本文实例讲述了android开发通过Scroller实现过渡滑动效果。分享给大家供大家参考,具体如下:
主要介绍一下Scroller这个类,它可以实现过渡滑动的效果,使滑动看起来不是那么生硬,当然它用大量的重绘来实现,invalidate();通过源码看:
看构造方法
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/** * Create a Scroller with the default duration and interpolator. */ public Scroller(Context context) { this (context, null ); } /** * Create a Scroller with the specified interpolator. If the interpolator is * null, the default (viscous) interpolator will be used. "Flywheel" behavior will * be in effect for apps targeting Honeycomb or newer. */ public Scroller(Context context, Interpolator interpolator) { this (context, interpolator, context.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.HONEYCOMB); } /** * Create a Scroller with the specified interpolator. If the interpolator is * null, the default (viscous) interpolator will be used. Specify whether or * not to support progressive "flywheel" behavior in flinging. */ public Scroller(Context context, Interpolator interpolator, boolean flywheel) { mFinished = true ; if (interpolator == null ) { mInterpolator = new ViscousFluidInterpolator(); } else { mInterpolator = interpolator; } mPpi = context.getResources().getDisplayMetrics().density * 160 .0f; mDeceleration = computeDeceleration(ViewConfiguration.getScrollFriction()); mFlywheel = flywheel; mPhysicalCoeff = computeDeceleration( 0 .84f); // look and feel tuning } |
我们用默认的就行,传个context就行了,其他的什么差值器,先不管了
然后调用startScroll,传递我们歧视滑动位置和滑动的偏移量,还有可选的默认持续时间,默认为250毫秒
这个方法是用来赋值的,接下来会调用invalidate()进行重新绘制,然后就会onDraw(),这时候会调用
computeScroll()这个方法,我们重写这个方法,computeScrollOffset()是判断动画有没有结束的一个方法,没结束的时候,我们根据滑动的偏移位置进行移动也就是scrollto到scroller的当前位置,再次调用invalidate(),由此无数的重回进行拼接形成了平滑的滑动
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/** * 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 ; } |
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public void startScroll( int startX, int startY, int dx, int dy) { startScroll(startX, startY, dx, dy, DEFAULT_DURATION); } 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; } |
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public class MoveFreeView extends View{ private int movedX; private int movedY; private Scroller mScroller; public MoveFreeView(Context context) { super (context); } public MoveFreeView(Context context, @Nullable AttributeSet attrs) { super (context, attrs); mScroller = new Scroller(context); } public MoveFreeView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) { super (context, attrs, defStyleAttr); } @Override public boolean onTouchEvent(MotionEvent event) { //获取触摸点到边界坐标 int x = ( int ) event.getX(); int y = ( int ) event.getY(); switch (event.getAction()){ case MotionEvent.ACTION_DOWN: movedX = x; movedY = y; break ; case MotionEvent.ACTION_MOVE: int offsetX = x-movedX; int offsetY = y-movedY; layout(getLeft()+offsetX,getTop()+offsetY,getRight()+offsetX,getBottom()+offsetY); break ; } return super .onTouchEvent(event); } //供外界调用通过传递x,y的的滑动距离 public void smoothScrollTo( int destinyX, int destinyY){ //向右侧,下方滑动,请传递负值 int scrollX = getScrollX(); int scrollY = getScrollY(); int delta = destinyX - scrollX; int deltaY = destinyY - scrollY; mScroller.startScroll(scrollX,scrollY,delta,deltaY, 5000 ); invalidate(); } @Override public void computeScroll() { super .computeScroll(); //true则表示滑动未结束 if (mScroller.computeScrollOffset()){ ((View) getParent()).scrollTo(mScroller.getCurrX(),mScroller.getCurrY()); invalidate(); } } } |
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private MoveFreeView button; @Override protected void onCreate(Bundle savedInstanceState) { super .onCreate(savedInstanceState); setContentView(R.layout.activity_main); button = (MoveFreeView) findViewById(R.id.custon); button.smoothScrollTo(- 400 ,- 300 ); // button.startAnimation(AnimationUtils.loadAnimation(this,R.anim.translate)); // ObjectAnimator animtor1 = ObjectAnimator.ofFloat(button, "translationX", 0, 300); // ObjectAnimator animtor2 = ObjectAnimator.ofFloat(button, "translationY", 0, 300); // ObjectAnimator animator3 = ObjectAnimator.ofFloat(button,"rotationX",0.0f,360f); // ObjectAnimator animator4 = ObjectAnimator.ofFloat(button,"scaleX",1.5f,0.5f); // AnimatorSet set= new AnimatorSet(); // set.setDuration(5000); // set.playTogether(animtor1,animtor2,animator3,animator4); // set.addListener(new Animator.AnimatorListener() { // @Override // public void onAnimationStart(Animator animator) { // // } // // @Override // public void onAnimationEnd(Animator animator) { // //动画结束时做一些事情 // } // // @Override // public void onAnimationCancel(Animator animator) { // // } // // @Override // public void onAnimationRepeat(Animator animator) { // // } // }); // set.start(); } } |
希望本文所述对大家Android程序设计有所帮助。
原文链接:https://blog.csdn.net/sinat_35670989/article/details/78194162