Task/algorithm of template method - oop

Question

I'd like to use the Template Method Pattern for drawing shapes GUI. Any suggestion as to what can be the task of the Template Method in the abstract class Shape? I mean, what can this method produce?
Thank you.

Answer 1

Draw method. Since every shape has different specification in rendering.

Answer 2

you can refer to the below example, i made comments in the code. hope it helps to you...
CustomShape.java - your abstract class
public abstract class CustomShape extends View {
int shapeType = 0;
int clr = Color.BLACK;
int x=0;
int y=0;
public CustomShape(Context context) {
super(context);
}
// OnDraw can act as Template Method
// This method holds the algorithm of shape creation
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
#Override
final public void onDraw(Canvas canvas) {
super.onDraw(canvas);
// you can put here more method to make your shape different
// for example setColor(); setStroke() .....
createRectangle(canvas);
}
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// Primitive operation sub classes must override
abstract void setShapeType(int type);
// Primitive operation sub classes must override
abstract void setShapeColor(int color);
// Primitive operation sub classes must override
abstract void setXY(int x1,int y1);
// Concreate Operation we dont want subclass to override
final void createRectangle(Canvas canvas) {
if (shapeType == 0) {
if (isColored()) {
canvas.drawRect(x, y, x+100, y+100, getPaint(clr, 1));
} else {
canvas.drawRect(x, y, x+100, y+100, getPaint(Color.BLACK, 1));
}
} else {
if (isColored()) {
canvas.drawCircle(x, y, 80, getPaint(clr, 1));
} else {
canvas.drawCircle(x, y, 80, getPaint(clr, 1));
}
}
}
// Concreate Operation we dont want subclass to override
final Paint getPaint(int color, int Stroke) {
Paint paint = new Paint();
paint.setColor(color);
paint.setStrokeWidth(Stroke);
return paint;
}
// HOOK - sub class can override but doesnt have to,
boolean isColored() {
return true;
}
}
CustomShape1.java - your concreate class
public class CustomShape1 extends CustomShape {
public CustomShape1(Context context) {
super(context);
}
boolean isColored(){
return true;
}
#Override
void setShapeType(int type) {
shapeType= type;
}
#Override
void setShapeColor(int color) {
clr = color;
}
#Override
void setXY(int x1, int y1) {
x = x1;
y =y1;
}
}
MainActivity.java
public class MainActivity extends Activity {
LinearLayout ln1,ln2;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ln1 = (LinearLayout)findViewById(R.id.ln1);
ln2= (LinearLayout)findViewById(R.id.ln2);
CustomShape1 cs1 = new CustomShape1(this);
cs1.setShapeType(1);
cs1.setShapeColor(Color.YELLOW);
cs1.setXY(100, 100);
CustomShape1 cs2 = new CustomShape1(this);
cs2.setShapeType(0);
cs2.setShapeColor(Color.RED);
cs2.setXY(300, 300);
ln2.addView(cs2);
ln1.addView(cs1);
}
}
activity_main.xml
<LinearLayout
android:id="#+id/ln1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
</LinearLayout>
<LinearLayout
android:id="#+id/ln2"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
</LinearLayout>
</RelativeLayout>