本文介绍如何通过重写父控件的触摸事件来实现仿支付宝首页的下拉刷新效果，主要涉及ListView和ScrollView的事件拦截与处理，以实现下拉事件从顶部响应的功能。
下拉刷新的功能，想必很多人闭着眼睛能写出来（仅限于功能实现）。而支付宝的首页下拉刷新和普通的下拉刷新有一点不一样。一般的下拉刷新是从刷新控件开始的位置向下，这个区域内响应手势事件，支付宝的是从ActionBar下面的view开始响应的。如图区域：
显然常规的下拉刷新的控件是需要改动才能实现这个功能的。怎么改动呢？既然是下拉事件的区域发生的变化，那就是手势的拦截咯。最容易想到的就是在下拉刷新控件的父控件中进行事件拦截，然后重写touch事件，在ACTION_MOVE中去处理，或者叫做指派刷新控件做相应的变化（对应刷新控件的ACTION_MOVE事件）。好了，现在捋一下思路：
1.重写父控件的onInterceptTouchEvent方法，对滑动或者点击事件区别处理；是滑动就拦截，反之不拦截。
2.重写父控件的onTouchEvent方法，处理touch事件，ACTION_MOVE的事件对应刷新控件的ACTION_MOVE事件（交给刷新控件做）。
那就开始干吧！今天就模拟一下这个场景下拉刷新，写了一个demo，分别重写ListView和ScrollView，这两个其实是一样的，仅有一点区别。
1.重写ListView：
public class RefreshListView extends ListView {
/**
* 1.如果listview滑出屏幕的距离为0时，下拉时header下面的view慢慢显示出来
* 2.如果listview滑出屏幕的距离不为0时，执行其自身的滑动
* 3.如果正在向下显示header下面的view时，上滑view也向上隐藏，隐藏完继续listview自身的滑动
*/
private RelativeLayout mHeader;
private View mRefreshView;
private int mTouchSlop;
private int mRefreshViewHeight, mHeaderHeight, mTargetHeight;
private float mLastX, mLastY;
private boolean mIsRefresh, mIsDrag;
private ViewGroup.LayoutParams params;
private BackRunnable mRunnable;
private RefreshListener mListener;
public interface RefreshListener {
void start();
}
public RefreshListView(Context context) {
this(context, null);
}
public RefreshListView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public RefreshListView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
}
public void setRefreshListener(RefreshListener listener) {
mListener = listener;
}
public void initHeader(View header, View refreshHeader) {
mHeader = new RelativeLayout(getContext());
if (refreshHeader == null) {
LinearLayout linearLayout = new LinearLayout(getContext());
linearLayout.setOrientation(LinearLayout.VERTICAL);
linearLayout.setGravity(Gravity.CENTER);
linearLayout.setPadding(0, 30, 0, 10);
linearLayout.addView(new ProgressBar(getContext()));
mRefreshView = new ProgressBar(getContext());
} else {
mRefreshView = refreshHeader;
}
RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
lp.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
lp.addRule(RelativeLayout.CENTER_HORIZONTAL);
mHeader.addView(mRefreshView, lp);
if (header != null) {
lp = new RelativeLayout.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
mHeader.addView(header, lp);
}
addHeaderView(mHeader);
}
private boolean isValidDrag(MotionEvent ev) {
if (ev == null) {
return false;
}
return Math.abs(mLastX - ev.getX()) < Math.abs(mLastY - ev.getY())
&& Math.abs(mLastY - ev.getY()) > mTouchSlop;
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if (mRefreshView == null || mHeader == null) {
return super.onInterceptTouchEvent(ev);
}
int action = ev.getActionMasked();
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastX = ev.getX();
mLastY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
if (isValidDrag(ev)) {
return true;
}
break;
}
return super.onInterceptTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
//需要处理header view里面的显示的话，要设置param，否则给父类自己来处理
if (mRefreshView == null || mHeader == null) {
return super.onTouchEvent(ev);
}
if (mRefreshViewHeight <= 0) {
mHeaderHeight = mHeader.getMeasuredHeight();
mRefreshViewHeight = mRefreshView.getMeasuredHeight();
mTargetHeight = mHeaderHeight + mRefreshViewHeight;
}
int action = ev.getActionMasked();
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastX = ev.getX();
mLastY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
if (mHeader.getTop() < 0 || mIsRefresh) {
break;
}
if (!mIsDrag && isValidDrag(ev)) {
mIsDrag = true;
}
if (mIsDrag) {
if (ev.getY() - mLastY > 0 && !mIsRefresh) {
moveLayout(ev.getY() - mLastY);
return true;
}
}
break;
case MotionEvent.ACTION_UP:
if (params == null) {
params = mHeader.getLayoutParams();
}
if (params.height <= mHeaderHeight) {
break;
}
mIsRefresh = params.height >= mTargetHeight;
if (!mIsRefresh) {
completeRefresh();
} else {
if (mListener != null) {
mListener.start();
}
}
break;
}
return super.onTouchEvent(ev);
}
public void completeRefresh() {
if (mRunnable == null) {
mRunnable = new BackRunnable(500);
}
mRunnable.start();
}
private void moveLayout(float y) {
params = mHeader.getLayoutParams();
float changeHeight = mHeaderHeight + 0.2f * y;
if (changeHeight >= mTargetHeight && params.height == mTargetHeight) {
return;
}
if (changeHeight > mTargetHeight) {
params.height = mTargetHeight;
} else {
params.height = (int) changeHeight;
}
mHeader.requestLayout();
}
private class BackRunnable implements Runnable {
private int mDuration;
private boolean mIsFinish;
private long mStartTime;
private Interpolator mInterpolator = new Interpolator() {
@Override
public float getInterpolation(float input) {
return (float) Math.pow(input, 5);
}
};
public BackRunnable(int duration) {
mDuration = duration;
mIsFinish = true;
}
public void start() {
if (mIsFinish) {
mStartTime = System.currentTimeMillis();
mIsFinish = false;
post(this);
}
}
public void cancel() {
this.mIsFinish = true;
}
@Override
public void run() {
if (!mIsFinish) {
long delta = System.currentTimeMillis() - mStartTime;
if (delta > mDuration) {
delta = mDuration;
}
params.height = (int) (mHeaderHeight + mRefreshViewHeight * mInterpolator.getInterpolation(1f - delta * 1f / mDuration));
mHeader.requestLayout();
if (params.height == mHeaderHeight) {
this.mIsFinish = true;
mIsRefresh = false;
return;
}
post(this);
}
}
}
}import android.content.Context; import android.util.AttributeSet; import android.view.Gravity; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.animation.Interpolator; import android.widget.LinearLayout; import android.widget.ListView; import android.widget.ProgressBar; import android.widget.RelativeLayout; /** * Created by wh on 17/7/24. */ public class RefreshListView extends ListView { /** * 1.如果listview滑出屏幕的距离为0时，下拉时header下面的view慢慢显示出来 * 2.如果listview滑出屏幕的距离不为0时，执行其自身的滑动 * 3.如果正在向下显示header下面的view时，上滑view也向上隐藏，隐藏完继续listview自身的滑动 */ private RelativeLayout mHeader; private View mRefreshView; private int mTouchSlop; private int mRefreshViewHeight, mHeaderHeight, mTargetHeight; private float mLastX, mLastY; private boolean mIsRefresh, mIsDrag; private ViewGroup.LayoutParams params; private BackRunnable mRunnable; private RefreshListener mListener; public interface RefreshListener { void start(); } public RefreshListView(Context context) { this(context, null); } public RefreshListView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public RefreshListView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop(); } public void setRefreshListener(RefreshListener listener) { mListener = listener; } public void initHeader(View header, View refreshHeader) { mHeader = new RelativeLayout(getContext()); if (refreshHeader == null) { LinearLayout linearLayout = new LinearLayout(getContext()); linearLayout.setOrientation(LinearLayout.VERTICAL); linearLayout.setGravity(Gravity.CENTER); linearLayout.setPadding(0, 30, 0, 10); linearLayout.addView(new ProgressBar(getContext())); mRefreshView = new ProgressBar(getContext()); } else { mRefreshView = refreshHeader; } RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams( ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT); lp.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM); lp.addRule(RelativeLayout.CENTER_HORIZONTAL); mHeader.addView(mRefreshView, lp); if (header != null) { lp = new RelativeLayout.LayoutParams( ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT); mHeader.addView(header, lp); } addHeaderView(mHeader); } private boolean isValidDrag(MotionEvent ev) { if (ev == null) { return false; } return Math.abs(mLastX - ev.getX()) < Math.abs(mLastY - ev.getY()) && Math.abs(mLastY - ev.getY()) > mTouchSlop; } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { if (mRefreshView == null || mHeader == null) { return super.onInterceptTouchEvent(ev); } int action = ev.getActionMasked(); switch (action) { case MotionEvent.ACTION_DOWN: mLastX = ev.getX(); mLastY = ev.getY(); break; case MotionEvent.ACTION_MOVE: if (isValidDrag(ev)) { return true; } break; } return super.onInterceptTouchEvent(ev); } @Override public boolean onTouchEvent(MotionEvent ev) { //需要处理header view里面的显示的话，要设置param，否则给父类自己来处理 if (mRefreshView == null || mHeader == null) { return super.onTouchEvent(ev); } if (mRefreshViewHeight <= 0) { mHeaderHeight = mHeader.getMeasuredHeight(); mRefreshViewHeight = mRefreshView.getMeasuredHeight(); mTargetHeight = mHeaderHeight + mRefreshViewHeight; } int action = ev.getActionMasked(); switch (action) { case MotionEvent.ACTION_DOWN: mLastX = ev.getX(); mLastY = ev.getY(); break; case MotionEvent.ACTION_MOVE: if (mHeader.getTop() < 0 || mIsRefresh) { break; } if (!mIsDrag && isValidDrag(ev)) { mIsDrag = true; } if (mIsDrag) { if (ev.getY() - mLastY > 0 && !mIsRefresh) { moveLayout(ev.getY() - mLastY); return true; } } break; case MotionEvent.ACTION_UP: if (params == null) { params = mHeader.getLayoutParams(); } if (params.height <= mHeaderHeight) { break; } mIsRefresh = params.height >= mTargetHeight; if (!mIsRefresh) { completeRefresh(); } else { if (mListener != null) { mListener.start(); } } break; } return super.onTouchEvent(ev); } public void completeRefresh() { if (mRunnable == null) { mRunnable = new BackRunnable(500); } mRunnable.start(); } private void moveLayout(float y) { params = mHeader.getLayoutParams(); float changeHeight = mHeaderHeight + 0.2f * y; if (changeHeight >= mTargetHeight && params.height == mTargetHeight) { return; } if (changeHeight > mTargetHeight) { params.height = mTargetHeight; } else { params.height = (int) changeHeight; } mHeader.requestLayout(); } private class BackRunnable implements Runnable { private int mDuration; private boolean mIsFinish; private long mStartTime; private Interpolator mInterpolator = new Interpolator() { @Override public float getInterpolation(float input) { return (float) Math.pow(input, 5); } }; public BackRunnable(int duration) { mDuration = duration; mIsFinish = true; } public void start() { if (mIsFinish) { mStartTime = System.currentTimeMillis(); mIsFinish = false; post(this); } } public void cancel() { this.mIsFinish = true; } @Override public void run() { if (!mIsFinish) { long delta = System.currentTimeMillis() - mStartTime; if (delta > mDuration) { delta = mDuration; } params.height = (int) (mHeaderHeight + mRefreshViewHeight * mInterpolator.getInterpolation(1f - delta * 1f / mDuration)); mHeader.requestLayout(); if (params.height == mHeaderHeight) { this.mIsFinish = true; mIsRefresh = false; return; } post(this); } } } }
2.重写ScrollView：
public class RefreshScrollView extends ScrollView {
/**
* 1.如果listview滑出屏幕的距离为0时，下拉时header下面的view慢慢显示出来
* 2.如果listview滑出屏幕的距离不为0时，执行其自身的滑动
* 3.如果正在向下显示header下面的view时，上滑view也向上隐藏，隐藏完继续listview自身的滑动
*/
private RelativeLayout mHeader;
private View mRefreshView;
private LinearLayout mContainer;
private int mTouchSlop;
private int mRefreshViewHeight, mHeaderHeight, mTargetHeight;
private float mLastX, mLastY;
private boolean mIsRefresh, mIsDrag;
private ViewGroup.LayoutParams params;
private BackRunnable mRunnable;
private RefreshListener mListener;
public interface RefreshListener {
void start();
}
public RefreshScrollView(Context context) {
this(context, null);
}
public RefreshScrollView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public RefreshScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
}
@Override
protected void onFinishInflate() {
super.onFinishInflate();
int count = getChildCount();
if (count != 1 || !(getChildAt(0) instanceof LinearLayout)) {
throw new IllegalArgumentException("scrollview must be one LinearLayout");
}
mContainer = (LinearLayout) getChildAt(0);
}
public void setRefreshListener(RefreshListener listener) {
mListener = listener;
}
public void initHeader(View header, View refreshHeader) {
mHeader = new RelativeLayout(getContext());
if (refreshHeader == null) {
LinearLayout linearLayout = new LinearLayout(getContext());
linearLayout.setOrientation(LinearLayout.VERTICAL);
linearLayout.setGravity(Gravity.CENTER);
linearLayout.setPadding(0, 30, 0, 10);
linearLayout.addView(new ProgressBar(getContext()));
mRefreshView = new ProgressBar(getContext());
} else {
mRefreshView = refreshHeader;
}
RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
lp.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
lp.addRule(RelativeLayout.CENTER_HORIZONTAL);
mHeader.addView(mRefreshView, lp);
if (header != null) {
lp = new RelativeLayout.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
mHeader.addView(header, lp);
}
mContainer.addView(mHeader, 0);
}
private boolean isValidDrag(MotionEvent ev) {
if (ev == null) {
return false;
}
return Math.abs(mLastX - ev.getX()) < Math.abs(mLastY - ev.getY())
&& Math.abs(mLastY - ev.getY()) > mTouchSlop;
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if (mRefreshView == null || mHeader == null || getScrollY() > 0) {
return super.onInterceptTouchEvent(ev);
}
int action = ev.getActionMasked();
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastX = ev.getX();
mLastY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
if (isValidDrag(ev)) {
return true;
}
break;
}
return super.onInterceptTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
//需要处理header view里面的显示的话，要设置param，否则给父类自己来处理
if (mRefreshView == null || mHeader == null || getScrollY() > 0) {
return super.onTouchEvent(ev);
}
if (mRefreshViewHeight <= 0) {
mHeaderHeight = mHeader.getMeasuredHeight();
mRefreshViewHeight = mRefreshView.getMeasuredHeight();
mTargetHeight = mHeaderHeight + mRefreshViewHeight;
}
int action = ev.getActionMasked();
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastX = ev.getX();
mLastY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
if (getScrollY() > 0 || mIsRefresh) {
break;
}
if (!mIsDrag && isValidDrag(ev)) {
mIsDrag = true;
}
if (mIsDrag) {
if (ev.getY() - mLastY > 0 && !mIsRefresh) {
moveLayout(ev.getY() - mLastY);
return true;
}
}
break;
case MotionEvent.ACTION_UP:
mIsDrag = false;
if (params == null) {
params = mHeader.getLayoutParams();
}
if (params.height <= mHeaderHeight) {
break;
}
mIsRefresh = params.height >= mTargetHeight;
if (!mIsRefresh) {
completeRefresh();
} else {
if (mListener != null) {
mListener.start();
}
}
break;
}
return super.onTouchEvent(ev);
}
public void completeRefresh() {
if (mRunnable == null) {
mRunnable = new BackRunnable(500);
}
mRunnable.start();
}
private void moveLayout(float y) {
params = mHeader.getLayoutParams();
float changeHeight = mHeaderHeight + 0.2f * y;
if (changeHeight >= mTargetHeight && params.height == mTargetHeight) {
return;
}
if (changeHeight > mTargetHeight) {
params.height = mTargetHeight;
} else {
params.height = (int) changeHeight;
}
mHeader.requestLayout();
}
private class BackRunnable implements Runnable {
private int mDuration;
private boolean mIsFinish;
private long mStartTime;
private Interpolator mInterpolator = new Interpolator() {
@Override
public float getInterpolation(float input) {
return (float) Math.pow(input, 5);
}
};
public BackRunnable(int duration) {
mDuration = duration;
mIsFinish = true;
}
public void start() {
if (mIsFinish) {
mStartTime = System.currentTimeMillis();
mIsFinish = false;
post(this);
}
}
public void cancel() {
this.mIsFinish = true;
}
@Override
public void run() {
if (!mIsFinish) {
long delta = System.currentTimeMillis() - mStartTime;
if (delta > mDuration) {
delta = mDuration;
}
params.height = (int) (mHeaderHeight + mRefreshViewHeight * mInterpolator.getInterpolation(1f - delta * 1f / mDuration));
mHeader.requestLayout();
if (params.height == mHeaderHeight) {
this.mIsFinish = true;
mIsRefresh = false;
return;
}
post(this);
}
}
}
}
import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.Gravity; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.animation.Interpolator; import android.widget.LinearLayout; import android.widget.ListView; import android.widget.ProgressBar; import android.widget.RelativeLayout; import android.widget.ScrollView; /** * Created by wh on 17/7/24. */ public class RefreshScrollView extends ScrollView { private RelativeLayout mHeader; private View mRefreshView; private LinearLayout mContainer; private int mTouchSlop; private int mRefreshViewHeight, mHeaderHeight, mTargetHeight; private float mLastX, mLastY; private boolean mIsRefresh, mIsDrag; private ViewGroup.LayoutParams params; private BackRunnable mRunnable; private RefreshListener mListener; public interface RefreshListener { void start(); } public RefreshScrollView(Context context) { this(context, null); } public RefreshScrollView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public RefreshScrollView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop(); } @Override protected void onFinishInflate() { super.onFinishInflate(); int count = getChildCount(); if (count != 1 || !(getChildAt(0) instanceof LinearLayout)) { throw new IllegalArgumentException("scrollview must be one LinearLayout"); } mContainer = (LinearLayout) getChildAt(0); } public void setRefreshListener(RefreshListener listener) { mListener = listener; } public void initHeader(View header, View refreshHeader) { mHeader = new RelativeLayout(getContext()); if (refreshHeader == null) { LinearLayout linearLayout = new LinearLayout(getContext()); linearLayout.setOrientation(LinearLayout.VERTICAL); linearLayout.setGravity(Gravity.CENTER); linearLayout.setPadding(0, 30, 0, 10); linearLayout.addView(new ProgressBar(getContext())); mRefreshView = new ProgressBar(getContext()); } else { mRefreshView = refreshHeader; } RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams( ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT); lp.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM); lp.addRule(RelativeLayout.CENTER_HORIZONTAL); mHeader.addView(mRefreshView, lp); if (header != null) { lp = new RelativeLayout.LayoutParams( ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT); mHeader.addView(header, lp); } mContainer.addView(mHeader, 0); } private boolean isValidDrag(MotionEvent ev) { if (ev == null) { return false; } return Math.abs(mLastX - ev.getX()) < Math.abs(mLastY - ev.getY()) && Math.abs(mLastY - ev.getY()) > mTouchSlop; } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { if (mRefreshView == null || mHeader == null || getScrollY() > 0) { return super.onInterceptTouchEvent(ev); } int action = ev.getActionMasked(); switch (action) { case MotionEvent.ACTION_DOWN: mLastX = ev.getX(); mLastY = ev.getY(); break; case MotionEvent.ACTION_MOVE: if (isValidDrag(ev)) { return true; } break; } return super.onInterceptTouchEvent(ev); } @Override public boolean onTouchEvent(MotionEvent ev) { //需要处理header view里面的显示的话，要设置param，否则给父类自己来处理 if (mRefreshView == null || mHeader == null || getScrollY() > 0) { return super.onTouchEvent(ev); } if (mRefreshViewHeight <= 0) { mHeaderHeight = mHeader.getMeasuredHeight(); mRefreshViewHeight = mRefreshView.getMeasuredHeight(); mTargetHeight = mHeaderHeight + mRefreshViewHeight; } int action = ev.getActionMasked(); switch (action) { case MotionEvent.ACTION_DOWN: mLastX = ev.getX(); mLastY = ev.getY(); break; case MotionEvent.ACTION_MOVE: if (getScrollY() > 0 || mIsRefresh) { break; } if (!mIsDrag && isValidDrag(ev)) { mIsDrag = true; } if (mIsDrag) { if (ev.getY() - mLastY > 0 && !mIsRefresh) { moveLayout(ev.getY() - mLastY); return true; } } break; case MotionEvent.ACTION_UP: mIsDrag = false; if (params == null) { params = mHeader.getLayoutParams(); } if (params.height <= mHeaderHeight) { break; } mIsRefresh = params.height >= mTargetHeight; if (!mIsRefresh) { completeRefresh(); } else { if (mListener != null) { mListener.start(); } } break; } return super.onTouchEvent(ev); } public void completeRefresh() { if (mRunnable == null) { mRunnable = new BackRunnable(500); } mRunnable.start(); } private void moveLayout(float y) { params = mHeader.getLayoutParams(); float changeHeight = mHeaderHeight + 0.2f * y; if (changeHeight >= mTargetHeight && params.height == mTargetHeight) { return; } if (changeHeight > mTargetHeight) { params.height = mTargetHeight; } else { params.height = (int) changeHeight; } mHeader.requestLayout(); } private class BackRunnable implements Runnable { private int mDuration; private boolean mIsFinish; private long mStartTime; private Interpolator mInterpolator = new Interpolator() { @Override public float getInterpolation(float input) { return (float) Math.pow(input, 5); } }; public BackRunnable(int duration) { mDuration = duration; mIsFinish = true; } public void start() { if (mIsFinish) { mStartTime = System.currentTimeMillis(); mIsFinish = false; post(this); } } public void cancel() { this.mIsFinish = true; } @Override public void run() { if (!mIsFinish) { long delta = System.currentTimeMillis() - mStartTime; if (delta > mDuration) { delta = mDuration; } params.height = (int) (mHeaderHeight + mRefreshViewHeight * mInterpolator.getInterpolation(1f - delta * 1f / mDuration)); mHeader.requestLayout(); if (params.height == mHeaderHeight) { this.mIsFinish = true; mIsRefresh = false; return; } post(this); } } } }
上面就是基本的demo代码了。这个和其他不一样的地方是：
1.重写ListView的用了header，header是一个相对布局，上面一层是要显示的view，比如一个九宫格的功能菜单选项；下面一层是下拉刷新的view；
2.onTouchEvent中，下拉的过程中刷新控件慢慢的从header中露出来，知道up的时候，要么回弹要么回调下拉刷新的接口；
3.重写Scrollview和listview是一个思路，只不过是把这个header放到了scrollview的子view的第一个位置；
4.这是一个简易的刷新，主要目的是实现这种不是从刷新控件顶部响应事件的场景，刷新的view完全可以换成自己的；
5.这个有个大问题是，没有扩展性，下拉刷新库要提供的move事件的移动或者动画的接口。
具体测试的代码就不上了，有错误的地方，还请指正！
另外，一个同事用了更简单的方法，利用CoordinatorLayout的Behavior来处理，也就是重写Behavior，让Behavior来拦截和处理下拉的事件，不清楚的可以学习Behavior的自定义。
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