * will open the database for use.  Most of this functionality will be
     * handled by the SQLiteOpenHelper parent class.  The purpose of extending
     * this class is to tell the class how to create (or update) the database.
     * 
     *
     *
     */
    private class CustomSQLiteOpenHelper extends SQLiteOpenHelper
    {
        public CustomSQLiteOpenHelper(Context context)
        {
            super(context, DB_NAME, null, DB_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db)
        {
            // This string is used to create the database.  It should
            // be changed to suit your needs.
            String newTableQueryString = "create table " +
                                        TABLE_NAME +
                                        " (" +
                                        TABLE_ROW_ID + " integer primary key autoincrement not null," +
                                        TABLE_ROW_ONE + " text," +
                                        TABLE_ROW_TWO + " text" +
                                        ");";
            // execute the query string to the database.
            db.execSQL(newTableQueryString);
        }


        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
        {
            // NOTHING TO DO HERE. THIS IS THE ORIGINAL DATABASE VERSION.
            // OTHERWISE, YOU WOULD SPECIFIY HOW TO UPGRADE THE DATABASE.
        }
    }

AndroidDatabaseActivity.java

package com.example.AndroidDatabase;

import java.util.ArrayList;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;

public class AndroidDatabaseActivity extends Activity
{
    // the text fields that users input new data into
    EditText    textFieldOne, textFieldTwo,
                idField, updateIDField, updateTextFieldOne, updateTextFieldTwo;

    // the buttons that listen for the user to select an action
    Button      addButton, deleteButton, retrieveButton, updateButton;

    // the table that displays the data
    TableLayout dataTable;

    // the class that opens or creates the database and makes sql calls to it
    DatabaseManager db;


    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        // this try catch block returns better error reporting to the log
        try
        {
            // Android specific calls
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);

            // create the database manager object
            db = new DatabaseManager(this);

            // create references and listeners for the GUI interface
            setupViews();

            // make the buttons clicks perform actions
            addButtonListeners();

            // load the data table
            updateTable();
        }
        catch (Exception e)
        {
            Log.e("ERROR", e.toString());
            e.printStackTrace();
        }
    }




    /**
     * creates references and listeners for the GUI interface
     */
    private void setupViews()
    {
        // THE DATA TABLE
        dataTable=          (TableLayout)findViewById(R.id.data_table);

        // THE DATA FORM FIELDS
        textFieldOne=       (EditText)findViewById(R.id.text_field_one);
        textFieldTwo=       (EditText)findViewById(R.id.text_field_two);
        idField=            (EditText)findViewById(R.id.id_field);
        updateIDField=      (EditText)findViewById(R.id.update_id_field);
        updateTextFieldOne= (EditText)findViewById(R.id.update_text_field_one);
        updateTextFieldTwo= (EditText)findViewById(R.id.update_text_field_two);

        // THE BUTTONS
        addButton =         (Button)findViewById(R.id.add_button);
        deleteButton =      (Button)findViewById(R.id.delete_button);
        retrieveButton =    (Button)findViewById(R.id.retrieve_button);
        updateButton =      (Button)findViewById(R.id.update_button);
    }




    /**
     * adds listeners to each of the buttons and sets them to call relevant methods
     */
    private void addButtonListeners()
    {
        addButton.setOnClickListener
        (
            new View.OnClickListener()
            {
                @Override public void onClick(View v) {addRow();}
            }
        );

        deleteButton.setOnClickListener
        (
            new View.OnClickListener()
            {
                @Override public void onClick(View v) {deleteRow();}
            }
        );

        updateButton.setOnClickListener
        (
            new View.OnClickListener()
            {
                @Override public void onClick(View v) {updateRow();}
            }
        );

        retrieveButton.setOnClickListener
        (
            new View.OnClickListener()
            {
                @Override public void onClick(View v) {retrieveRow();}
            }
        );

    }




    /**
     * adds a row to the database based on information contained in the
     * add row fields.
     */
    private void addRow()
    {
        try
        {
            // ask the database manager to add a row given the two strings
            db.addRow
            (
                    textFieldOne.getText().toString(),
                    textFieldTwo.getText().toString()
            );

            // request the table be updated
            updateTable();

            // remove all user input from the Activity
            emptyFormFields();
        }
        catch (Exception e)
        {
            Log.e("Add Error", e.toString());
            e.printStackTrace();
        }
    }




    /**
     * deletes a row from the database with the id number in the corresponding 
     * user entry field
     */
    private void deleteRow()
    {
        try
        {
            // ask the database manager to delete the row with the give rowID.
            db.deleteRow(Long.parseLong(idField.getText().toString()));

            // request the table be updated
            updateTable();

            // remove all user input from the Activity
            emptyFormFields();
        }
        catch (Exception e)
        {
            Log.e("Delete Error", e.toString());
            e.printStackTrace();
        }
    }




    /**
     * retrieves a row from the database with the id number in the corresponding
     * user entry field
     */
    private void retrieveRow()
    {
        try
        {
            // The ArrayList that holds the row data
            ArrayList<Object> row;
            // ask the database manager to retrieve the row with the given rowID
            row = db.getRowAsArray(Long.parseLong(updateIDField.getText().toString()));

            // update the form fields to hold the retrieved data
            updateTextFieldOne.setText((String)row.get(1));
            updateTextFieldTwo.setText((String)row.get(2));
        }
        catch (Exception e)
        {
            Log.e("Retrieve Error", e.toString());
            e.printStackTrace();
        }
    }




    /**
     * updates a row with the given information in the corresponding user entry
     * fields
     */
    private void updateRow()
    {
        try
        {
            // ask the database manager to update the row based on the information
            // found in the corresponding user entry fields
            db.updateRow
            (
                Long.parseLong(updateIDField.getText().toString()),
                updateTextFieldOne.getText().toString(),
                updateTextFieldTwo.getText().toString()
            );

            // request the table be updated
            updateTable();

            // remove all user input from the Activity
            emptyFormFields();
        }
        catch (Exception e)
        {
            Log.e("Update Error", e.toString());
            e.printStackTrace();
        }
    }



    /**
     * helper method to empty all the fields in all the forms.
     */
    private void emptyFormFields()
    {
        textFieldOne.setText("");
        textFieldTwo.setText("");
        idField.setText("");
        updateIDField.setText("");
        updateTextFieldOne.setText("");
        updateTextFieldTwo.setText("");
    }




    /**
     * updates the table from the database.
     */
    private void updateTable()
    {
        // delete all but the first row.  remember that the count 
        // starts at one and the index starts at zero
        while (dataTable.getChildCount() > 1)
        {
            // while there are at least two rows in the table widget, delete
            // the second row.
            dataTable.removeViewAt(1);
        }

        // collect the current row information from the database and
        // store it in a two dimensional ArrayList
        ArrayList<ArrayList<Object>> data = db.getAllRowsAsArrays();

        // iterate the ArrayList, create new rows each time and add them
        // to the table widget.
        for (int position=0; position < data.size(); position++)
        {
            TableRow tableRow= new TableRow(this);

            ArrayList<Object> row = data.get(position);

            TextView idText = new TextView(this);
            idText.setText(row.get(0).toString());
            tableRow.addView(idText);

            TextView textOne = new TextView(this);
            textOne.setText(row.get(1).toString());
            tableRow.addView(textOne);

            TextView textTwo = new TextView(this);
            textTwo.setText(row.get(2).toString());
            tableRow.addView(textTwo);

            dataTable.addView(tableRow);
        }
    }

Main.xml

<!-- ADD A DATA ENTRY FORM -->
<TextView
    android:text="@string/add_directions"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    />
<LinearLayout
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    >
    <EditText
        android:id="@+id/text_field_one"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:minWidth="100px"
        />
    <EditText
        android:id="@+id/text_field_two"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:minWidth="100px"
        />
    <Button
        android:id="@+id/add_button"
        android:text="@string/add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
</LinearLayout>

<!-- DELETE A DATA ENTRY FORM -->
<TextView
            android:text="@string/delete_directions"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    />
<LinearLayout
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    >
    <EditText
        android:id="@+id/id_field"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:minWidth="100px"
        />
    <Button
        android:id="@+id/delete_button"
        android:text="@string/delete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
</LinearLayout>

<!-- UPDATE A DATA ENTRY FORM -->
<TextView
    android:text="@string/update_directions"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    />
<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    >
    <EditText
        android:id="@+id/update_id_field"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:minWidth="45px"
        />          
    <Button
        android:id="@+id/retrieve_button"
        android:text="@string/retrieve"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
    <EditText
        android:id="@+id/update_text_field_one"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:minWidth="70px"
        />
    <EditText
        android:id="@+id/update_text_field_two"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:minWidth="70px"
        />
    <Button
        android:id="@+id/update_button"
        android:text="@string/update"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />

</LinearLayout>

<!-- THE DATA TABLE -->
<TableLayout
    android:id="@+id/data_table"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    >
    <TableRow>
        <TextView 
            android:text="@string/th_id"
            android:minWidth="50px"
            />
        <TextView
                            android:text="@string/th_text_one"
            android:minWidth="125px"
            />
        <TextView
            android:text="@string/th_text_two"
            android:minWidth="125px"
            />
    </TableRow>
</TableLayout>

String.xml

Database Application

<string name="add_directions">Fill in both fields with text and click the "add" button.</string>
<string name="add">add</string>

<string name="delete_directions">To delete a row, type the "id" of the row in the field provided and press the "delete" button.</string>
<string name="delete">delete</string>

<string name="update_directions">To update a row, type the "id" of the row in the first field and type the new information into the next two fields.</string>
<string name="retrieve">get</string>
<string name="update">update</string>

<string name="th_id">ID</string>
<string name="th_text_one">Text Field One</string>
<string name="th_text_two">Text Field Two</string>

AndroidManifest.xml

<application android:icon="@drawable/icon" android:label="@string/app_name">
    <activity android:name=".DatabaseManager"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

</application>

Everytime I try to launch this app, it gives me a warning " The application has stopped unexpectedly. Please try again." Can someone guide me as to what is going wrong ?

Error:

[2011-04-25 16:07:57 - AndroidDatabaseManager] ------------------------------
[2011-04-25 16:07:57 - AndroidDatabaseManager] Android Launch!
[2011-04-25 16:07:57 - AndroidDatabaseManager] adb is running normally.
[2011-04-25 16:07:57 - AndroidDatabaseManager] Performi   com.example.AndroidDatabase.DatabaseManager activity launch
[2011-04-25 16:07:57 - AndroidDatabaseManager] Automatic Target Mode: launching new emulator with compatible AVD 'my_avd'
[2011-04-25 16:07:57 - AndroidDatabaseManager] Launching a new emulator with Virtual Device 'my_avd'
[2011-04-25 16:08:05 - AndroidDatabaseManager] New emulator found: emulator-5554
[2011-04-25 16:08:05 - AndroidDatabaseManager] Waiting for HOME ('android.process.acore') to be launched...
[2011-04-25 16:08:49 - AndroidDatabaseManager] HOME is up on device 'emulator-5554'
[2011-04-25 16:08:49 - AndroidDatabaseManager] Uploading AndroidDatabaseManager.apk onto device 'emulator-5554'
[2011-04-25 16:08:49 - AndroidDatabaseManager] Installing AndroidDatabaseManager.apk...
[2011-04-25 16:12:01 - AndroidDatabaseManager] Failed to install AndroidDatabaseManager.apk on device 'emulator-5554!
[2011-04-25 16:12:01 - AndroidDatabaseManager] (null)
[2011-04-25 16:12:06 - AndroidDatabaseManager] Launch canceled!

---

Your manifest is wrong, DatabaseManager isn't an activity, it's a class. Replace it with

<activity android:name=".AndroidDatabaseActivity"

Also you don't have a proper root element in your main.xml, you need to change it to something like:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent" 
   android:background="#ffffff">
   ---------
   YOUR EXISTING XML
   ---------
</LinearLayout>

.