The document discusses creating Android activities and views for drawing graphics. It explains how to: 1. Create a custom View class that overrides the onDraw() method to draw graphics on a Canvas using Paint objects. 2. Implement common drawing primitives like rectangles, circles, text in the onDraw() method using the Canvas. 3. Handle touch events on the View by overriding the onTouchEvent() method and retrieving the touch coordinates.

1. Introducing
Activity and
Intent
1

2. Memory
TextView
ListView
2
LinearLayout,
weight=2
LinearLayout,
weight=1

3. How to create xml file
Right click
(on the
folder)
3

4. The menu.xml
<?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">
<LinearLayout android:orientation="vertical"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:layout_weight="2">
<TextView android:id="@+id/TextView01" android:layout_width="wrap_content”
android:layout_height="wrap_content“ android:textSize="@dimen/screen_title_size"
android:text="@string/menu" android:layout_gravity="center"
android:shadowColor="@android:color/white"
android:textColor="@color/title_color" />
</LinearLayout>
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5. The menu.xml cont.
<LinearLayout android:orientation="vertical"
android:layout_width="fill_parent" android:layout_height="fill_parent“ android:layout_weight="1">
<ListView android:layout_height="wrap_content" android:id="@+id/list_menu"
android:layout_width="fill_parent" android:layout_gravity="center_horizontal"
android:divider="@drawable/divider"
android:listSelector="@drawable/textured">
</ListView>
</LinearLayout>
</LinearLayout>
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6. The dimens.xml (in values
folder)
<?xml version="1.0" encoding="utf-8"?>
<resources>
<dimen
name="logo_size">24pt</dimen>
<dimen
name="version_size">5pt</dimen>
<dimen
name="version_spacing">3pt</dimen>
<dimen
name="screen_title_size">16pt</dimen>
<dimen
name="menu_item_size">16pt</dimen>
<dimen
name="game_question_size">10pt</dimen>
<dimen
name="help_text_size">7pt</dimen>
<dimen
name="help_text_padding">20px</dimen>
</resources>
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7. The colors.xml (in values
folder)
<?xml version="1.0" encoding="utf-8"?>
<resources>
<color
name="logo_color">#FFFF0F</color>
<color
name="version_color">#f0f0f0</color>
<color
name="version_bkgrd">#1a1a48</color>
<color
name="title_color">#f0f0f0</color>
<color
name="title_glow">#F00</color>
<color
name="menu_color">#FFFF0F</color>
<color
name="menu_glow">#F00</color>
<color
name="error_color">#F00</color>
</resources>
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8. How to create java file
Right click
(on the
folder)
8

9. How to override a method
Right click
on the code
pane
9

10. How to override a method cont.
Select the
method to
overridem
eg, onCreate
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11. The strings.xml (in values
folder)
<Resources>
….
<string name="menu">Memory</string>
<string name="menu_item_settings">Settings</string>
<string name="menu_item_play">Play Game</string>
<string name="menu_item_scores">View Scores</string>
<string name="menu_item_help">Help</string>
…
</Resources>
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12. Create ListView from resource
ListView menuList = (ListView) findViewById(R.id.list_menu);
String[] items = { getResources().getString(R.string.menu_item_play),
getResources().getString(R.string.menu_item_scores),
getResources().getString(R.string.menu_item_settings),
getResources().getString(R.string.menu_item_help) };
ArrayAdapter<String> adapt = new ArrayAdapter<String>
(this,R.layout.menu_item, items);
menuList.setAdapter(adapt);
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13. Starting an Activity class
public class Memory extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.menu);
ListView menuList = (ListView) findViewById(R.id.list_menu);
String[] items = { getResources().getString(R.string.menu_item_play),
getResources().getString(R.string.menu_item_scores),
getResources().getString(R.string.menu_item_settings),
getResources().getString(R.string.menu_item_help) };
ArrayAdapter<String> adapt = new ArrayAdapter<String>(this,R.layout.menu_item, items);
menuList.setAdapter(adapt);
menuList.setSelection(-1);
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14. Starting an Activity class
menuList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View itemClicked, int position, long id)
{
// Note: if the list was built "by hand" the id could be used.
// As-is, though, each item has the same id
TextView textView = (TextView) itemClicked;
String strText = textView.getText().toString();
if (strText.equalsIgnoreCase(
getResources().getString(R.string.menu_item_play))) {
startActivity(new Intent(Memory.this, MemoryPlayGame.class));
} else if (strText.equalsIgnoreCase(getResources().getString(R.string.menu_item_help))) {
//
startActivity(new Intent(Memory.this, MemoryHelp.class));
}
}
});
}
}
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15. Include the Activity in the
manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.plearn" android:versionCode="1" android:versionName="1.0">
<uses-sdk android:minSdkVersion="8" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".Memory" 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=".PlayGame" android:label="@string/app_name">
</activity>
</application>
</manifest>
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16. Introducing
Graphics
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17. Using View to draw graphics
public class GraphicsExample extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new ViewGraphics(this));
}
class ViewGraphics extends View{
public ViewGraphics(Context context){
super(context);
}
public void onDraw(Canvas canvas){ // canvas to draw on
}
}
}
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18. Paint contains drawing
properties
Paint mPaint=new Paint(); // Paint contains properties to use when drawing
Typeface mTypeFace;
public ViewGraphics(Context context){
super(context);
mPaint.setStrokeWidth(3);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setTextSize(30);
mPaint.setTypeface(Typeface.create(Typeface.SERIF,
Typeface.BOLD_ITALIC));
mFace = Typeface.createFromAsset(getContext().getAssets(),
"fonts/gigi.ttf");
//copy a font file in to Assets/fonts folder
}
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19. Drawing primitives in onDraw()
public void onDraw(Canvas canvas){
canvas.drawColor(Color.WHITE);
mPaint.setColor(Color.BLUE);
canvas.drawText(“Android Graphics", 10, 70, mPaint);
mPaint.setStyle(Style.STROKE);
float x1=100, y1=200, x2=x1+170, y2=y1+150; //top-left, bottomright
canvas.drawRect(x1,y1,x2,y2, mPaint); //RectF : Rectangle
//with flaoting number
canvas.drawLine(x1,x2,y1,y2, mPaint);
mPaint.setColor(Color.MAGENTA);
canvas.drawOval(new RectF(x1,y1,x2,y2), mPaint);
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}

20. Drawing primitives cont.
mPaint.setStyle(Style.FILL);
canvas.drawArc(new RectF(x1,y1,x2,y2), 90, 100, true, mPaint);
(start angle, num angle, use radius)
mPaint.setTypeface(mFace);
mPaint.setColor(Color.BLACK); mPaint.setTextSize(40);
canvas.drawText("Custom Fontface from assets", 10, 150, mPaint);
// Draw a Drawable (image file)
Drawable mDrawable =
mContext.getResources().getDrawable(R.drawable.cherry);
mDrawable.setBounds(new Rect(100, 400, 250, 550));
mDrawable.draw(canvas);
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21. The onTouchEvent
The onTouchEvent method occurred when the user touch the screen.
The (getX(), getY()) is the coordinate (x,y) axis where the screen is touched.
public boolean onTouchEvent(MotionEvent event) {
super.onTouchEvent(event);
float x = event.getX();
float y = event.getY();
return true;
}
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22. The PlayGame Activity
public class PlayGame extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
GameView gameView = new GameView(this);
setContentView(gameView);
}
}
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23. The PlayGame Activity cont.
public class PlayGame extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
GameView gameView = new GameView(this);
setContentView(gameView);
}
}
class GameView extends View {
public GameView(Context context){
}
public void onDraw(Canvas canvas) {
}
public boolean onTouchEvent(MotionEvent event) {
}
}
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24. Assignment 6
1. Implement the graphic primitives in the onDraw() method
of the PlayGame Activity.
2. Implement the TouchEvent method to show the
coordinate (x,y) using the Toast.makeText().
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