自定义View实现百度Loading动画

基本绘制

实现思路:先绘制背景色文字,然后讲Canvas裁切这个path路径,然后绘制白色的文字

绘制正弦曲线

这里使用贝塞尔曲线实现正弦曲线的绘制,使用ValueAnimator不断通知重绘

private Path getActionPath(float curPercent) {        final Path path = new Path();        int x = -mWidth;        x += curPercent * mWidth;        path.moveTo(x, mHeight / 2);        // 计算控制点        int quadWidth = mWidth / 4;        int quadHeight = mHeight / 20 * 3;        // 第一个周期        path.rQuadTo(quadWidth, quadHeight, quadWidth * 2, 0);        path.rQuadTo(quadWidth, -quadHeight, quadWidth * 2, 0);        // 第二个周期        path.rQuadTo(quadWidth, quadHeight, quadWidth * 2, 0);        path.rQuadTo(quadWidth, -quadHeight, quadWidth * 2, 0);        // 右侧的直线        path.lineTo(x + mWidth * 2, mHeight);        path.lineTo(x, mHeight);        path.close();        return path;    }

这里涉及到Path类的使用,使用path的rQuadTo()表示相对与上一个点位置进行二阶贝塞尔变换,而使用quadTo()是相对于原始坐标系进行贝塞尔变换.

绘制文字

mTextPaint.setTextSize(mTextHeight);// 先绘制背景色文字mTextPaint.setColor(mColor);//绘制 文字Rect rect = new Rect(0, 0, mWidth, mHeight);mTextPaint.setTextAlign(Paint.Align.CENTER);Paint.FontMetrics metrics = mTextPaint.getFontMetrics();float top = metrics.top;float bottom = metrics.bottom;int centerY = (int) (rect.centerY() - top / 2 - bottom / 2);canvas.drawText(mText, rect.centerX(), centerY, mTextPaint);

实现裁切效果

实现方式1:使用Canvas.clipPath()实现

使用canvas.clipPath()可以将Canvas裁切成成指定的Path效果,前提是曲线必须闭合

完整的onDraw()代码如下

// 先绘制背景色文字,然后讲Canvas裁切这个path路径,然后绘制白色的文字    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        Log.d(TAG, "onDraw: mCurPercent " + mCurPercent);        mTextPaint.setTextSize(mTextHeight);        // 先绘制背景色文字        mTextPaint.setColor(mColor);        //绘制 文字        Rect rect = new Rect(0, 0, mWidth, mHeight);        mTextPaint.setTextAlign(Paint.Align.CENTER);        Paint.FontMetrics metrics = mTextPaint.getFontMetrics();        float top = metrics.top;        float bottom = metrics.bottom;        int centerY = (int) (rect.centerY() - top / 2 - bottom / 2);        canvas.drawText(mText, rect.centerX(), centerY, mTextPaint);        // 生成闭合波浪路径        mPath = getActionPath(mCurPercent);        // 将Canvas按照Path的规则进行裁剪        canvas.clipPath(mPath);        canvas.drawCircle(mWidth / 2, mHeight / 2, mWidth / 2, mPaint);        mTextPaint.setColor(Color.WHITE);        canvas.drawText(mText, rect.centerX(), centerY, mTextPaint);    }

实现方式2: 使用xfermode代替Canvas裁切路径

xfermode的模式:

xfermode使用注意:

1. 使用xfermode的时候记得先使用Canvas的离屏缓冲,不然会将后绘制的src黑色背景一块绘制上去
2. 使用xfermode完毕后及时将paint的xfermode设置为null,避免影响下次绘制paint.setXfermode(null)

这里主要使用了两种模式:
SRC_IN: 在源图像(后绘制的)和目标图像相交的地方,取源图像
SRC_ATOP:在源图像和目标图像相交的地方绘制源图像
这两种模式的应用在代码注释里也有相应的解释

onDraw的代码将改写成:

 // 先绘制背景色文字,然后讲Canvas裁切这个path路径,然后绘制白色的文字    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        Log.d(TAG, "onDraw: mCurPercent " + mCurPercent);        mTextPaint.setTextSize(mTextHeight);        // 先绘制背景色文字        mTextPaint.setColor(mColor);        //绘制 文字        Rect rect = new Rect(0, 0, mWidth, mHeight);        mTextPaint.setTextAlign(Paint.Align.CENTER);        Paint.FontMetrics metrics = mTextPaint.getFontMetrics();        float top = metrics.top;        float bottom = metrics.bottom;        int centerY = (int) (rect.centerY() - top / 2 - bottom / 2);        canvas.drawText(mText, rect.centerX(), centerY, mTextPaint);        // 启动离屏缓冲        final int saved = canvas.saveLayer(0, 0, canvas.getWidth(), canvas.getHeight(), null, Canvas.ALL_SAVE_FLAG);        final Bitmap circle = getCircleBitmap(mWidth, mHeight);        // 生成闭合波浪路径        mPath = getActionPath(mCurPercent);        canvas.drawPath(mPath, mPaint);        // SRC_IN  在src(bitmap)和dst(path)相交的地方取源图像        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));        // 如果直接使用canvas.drawCircle()绘制圆形,canvas绘制圆形之外的部分没有alpha通道        // 而xfermode计算图片层叠样式的原理是通过alpha通道,所以这里必须使用一个bitmap来绘制        // 才能裁切掉多余的矩形        canvas.drawBitmap(circle, 0, 0, mPaint);        // SRC_ATOP在src(text)和dst(bitmap+path)相交的地方绘制源图像        mTextPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_ATOP));        mTextPaint.setColor(Color.WHITE);        canvas.drawText(mText, rect.centerX(), centerY, mTextPaint);        canvas.restoreToCount(saved);        // onDraw()结束前记得将xfermode设置为null,避免影响下次绘制        mPaint.setXfermode(null);        mTextPaint.setXfermode(null);    }

　实现方式１完整代码

/** * Created by yangtianrui on 17-8-12. * 使用Cavas Clip实现贴吧小球 */@SuppressLint("DrawAllocation")public class CanvasClipWave extends View {    private static final String TAG = "ytr";    private final String mText;    private final int mColor;    private final Paint mPaint;    private final Paint mTextPaint;    private Path mPath;    private float mCurPercent;    private int mTextHeight;    private int mWidth;    private int mHeight;    public CanvasClipWave(Context context) {        this(context, null);    }    public CanvasClipWave(Context context, @Nullable AttributeSet attrs) {        this(context, attrs, 0);    }    public CanvasClipWave(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CanvasClipWave);        mText = a.getString(R.styleable.CanvasClipWave_text);        mColor = a.getColor(R.styleable.CanvasClipWave_color, Color.BLUE);        a.recycle();        mPaint = new Paint();        mPaint.setAntiAlias(true);        mPaint.setStyle(Paint.Style.FILL);        mPaint.setColor(mColor);        // 设置防抖动        mPaint.setDither(true);        mTextPaint = new Paint();        mTextPaint.setTypeface(Typeface.DEFAULT_BOLD);        // 不断重绘        ValueAnimator va = ValueAnimator.ofFloat(0F, 1F);        va.setInterpolator(new LinearInterpolator());        va.setRepeatMode(ValueAnimator.RESTART);        va.setRepeatCount(ValueAnimator.INFINITE);        va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {            @Override            public void onAnimationUpdate(ValueAnimator animation) {                mCurPercent = (float) animation.getAnimatedValue();                postInvalidate();            }        });        va.setDuration(1000);        va.start();    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        final int wMode = MeasureSpec.getMode(widthMeasureSpec);        final int wSize = MeasureSpec.getSize(widthMeasureSpec);        final int hMode = MeasureSpec.getMode(heightMeasureSpec);        final int hSize = MeasureSpec.getSize(heightMeasureSpec);        if (wMode == MeasureSpec.EXACTLY && hMode == MeasureSpec.EXACTLY) {            mTextHeight = hSize / 2;            mWidth = wSize;            mHeight = hSize;        }        super.onMeasure(widthMeasureSpec, heightMeasureSpec);    }    // 先绘制背景色文字,然后讲Canvas裁切这个path路径,然后绘制白色的文字    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        Log.d(TAG, "onDraw: mCurPercent " + mCurPercent);        mTextPaint.setTextSize(mTextHeight);        // 先绘制背景色文字        mTextPaint.setColor(mColor);        //绘制 文字        Rect rect = new Rect(0, 0, mWidth, mHeight);        mTextPaint.setTextAlign(Paint.Align.CENTER);        Paint.FontMetrics metrics = mTextPaint.getFontMetrics();        float top = metrics.top;        float bottom = metrics.bottom;        int centerY = (int) (rect.centerY() - top / 2 - bottom / 2);        canvas.drawText(mText, rect.centerX(), centerY, mTextPaint);        // 生成闭合波浪路径        mPath = getActionPath(mCurPercent);        // 将Canvas按照Path的规则进行裁剪        canvas.clipPath(mPath);        canvas.drawCircle(mWidth / 2, mHeight / 2, mWidth / 2, mPaint);        mTextPaint.setColor(Color.WHITE);        canvas.drawText(mText, rect.centerX(), centerY, mTextPaint);    }    private Path getActionPath(float curPercent) {        final Path path = new Path();        int x = -mWidth;        x += curPercent * mWidth;        path.moveTo(x, mHeight / 2);        // 计算控制点        int quadWidth = mWidth / 4;        int quadHeight = mHeight / 20 * 3;        // 第一个周期        path.rQuadTo(quadWidth, quadHeight, quadWidth * 2, 0);        path.rQuadTo(quadWidth, -quadHeight, quadWidth * 2, 0);        // 第二个周期        path.rQuadTo(quadWidth, quadHeight, quadWidth * 2, 0);        path.rQuadTo(quadWidth, -quadHeight, quadWidth * 2, 0);        // 右侧的直线        path.lineTo(x + mWidth * 2, mHeight);        path.lineTo(x, mHeight);        path.close();        return path;    }}

实现方式2完整代码:

/** * Created by yangtianrui on 17-8-13. * 使用Xfermode实现这样的Canvas裁切效果, 代码基本上与CanvasClipWave相同 */@SuppressLint("DrawAllocation")public class XfermodeWave extends View {    private static final String TAG = "ytr";    private final String mText;    private final int mColor;    private final Paint mPaint;    private final Paint mTextPaint;    private Path mPath;    private float mCurPercent;    private int mTextHeight;    private int mWidth;    private int mHeight;    public XfermodeWave(Context context) {        this(context, null);    }    public XfermodeWave(Context context, @Nullable AttributeSet attrs) {        this(context, attrs, 0);    }    public XfermodeWave(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CanvasClipWave);        mText = a.getString(R.styleable.CanvasClipWave_text);        mColor = a.getColor(R.styleable.CanvasClipWave_color, Color.BLUE);        a.recycle();        mPaint = new Paint();        mPaint.setAntiAlias(true);        mPaint.setStyle(Paint.Style.FILL);        mPaint.setColor(mColor);        // 设置防抖动        mPaint.setDither(true);        mTextPaint = new Paint();        mTextPaint.setTypeface(Typeface.DEFAULT_BOLD);        // 不断重绘        ValueAnimator va = ValueAnimator.ofFloat(0F, 1F);        va.setInterpolator(new LinearInterpolator());        va.setRepeatMode(ValueAnimator.RESTART);        va.setRepeatCount(ValueAnimator.INFINITE);        va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {            @Override            public void onAnimationUpdate(ValueAnimator animation) {                mCurPercent = (float) animation.getAnimatedValue();                postInvalidate();            }        });        va.setDuration(1000);        va.start();    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        final int wMode = MeasureSpec.getMode(widthMeasureSpec);        final int wSize = MeasureSpec.getSize(widthMeasureSpec);        final int hMode = MeasureSpec.getMode(heightMeasureSpec);        final int hSize = MeasureSpec.getSize(heightMeasureSpec);        if (wMode == MeasureSpec.EXACTLY && hMode == MeasureSpec.EXACTLY) {            mTextHeight = hSize / 2;            mWidth = wSize;            mHeight = hSize;        }        super.onMeasure(widthMeasureSpec, heightMeasureSpec);    }    // 先绘制背景色文字,然后讲Canvas裁切这个path路径,然后绘制白色的文字    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        Log.d(TAG, "onDraw: mCurPercent " + mCurPercent);        mTextPaint.setTextSize(mTextHeight);        // 先绘制背景色文字        mTextPaint.setColor(mColor);        //绘制 文字        Rect rect = new Rect(0, 0, mWidth, mHeight);        mTextPaint.setTextAlign(Paint.Align.CENTER);        Paint.FontMetrics metrics = mTextPaint.getFontMetrics();        float top = metrics.top;        float bottom = metrics.bottom;        int centerY = (int) (rect.centerY() - top / 2 - bottom / 2);        canvas.drawText(mText, rect.centerX(), centerY, mTextPaint);        // 启动离屏缓冲        final int saved = canvas.saveLayer(0, 0, canvas.getWidth(), canvas.getHeight(), null, Canvas.ALL_SAVE_FLAG);        final Bitmap circle = getCircleBitmap(mWidth, mHeight);        // 生成闭合波浪路径        mPath = getActionPath(mCurPercent);        canvas.drawPath(mPath, mPaint);        // SRC_IN  在src(bitmap)和dst(path)相交的地方取源图像        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));        // 如果直接使用canvas.drawCircle()绘制圆形,canvas绘制圆形之外的部分没有alpha通道        // 而xfermode计算图片层叠样式的原理是通过alpha通道,所以这里必须使用一个bitmap来绘制        // 才能裁切掉多余的矩形        canvas.drawBitmap(circle, 0, 0, mPaint);        // SRC_ATOP在src(text)和dst(bitmap+path)相交的地方绘制源图像        mTextPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_ATOP));        mTextPaint.setColor(Color.WHITE);        canvas.drawText(mText, rect.centerX(), centerY, mTextPaint);        canvas.restoreToCount(saved);        // onDraw()结束前记得将xfermode设置为null,避免影响下次绘制        mPaint.setXfermode(null);        mTextPaint.setXfermode(null);    }    /**     * 创建一个中间绘制圆形的bitmap     */    private Bitmap getCircleBitmap(int width, int height) {        Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ALPHA_8);        Canvas canvas = new Canvas(bitmap);        canvas.drawCircle(width / 2, height / 2, width / 2, mPaint);        return bitmap;    }    private Path getActionPath(float curPercent) {        final Path path = new Path();        int x = -mWidth;        x += curPercent * mWidth;        path.moveTo(x, mHeight / 2);        // 计算控制点        int quadWidth = mWidth / 4;        int quadHeight = mHeight / 20 * 3;        // 第一个周期        path.rQuadTo(quadWidth, quadHeight, quadWidth * 2, 0);        path.rQuadTo(quadWidth, -quadHeight, quadWidth * 2, 0);        // 第二个周期        path.rQuadTo(quadWidth, quadHeight, quadWidth * 2, 0);        path.rQuadTo(quadWidth, -quadHeight, quadWidth * 2, 0);        // 右侧的直线        path.lineTo(x + mWidth * 2, mHeight);        path.lineTo(x, mHeight);        path.close();        return path;    }}