Open codingWang opened 6 years ago
public void startScroll(int startX, int startY, int dx, int dy, int duration) { mMode = SCROLL_MODE; mFinished = false; mDuration = duration; mStartTime = AnimationUtils.currentAnimationTimeMillis(); mStartX = startX; mStartY = startY; mFinalX = startX + dx; mFinalY = startY + dy; mDeltaX = dx; mDeltaY = dy; mDurationReciprocal = 1.0f / (float) mDuration; }
/** * Call this when you want to know the new location. If it returns true, * the animation is not yet finished. */ public boolean computeScrollOffset() { if (mFinished) { return false; } int timePassed = (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime); if (timePassed < mDuration) { switch (mMode) { case SCROLL_MODE: final float x = mInterpolator.getInterpolation(timePassed * mDurationReciprocal); mCurrX = mStartX + Math.round(x * mDeltaX); mCurrY = mStartY + Math.round(x * mDeltaY); break; case FLING_MODE: final float t = (float) timePassed / mDuration; final int index = (int) (NB_SAMPLES * t); float distanceCoef = 1.f; float velocityCoef = 0.f; if (index < NB_SAMPLES) { final float t_inf = (float) index / NB_SAMPLES; final float t_sup = (float) (index + 1) / NB_SAMPLES; final float d_inf = SPLINE_POSITION[index]; final float d_sup = SPLINE_POSITION[index + 1]; velocityCoef = (d_sup - d_inf) / (t_sup - t_inf); distanceCoef = d_inf + (t - t_inf) * velocityCoef; } mCurrVelocity = velocityCoef * mDistance / mDuration * 1000.0f; mCurrX = mStartX + Math.round(distanceCoef * (mFinalX - mStartX)); // Pin to mMinX <= mCurrX <= mMaxX mCurrX = Math.min(mCurrX, mMaxX); mCurrX = Math.max(mCurrX, mMinX); mCurrY = mStartY + Math.round(distanceCoef * (mFinalY - mStartY)); // Pin to mMinY <= mCurrY <= mMaxY mCurrY = Math.min(mCurrY, mMaxY); mCurrY = Math.max(mCurrY, mMinY); if (mCurrX == mFinalX && mCurrY == mFinalY) { mFinished = true; } break; } } else { mCurrX = mFinalX; mCurrY = mFinalY; mFinished = true; } return true; }
Scroller滚动基础
基本方法:
此方法只是做一些基本全局变量的赋值
此方法计算View的新坐标mCurrX,mCurrY,可以通过此方法判断滚动是否结束,false结束,true没结束
上面的方法都是辅助方法,真正滚动需要配合View的scrollTo和scrollBy方法还有computeScroll方法一起使用,典型的弹性滑动demo: