Using Eclipse, create an Android project and name it as shown in Figure 6-1.

Figure 6-1. FIGURE 6-1

Add the following statements in bold to the main.xml file:

<?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" >
<SeekBar
    android:id="@+id/SeekBar01"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>
<TextView
    android:id="@+id/TextView01"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"/>
<EditText
    android:id="@+id/EditText01"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>
<Button
    android:id="@+id/btnSave"
    android:text="Save"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>
</LinearLayout>

Add the following statements in bold to the MainActivity.java file:

package net.learn2develop.SharedPreferences;

import android.app.Activity;
import android.os.Bundle;

import android.content.SharedPreferences;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.Toast;

public class MainActivity extends Activity {
    private SharedPreferences prefs;
    private String prefName = "MyPref";
    private EditText editText;
    private SeekBar seekBar;
    private Button btn;

    private static final String FONT_SIZE_KEY = "fontsize";
    private static final String TEXT_VALUE_KEY = "textvalue";

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        editText = (EditText) findViewById(R.id.EditText01);
        seekBar = (SeekBar) findViewById(R.id.SeekBar01);

btn = (Button) findViewById(R.id.btnSave);

        btn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                //---get the SharedPreferences object---
                prefs = getSharedPreferences(prefName, MODE_PRIVATE);
                SharedPreferences.Editor editor = prefs.edit();

                //---save the values in the EditText view to preferences---
                editor.putFloat(FONT_SIZE_KEY, editText.getTextSize());
                editor.putString(TEXT_VALUE_KEY, editText.getText().toString());

                //---saves the values---
                editor.commit();

                //---display file saved message---
                Toast.makeText(getBaseContext(),
                    "Font size saved successfully!",
                    Toast.LENGTH_SHORT).show();
            }
        });

        //---load the SharedPreferences object---
        SharedPreferences prefs = getSharedPreferences(prefName, MODE_PRIVATE);

        //---set the TextView font size to the previously saved values---
        float fontSize = prefs.getFloat(FONT_SIZE_KEY, 12);

        //---init the SeekBar and EditText---
        seekBar.setProgress((int) fontSize);
        editText.setText(prefs.getString(TEXT_VALUE_KEY, ""));
        editText.setTextSize(seekBar.getProgress());

        seekBar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
            }

            @Override
            public void onProgressChanged(SeekBar seekBar, int progress,
                    boolean fromUser) {
                //---change the font size of the EditText---
                editText.setTextSize(progress);
            }
        });
    }
}

Press F11 to debug the application on the Android Emulator.

Enter some text into the EditText view and then change its font size by adjusting the SeekBar view (see Figure 6-2). Click Save.

Figure 6-2. FIGURE 6-2

Return to Eclipse and press F11 to debug the application on the Android Emulator again. The application now displays the same text that you entered earlier using the same font size set earlier.

Using Eclipse, create an Android project and name it as shown in Figure 6-5.

In the main.xml file, add the following statements in bold:

<?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" >
<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Please enter some text"
    />
<EditText
    android:id="@+id/txtText1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>
<Button
    android:id="@+id/btnSave"
    android:text="Save"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>
<Button
    android:id="@+id/btnLoad"
    android:text="Load"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>
</LinearLayout>

Figure 6-5. FIGURE 6-5

In the MainActivity.java file, add the following statements in bold:

package net.learn2develop.Files;

import android.app.Activity;
import android.view.View;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import android.os.Bundle;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
    private EditText textBox;
    private static final int READ_BLOCK_SIZE = 100;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        textBox = (EditText) findViewById(R.id.txtText1);

Button saveBtn = (Button) findViewById(R.id.btnSave);
Button loadBtn = (Button) findViewById(R.id.btnLoad);

saveBtn.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        String str = textBox.getText().toString();
        try
        {
            FileOutputStream fOut =
                openFileOutput("textfile.txt",
                MODE_WORLD_READABLE);
            OutputStreamWriter osw = new
                OutputStreamWriter(fOut);

            //---write the string to the file---
            osw.write(str);
            osw.flush();
            osw.close();

            //---display file saved message---
            Toast.makeText(getBaseContext(),
                "File saved successfully!",
                Toast.LENGTH_SHORT).show();

            //---clears the EditText---
            textBox.setText("");
         }
         catch (IOException ioe)
         {
            ioe.printStackTrace();
         }
    }
});

loadBtn.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        try
        {
            FileInputStream fIn =
                openFileInput("textfile.txt");
            InputStreamReader isr = new
                InputStreamReader(fIn);

            char[] inputBuffer = newchar[READ_BLOCK_SIZE];
            String s = "";

            int charRead;
            while ((charRead = isr.read(inputBuffer))>0)
            {
                //---convert the chars to a String---
                String readString =
                    String.copyValueOf(inputBuffer, 0,
                    charRead);
                s += readString;

               inputBuffer = newchar[READ_BLOCK_SIZE];

}
                    //---set the EditText to the text that has been
                    // read---
                    textBox.setText(s);

                    Toast.makeText(getBaseContext(),
                        "File loaded successfully!",
                        Toast.LENGTH_SHORT).show();
                }
                catch (IOException ioe) {
                    ioe.printStackTrace();
                }
            }
        });
    }
}

Press F11 to debug the application on the Android Emulator.

Type some text into the EditText view (see Figure 6-6) and then click the Save button.

Figure 6-6. FIGURE 6-6

If the file is saved successfully, you will see the Toast class displaying the "File saved successfully!" message. The text in the EditText view should disappear.

Click the Load button and you should see the string appearing in the EditText view again. This confirms that the text is saved correctly.

Using Eclipse, create an Android project and name it Databases.

Add a new class file to the project and name it DBAdapter.java (see Figure 6-10).

Figure 6-10. FIGURE 6-10

Add the following statements in bold to the DBAdapter.java file:

package net.learn2develop.Databases;

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 DBAdapter {
    public static final String KEY_ROWID = "_id";
    public static final String KEY_NAME = "name";
    public static final String KEY_EMAIL = "email";
    private static final String TAG = "DBAdapter";

    private static final String DATABASE_NAME = "MyDB";
    private static final String DATABASE_TABLE = "contacts";
    private static final int DATABASE_VERSION = 1;

    private static final String DATABASE_CREATE =
        "create table contacts (_id integer primary key autoincrement, "
        + "name text not null, email text not null);";

    private final Context context;

    private DatabaseHelper DBHelper;
    private SQLiteDatabase db;

    public DBAdapter(Context ctx)
    {
        this.context = ctx;
        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)
        {
            try {
                db.execSQL(DATABASE_CREATE);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
        {
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                    + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS contacts");

onCreate(db);
    }
}

//---opens the database---
public DBAdapter open() throws SQLException
{
    db = DBHelper.getWritableDatabase();
    returnthis;
}

//---closes the database---
public void close()
{
    DBHelper.close();
}

//---insert a contact into the database---
publiclong insertContact(String name, String email)
{
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_NAME, name);
    initialValues.put(KEY_EMAIL, email);
    return db.insert(DATABASE_TABLE, null, initialValues);
}

//---deletes a particular contact---
public boolean deleteContact(long rowId)
{
    return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}

//---retrieves all the contacts---
public Cursor getAllContacts()
{
    return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NAME,
            KEY_EMAIL}, null, null, null, null, null);
}

//---retrieves a particular contact---
public Cursor getContact(long rowId) throws SQLException
{
    Cursor mCursor =
            db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
            KEY_NAME, KEY_EMAIL}, KEY_ROWID + "=" + rowId, null,
            null, null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

//---updates a contact---
public boolean updateContact(long rowId, String name, String email)

{
        ContentValues args = new ContentValues();
        args.put(KEY_NAME, name);
        args.put(KEY_EMAIL, email);
        return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
    }
}