https://github.com/nirhart/ParallaxScroll这个gethub上的地址
本文转自http://www.2cto.com/kf/201502/376970.html
最近在项目中，有用到一个仿照Path的Parallax效果，苦苦搜寻，在github上面，有一个类似的效果，不过是listview的，加一个顶部的headerView，实现了该效果，不过我需要的是ScrollerView的，于是对该代码进行的修改，实现了ScrollerView下面的Parallax效果，效果图参照如下：
在阅读下面代码前，可以先查看下Github上面的源码
我对于原先的代码进行了大量的删减，只实现了我需要的效果，看起来简单易懂，最怕那种绕来绕去的代码了，看核心的实现代码：
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public class ParallaxScollView extends ScrollView implements OnScrollListener {
public final static double NO_ZOOM = 1;
public final static double ZOOM_X2 = 2;
private ImageView mImageView;
private int mImageViewHeight = -1;
private int mDefaultImageViewHeight = 0;
private int originImageViewHeight;
private int mMaxHeight;
private interface OnOverScrollByListener {
public boolean overScrollBy(int deltaX, int deltaY, int scrollX,
int scrollY, int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent);
}
private interface OnTouchEventListener {
public void onTouchEvent(MotionEvent ev);
}
public ParallaxScollView(Context context, AttributeSet attrs,
int defStyle) {
super(context, attrs, defStyle);
init(context);
}
public ParallaxScollView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public ParallaxScollView(Context context) {
super(context);
init(context);
}
public void init(Context context) {
mDefaultImageViewHeight = context.getResources().getDimensionPixelSize(R.dimen.size_default_height);
originImageViewHeight = context.getResources().getDimensionPixelSize(R.dimen.size_default_height);
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
@Override
protected boolean overScrollBy(int deltaX, int deltaY, int scrollX,
int scrollY, int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {
boolean isCollapseAnimation = false;
isCollapseAnimation = scrollByListener.overScrollBy(deltaX, deltaY,
scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX,
maxOverScrollY, isTouchEvent)
|| isCollapseAnimation;
/*return isCollapseAnimation ? true : super.overScrollBy(deltaX, deltaY,
scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX,
0, isTouchEvent);*/
return false;
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
View firstView = (View) mImageView.getParent();
// firstView.getTop < getPaddingTop means mImageView will be covered by top padding,
// so we can layout it to make it shorter
if (firstView.getTop() < getPaddingTop() && mImageView.getHeight() > mImageViewHeight) {
mImageView.getLayoutParams().height = Math.max(mImageView.getHeight() - (getPaddingTop() - firstView.getTop()), mImageViewHeight);
// to set the firstView.mTop to 0,
// maybe use View.setTop() is more easy, but it just support from Android 3.0 (API 11)
firstView.layout(firstView.getLeft(), 0, firstView.getRight(), firstView.getHeight());
mImageView.requestLayout();
}
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
touchListener.onTouchEvent(ev);
return super.onTouchEvent(ev);
}
public void setParallaxImageView(ImageView iv) {
mImageView = iv;
mImageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
}
public void setViewsBounds(double zoomRatio) {
if (mImageViewHeight == -1) {
mImageViewHeight = mImageView.getHeight();
if (mImageViewHeight <= 0) {
mImageViewHeight = mDefaultImageViewHeight;
}
double ratio = ((double) mImageView.getDrawable().getIntrinsicWidth()) / ((double) mImageView.getWidth());
}
}
private OnOverScrollByListener scrollByListener = new OnOverScrollByListener() {
@Override
public boolean overScrollBy(int deltaX, int deltaY, int scrollX,
int scrollY, int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {
if (isTouchEvent) {
if (true) {
mImageView.getLayoutParams().height = mImageView.getHeight() - deltaY / 2;
mImageView.requestLayout();
}
}
return false;
}
};
private OnTouchEventListener touchListener = new OnTouchEventListener() {
@Override
public void onTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_UP) {
if (mImageViewHeight - 1 < mImageView.getHeight()) {
ResetAnimimation animation = new ResetAnimimation(
mImageView, mImageViewHeight);
animation.setDuration(300);
mImageView.startAnimation(animation);
}
}
}
};
public class ResetAnimimation extends Animation {
int targetHeight;
int originalHeight;
int extraHeight;
View mView;
protected ResetAnimimation(View view, int targetHeight) {
this.mView = view;
this.targetHeight = targetHeight;
originalHeight = view.getHeight();
extraHeight = this.originalHeight - originImageViewHeight;
Log.i(debug, target heitht + targetHeight + original height + originalHeight + extraheight + extraHeight);
}
@Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
int newHeight;
newHeight = (int) (originImageViewHeight + extraHeight * (1 - interpolatedTime));
mView.getLayoutParams().height = newHeight;
mView.requestLayout();
}
}
} |
第二布：在xml中，引用该ParallaxScollView：
最后一步，在activity中，引用ParallaxScrollerView，并且设置imageview：
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mImageView = (ImageView) findViewById(R.id.headview); scrollView = (ParallaxScollView) findViewById(R.id.parallax_scroll_view);
scrollView.setParallaxImageView(mImageView);
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大功告成，也可以在ScrollerView上实现炫酷的Parallax效果了