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
/** * 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
/** * 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; }
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; }
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(); } }}
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(); }}
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