Android自定义View和Canvas绘图解析

/**
 * Created by gao_feng on 2016/12/20 下午9:17.
 */

public class WaveView extends View {
    private Path mPath;
    private Paint mPaint;
    private int vWidth , vHeight;//控件宽高
    private float ctrx , ctry;//控制点的xy坐标
    private float waveY;//整个Wave顶部两端的Y坐标

    private boolean isInc; //判断控制点是右移还是左移


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

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

    public WaveView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG);
        mPaint.setColor(0xFFA2D6AE);

        //实例化路径对象
        mPath = new Path();

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        Log.d("a", "onMeasure");

    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        //获取控件宽、高
        vWidth = w;
        vHeight = h;
        waveY = 1 / 8F * vHeight;
        //计算端点Y坐标
        ctry = -1 / 16F * vHeight;



    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        mPath.moveTo(-1 / 4F * vWidth , waveY);//起始点
        mPath.quadTo(ctrx , ctry , vWidth + 1/4F * vWidth , waveY);
        mPath.lineTo(vWidth + 1/4F * vWidth, vHeight);
        mPath.lineTo(-1 / 4f * vWidth, vHeight);
        mPath.close();
        canvas.drawPath(mPath, mPaint);

        if (ctrx >= vWidth + 1/4F * vWidth) {
            isInc = false;
        } else if (ctrx <= -1 / 4F * vWidth) {
            isInc = true;
        }
        ctrx = isInc ? ctrx + 20 : ctrx - 20;
        if (ctry <= vHeight) {
            ctry += 2;
            waveY += 2;
        }
        mPath.reset();
        invalidate();
    }
}