android自定义View练习之波浪View

文章转载自

http://blog.csdn.NET/wingichoy/article/details/50460213

先上效果图:

就是这样子的波浪View.类似口香糖包装纸.

其实原理很简单,就是一个矩形加上好多个小三角形或者是矩形加上好多小半圆形

首先.创建一个类继承自View,重写其构造方法,并重写Draw()方法.如下

 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);
        mContext = context;
        TypedArray a = context.obtainStyledAttributes(attrs,R.styleable.WaveView,defStyleAttr,0);
        mWaveCount = a.getInt(R.styleable.WaveView_waveCount,10);
        mWaveWidth = a.getInt(R.styleable.WaveView_waveWidth,20);
        mMode = a.getInteger(R.styleable.WaveView_mode,-2);
        mColor = a.getColor(R.styleable.WaveView_android_color,Color.parseColor("#2C97DE"));
        a.recycle();
    }

第三个构造方法中为自定义属性的说明.另外,最后还要调用recycle()方法.

下面为自定义属性:

布局文件如下:

然后我们就开始画图了~

首先在onMeasure()方法里面,确定View的大小

@Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        //由于设置的是wrap_content,所以用AT_MOST,直接给定一个值
        if(widthMode == MeasureSpec.AT_MOST){
            mWidth = PxUtils.dpToPx(300,mContext);
            mRectWidth = (float) (mWidth * 0.8);
        }
        if(heightMode == MeasureSpec.AT_MOST){
            mHeight = PxUtils.dpToPx(200,mContext);
            mRectHeight = (float) (mHeight * 0.8);
        }
        setMeasuredDimension(mWidth, mHeight);
    }

至于PxUtils,是一个工具类,进行px,dp,sp之间转换的.

如下:

public class PxUtils {

    public static int dpToPx(int dp, Context context) {
        return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, context.getResources().getDisplayMetrics());
    }

    public static int spToPx(int sp,Context context) {
        return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, sp, context.getResources().getDisplayMetrics());
    }


}

接下来开始绘图。首先 画一个矩形。

这个矩形让他处于view的中间，看图：

由图可知， 矩形的左上坐标为 padding ,padding 矩形的右下坐标为padding +mRectWidth, padding + mRectHeight 

,其中padding 为 (mWidth - mRectWidth)/2

@Override
    protected void onDraw(Canvas canvas) {
        Paint p = new Paint();
        p.setColor(mColor);

        //计算每个三角形的高
        mWaveHeight = mRectHeight / mWaveCount;

        //绘制矩形

        //计算padding
        float padding = ((mWidth - mRectWidth) / 2);
        canvas.drawRect(padding, padding, mRectWidth + padding, mRectHeight + padding, p);


        //如果是三角模式
        if(mMode == MODE_TRIANGLE) {
            //绘制右边的波浪
            float startX = padding + mRectWidth;
            float startY = padding;
            Path path = new Path();
            path.moveTo(startX, startY);
            for (int i = 0; i < mWaveCount; i++) {
                path.lineTo(startX + mWaveWidth, startY + i * mWaveHeight + (mWaveHeight / 2));
                path.lineTo(startX, startY + mWaveHeight * (i + 1));

            }
            path.close();
            canvas.drawPath(path, p);

            //绘制左边的波浪
            startX = padding;
            startY = padding;
            path.moveTo(startX, startY);
            for (int i = 0; i < mWaveCount; i++) {
                path.lineTo(startX - mWaveWidth, startY + i * mWaveHeight + (mWaveHeight / 2));
                path.lineTo(startX, startY + mWaveHeight * (i + 1));
            }

            path.close();
            canvas.drawPath(path, p);
        }else {
            //绘制边框为半圆的图形
            //先计算半径
            mRadius = mRectHeight / mWaveCount;
            //绘制右边波浪
            float startX = padding + mRectWidth;
            float startY = padding;
            for(int i = 0;i

这样下来,图形就绘制好了.