1 excludeFromSuggestions=true 2 page.title=Notepad Exercise 1 3 parent.title=Notepad Tutorial 4 parent.link=index.html 5 @jd:body 6 7 8 <p><em>In this exercise, you will construct a simple notes list that lets the 9 user add new notes but not edit them. The exercise demonstrates:</em></p> 10 <ul> 11 <li><em>The basics of <code>ListActivities</code> and creating and handling menu 12 options. </em></li> 13 <li><em>How to use a SQLite database to store the notes.</em></li> 14 <li><em>How to bind data from a database cursor into a ListView using a 15 SimpleCursorAdapter.</em></li> 16 <li><em>The basics of screen layouts, including how to lay out a list view, how 17 you can add items to the activity menu, and how the activity handles those menu 18 selections. </em></li> 19 </ul> 20 21 <div style="float:right;white-space:nowrap"> 22 <span style="color:#BBB;"> 23 [<a href="notepad-ex1.html" style="color:#BBB;">Exercise 1</a>]</span> 24 [<a href="notepad-ex2.html">Exercise 2</a>] 25 [<a href="notepad-ex3.html">Exercise 3</a>] 26 [<a href="notepad-extra-credit.html">Extra Credit</a>] 27 </div> 28 29 30 31 <h2>Step 1</h2> 32 33 <p>Open up the <code>Notepadv1</code> project in Eclipse.</p> 34 35 <p><code>Notepadv1</code> is a project that is provided as a starting point. It 36 takes care of some of the boilerplate work that you have already seen if you 37 followed the <a href="{@docRoot}training/basics/firstapp/index.html">Hello, 38 World</a> tutorial.</p> 39 40 <ol> 41 <li> 42 Start a new Android Project by clicking <strong>File</strong> > 43 <strong>New</strong> > <strong>Android Project</strong>.</li> 44 <li> 45 In the New Android Project dialog, select <strong>Create project from existing source</strong>.</li> 46 <li> 47 Click <strong>Browse</strong> and navigate to where you copied the <code>NotepadCodeLab</code> 48 (downloaded during <a href="{@docRoot}training/notepad/index.html#preparing">setup</a>) 49 and select <code>Notepadv1</code>.</li> 50 <li> 51 The Project Name and other properties should be automatically filled for you. 52 You must select the Build Target—we recommend selecting a target with the 53 lowest platform version available. Also add an integer to the Min SDK Version field 54 that matches the API Level of the selected Build Target.</li> 55 <li> 56 Click <strong>Finish</strong>. The <code>Notepadv1</code> project should open and be 57 visible in your Eclipse package explorer.</li> 58 </ol> 59 60 <p>If you see an error about <code>AndroidManifest.xml</code>, or some 61 problems related to an Android zip file, right click on the project and 62 select <strong>Android Tools</strong> > <strong>Fix Project Properties</strong>. 63 (The project is looking in the wrong location for the library file, 64 this will fix it for you.)</p> 65 66 <h2>Step 2</h2> 67 68 <div class="sidebox-wrapper"> 69 <div class="sidebox"> 70 <h2>Accessing and modifying data</h2> 71 <p>For this 72 exercise, we are using a SQLite database to store our data. This is useful 73 if only <em>your</em> application will need to access or modify the data. If you wish for 74 other activities to access or modify the data, you have to expose the data using a 75 {@link android.content.ContentProvider ContentProvider}.</p> 76 <p>If you are interested, you can find out more about 77 <a href="{@docRoot}guide/topics/providers/content-providers.html">content providers</a> or the 78 whole 79 subject of <a href="{@docRoot}guide/topics/data/data-storage.html">Data Storage</a>. 80 The NotePad sample in the <code>samples/</code> folder of the SDK also has an example of how 81 to create a ContentProvider.</p> 82 </div> 83 </div> 84 85 <p>Take a look at the <code>NotesDbAdapter</code> class — this class is provided to 86 encapsulate data access to a SQLite database that will hold our notes data 87 and allow us to update it.</p> 88 <p>At the top of the class are some constant definitions that will be used in the application 89 to look up data from the proper field names in the database. There is also a database creation 90 string defined, which is used to create a new database schema if one doesn't exist already.</p> 91 <p>Our database will have the name <code>data</code>, and have a single table called 92 <code>notes</code>, which in turn has three fields: <code>_id</code>, <code>title</code> and 93 <code>body</code>. The <code>_id</code> is named with an underscore convention used in a number of 94 places inside the Android SDK and helps keep a track of state. The <code>_id</code> 95 usually has to be specified when querying or updating the database (in the column projections 96 and so on). The other two fields are simple text fields that will store data. 97 </p> 98 <p>The constructor for <code>NotesDbAdapter</code> takes a Context, which allows it to communicate with aspects 99 of the Android operating system. This is quite common for classes that need to touch the 100 Android system in some way. The Activity class implements the Context class, so usually you will just pass 101 <code>this</code> from your Activity, when needing a Context.</p> 102 <p>The <code>open()</code> method calls up an instance of DatabaseHelper, which is our local 103 implementation of the SQLiteOpenHelper class. It calls <code>getWritableDatabase()</code>, 104 which handles creating/opening a database for us.</p> 105 <p><code>close()</code> just closes the database, releasing resources related to the 106 connection.</p> 107 <p><code>createNote()</code> takes strings for the title and body of a new note, 108 then creates that note in the database. Assuming the new note is created successfully, the 109 method also returns the row <code>_id</code> value for the newly created note.</p> 110 <p><code>deleteNote()</code> takes a <var>rowId</var> for a particular note, and deletes that note from 111 the database.</p> 112 113 <p><code>fetchAllNotes()</code> issues a query to return a {@link android.database.Cursor} over all notes in the 114 database. The <code>query()</code> call is worth examination and understanding. The first field is the 115 name of the database table to query (in this case <code>DATABASE_TABLE</code> is "notes"). 116 The next is the list of columns we want returned, in this case we want the <code>_id</code>, 117 <code>title</code> and <code>body</code> columns so these are specified in the String array. 118 The remaining fields are, in order: <code>selection</code>, 119 <code>selectionArgs</code>, <code>groupBy</code>, <code>having</code> and <code>orderBy</code>. 120 Having these all <code>null</code> means we want all data, need no grouping, and will take the default 121 order. See {@link android.database.sqlite.SQLiteDatabase SQLiteDatabase} for more details.</p> 122 <p class="note"><b>Note:</b> A Cursor is returned rather than a collection of rows. This allows 123 Android to use resources efficiently -- instead of putting lots of data straight into memory 124 the cursor will retrieve and release data as it is needed, which is much more efficient for 125 tables with lots of rows.</p> 126 127 <p><code>fetchNote()</code> is similar to <code>fetchAllNotes()</code> but just gets one note 128 with the <var>rowId</var> we specify. It uses a slightly different version of the 129 {@link android.database.sqlite.SQLiteDatabase} <code>query()</code> method. 130 The first parameter (set <em>true</em>) indicates that we are interested 131 in one distinct result. The <var>selection</var> parameter (the fourth parameter) has been specified to search 132 only for the row "where _id =" the <var>rowId</var> we passed in. So we are returned a Cursor on 133 the one row.</p> 134 <p>And finally, <code>updateNote()</code> takes a <var>rowId</var>, <var>title</var> and <var>body</var>, and uses a 135 {@link android.content.ContentValues ContentValues} instance to update the note of the given 136 <var>rowId</var>.</p> 137 138 <h2 style="clear:right;">Step 3</h2> 139 140 <div class="sidebox-wrapper"> 141 <div class="sidebox"> 142 <h2>Layouts and activities</h2> 143 <p>Most Activity classes will have a layout associated with them. The layout 144 will be the "face" of the Activity to the user. In this case our layout will 145 take over the whole screen and provide a list of notes.</p> 146 <p>Full screen layouts are not the only option for an Activity however. You 147 might also want to use a <a 148 href="{@docRoot}resources/faq/commontasks.html#floatingorfull">floating 149 layout</a> (for example, a <a 150 href="{@docRoot}resources/faq/commontasks.html#dialogsandalerts">dialog 151 or alert</a>), 152 or perhaps you don't need a layout at all (the Activity will be invisible 153 to the user unless you specify some kind of layout for it to use).</p> 154 </div> 155 </div> 156 157 <p>Open the <code>notepad_list.xml</code> file in <code>res/layout</code> 158 and 159 take a look at it. (You may have to 160 hit the <em>xml</em> tab, at the bottom, in order to view the XML markup.)</p> 161 162 <p>This is a mostly-empty layout definition file. Here are some 163 things you should know about a layout file:</p> 164 165 166 <ul> 167 <li> 168 All Android layout files must start with the XML header line: 169 <code><?xml version="1.0" encoding="utf-8"?></code>. </li> 170 <li> 171 The next definition will often (but not always) be a layout 172 definition of some kind, in this case a <code>LinearLayout</code>. </li> 173 <li> 174 The XML namespace of Android should always be defined in 175 the top level component or layout in the XML so that <code>android:</code> tags can 176 be used through the rest of the file: 177 <p><code>xmlns:android="http://schemas.android.com/apk/res/android"</code></p> 178 </li> 179 </ul> 180 181 <h2 style="clear:right;">Step 4</h2> 182 <p>We need to create the layout to hold our list. Add code inside 183 of the <code>LinearLayout</code> element so the whole file looks like this: </p> 184 <pre> 185 <?xml version="1.0" encoding="utf-8"?> 186 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"; 187 android:layout_width="wrap_content" 188 android:layout_height="wrap_content"> 189 190 <ListView android:id="@android:id/list" 191 android:layout_width="wrap_content" 192 android:layout_height="wrap_content"/> 193 <TextView android:id="@android:id/empty" 194 android:layout_width="wrap_content" 195 android:layout_height="wrap_content" 196 android:text="@string/no_notes"/> 197 198 </LinearLayout> 199 </pre> 200 <ul> 201 <li> 202 The <strong>@</strong> symbol in the id strings of the <code>ListView</code> and 203 <code>TextView</code> tags means 204 that the XML parser should parse and expand the rest of 205 the id string and use an ID resource.</li> 206 <li> 207 The <code>ListView</code> and <code>TextView</code> can be 208 thought as two alternative views, only one of which will be displayed at once. 209 ListView will be used when there are notes to be shown, while the TextView 210 (which has a default value of "No Notes Yet!" defined as a string 211 resource in <code>res/values/strings.xml</code>) will be displayed if there 212 aren't any notes to display.</li> 213 <li>The <code>list</code> and <code>empty</code> IDs are 214 provided for us by the Android platform, so, we must 215 prefix the <code>id</code> with <code>android:</code> (e.g., <code>@android:id/list</code>).</li> 216 <li>The View with the <code>empty</code> id is used 217 automatically when the {@link android.widget.ListAdapter} has no data for the ListView. The 218 ListAdapter knows to look for this name by default. Alternatively, you could change the 219 default empty view by using {@link android.widget.AdapterView#setEmptyView(View)} 220 on the ListView. 221 <p> 222 More broadly, the <code>android.R</code> class is a set of predefined 223 resources provided for you by the platform, while your project's 224 <code>R</code> class is the set of resources your project has defined. 225 Resources found in the <code>android.R</code> resource class can be 226 used in the XML files by using the <code>android:</code> name space prefix 227 (as we see here).</p> 228 </li> 229 </ul> 230 231 <h2 style="clear:right;">Step 5</h2> 232 233 <div class="sidebox-wrapper"> 234 <div class="sidebox"> 235 <h2>Resources and the R class</h2> 236 <p>The folders under res/ in the Eclipse project are for resources. 237 There is a <a href="{@docRoot}resources/faq/commontasks.html#filelist">specific structure</a> 238 to the 239 folders and files under res/.</p> 240 <p>Resources defined in these folders and files will have 241 corresponding entries in the R class allowing them to be easily accessed 242 and used from your application. The R class is automatically generated using the contents 243 of the res/ folder by the eclipse plugin (or by aapt if you use the command line tools). 244 Furthermore, they will be bundled and deployed for you as part of the application.</p> 245 </p> 246 </div> 247 </div> 248 249 <p>To make the list of notes in the ListView, we also need to define a View for each row:</p> 250 <ol> 251 <li> 252 Create a new file under <code>res/layout</code> called 253 <code>notes_row.xml</code>. </li> 254 <li> 255 Add the following contents (note: again the XML header is used, and the 256 first node defines the Android XML namespace)<br> 257 <pre style="overflow:auto"> 258 <?xml version="1.0" encoding="utf-8"?> 259 <TextView android:id="@+id/text1" 260 xmlns:android="http://schemas.android.com/apk/res/android"; 261 android:layout_width="wrap_content" 262 android:layout_height="wrap_content"/></pre> 263 <p> 264 This is the View that will be used for each notes title row — it has only 265 one text field in it. </p> 266 <p>In this case we create a new id called <code>text1</code>. The 267 <strong>+</strong> after the <strong>@</strong> in the id string indicates that the id should 268 be automatically created as a resource if it does not already exist, so we are defining 269 <code>text1</code> on the fly and then using it.</p> 270 </li> 271 <li>Save the file.</li> 272 </ol> 273 <p>Open the <code>R.java</code> class in the 274 project and look at it, you should see new definitions for 275 <code>notes_row</code> and <code>text1</code> (our new definitions) 276 meaning we can now gain access to these from the our code. </p> 277 278 <h2 style="clear:right;">Step 6</h2> 279 <p>Next, open the <code>Notepadv1</code> class in the source. In the following steps, we are going to 280 alter this class to become a list adapter and display our notes, and also 281 allow us to add new notes.</p> 282 283 <p><code>Notepadv1</code> will inherit from a subclass 284 of <code>Activity</code> called a <code>ListActivity</code>, 285 which has extra functionality to accommodate the kinds of 286 things you might want to do with a list, for 287 example: displaying an arbitrary number of list items in rows on the screen, 288 moving through the list items, and allowing them to be selected.</p> 289 290 <p>Take a look through the existing code in <code>Notepadv1</code> class. 291 There is a currently an unused private field called <code>mNoteNumber</code> that 292 we will use to create numbered note titles.</p> 293 <p>There are also three override methods defined: 294 <code>onCreate</code>, <code>onCreateOptionsMenu</code> and 295 <code>onOptionsItemSelected</code>; we need to fill these 296 out:</p> 297 <ul> 298 <li><code>onCreate()</code> is called when the activity is 299 started — it is a little like the "main" method for an Activity. We use 300 this to set up resources and state for the activity when it is 301 running.</li> 302 <li><code>onCreateOptionsMenu()</code> is used to populate the 303 menu for the Activity. This is shown when the user hits the menu button, 304 and 305 has a list of options they can select (like "Create 306 Note"). </li> 307 <li><code>onOptionsItemSelected()</code> is the other half of the 308 menu equation, it is used to handle events generated from the menu (e.g., 309 when the user selects the "Create Note" item). 310 </li> 311 </ul> 312 313 <h2>Step 7</h2> 314 <p>Change the inheritance of <code>Notepadv1</code> from 315 <code>Activity</code> 316 to <code>ListActivity</code>:</p> 317 <pre>public class Notepadv1 extends ListActivity</pre> 318 <p>Note: you will have to import <code>ListActivity</code> into the 319 Notepadv1 320 class using Eclipse, <strong>ctrl-shift-O</strong> on Windows or Linux, or 321 <strong>cmd-shift-O</strong> on the Mac (organize imports) will do this for you 322 after you've written the above change.</p> 323 324 <h2>Step 8</h2> 325 <p>Fill out the body of the <code>onCreate()</code> method.</p> 326 <p>Here we will set the title for the Activity (shown at the top of the 327 screen), use the <code>notepad_list</code> layout we created in XML, 328 set up the <code>NotesDbAdapter</code> instance that will 329 access notes data, and populate the list with the available note 330 titles:</p> 331 <ol> 332 <li> 333 In the <code>onCreate</code> method, call <code>super.onCreate()</code> with the 334 <code>savedInstanceState</code> parameter that's passed in.</li> 335 <li> 336 Call <code>setContentView()</code> and pass <code>R.layout.notepad_list</code>.</li> 337 <li> 338 At the top of the class, create a new private class field called <code>mDbHelper</code> of class 339 <code>NotesDbAdapter</code>. 340 </li> 341 <li> 342 Back in the <code>onCreate</code> method, construct a new 343 <code>NotesDbAdapter</code> 344 instance and assign it to the <code>mDbHelper</code> field (pass 345 <code>this</code> into the constructor for <code>DBHelper</code>) 346 </li> 347 <li> 348 Call the <code>open()</code> method on <code>mDbHelper</code> to open (or create) the 349 database. 350 </li> 351 <li> 352 Finally, call a new method <code>fillData()</code>, which will get the data and 353 populate the ListView using the helper — we haven't defined this method yet. </li> 354 </ol> 355 <p> 356 <code>onCreate()</code> should now look like this:</p> 357 <pre> 358 @Override 359 public void onCreate(Bundle savedInstanceState) { 360 super.onCreate(savedInstanceState); 361 setContentView(R.layout.notepad_list); 362 mDbHelper = new NotesDbAdapter(this); 363 mDbHelper.open(); 364 fillData(); 365 }</pre> 366 <p>And be sure you have the <code>mDbHelper</code> field definition (right 367 under the mNoteNumber definition): </p> 368 <pre> private NotesDbAdapter mDbHelper;</pre> 369 370 <h2>Step 9</h2> 371 372 <div class="sidebox-wrapper"> 373 <div class="sidebox"> 374 <h2>More about menus</h2> 375 <p>The notepad application we are constructing only scratches the 376 surface with <a href="{@docRoot}resources/faq/commontasks.html#addmenuitems">menus</a>. </p> 377 <p>You can also <a href="{@docRoot}resources/faq/commontasks.html#menukeyshortcuts">add 378 shortcut keys for menu items</a>, <a 379 href="{@docRoot}resources/faq/commontasks.html#menukeyshortcuts">create 380 submenus</a> and even <a href="{@docRoot}resources/faq/commontasks.html#addingtoothermenus">add 381 menu items to other applications!</a>. </p> 382 </div> 383 </div> 384 385 <p>Fill out the body of the <code>onCreateOptionsMenu()</code> method.</p> 386 387 <p>We will now create the "Add Item" button that can be accessed by pressing the menu 388 button on the device. We'll specify that it occupy the first position in the menu.</p> 389 390 <ol> 391 <li> 392 In <code>strings.xml</code> resource (under <code>res/values</code>), add 393 a new string named "menu_insert" with its value set to <code>Add Item</code>: 394 <pre><string name="menu_insert">Add Item</string></pre> 395 <p>Then save the file and return to <code>Notepadv1</code>.</p> 396 </li> 397 <li>Create a menu position constant at the top of the class: 398 <pre>public static final int INSERT_ID = Menu.FIRST;</pre> 399 </li> 400 <li>In the <code>onCreateOptionsMenu()</code> method, change the 401 <code>super</code> call so we capture the boolean return as <code>result</code>. We'll return this value at the end.</li> 402 <li>Then add the menu item with <code>menu.add()</code>.</li> 403 </ol> 404 <p>The whole method should now look like this: 405 <pre> 406 @Override 407 public boolean onCreateOptionsMenu(Menu menu) { 408 boolean result = super.onCreateOptionsMenu(menu); 409 menu.add(0, INSERT_ID, 0, R.string.menu_insert); 410 return result; 411 }</pre> 412 <p>The arguments passed to <code>add()</code> indicate: a group identifier for this menu (none, 413 in this case), a unique ID (defined above), the order of the item (zero indicates no preference), 414 and the resource of the string to use for the item.</p> 415 416 <h2 style="clear:right;">Step 10</h2> 417 <p>Fill out the body of the <code>onOptionsItemSelected()</code> method:</p> 418 <p>This is going 419 to handle our new "Add Note" menu item. When this is selected, the 420 <code>onOptionsItemSelected()</code> method will be called with the 421 <code>item.getId()</code> set to <code>INSERT_ID</code> (the constant we 422 used to identify the menu item). We can detect this, and take the 423 appropriate actions:</p> 424 <ol> 425 <li> 426 The <code>super.onOptionsItemSelected(item)</code> method call goes at the 427 end of this method — we want to catch our events first! </li> 428 <li> 429 Write a switch statement on <code>item.getItemId()</code>. 430 <p>In the case of <var>INSERT_ID</var>, call a new method, <code>createNote()</code>, 431 and return true, because we have handled this event and do not want to 432 propagate it through the system.</p> 433 </li> 434 <li>Return the result of the superclass' <code>onOptionsItemSelected()</code> 435 method at the end.</li> 436 </ol> 437 <p> 438 The whole <code>onOptionsItemSelect()</code> method should now look like 439 this:</p> 440 <pre> 441 @Override 442 public boolean onOptionsItemSelected(MenuItem item) { 443 switch (item.getItemId()) { 444 case INSERT_ID: 445 createNote(); 446 return true; 447 } 448 449 return super.onOptionsItemSelected(item); 450 }</pre> 451 452 <h2>Step 11</h2> 453 <p>Add a new <code>createNote()</code> method:</p> 454 <p>In this first version of 455 our application, <code>createNote()</code> is not going to be very useful. 456 We will simply 457 create a new note with a title assigned to it based on a counter ("Note 1", 458 "Note 2"...) and with an empty body. At present we have no way of editing 459 the contents of a note, so for now we will have to be content making one 460 with some default values:</p> 461 <ol> 462 <li>Construct the name using "Note" and the counter we defined in the class: <code> 463 String noteName = "Note " + mNoteNumber++</code></li> 464 <li> 465 Call <code>mDbHelper.createNote()</code> using <code>noteName</code> as the 466 title and <code>""</code> for the body 467 </li> 468 <li> 469 Call <code>fillData()</code> to populate the list of notes (inefficient but 470 simple) — we'll create this method next.</li> 471 </ol> 472 <p> 473 The whole <code>createNote()</code> method should look like this: </p> 474 <pre> 475 private void createNote() { 476 String noteName = "Note " + mNoteNumber++; 477 mDbHelper.createNote(noteName, ""); 478 fillData(); 479 }</pre> 480 481 482 <h2>Step 12</h2> 483 <div class="sidebox-wrapper"> 484 <div class="sidebox"> 485 <h2>List adapters</h2> 486 <p>Our example uses a {@link android.widget.SimpleCursorAdapter 487 SimpleCursorAdapter} to bind a database {@link android.database.Cursor Cursor} 488 into a ListView, and this is a common way to use a {@link android.widget.ListAdapter 489 ListAdapter}. Other options exist like {@link android.widget.ArrayAdapter ArrayAdapter} which 490 can be used to take a List or Array of in-memory data and bind it in to 491 a list as well.</p> 492 </div> 493 </div> 494 495 <p>Define the <code>fillData()</code> method:</p> 496 <p>This 497 method uses <code>SimpleCursorAdapter,</code> which takes a database <code>Cursor</code> 498 and binds it to fields provided in the layout. These fields define the row elements of our list 499 (in this case we use the <code>text1</code> field in our 500 <code>notes_row.xml</code> layout), so this allows us to easily populate the list with 501 entries from our database.</p> 502 <p>To do this we have to provide a mapping from the <code>title</code> field in the returned Cursor, to 503 our <code>text1</code> TextView, which is done by defining two arrays: the first a string array 504 with the list of columns to map <em>from</em> (just "title" in this case, from the constant 505 <code>NotesDbAdapter.KEY_TITLE</code>) and, the second, an int array 506 containing references to the views that we'll bind the data <em>into</em> 507 (the <code>R.id.text1</code> TextView).</p> 508 <p>This is a bigger chunk of code, so let's first take a look at it:</p> 509 510 <pre> 511 private void fillData() { 512 // Get all of the notes from the database and create the item list 513 Cursor c = mDbHelper.fetchAllNotes(); 514 startManagingCursor(c); 515 516 String[] from = new String[] { NotesDbAdapter.KEY_TITLE }; 517 int[] to = new int[] { R.id.text1 }; 518 519 // Now create an array adapter and set it to display using our row 520 SimpleCursorAdapter notes = 521 new SimpleCursorAdapter(this, R.layout.notes_row, c, from, to); 522 setListAdapter(notes); 523 }</pre> 524 525 <p>Here's what we've done:</p> 526 <ol> 527 <li> 528 After obtaining the Cursor from <code>mDbHelper.fetchAllNotes()</code>, we 529 use an Activity method called 530 <code>startManagingCursor()</code> that allows Android to take care of the 531 Cursor lifecycle instead of us needing to worry about it. (We will cover the implications 532 of the lifecycle in exercise 3, but for now just know that this allows Android to do some 533 of our resource management work for us.)</li> 534 <li> 535 Then we create a string array in which we declare the column(s) we want 536 (just the title, in this case), and an int array that defines the View(s) 537 to which we'd like to bind the columns (these should be in order, respective to 538 the string array, but here we only have one for each).</li> 539 <li> 540 Next is the SimpleCursorAdapter instantiation. 541 Like many classes in Android, the SimpleCursorAdapter needs a Context in order to do its 542 work, so we pass in <code>this</code> for the context (since subclasses of Activity 543 implement Context). We pass the <code>notes_row</code> View we created as the receptacle 544 for the data, the Cursor we just created, and then our arrays.</li> 545 </ol> 546 <p> 547 In the future, remember that the mapping between the <strong>from</strong> columns and <strong>to</strong> resources 548 is done using the respective ordering of the two arrays. If we had more columns we wanted 549 to bind, and more Views to bind them in to, we would specify them in order, for example we 550 might use <code>{ NotesDbAdapter.KEY_TITLE, NotesDbAdapter.KEY_BODY }</code> and 551 <code>{ R.id.text1, R.id.text2 }</code> to bind two fields into the row (and we would also need 552 to define text2 in the notes_row.xml, for the body text). This is how you can bind multiple fields 553 into a single row (and get a custom row layout as well).</p> 554 <p> 555 If you get compiler errors about classes not being found, ctrl-shift-O or 556 (cmd-shift-O on the mac) to organize imports. 557 </p> 558 559 <h2 style="clear:right;">Step 13</h2> 560 <p>Run it! 561 <ol> 562 <li> 563 Right click on the <code>Notepadv1</code> project.</li> 564 <li> 565 From the popup menu, select <strong>Run As</strong> > 566 <strong>Android Application</strong>.</li> 567 <li> 568 If you see a dialog come up, select Android Launcher as the way of running 569 the application (you can also use the link near the top of the dialog to 570 set this as your default for the workspace; this is recommended as it will 571 stop the plugin from asking you this every time).</li> 572 <li>Add new notes by hitting the menu button and selecting <em>Add 573 Item</em> from the menu.</li> 574 </ol> 575 576 <h2 style="clear:right;">Solution and Next Steps</h2> 577 <p>You can see the solution to this class in <code>Notepadv1Solution</code> 578 from 579 the zip file to compare with your own.</p> 580 581 <p>Once you are ready, move on to <a href="notepad-ex2.html">Tutorial 582 Exercise 2</a> to add the ability to create, edit and delete notes.</p> 583 584
