該控件具有下拉放大背景圖和貝塞爾曲線的效果.

該控件效果基于PullZoomView源碼改動(dòng)的而來,感謝Frank-Zhu的開源代碼.

github:https://github.com/X-FAN/PullBezierZoomView 歡迎star

我主要寫了一個(gè)自定義貝塞爾曲線效果的控件并整合到了Frank-Zhu的項(xiàng)目中的一個(gè)子項(xiàng)中.

這里面有個(gè)小數(shù)學(xué)知識(shí)的求解,因?yàn)樾Ч愘悹柷€的曲線頂點(diǎn)要恰好在控件底部邊界的重點(diǎn).所以我們是知道ABC三點(diǎn),去求貝塞爾曲線的控制點(diǎn).具體求解過程就不分析了,大家google二階貝塞爾曲線的公式,很容易就可以推算出來.

這里寫圖片描述

貝塞爾曲線效果控件源碼如下:

public class BezierView extends View {

    private int mWidth = 500;
    private int mHeight = 500;
    private float mMaxHeight = Integer.MAX_VALUE;
    private float mY = 0;

    private Paint mPaint;
    private Path mPath;


    public BezierView(Context context) {
        this(context, null);
    }

    public BezierView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public BezierView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mPath = new Path();
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setColor(Color.WHITE);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int width;
        int height;

        if (widthMode == MeasureSpec.EXACTLY) {
            width = widthSize;
        } else if (widthMode == MeasureSpec.AT_MOST) {
            width = Math.min(mWidth, widthSize);
        } else {
            width = mWidth;
        }

        if (heightMode == MeasureSpec.EXACTLY) {
            height = heightSize;
        } else if (heightMode == MeasureSpec.AT_MOST) {
            height = Math.min(mHeight, heightSize);
        } else {
            height = mHeight;
        }
        setMeasuredDimension(width, height);
    }


    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mWidth = w;
        mHeight = h;
    }


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        mPath.reset();//繪制的主要邏輯代碼
        mPath.moveTo(0, mHeight - mY);
        mPath.quadTo(mWidth / 2, mHeight + mY, mWidth, mHeight - mY);
        mPath.lineTo(mWidth, mHeight);
        mPath.lineTo(0, mHeight);
        mPath.close();
        canvas.drawPath(mPath, mPaint);
    }

    public void setArcHeight(float height) {
        if (Math.abs(height) < mMaxHeight) {
            mY = height;
            invalidate();
        }
    }

    public float getArcHeight() {
        return mY;
    }

    public void setColor(int color) {
        mPaint.setColor(color);
    }

    public void setMaxHeight(float height) {
        mMaxHeight = height;
    }

這里提下Frank-Zhu的項(xiàng)目中放大縮小功能的實(shí)現(xiàn)是相當(dāng)?shù)穆斆?看了源碼發(fā)現(xiàn)他是利用ImagView中的scaleType="centerCrop"屬性,只要改變控件的高度,就具有了放大縮小的效果.不用自己寫額外的代碼,確實(shí)很方便.

效果圖:

bezier.gif