android开发通过Scroller实现过渡滑动效果操作示例

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

 
  public Scroller(Context context) {
    this(context, null);
  }
  
  public Scroller(Context context, Interpolator interpolator) {
    this(context, interpolator,
        context.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.HONEYCOMB);
  }
  
  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

  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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希望本文所述对大家Android程序设计有所帮助。

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