Download Working with Databases

Working with Databases
In today’s lesson, we spent a lot of time looking at SQLite databases, tools, and the SQL language. As
such, we have just enough time to start our Lesson 6 application that uses SQLite. Today, we’ll build the
main activities, and layouts needed for our application, while our next lesson will provide the remaining
code.
Let’s begin with a new Eclipse project, with the following settings:
Project name: A2L56_Database
Create new project in workspace should be selected.
Build Target: Android 4.0.3 (or any other version you’d like to work with 2.1 or higher)
Application Name: A2L56_Database
Package name: lastname.firstname. database (substitute lastname.firstname with your last name and
first name – no spaces, apostrophes or dashes.)
Create Activity should be checked, and DatabaseActivity should be the text for it.
Min SDK Version: 15 (If using Android OS other than 15, use the correct SDK version here).
Click Finish.
Let’s begin, as we always do, with the user interface. Open the main.xml file, from the Res/Layout
folder. We’re adding three buttons to the layout.
This screen will be our main menu, and allow us to view a list of items in our SQLite table as ListView, or
via a Cursor. In addition to that, we’ll add a “Add New” button to allow to add records to the database.
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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_gravity="center_horizontal"
android:layout_margin="15dp"
android:orientation="vertical" >
<Button
android:id="@+id/btnShow"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:layout_marginRight="20dp"
android:text="Show Data" >
</Button>
<Button
android:id="@+id/btnShowList"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:layout_marginRight="20dp"
android:text="Show List" >
</Button>
<Button
android:id="@+id/btnAddNew"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:layout_marginRight="20dp"
android:text="Add New" >
</Button>
</LinearLayout>
Now, let’s create the rest of the XML UI files that we’ll need for this application. The first will be called
by our “Show Data” activity, and will be a simple cursor outputting information as text. Add a new UI
file to your project (we’ve done this before, so I’m leaving out the details of how to create a layout XML
file). The new file should be called data_cursor.xml, and contain a vertical LinearLayout. To that, add a
TextView. See code below for the complete XML of the UI.
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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/txtOut"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
</TextView>
</LinearLayout>
Save and close data_cursor.xml.
Now, let’s create the UI that displays our data in a ListView. At the top of the ListView, we’ll add two
buttons. The first will allow us to add a record (take us to the activity where we can add a record), and
the second will take us back to the main menu (same as pressing the back button on the device).
Create a new UI file, and call it data_list.xml. Make the UI look like this:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical|center_horizontal" >
<Button
android:id="@+id/btnGoMain"
android:layout_width="120dp"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:text="Main Menu" />
<Button
android:id="@+id/btnGoNew"
android:layout_width="120dp"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:text="Add New" />
</LinearLayout>
<ListView
android:id="@+id/android:list"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1.0" />
</LinearLayout>
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Save and close the data_list.xml file.
Now, we need to create a row that will be used by the ListView. The row.xml file will allow us to define
which fields we want to see on each row of the ListView. Create a new layout XML file called row.xml,
and add the following code:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:id="@+id/txtID"
android:layout_width="30dip"
android:layout_height="40dip"
android:textSize="15dip" />
<TextView
android:id="@+id/txtAuthor"
android:layout_width="200dip"
android:layout_height="wrap_content"
android:gravity="left"
android:textStyle="bold" />
<TextView
android:id="@+id/txtYearBorn"
android:layout_width="50dip"
android:layout_height="wrap_content"
android:gravity="right"
android:textStyle="bold" />
</LinearLayout>
The above layout creates three textviews, that we will populate with data from our SQLite database.
Then each row in our ListView will use this type of row.
Save and close row.xml.
Our last UI file is the Add / Edit screen. Create a new UI file called add_edit_data.xml, and add the
following code:
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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:layout_gravity="center_horizontal" android:layout_margin="15dp" android:orientation="vertical" >
<TextView
android:id="@+id/AuID"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visible="gone" >
</TextView>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Author:" >
</TextView>
<EditText
android:id="@+id/txtAuthor"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="text"
android:text="" >
</EditText>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Year Born:" >
</TextView>
<EditText
android:id="@+id/txtYearBorn"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="number"
android:text="" >
</EditText>
<LinearLayout
android:id="@+id/linearLayout1" android:layout_width="match_parent"
android:layout_height="wrap_content" android:layout_gravity="center_horizontal"
android:gravity="center_horizontal" android:orientation="horizontal" >
<Button
android:id="@+id/btnInsert"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:text="Insert" >
</Button>
<Button
android:id="@+id/btnUpdate"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:text="Update" >
</Button>
<Button
android:id="@+id/btnDelete"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:text="Delete" >
</Button>
</LinearLayout>
</LinearLayout>
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The end result will look like this:
Ok, all of the UI files are done! We’re going to wrap up this session by creating the rest of the class
(java) files, and linking up our three buttons on the main.xml interface on our main activity.
Create the following three activities. Each one should extend Activity, except for DataListActivity which
extends ListActivity, and have a basic onCreate event. Link up the appropriate user interface to each
using the setContentView method. Below is the code for each of the new classes.
DataCursorActivity
package tushinsky.alex.database;
import android.app.Activity;
import android.os.Bundle;
public class DataCursorActivity extends Activity {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.data_cursor);
}
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DataListActivity
package tushinsky.alex.database;
import android.app.Activity;
import android.os.Bundle;
public class DataListActivity extends ListActivity {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.data_list);
}
AddEditDataActivity
package tushinsky.alex.database;
import android.app.Activity;
import android.os.Bundle;
public class AddEditDataActivity extends Activity {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_edit_data);
}
The last class will be our SQL database helper class, and we’ll add that during lesson 6.
Add the new activities to your Android Manifest file in order to register them for use. Remember that if
you don’t do this step, your app will crash every time it’s launched and one of these new activities is
requested.
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<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:name=".DatabaseActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".DataCursorActivity"></activity>
<activity android:name=".DataListActivity"></activity>
<activity android:name=".AddEditDataActivity"></activity>
</application>
Now, open DatabaseActivity.java for editing. We’re going to add our three button click events, and wire
them up to open the correct activity when each of the buttons is selected.
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final Button btnShowData = (Button) findViewById(R.id.btnShow);
btnShowData.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
finish();
startActivity(new Intent(getBaseContext(), DataCursorActivity.class));
}
});
final Button btnShowList = (Button) findViewById(R.id.btnShowList);
btnShowList.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
finish();
startActivity(new Intent(getBaseContext(), DataListActivity.class));
}
});
final Button btnAddNew = (Button) findViewById(R.id.btnAddNew);
btnAddNew.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent myIntent = new Intent(v.getContext(), AddEditDataActivity.class);
Bundle b = new Bundle();
b.putLong("id", 0);
myIntent.putExtras(b);
finish();
startActivity(myIntent);
}
});
}
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For btnShowData and btnShowList, things are fairly simple. We simply call a new activity, which opens
to the appropriate screen. On the last button, btnAddNew, we launch the activity a bit differently.
That’s because we also pass in a parameter to the activity (“id” = 0). This will be used by the
AddEditDataActivity to determine if it should create a new record, or update an existing one.
Now, open DataListActivity, and add the following click events to its onCreate method.
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.data_list);
final Button btnMain = (Button) findViewById(R.id.btnGoMain);
btnMain.setOnClickListener(new View.OnClickListener() {
});
public void onClick(View v) {
finish();
startActivity(new Intent(getBaseContext(), DatabaseActivity.class));
}
final Button btnGoNew = (Button) findViewById(R.id.btnGoNew);
btnGoNew.setOnClickListener(new View.OnClickListener() {
});
public void onClick(View v) {
Intent myIntent = new Intent(v.getContext(), AddEditDataActivity.class);
Bundle b = new Bundle();
b.putLong("id", 0);
myIntent.putExtras(b);
finish();
startActivity(myIntent);
}
}
As a final step, add the following code to each of the three created classes. This method will be
triggered whenever the user selects the back button on their device. It will let them naturally navigate
to the main menu each time.
@Override
public void onBackPressed() {
startActivity(new Intent(getBaseContext(), DatabaseActivity.class));
return;
}
This method should be the last method in DataCursorActivity, DataListActivity, and AddEditDataActivity.
Save all of your files, and run your project. You should be able to navigate between screens without
much issue.
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