In software development, we often use if else to judge the conditions, and then carry out the corresponding operations, but this will make it difficult to maintain the project in the future. Therefore, when encountering a more complex if else structure, the use of policy mode is a good choice
Take a simple example, such as adding, subtracting, multiplying and dividing two numbers
The first step is to define the calculation interface
public interface CalculateStrategy {
int calculateComeout(int number1, int number2);
}Step 2: implement the strategy class
- Addition strategy
public class PlusStrategy implements CalculateStrategy {
@Override
public int calculateComeout(int number1, int number2) {
return number1 + number2;
}
}- Subtraction strategy
public class MinusStrategy implements CalculateStrategy {
@Override
public int calculateComeout(int number1, int number2) {
return number1 - number2;
}
}Instance running
public class Main {
public static void main(String[] args) {
int number1 = 20, number2 = 10;
new PlusStrategy().calculateComeout(number1, number2);
new MinusStrategy().calculateComeout(number1,number2);
}
}Of course, this is just a very simple example. In practical application, it is far from such a "chicken rib". For example, I once developed a small project
Strategy mode Practice
OpeningStartAnimation is an open screen animation View, so the strategy mode here is related to the painting strategy
- Drawing strategy interface
public interface DrawStrategy {
/**
* Draw app name text
* @param canvas canvas
* @param fraction % complete
* @param colorOfAppName Font color
* @param name Written words
* @param widthAndHeightOfView view Width and height of
*/
void drawAppName(Canvas canvas, float fraction, String name, int colorOfAppName,
WidthAndHeightOfView widthAndHeightOfView);
/**
* Draw app Icon
* @param canvas canvas
* @param fraction % complete
* @param colorOfIcon Draw icon color
* @param icon Icon
* @param widthAndHeightOfView view Width and height of
*/
void drawAppIcon(Canvas canvas, float fraction, Drawable icon, int colorOfIcon,
WidthAndHeightOfView widthAndHeightOfView);
/**
* Draw one sentence description of app
* @param canvas canvas
* @param fraction % complete
* @param statement One sentence description
* @param colorOfStatement Font color
* @param widthAndHeightOfView view Width and height of
*/
void drawAppStatement(Canvas canvas, float fraction, String statement, int colorOfStatement,
WidthAndHeightOfView widthAndHeightOfView);
}
- A concrete implementation
public class LineDrawStrategy implements DrawStrategy {
public LineDrawStrategy(){
}
@Override
public void drawAppName(Canvas canvas, float fraction, String name, int colorOfAppName,
WidthAndHeightOfView widthAndHeightOfView) {
canvas.save();
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(colorOfAppName);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(5);
paint.setTextSize(50);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setTextAlign(Paint.Align.LEFT);
float x = widthAndHeightOfView.getWidth() / 2;
int centerY = widthAndHeightOfView.getHeight() / 2;
float y = centerY - 275;
Path path = new Path();
path.moveTo(x, y);
if (fraction <= 0.50) {
path.lineTo(x, y + (25 + name.length() + 250) * (fraction / 0.50f));
canvas.drawPath(path, paint);
} else {
path.lineTo(x, y + (25 + name.length() + 250) * ((1 - fraction)/ 0.50f));
canvas.drawPath(path, paint);
paint.setStyle(Paint.Style.FILL);
canvas.drawText(name, x + 20, y + 150, paint);
}
canvas.restore();
}
@Override
public void drawAppIcon(Canvas canvas, float fraction, Drawable icon, int colorOfIcon,
WidthAndHeightOfView widthAndHeightOfView) {
int centerX = widthAndHeightOfView.getWidth() / 2;
int centerY = widthAndHeightOfView.getHeight() / 2;
Bitmap bitmap = ((BitmapDrawable) icon).getBitmap();
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(colorOfIcon);
paint.setStrokeWidth(3);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStyle(Paint.Style.STROKE);
float bitmapLeft = centerX - 250;
float bitmapRight = bitmapLeft + bitmap.getWidth() * 1.7f;
float bitmapTop = centerY - 250;
float bitmapBottom = bitmapTop + bitmap.getHeight() * 1.7f;
canvas.save();
if (fraction <= 0.75) {
float newfraction = fraction / 0.75f;
if (newfraction <= 0.25) {
canvas.drawLine(bitmapLeft, bitmapBottom, bitmapLeft,
bitmapBottom - (bitmapBottom - bitmapTop) * (newfraction / 0.25f), paint);
// path.lineTo(bitmapLeft, bitmapBottom + (bitmapBottom - bitmapTop) * (newfraction / 0.25f));
} else {
canvas.drawLine(bitmapLeft, bitmapBottom, bitmapLeft, bitmapTop, paint);
// path.lineTo(bitmapLeft, bitmapTop);
}
if (newfraction > 0.25) {
if (newfraction <= 0.50) {
canvas.drawLine(bitmapLeft, bitmapTop,
bitmapLeft + (bitmapRight - bitmapLeft) * ((newfraction - 0.25f)/0.25f),
bitmapTop, paint);
// path.lineTo(bitmapLeft + (bitmapRight - bitmapLeft) * ((newfraction - 0.25f)/0.25f),
// bitmapTop);
} else {
canvas.drawLine(bitmapLeft, bitmapTop, bitmapRight, bitmapTop, paint);
// path.lineTo(bitmapRight, bitmapTop);
}
}
if (newfraction > 0.50) {
if (newfraction <= 0.75) {
canvas.drawLine(bitmapRight, bitmapTop, bitmapRight,
bitmapTop + (bitmapBottom - bitmapTop) * ((newfraction - 0.50f) / 0.25f),
paint);
//path.lineTo(bitmapRight, bitmapTop + (bitmapBottom - bitmapTop) * ((fraction - 0.50f) / 0.25f));
} else {
canvas.drawLine(bitmapRight, bitmapTop, bitmapRight, bitmapBottom, paint);
//path.lineTo(bitmapRight, bitmapBottom);
}
}
if (newfraction > 0.75) {
if (newfraction <= 1) {
canvas.drawLine(bitmapRight, bitmapBottom, bitmapRight - (bitmapRight - bitmapLeft) * ((newfraction - 0.75f)/ 0.25f),
bitmapBottom, paint);
// path.lineTo(bitmapLeft + (bitmapRight - bitmapLeft) * ((fraction - 0.75f)/ 0.25f),
// bitmapBottom);
} else {
canvas.drawLine(bitmapRight, bitmapBottom, bitmapLeft, bitmapBottom, paint);
// path.lineTo(bitmapLeft, bitmapBottom);
}
}
}
canvas.restore();
canvas.save();
if (fraction > 0.75) {
canvas.clipRect(bitmapLeft + (bitmap.getWidth()/2f) * ((1 - fraction) /0.25f),
bitmapTop + (bitmap.getHeight()/2f)* ((1 - fraction) / 0.25f),
bitmapRight - (bitmap.getWidth()/2f) * ((1 - fraction) /0.25f),
bitmapBottom - (bitmap.getHeight()/2f)* ((1 - fraction) / 0.25f));
Matrix matrix = new Matrix();
matrix.postScale(1.7f, 1.7f, (bitmapLeft + bitmapRight) * 0.5f,
(bitmapTop + bitmapBottom) * 0.5f);
canvas.concat(matrix);
canvas.drawBitmap(bitmap, (bitmapLeft + bitmapRight) / 2 - bitmap.getWidth() / 2,
(bitmapTop + bitmapBottom) / 2 - bitmap.getHeight() / 2, paint);
}
canvas.restore();
}
@Override
public void drawAppStatement(Canvas canvas, float fraction, String statement, int colorOfStatement,
WidthAndHeightOfView widthAndHeightOfView) {
canvas.save();
int width = widthAndHeightOfView.getWidth();
int height = widthAndHeightOfView.getHeight();
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(colorOfStatement);
paint.setStyle(Paint.Style.STROKE);
paint.setTextSize(45);
paint.setTextSkewX(-0.2f);
paint.setTextAlign(Paint.Align.CENTER);
RectF rectF = new RectF(width / 4 - statement.length(), height * 7 / 8,
width * 3, height);
if (fraction <= 0.60f) {
Path path = new Path();
path.addArc(rectF,193,40 * fraction * 1.67f);
canvas.drawPath(path, paint);
} else {
Path path = new Path();
path.addArc(rectF, 193, 40);
canvas.drawPath(path, paint);
canvas.drawTextOnPath(statement, path, 0, 0, paint);
}
canvas.restore();
}
}- Example
This is the way to choose a strategy
/**
* Open drawing policy interface, which can be defined by users themselves
* @param drawStrategy Drawing interface
* @return Builder object
*/
public Builder setDrawStategy(DrawStrategy drawStrategy) {
mOpeningStartAnimation.mDrawStrategy = drawStrategy;
return this;
}Specific implementation of the strategy
@Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(colorOfBackground); //Draw background color
super.onDraw(canvas);
mWidthAndHeightOfView.setHeight(getHeight());
mWidthAndHeightOfView.setWidth(getWidth());
mDrawStrategy.drawAppIcon(canvas, fraction, mDrawable, colorOfAppIcon,
mWidthAndHeightOfView);
mDrawStrategy.drawAppName(canvas, fraction, appName, colorOfAppName,
mWidthAndHeightOfView);
mDrawStrategy.drawAppStatement(canvas, fraction, appStatement, colorOfAppStatement,
mWidthAndHeightOfView);
}Specific items can be seen