android仿音悦台页面交互效果实例代码

 private void init(Context context, AttributeSet attrs) {

    final float density = getResources().getDisplayMetrics().density;
    final float minVel = MIN_FLING_VELOCITY * density;

    ViewGroupCompat.setMotionEventSplittingEnabled(this, false);
    FlexCallback flexCallback = new FlexCallback();
    mDragHelper = ViewDragHelper.create(this, 1.0f, flexCallback);
    // 最小拖动速度
    mDragHelper.setMinVelocity(minVel);

    post(new Runnable() {
      @Override
      public void run() {

        // 需要添加的两个子View，其中mFlexView作为拖动的响应View，mLinkView作为跟随View
        mFlexView = getChildAt(0);
        mFollowView = getChildAt(1);

        mDragHeight = getMeasuredHeight() - mFlexView.getMeasuredHeight();

        mFlexWidth = mFlexView.getMeasuredWidth();
        mFlexHeight = mFlexView.getMeasuredHeight();

      }
    });

  }

 private class FlexCallback extends ViewDragHelper.Callback {

    @Override
    public boolean tryCaptureView(View child, int pointerId) {
      // mFlexView来响应触摸事件
      return mFlexView == child;
    }

    @Override
    public int clampViewPositionHorizontal(View child, int left, int dx) {
      return Math.max(Math.min(mDragWidth, left), -mDragWidth);
    }

    @Override
    public int getViewHorizontalDragRange(View child) {
      return mDragWidth * 2;
    }

    @Override
    public int clampViewPositionVertical(View child, int top, int dy) {
      if (!mVerticalDragEnable) {
        // 不允许垂直拖动的时候是mFlexView在底部水平拖动一定距离时设置的，返回mDragHeight就不能再垂直做拖动了
        return mDragHeight;
      }
      return Math.max(Math.min(mDragHeight, top), 0);
    }

    @Override
    public int getViewVerticalDragRange(View child) {
      return mDragHeight;
    }

    @Override
    public void onViewReleased(View releasedChild, float xvel, float yvel) {

      if (mHorizontalDragEnable) {
        // 如果水平拖动有效，首先根据拖动的速度决定关闭页面，方向根据速度正负决定
        if (xvel > 1500) {
          mDragHelper.settleCapturedViewAt(mDragWidth, mDragHeight);
          mIsClosing = true;
        } else if (xvel < -1500) {
          mDragHelper.settleCapturedViewAt(-mDragWidth, mDragHeight);
          mIsClosing = true;
        } else {
          // 速度没到关闭页面的要求，根据透明度来决定关闭页面，方向根据releasedChild.getLeft()正负决定
          float alpha = releasedChild.getAlpha();
          if (releasedChild.getLeft() < 0 && alpha <= 0.4f) {
            mDragHelper.settleCapturedViewAt(-mDragWidth, mDragHeight);
            mIsClosing = true;
          } else if (releasedChild.getLeft() > 0 && alpha <= 0.4f) {
            mDragHelper.settleCapturedViewAt(mDragWidth, mDragHeight);
            mIsClosing = true;
          } else {
            mDragHelper.settleCapturedViewAt(0, mDragHeight);
          }
        }
      } else {
        // 根据垂直方向的速度正负决定布局的展示方式
        if (yvel > 1500) {
          mDragHelper.settleCapturedViewAt(0, mDragHeight);
        } else if (yvel < -1500) {
          mDragHelper.settleCapturedViewAt(0, 0);
        } else {
          // 根据releasedChild.getTop()决定布局的展示方式
          if (releasedChild.getTop() <= mDragHeight / 2) {
            mDragHelper.settleCapturedViewAt(0, 0);
          } else {
            mDragHelper.settleCapturedViewAt(0, mDragHeight);
          }
        }
      }
      invalidate();
    }

    @Override
    public void onViewPositionChanged(final View changedView, int left, int top, int dx, int dy) {

      float fraction = top * 1.0f / mDragHeight;

      // mFlexView缩放的比率
      mFlexScaleRatio = 1 - 0.5f * fraction;
      mFlexScaleOffset = changedView.getWidth() / 20;
      // 设置缩放基点
      changedView.setPivotX(changedView.getWidth() - mFlexScaleOffset);
      changedView.setPivotY(changedView.getHeight() - mFlexScaleOffset);
      // 设置比例
      changedView.setScaleX(mFlexScaleRatio);
      changedView.setScaleY(mFlexScaleRatio);

      // mFollowView透明度的比率
      float alphaRatio = 1 - fraction;
      // 设置透明度
      mFollowView.setAlpha(alphaRatio);
      // 根据垂直方向的dy设置top，产生跟随mFlexView的效果
      mFollowView.setTop(mFollowView.getTop() + dy);

      // 到底部的时候，changedView的top刚好等于mDragHeight，以此作为水平拖动的基准
      mHorizontalDragEnable = top == mDragHeight;

      if (mHorizontalDragEnable) {
        // 如果水平拖动允许的话，由于设置缩放不会影响mFlexView的宽高（比如getWidth），所以水平拖动距离为mFlexView宽度一半
        mDragWidth = (int) (changedView.getMeasuredWidth() * 0.5f);

        // 设置mFlexView的透明度，这里向左右水平拖动透明度都随之变化
        changedView.setAlpha(1 - Math.abs(left) * 1.0f / mDragWidth);

        // 水平拖动一定距离的话，垂直拖动将被禁止
        mVerticalDragEnable = left < 0 && left >= -mDragWidth * 0.05;

      } else {
        // 不是水平拖动的处理
        changedView.setAlpha(1);
        mDragWidth = 0;

        mVerticalDragEnable = true;

      }

      if (mFlexLayoutPosition == null) {
        // 创建子元素位置缓存
        mFlexLayoutPosition = new ChildLayoutPosition();
        mFollowLayoutPosition = new ChildLayoutPosition();
      }

      // 记录子元素的位置
      mFlexLayoutPosition.setPosition(mFlexView.getLeft(), mFlexView.getRight(), mFlexView.getTop(), mFlexView.getBottom());
      mFollowLayoutPosition.setPosition(mFollowView.getLeft(), mFollowView.getRight(), mFollowView.getTop(), mFollowView.getBottom());

      //      Log.e("FlexCallback", "225行-onViewPositionChanged(): 【" + mFlexView.getLeft() + ":" + mFlexView.getRight() + ":" + mFlexView.getTop() + ":" + mFlexView
      //          .getBottom() + "】 【" + mFollowView.getLeft() + ":" + mFollowView.getRight() + ":" + mFollowView.getTop() + ":" + mFollowView.getBottom() + "】");

    }

  }

@Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

    int desireHeight = 0;
    int desireWidth = 0;

    int tmpHeight = 0;

    if (getChildCount() != 2) {
      throw new IllegalArgumentException("只允许容器添加两个子View！");
    }

    if (getChildCount() > 0) {
      for (int i = 0; i < getChildCount(); i++) {
        final View child = getChildAt(i);
        // 测量子元素并考虑外边距
        // 参数heightUse：父容器竖直已经被占用的空间，比如被父容器的其他子 view 所占用的空间；这里我们需要的是子View垂直排列，所以需要设置这个值
        measureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, tmpHeight);
        // 获取子元素的布局参数
        final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
        // 计算子元素宽度，取子控件最大宽度
        desireWidth = Math.max(desireWidth, child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin);
        // 计算子元素高度
        tmpHeight = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
        desireHeight += tmpHeight;
      }
      // 考虑父容器内边距
      desireWidth += getPaddingLeft() + getPaddingRight();
      desireHeight += getPaddingTop() + getPaddingBottom();
      // 尝试比较建议最小值和期望值的大小并取大值
      desireWidth = Math.max(desireWidth, getSuggestedMinimumWidth());
      desireHeight = Math.max(desireHeight, getSuggestedMinimumHeight());
    }
    // 设置最终测量值
    setMeasuredDimension(resolveSize(desireWidth, widthMeasureSpec), resolveSize(desireHeight, heightMeasureSpec));
  }

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {

    if (mFlexLayoutPosition != null) {
      // 因为在用到ViewDragHelper处理布局交互的时候，若是有子View的UI更新导致重新Layout的话，需要我们自己处理ViewDragHelper拖动时子View的位置，否则会导致位置错误
      // Log.e("YytLayout1", "292行-onLayout(): " + "自己处理布局位置");
      mFlexView.layout(mFlexLayoutPosition.getLeft(), mFlexLayoutPosition.getTop(), mFlexLayoutPosition.getRight(), mFlexLayoutPosition.getBottom());
      mFollowView.layout(mFollowLayoutPosition.getLeft(), mFollowLayoutPosition.getTop(), mFollowLayoutPosition.getRight(), mFollowLayoutPosition.getBottom());
      return;
    }

    final int paddingLeft = getPaddingLeft();
    final int paddingTop = getPaddingTop();

    int multiHeight = 0;

    int count = getChildCount();

    if (count != 2) {
      throw new IllegalArgumentException("此容器的子元素个数必须为2！");
    }

    for (int i = 0; i < count; i++) {
      // 遍历子元素并对其进行定位布局
      final View child = getChildAt(i);
      MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();

      int left = paddingLeft + lp.leftMargin;
      int right = child.getMeasuredWidth() + left;

      int top = (i == 0 ? paddingTop : 0) + lp.topMargin + multiHeight;
      int bottom = child.getMeasuredHeight() + top;

      child.layout(left, top, right, bottom);

      multiHeight += (child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin);
    }

  }

 @Override
  public boolean onInterceptTouchEvent(MotionEvent ev) {

    // Log.e("YytLayout", mFlexView.getLeft() + ";" + mFlexView.getTop() + " --- " + ev.getX() + ":" + ev.getY());

    // 由于缩放不会影响mFlexView真实宽高，这里手动计算视觉上的范围
    float left = mFlexView.getLeft() + mFlexWidth * (1 - mFlexScaleRatio) - mFlexScaleOffset * (1 - mFlexScaleRatio);
    float top = mFlexView.getTop() + mFlexHeight * (1 - mFlexScaleRatio) - mFlexScaleOffset * (1 - mFlexScaleRatio);

    // 这里所做的是判断手指是否落在mFlexView视觉上的范围内
    mInFlexViewTouchRange = ev.getX() >= left && ev.getY() >= top;

    if (mInFlexViewTouchRange) {

      return mDragHelper.shouldInterceptTouchEvent(ev);

    } else {
      return super.onInterceptTouchEvent(ev);
    }
  }

  @Override
  public boolean onTouchEvent(MotionEvent event) {
    if (mInFlexViewTouchRange) {
      // 这里还要做判断是因为，即使我不阻断事件，但是此Layout的子View不消费的话，事件还是给回此Layout
      mDragHelper.processTouchEvent(event);
      return true;
    } else {
      // 不在mFlexView触摸范围内，并且子View没有消费，返回false，把事件传递回去
      return false;
    }
  }

 @Override
  public void computeScroll() {
    if (mDragHelper.continueSettling(true)) {
      invalidate();
    } else if (mIsClosing && mOnLayoutStateListener != null) {
      // 正在关闭的情况下，并且拖动结束后，告知将要关闭页面
      mOnLayoutStateListener.onClose();
      mIsClosing = false;
    }
  }

  /**
   * 监听布局是否水平拖动关闭了
   */
  public interface OnLayoutStateListener {

    void onClose();

  }

  public void setOnLayoutStateListener(OnLayoutStateListener onLayoutStateListener) {
    mOnLayoutStateListener = onLayoutStateListener;
  }

  /**
   * 展开布局
   */
  public void expand() {
    mDragHelper.smoothSlideViewTo(mFlexView, 0, 0);
    invalidate();
  }