[转]Android开发：Parallax效果的ScrollerView，改编自ParallaxListView

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：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163

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：

?

1 2 3

mImageView = (ImageView) findViewById(R.id.headview);         scrollView = (ParallaxScollView) findViewById(R.id.parallax_scroll_view);         scrollView.setParallaxImageView(mImageView);

大功告成，也可以在ScrollerView上实现炫酷的Parallax效果了