Android Open Source - utexas-utilities Simple Scroll View

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License

The source code is released under:

Apache License

Java Source Code

package com.mapsaurus.paneslayout;
/* www. j a  v a 2  s  . c  o m*/
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.Scroller;

public class SimpleScrollView extends FrameLayout {

  private Scroller mScroller;

  /**
   * True when the layout has changed but the traversal has not come through yet.
   * Ideally the view hierarchy would keep track of this for us.
   */
  private boolean mIsLayoutDirty = true;

  public SimpleScrollView(Context context) {
    super(context);
    mScroller = new Scroller(context);
  }

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

    final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    if (widthMode == MeasureSpec.UNSPECIFIED) {
      return;
    }

    if (getChildCount() > 0) {
      final View child = getChildAt(0);
      int width = getMeasuredWidth();
      if (child.getMeasuredWidth() < width) {
        final LayoutParams lp = (LayoutParams) child.getLayoutParams();

        int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec,
            getPaddingTop() + getPaddingBottom(), lp.height);
        width -= getPaddingLeft();
        width -= getPaddingRight();
        int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);

        child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
      }
    }
  }

  @Override
  protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) {
    ViewGroup.LayoutParams lp = child.getLayoutParams();

    int childWidthMeasureSpec;
    int childHeightMeasureSpec;

    childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec,
        getPaddingTop() + getPaddingBottom(), lp.height);

    childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);

    child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
  }

  @Override
  protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed,
      int parentHeightMeasureSpec, int heightUsed) {
    final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();

    final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec,
        getPaddingTop() + getPaddingBottom() + lp.topMargin + lp.bottomMargin
        + heightUsed, lp.height);
    final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
        lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED);

    child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
  }

  @Override
  public void computeScroll() {
    if (mScroller.computeScrollOffset()) {
      int oldX = getScrollX();
      int oldY = getScrollY();
      int x = mScroller.getCurrX();
      int y = mScroller.getCurrY();
      if (getChildCount() > 0) {
        View child = getChildAt(0);
        x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth());
        y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight());
      }

      scrollTo(x, y);

      if (oldX != getScrollX() || oldY != getScrollY()) {
        onScrollChanged(getScrollX(), getScrollY(), oldX, oldY);
      }

      // Keep on drawing until the animation has finished.
      postInvalidate();
    }
  }

  private int clamp(int n, int my, int child) {
    if (my >= child || n < 0) {
      return 0;
    }
    if ((my + n) > child) {
      return child - my;
    }
    return n;
  }

  @Override
  public void requestLayout() {
    mIsLayoutDirty = true;
    super.requestLayout();
  }

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    super.onLayout(changed, l, t, r, b);
    mIsLayoutDirty = false;

    // Calling this with the present values causes it to re-clam them
    scrollTo(getScrollX(), getScrollY());
  }
  
  public boolean isLayoutDirty() {
    return mIsLayoutDirty;
  }

  /* ************************************************************************
   * Edited by Kenrick. Simple smooth scroll!
   */

  /**
   * Like {@link android.view.View#scrollBy}, but scroll smoothly instead of immediately.
   *
   * @param dx the number of pixels to scroll by on the X axis
   * @param dy the number of pixels to scroll by on the Y axis
   */
  public final void smoothScrollBy(int dx, int dy) {
    mScroller.startScroll(getScrollX(), getScrollY(), dx, dy);
    invalidate();
    mIsLayoutDirty = true;
  }

  /**
   * Like {@link #scrollTo}, but scroll smoothly instead of immediately.
   *
   * @param x the position where to scroll on the X axis
   * @param y the position where to scroll on the Y axis
   */
  public final void smoothScrollTo(int x, int y) {
    smoothScrollBy(x - getScrollX(), y - getScrollY());
  }

}

Java Source Code List

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