源码简介：仿QQ空间可拉伸头部，经典好用，值得一试。
源码效果：
源码片段：
package com.example.tz_demo_6_27;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.Transformation;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
import android.widget.ListView;
public class ParallaxListView extends ListView {
private ImageView mImageView;
// 初始高度
private int mImageViewHeight = -1;
// ***拉伸高度
private int mDrawableMaxHeight = -1;
public ParallaxListView(Context context, AttributeSet attrs) {
super(context, attrs);
}
/**
* 设置拉伸的图片
*
* @param imageView
*/
public void setParallaxImageView(ImageView imageView) {
this.mImageView = imageView;
// 设置伸缩类型 -- 居中填充
this.mImageView.setScaleType(ScaleType.CENTER_CROP);
}
/**
* 初始化图片加载进来最初的高度
*
*/
public void setViewBounds() {
if (mImageViewHeight == -1) {
mImageViewHeight = mImageView.getHeight();
if (mImageViewHeight < 0) {
mImageViewHeight = getContext().getResources()
.getDimensionPixelSize(R.dimen.size_default);
}
}
}
/**
* 滑动过头的时候回调
*/
@Override
protected boolean overScrollBy(int deltaX, int deltaY, int scrollX,
int scrollY, int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {
// 控制ImageView的高度不断增加
boolean isCollapse = resizeOverScrollBy(deltaY);
// return true:下拉到边界的某个地方的时候不再往下拉
return isCollapse ? true : super.overScrollBy(deltaX, deltaY, scrollX,
scrollY, scrollRangeX, scrollRangeY, maxOverScrollX,
maxOverScrollY, isTouchEvent);
}
/**
* 监听ListView滑动
*/
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
// 获得ImageView的父控件
View header = (View) mImageView.getParent();
if (header.getTop() < 0 && mImageView.getHeight() > mImageViewHeight) {
// 减小ImageView的高度 -- 不能超过图片最原始的高度
mImageView.getLayoutParams().height = Math.max(
mImageView.getHeight() + header.getTop(), mImageViewHeight);
// ImageView所在的容器的高度也要变化：getTop--->0
header.layout(header.getLeft(), 0, header.getRight(),
header.getHeight());
mImageView.requestLayout();
}
}
private boolean resizeOverScrollBy(int deltaY) {
// 下拉的过程当中，不断地控制ImageView的高度
/**
* deltaY:是在超出滑动的时候每毫秒滑动的距离 -- 增量 (-往下拉过渡，+往上拉过渡) 大小：根据用户滑动的速度决定 一般滑动的速度
* -50~50
*/
if (deltaY < 0) {
// 下拉过渡，不断增加ImageView的高度，deltay是负数，增加高度就是减去
mImageView.getLayoutParams().height = mImageView.getHeight()
- deltaY;
// View重新调整宽高
mImageView.requestLayout(); // onMeasure-->onLayout
} else {
// 上拉过渡，不断减小ImageView的高度，deltay是正数，减小高度还是减去
if (mImageView.getHeight()>mImageViewHeight) {
mImageView.getLayoutParams().height = Math.max(
mImageView.getHeight() - deltaY, mImageViewHeight);
// View重新调整宽高
mImageView.requestLayout(); // onMeasure-->onLayout
}
}
return false;
}
/**
* 监听触摸 -- 松开手
*/
@Override
public boolean onTouchEvent(MotionEvent ev) {
// 判断
if (ev.getAction()== MotionEvent.ACTION_UP) {
// 开启回弹的动画
ResetAnimation animation=new ResetAnimation(mImageView,mImageViewHeight);
animation.setDuration(300);
mImageView.startAnimation(animation);
}
return super.onTouchEvent(ev);
}
public class ResetAnimation extends Animation{
private ImageView mView;
private int targetHeight;
// 动画执行前的高度
private int originalHeight;
// 高度差
private int extraHeight;
public ResetAnimation(ImageView mImageView,int targetHeight) {
this.mView=mImageView;
this.targetHeight=targetHeight;
this.originalHeight=mImageView.getHeight();
extraHeight=originalHeight-targetHeight;
}
/**
* 动画不断地执行的时候会回调该方法
* interpolatedTime：范围是0
* 0ms-------------->300ms
* 当前的图片高度--->动画执行之前的高度-高度差*interpolatedTime
* extraHeight------>0
*/
@Override
protected void applyTransformation(float interpolatedTime,
Transformation t) {
mView.getLayoutParams().height=(int) (originalHeight-extraHeight*interpolatedTime);
mView.requestLayout();
super.applyTransformation(interpolatedTime, t);
}
}
}
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