Methods of path related comments (I)

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The past is mainly about Canvas Of translate( translation ) 、scale( The zoom ) 、rotate( rotate ) 、skew( Crosscutting ). The next few articles are mainly about android Inside Path（ Encapsulates the Bezier curve ）& Canvas Inside drawPath(path,paint);

Many people hear Bezier curve , I think it seems to be quite high-end and elegant . I will unveil it with you later , See the truth ;

Path（ route ）：

Let's see Path What methods are there in the class

Let's look down ：

There are two constructors . They are

    /**
     * Create an empty path
     */
    public Path() {
        mNativePath = init1();
        mDetectSimplePaths = HardwareRenderer.isAvailable();
    }

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and

    /**
     * Create a new path, copying the contents from the src path.
     *
     * @param src The path to copy from when initializing the new path
     */
    public Path(Path src) {
        int valNative = 0;
        if (src != null) {
            valNative = src.mNativePath;
        }
        mNativePath = init2(valNative);
        mDetectSimplePaths = HardwareRenderer.isAvailable();
    }

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There's nothing to say , The other is direct reuse src Create a new Path object .

path.reset(): Remove path Lines and curves in , But it won't change fill－type( Back setFillType Besides, );

path.rewind(): Remove path Lines and curves in , However, the internal data structure will be preserved for reuse ;

path.set(Path src); use src Replace the original with the content of path The content of , Let's look at a small sample ：

Create a path, Add a solid circle to path in

mEndPath = new Path();
mEndPath.addCircle(300, 300, 100, Direction.CW);

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Draw the path：

canvas.drawPath(mEndPath, mPaint);

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The effect is as follows , it ：

At this time in path Add a rectangle in ：

mEndPath = new Path();
mEndPath.addCircle(300, 300, 100, Direction.CW);
mEndPath.addRect(new RectF(50, 50, 250, 200), Direction.CW);

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The effect is as follows ：

Make the following modifications, for example ：

mEndPath = new Path();
mEndPath.addCircle(300, 300, 100, Direction.CW);
//mEndPath.addRect(new RectF(50, 50, 250, 200), Direction.CW);

mSrcPath = new Path();
mSrcPath.addRect(new RectF(50, 50, 250, 200), Direction.CW);
mEndPath.set(mSrcPath);

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Direct execution , Suppose that 4.0 On the above machine (4.0 And above hardware acceleration is enabled by default ), You will find nothing on the screen , It shows that this method will be affected by hardware acceleration , Turn off hardware acceleration , Look at the effect again. ：

Let's take a look Path Of FillType － Fill mode ：

android There are four kinds of FillType, They are ：

WINDING (0),

EVEN_ODD (1),

INVERSE_WINDING (2),

INVERSE_EVEN_ODD (3)

There is a diagram that can be used specifically to illustrate the differences between these four modes ：

The above diagram is very clear , Let's use the following code for testing ：

mEndPath = new Path();mEndPath.addCircle(300, 300, 150, Direction.CW);mEndPath.addCircle(380, 380, 150, Direction.CW);mEndPath.setFillType(FillType.INVERSE_EVEN_ODD);mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);mPaint.setStyle(Style.FILL);mPaint.setColor(Color.RED);

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The test results are shown in the following figure ：

Not set up FillType:

setFillType(FillType.WINDING) setFillType(FillType.EVEN_ODD):

setFillType(FillType.INVERSE_WINDING): setFillType(FillType.INVERSE_EVEN_ODD):

According to the above figure ,Path Of FillType Be able to summarize the following ：

1.Path Default FillType by FillType.WINDING;

2. The scope of action is to draw Path Of Canvas The overall . Instead of path Area ;

3.FillType.WINDING： take path All areas ;

4.FillType.EVEN_ODD： take path In areas that do not intersect ;

5.FillType.INVERSE_WINDING： take path All unoccupied areas ;

6.FillType.INVERSE_EVEN_ODD： take path Unoccupied or intersecting areas ;

Here are a few methods related to fill patterns ：

getFillType(): Needless to say . return Path Fill patterns for ;

setFillType(): Set up Path Fill patterns for ;

isInverseFillType(): Whether it is The inverse Fill mode ：

WINDING and EVEN_ODD return false,INVERSE_WINDING and INVERSE_EVEN_ODD return true.

toggleInverseFillType(): Switch the opposite fill mode . Take a small example ：

        mEndPath = new Path();        mEndPath.addCircle(300, 300, 150, Direction.CW);        mEndPath.addCircle(380, 380, 150, Direction.CW);        mEndPath.setFillType(FillType.WINDING);        mEndPath.toggleInverseFillType();        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mPaint.setStyle(Style.FILL);        mPaint.setColor(Color.RED);

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Now give Path Set up WINDING Fill patterns for , call toggleInverseFillType(). The final pattern is ：

FillType.INVERSE_WINDING

isEmpty():path Is it empty , hypothesis path It does not include any lines and curves , Then return to true, Otherwise return to false;

isRect(RectF rect): hypothesis path The designated one is rect, Then return to true, Otherwise return to false. Suppose we return to true & rect Not for null. Then the rect Set to path Region ;

computeBounds(RectF bounds,boolean exact)： Calculation path Area , And write the result to bounds, Suppose the whole path Only include 0 or 1 A little bit , Will return (0,0,0,0):

Use the following code to test ：

        mComputeRect = new RectF();        mEndPath = new Path();        mEndPath.addCircle(380, 380, 150, Direction.CW);        mEndPath.addRect(new RectF(200, 300, 500, 500), Direction.CW);        mEndPath.computeBounds(mComputeRect, false);        Toast.makeText(                mContext,                "" + mComputeRect.left + "," + mComputeRect.top + "," + mComputeRect.right + ","                        + mComputeRect.bottom,                Toast.LENGTH_LONG).show();

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The return result is （200,230,530,530）, namely path The boundary area of the content

incReserve(int extraPtCount)： Tips path Will be added extraPtCount A little bit . This enables path Allocate its storage space efficiently .

Okay , This article mainly introduces these methods . The following is mainly about Path in XXXTo and addXXX Related methods , Finally, we'll use it together Path Make an example ！

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