先看一下效果：
無論多複雜的動畫我們都是可以分割成小單元的，然後分步來實現。這個動畫大概分為收縮，準備，載入，完成幾個部分。為此定義一個列舉類來描述view的狀態。public enum Status {
NORMAL, START, PRE, EXPAND, LOAD, END
}
收縮動畫
使用動畫不斷改變圓角矩形的寬度，觸發重繪。程式碼如下：
private void initAnim() {
Animation animation1 = new Animation() {
@Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
mCurrLength = mWidth * (1 - interpolatedTime);
if (mCurrLength < mHeight) {
mCurrLength = mHeight;
clearAnimation();
mAngleAnim.start();
}
invalidate();
}
};
animation1.setDuration(mShrinkDuration);
animation1.setInterpolator(new LinearInterpolator());
animation1.setAnimationListener(new Animation.AnimationListener() {
@Override
public void onAnimationStart(Animation animation) {
mStatus = Status.START;
}
@Override
public void onAnimationEnd(Animation animation) {
}
@Override
public void onAnimationRepeat(Animation animation) {
}
});
mShrinkAnim = animation1;
...
}複製程式碼onDraw中繪製：
if (mStatus == Status.START || mStatus == Status.NORMAL) {
float left = (mWidth - mCurrLength) / 2f;
float right = (mWidth + mCurrLength) / 2f;
float r = mHeight / 2f;
canvas.drawRoundRect(new RectF(left, 0, right, mHeight), r, r, mBgPaint);
if (mStatus == Status.NORMAL) {
Paint.FontMetrics fm = mTextPaint.getFontMetrics();
float y = mHeight / 2 + (fm.descent - fm.ascent) / 2 - fm.descent;
canvas.drawText("下載", mWidth / 2, y, mTextPaint);
}
}複製程式碼準備動畫
此時旋轉動畫，是通過canvas繪製背景圓和三個小圓，然後不斷旋轉畫布來實現的，具體求圓心座標和角度動畫我們直接看程式碼：
ValueAnimator animator = ValueAnimator.ofFloat(0, 1);
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
mAngle += mPreAnimSpeed;
invalidate();
}
});
animator.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
mStatus = Status.PRE;
}
@Override
public void onAnimationEnd(Animator animation) {
mAngleAnim.cancel();
startAnimation(mTranslateAnim);
}
@Override
public void onAnimationCancel(Animator animation) {
}
@Override
public void onAnimationRepeat(Animator animation) {
}
});
animator.setDuration(mPreAnimDuration);
animator.setInterpolator(new LinearInterpolator());
mAngleAnim = animator;複製程式碼onDraw中繪製程式碼：
if (mStatus == Status.PRE) {
canvas.drawCircle(mWidth / 2f, mHeight / 2f, mHeight / 2f, mBgPaint);
canvas.save();
mTextPaint.setStyle(Paint.Style.FILL);
canvas.rotate(mAngle, mWidth / 2, mHeight / 2);
//大圓的圓心 半徑
float cX = mWidth / 2f;
float cY = mHeight / 2f;
float radius = mHeight / 2 / 3f;
canvas.drawCircle(cX, cY, radius, mTextPaint);
//上方小圓的引數
float rr = radius / 2f;
float cYY = mHeight / 2 - (radius + rr / 3);
canvas.drawCircle(cX, cYY, rr, mTextPaint);
//左下小圓引數
float cXX = (float) (cX - Math.sqrt(2) / 2f * (radius + rr / 3f));
cYY = (float) (mHeight / 2 + Math.sqrt(2) / 2f * (radius + rr / 3f));
canvas.drawCircle(cXX, cYY, rr, mTextPaint);
//右下小圓引數
cXX = (float) (cX + Math.sqrt(2) / 2f * (radius + rr / 3f));
canvas.drawCircle(cXX, cYY, rr, mTextPaint);
canvas.restore();
}複製程式碼展開動畫
展開動畫也是不斷改變view的寬度並重繪圓角矩形，同時需要對準備動畫的狀態進行向右位移。
Animation animator1 = new Animation() {
@Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
mCurrLength = mHeight + (mWidth - mHeight) * interpolatedTime;
mTranslationX = (mWidth - mHeight) / 2 * interpolatedTime;
invalidate();
}
};
animator1.setAnimationListener(new Animation.AnimationListener() {
@Override
public void onAnimationStart(Animation animation) {
mStatus = Status.EXPAND;
}
@Override
public void onAnimationEnd(Animation animation) {
clearAnimation();
mLoadAngleAnim.start();
mMovePointAnim.start();
}
@Override
public void onAnimationRepeat(Animation animation) {
}
});
animator1.setDuration(mExpandAnimDuration);
animator1.setInterpolator(new LinearInterpolator());
mTranslateAnim = animator1;複製程式碼onDraw中繪製程式碼
if (mStatus == Status.EXPAND) {
float left = (mWidth - mCurrLength) / 2f;
float right = (mWidth + mCurrLength) / 2f;
float r = mHeight / 2f;
canvas.drawRoundRect(new RectF(left, 0, right, mHeight), r, r, mBgPaint);
canvas.save();
mTextPaint.setStyle(Paint.Style.FILL);
canvas.translate(mTranslationX, 0);
//大圓的圓心 半徑
float cX = mWidth / 2f;
float cY = mHeight / 2f;
float radius = mHeight / 2 / 3f;
canvas.drawCircle(cX, cY, radius, mTextPaint);
//上方小圓的引數
float rr = radius / 2f;
float cYY = mHeight / 2 - (radius + rr / 3);
canvas.drawCircle(cX, cYY, rr, mTextPaint);
//左下小圓引數
float cXX = (float) (cX - Math.sqrt(2) / 2f * (radius + rr / 3f));
cYY = (float) (mHeight / 2 + Math.sqrt(2) / 2f * (radius + rr / 3f));
canvas.drawCircle(cXX, cYY, rr, mTextPaint);
//右下小圓引數
cXX = (float) (cX + Math.sqrt(2) / 2f * (radius + rr / 3f));
canvas.drawCircle(cXX, cYY, rr, mTextPaint);
canvas.restore();
}複製程式碼載入動畫
載入動畫分三部分，右側的旋轉動畫，正弦軌跡運動的小球動畫，進度更新的動畫。正弦動畫要求出正弦函式的週期，y軸偏移量，x軸偏移量。
ValueAnimator animator2 = ValueAnimator.ofFloat(0, 1);
animator2.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
mLoadAngle += mLoadRotateAnimSpeed;
invalidate();
}
});
animator2.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
mStatus = Status.LOAD;
}
@Override
public void onAnimationEnd(Animator animation) {
mLoadAngleAnim.cancel();
}
@Override
public void onAnimationCancel(Animator animation) {
}
@Override
public void onAnimationRepeat(Animator animation) {
}
});
animator2.setDuration(Integer.MAX_VALUE);
animator2.setInterpolator(new LinearInterpolator());
mLoadAngleAnim = animator2;複製程式碼onDraw中繪製程式碼：
if (mStatus == Status.LOAD || mStatus == Status.END) {
float left = (mWidth - mCurrLength) / 2f;
float right = (mWidth + mCurrLength) / 2f;
float r = mHeight / 2f;
mBgPaint.setColor(mProgressColor);
canvas.drawRoundRect(new RectF(left, 0, right, mHeight), r, r, mBgPaint);
if (mProgress != 100) {
for (int i = 0; i < mFourMovePoints.length; i++) {
if (mFourMovePoints[i].isDraw)
canvas.drawCircle(mFourMovePoints[i].moveX, mFourMovePoints[i].moveY, mFourMovePoints[i].radius, mTextPaint);
}
}
float progressRight = mProgress * mWidth / 100f;
mBgPaint.setColor(mBgColor);
canvas.save();
canvas.clipRect(0, 0, progressRight, mHeight);
canvas.drawRoundRect(new RectF(left, 0, right, mHeight), r, r, mBgPaint);
canvas.restore();
if (mProgress != 100) {
canvas.drawCircle(mWidth - mHeight / 2, mHeight / 2, mHeight / 2, mBgPaint);
canvas.save();
mTextPaint.setStyle(Paint.Style.FILL);
canvas.rotate(mLoadAngle, mWidth - mHeight / 2, mHeight / 2);
canvas.drawCircle(mWidth - mHeight + 30, getCenterY(mWidth - mHeight + 30, 5), 5, mTextPaint);
canvas.drawCircle(mWidth - mHeight + 45, getCenterY(mWidth - mHeight + 45, 8), 8, mTextPaint);
canvas.drawCircle(mWidth - mHeight + 68, getCenterY(mWidth - mHeight + 68, 11), 11, mTextPaint);
canvas.drawCircle(mWidth - mHeight + 98, getCenterY(mWidth - mHeight + 98, 14), 14, mTextPaint);
canvas.restore();
}
Paint.FontMetrics fm = mTextPaint.getFontMetrics();
float y = mHeight / 2 + (fm.descent - fm.ascent) / 2 - fm.descent;
canvas.drawText(mProgress + "%", mWidth / 2, y, mTextPaint);
}複製程式碼完整程式碼見GitHub。