自定义ViewGroup学习（LinearLayout的布局方式，可以滚动和嵌套）
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自定义ViewGroup学习（LinearLayout的布局方式，可以滚动和嵌套）
首先先看效果图
自定义ViewGroup，必须重写onLayout()方法
当然，还需要onMeasure()
下边就是最基本的
public class MyViewGroup extends ViewGroup
public MyViewGroup(Context context, AttributeSet attrs)
super(context, attrs);
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b)
//摆放测量后子类位置
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
//测量
首先来看测量onMeasure
要自定义一个类似LinearLayout的容器，先只看水平方向上
容器的width=所有子View的宽的和(先不考虑padding，margin)
容器的height=所有View中最高的高度
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
childWidth = 0;//容器的宽高
childHeight = 0;
int childCount = getChildCount();
for (int i = 0; i < childCount; i++)
View child = getChildAt(i);
if (child.getVisibility() != View.GONE)
measureChild(child, widthMeasureSpec,
heightMeasureSpec);
childWidth += child.getMeasuredWidth();
childHeight = Math.max(childHeight, child.getMeasuredHeight());
setMeasuredDimension(resolveSize(childWidth, widthMeasureSpec), resolveSize(childHeight, heightMeasureSpec));
测量完，在onLayout中摆放
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b)
int childLeft = 0;
int childTop = 0;
final int height = b - t;
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++)
View child = getChildAt(i);
if (child.getVisibility() != View.GONE)
final int childWidth = child.getMeasuredWidth();
final int childHeight = child.getMeasuredHeight();
child.layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight);
childLeft += childWidth;
childTop = 0;
这最基本的ViewGroup就完成了
接下来加入padding和margin以及gravity，orientation属性
首先attrs中添加orientation和gravity两个自定义属性
<declare-styleable name="MyViewGroup">
<attr name="orientation">
<enum name="horizontal" value="0" />
<enum name="vertical" value="1" />
</attr>
<attr name="gravity">
<flag name="top" value="0x30" />
<flag name="bottom" value="0x50" />
<flag name="left" value="0x03" />
<flag name="right" value="0x05" />
<flag name="center_vertical" value="0x10" />
<flag name="fill_vertical" value="0x70" />
<flag name="center_horizontal" value="0x01" />
<flag name="fill_horizontal" value="0x07" />
<flag name="center" value="0x11" />
<flag name="fill" value="0x77" />
<flag name="clip_vertical" value="0x80" />
<flag name="clip_horizontal" value="0x08" />
<flag name="start" value="0x00800003" />
<flag name="end" value="0x00800005" />
</attr>
</declare-styleable>@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mPaddingTop = getPaddingTop();
mPaddingLeft = getPaddingLeft();
mPaddingRight = getPaddingRight();
mPaddingBottom = getPaddingBottom();
childWidth = 0;//所有child占用的总宽高
childHeight = 0;
int childCount = getChildCount();
for (int i = 0; i < childCount; i++)
View child = getChildAt(i);
if (child.getVisibility() != View.GONE)
//为了添加child的margin属性值（直接强转成MarginLayoutParams会报错，需要重写，或者继承MarginLayoutParams,重写它的generateLayoutParams方法）
LayoutParams lp = (LayoutParams) child.getLayoutParams();
//▲变化1：将measureChild改为measureChildWithMargin
measureChildWithMargins(child, widthMeasureSpec, 0,
heightMeasureSpec, 0);
/*原来： measureChild(child, widthMeasureSpec,
heightMeasureSpec);*/
if (mOrientation == HORIZONTAL)
childWidth += child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
childHeight = Math.max(childHeight, child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin);
else
childWidth = Math.max(childWidth, child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin);
childHeight += child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
childWidth += mPaddingLeft + mPaddingRight;
childHeight += mPaddingTop + mPaddingBottom;
setMeasuredDimension(resolveSize(childWidth, widthMeasureSpec), resolveSize(childHeight, heightMeasureSpec));
child.getLayoutParams()直接强转成MarginLayoutParams会报错，需要重写，或者继承MarginLayoutParams,重写它的generateLayoutParams方法
@Override
protected android.view.ViewGroup.LayoutParams generateDefaultLayoutParams()
return new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.MATCH_PARENT);
@Override
public android.view.ViewGroup.LayoutParams generateLayoutParams(
AttributeSet attrs)
return new LayoutParams(getContext(), attrs);
@Override
protected android.view.ViewGroup.LayoutParams generateLayoutParams(
android.view.ViewGroup.LayoutParams p)
return new LayoutParams(p);
public static class LayoutParams extends MarginLayoutParams
public int gravity = -1;
public LayoutParams(Context c, AttributeSet attrs)
super(c, attrs);
TypedArray ta = c.obtainStyledAttributes(attrs,
R.styleable.MyViewGroup);
gravity = ta.getInt(R.styleable.MyViewGroup_gravity, -1);
ta.recycle();
public LayoutParams(int width, int height)
this(width, height, -1);
public LayoutParams(int width, int height, int gravity)
super(width, height);
this.gravity = gravity;
public LayoutParams(android.view.ViewGroup.LayoutParams source)
super(source);
public LayoutParams(MarginLayoutParams source)
super(source);
onLayout中区分方向，区分gravity重心，并添加padding和margin值来摆放view
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b)
if (mOrientation == VERTICAL)
layoutVertical(l, t, r, b);
else
layoutHorizontal(l, t, r, b);
//摆放好后getParent()才有值
if (getParent() instanceof MyViewGroup)
sameDirection = ((MyViewGroup) getParent()).getOrientation() == getOrientation();
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
void layoutHorizontal(int l, int t, int r, int b)
int childLeft = mPaddingLeft;
int childTop = mPaddingTop;
final int height = b - t;
int childBottom = height - mPaddingBottom;
int childSpace = height - mPaddingTop - mPaddingBottom;
final int childCount = getChildCount();
final int majorGravity = mGravity & Gravity.RELATIVE_HORIZONTAL_GRAVITY_MASK;
final int minorGravity = mGravity & Gravity.VERTICAL_GRAVITY_MASK;
final int layoutDirection = getLayoutDirection();
switch (Gravity.getAbsoluteGravity(majorGravity, layoutDirection))
case Gravity.RIGHT:
childLeft = mPaddingLeft + r - l - childWidth;
break;
case Gravity.CENTER_HORIZONTAL:
childLeft = mPaddingLeft + (r - l - childWidth) / 2;
break;
case Gravity.LEFT:
default:
childLeft = mPaddingLeft;
break;
for (int i = 0; i < childCount; i++)
View child = getChildAt(i);
if (child.getVisibility() != View.GONE)
LayoutParams params = (LayoutParams) child.getLayoutParams();
final int childWidth = child.getMeasuredWidth();
final int childHeight = child.getMeasuredHeight();
int gravity = params.gravity;
if (gravity < 0)
gravity = minorGravity;
switch (gravity & Gravity.VERTICAL_GRAVITY_MASK)
case Gravity.TOP:
childTop = mPaddingTop + params.topMargin;
break;
case Gravity.CENTER_VERTICAL:
childTop = mPaddingTop + ((childSpace - childHeight) / 2)
+ params.topMargin - params.bottomMargin;
break;
case Gravity.BOTTOM:
childTop = childBottom - childHeight - params.bottomMargin;
break;
default:
childTop = mPaddingTop;
break;
childLeft += params.leftMargin;
childTop += params.topMargin;
child.layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight);
childLeft += childWidth + params.rightMargin;
childTop = mPaddingTop;
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
void layoutVertical(int l, int t, int r, int b)
int childLeft = mPaddingLeft;
int childTop = mPaddingTop;
final int width = r - l;
int childRight = width - mPaddingRight;
int childSpace = width - mPaddingLeft - mPaddingRight;
final int childCount = getChildCount();
final int majorGravity = mGravity & Gravity.VERTICAL_GRAVITY_MASK;
final int minorGravity = mGravity & Gravity.RELATIVE_HORIZONTAL_GRAVITY_MASK;
switch (majorGravity)
case Gravity.BOTTOM:
childTop = mPaddingTop + b - t - childHeight;
break;
case Gravity.CENTER_VERTICAL:
childTop = mPaddingTop + (b - t - childHeight) / 2;
break;
case Gravity.TOP:
default:
childTop = mPaddingTop;
break;
for (int i = 0; i < childCount; i++)
View child = getChildAt(i);
if (child == null)
childTop += 0;
else if (child.getVisibility() != GONE)
LayoutParams params = (LayoutParams) child.getLayoutParams();
final int childWidth = child.getMeasuredWidth();
final int childHeight = child.getMeasuredHeight();
int gravity = params.gravity;
if (gravity < 0)
gravity = minorGravity;
final int layoutDirection = getLayoutDirection();
final int absoluteGravity = Gravity.getAbsoluteGravity(gravity, layoutDirection);
switch (absoluteGravity & Gravity.HORIZONTAL_GRAVITY_MASK)
case Gravity.CENTER_HORIZONTAL:
childLeft = mPaddingLeft + ((childSpace - childWidth) / 2)
+ params.leftMargin - params.rightMargin;
break;
case Gravity.RIGHT:
childLeft = childRight - childWidth - params.rightMargin;
break;
case Gravity.LEFT:
default:
childLeft = mPaddingLeft + params.leftMargin;
break;
childLeft += params.leftMargin;
childTop += params.topMargin;
child.layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight);
childLeft = mPaddingTop;
childTop += childHeight + params.bottomMargin;
以上已经完成了具有orientation和gravity属性，并且考虑padding，以及子view的padding和margin的容器
接下来是让它能够滚动
只需要重写onTouchEnvent，在ACTION_MOVE中scrollBy(-offsetX, 0);就可以滚动了
下面是完整代码
package ai.houzi.xiao.widget;
import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Build;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;
import com.juxin.common.utils.Logg;
import ai.houzi.xiao.R;
/**
* 自定义容器(LinearLayout),支持padding，margin，设置水平垂直方向，和gravity
*/
public class MyViewGroup extends ViewGroup
private int mOrientation;
private int mGravity;
private int mPaddingTop;
private int mPaddingLeft;
private int mPaddingRight;
private int mPaddingBottom;
private int childWidth;
private int childHeight;
public static final int HORIZONTAL = 0;
public static final int VERTICAL = 1;
private static final int[] ORIENTATION_FLAGS =
HORIZONTAL, VERTICAL
;
private Scroller mScroller;
private int mTouchSlop;
private boolean sameDirection;//是否同向(嵌套时)
private float downX, downY, moveX, moveY, lastX, lastY;
private boolean isFirst;
private VelocityTracker mVelocityTracker;
private int mPointerId;
private int mMaxVelocity;//最大速度
public MyViewGroup(Context context, AttributeSet attrs)
super(context, attrs);
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.MyViewGroup);
mOrientation = ORIENTATION_FLAGS[a.getInt(R.styleable.MyViewGroup_orientation, 0)];
mGravity = a.getInt(R.styleable.MyViewGroup_gravity, Gravity.START | Gravity.TOP);
a.recycle();
mMaxVelocity = ViewConfiguration.get(context).getScaledMaximumFlingVelocity();
mScroller = new Scroller(context);
mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b)
if (mOrientation == VERTICAL)
layoutVertical(l, t, r, b);
else
layoutHorizontal(l, t, r, b);
//摆放好后getParent()才有值
if (getParent() instanceof MyViewGroup)
sameDirection = ((MyViewGroup) getParent()).getOrientation() == getOrientation();
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
void layoutHorizontal(int l, int t, int r, int b)
int childLeft = mPaddingLeft;
int childTop = mPaddingTop;
final int height = b - t;
int childBottom = height - mPaddingBottom;
int childSpace = height - mPaddingTop - mPaddingBottom;
final int childCount = getChildCount();
final int majorGravity = mGravity & Gravity.RELATIVE_HORIZONTAL_GRAVITY_MASK;
final int minorGravity = mGravity & Gravity.VERTICAL_GRAVITY_MASK;
final int layoutDirection = getLayoutDirection();
switch (Gravity.getAbsoluteGravity(majorGravity, layoutDirection))
case Gravity.RIGHT:
childLeft = mPaddingLeft + r - l - childWidth;
break;
case Gravity.CENTER_HORIZONTAL:
childLeft = mPaddingLeft + (r - l - childWidth) / 2;
break;
case Gravity.LEFT:
default:
childLeft = mPaddingLeft;
break;
for (int i = 0; i < childCount; i++)
View child = getChildAt(i);
if (child.getVisibility() != View.GONE)
LayoutParams params = (LayoutParams) child.getLayoutParams();
final int childWidth = child.getMeasuredWidth();
final int childHeight = child.getMeasuredHeight();
int gravity = params.gravity;
if (gravity < 0)
gravity = minorGravity;
switch (gravity & Gravity.VERTICAL_GRAVITY_MASK)
case Gravity.TOP:
childTop = mPaddingTop + params.topMargin;
break;
case Gravity.CENTER_VERTICAL:
childTop = mPaddingTop + ((childSpace - childHeight) / 2)
+ params.topMargin - params.bottomMargin;
break;
case Gravity.BOTTOM:
childTop = childBottom - childHeight - params.bottomMargin;
break;
default:
childTop = mPaddingTop;
break;
childLeft += params.leftMargin;
childTop += params.topMargin;
child.layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight);
childLeft += childWidth + params.rightMargin;
childTop = mPaddingTop;
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
void layoutVertical(int l, int t, int r, int b)
int childLeft = mPaddingLeft;
int childTop = mPaddingTop;
final int width = r - l;
int childRight = width - mPaddingRight;
int childSpace = width - mPaddingLeft - mPaddingRight;
final int childCount = getChildCount();
final int majorGravity = mGravity & Gravity.VERTICAL_GRAVITY_MASK;
final int minorGravity = mGravity & Gravity.RELATIVE_HORIZONTAL_GRAVITY_MASK;
switch (majorGravity)
case Gravity.BOTTOM:
childTop = mPaddingTop + b - t - childHeight;
break;
case Gravity.CENTER_VERTICAL:
childTop = mPaddingTop + (b - t - childHeight) / 2;
break;
case Gravity.TOP:
default:
childTop = mPaddingTop;
break;
for (int i = 0; i < childCount; i++)
View child = getChildAt(i);
if (child == null)
childTop += 0;
else if (child.getVisibility() != GONE)
LayoutParams params = (LayoutParams) child.getLayoutParams();
final int childWidth = child.getMeasuredWidth();
final int childHeight = child.getMeasuredHeight();
int gravity = params.gravity;
if (gravity < 0)
gravity = minorGravity;
final int layoutDirection = getLayoutDirection();
final int absoluteGravity = Gravity.getAbsoluteGravity(gravity, layoutDirection);
switch (absoluteGravity & Gravity.HORIZONTAL_GRAVITY_MASK)
case Gravity.CENTER_HORIZONTAL:
childLeft = mPaddingLeft + ((childSpace - childWidth) / 2)
+ params.leftMargin - params.rightMargin;
break;
case Gravity.RIGHT:
childLeft = childRight - childWidth - params.rightMargin;
break;
case Gravity.LEFT:
default:
childLeft = mPaddingLeft + params.leftMargin;
break;
childLeft += params.leftMargin;
childTop += params.topMargin;
child.layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight);
childLeft = mPaddingTop;
childTop += childHeight + params.bottomMargin;
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mPaddingTop = getPaddingTop();
mPaddingLeft = getPaddingLeft();
mPaddingRight = getPaddingRight();
mPaddingBottom = getPaddingBottom();
childWidth = 0;//所有child占用的总宽高
childHeight = 0;
int childCount = getChildCount();
for (int i = 0; i < childCount; i++)
View child = getChildAt(i);
if (child.getVisibility() != View.GONE)
//为了添加child的margin属性值
LayoutParams lp = (LayoutParams) child.getLayoutParams();
//▲变化1：将measureChild改为measureChildWithMargin
measureChildWithMargins(child, widthMeasureSpec, 0,
heightMeasureSpec, 0);
/*原来： measureChild(child, widthMeasureSpec,
heightMeasureSpec);*/
if (mOrientation == HORIZONTAL)
childWidth += child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
childHeight = Math.max(childHeight, child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin);
else
childWidth = Math.max(childWidth, child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin);
childHeight += child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
childWidth += mPaddingLeft + mPaddingRight;
childHeight += mPaddingTop + mPaddingBottom;
setMeasuredDimension(resolveSize(childWidth, widthMeasureSpec), resolveSize(childHeight, heightMeasureSpec));
@Override
protected android.view.ViewGroup.LayoutParams generateDefaultLayoutParams()
return new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.MATCH_PARENT);
@Override
public android.view.ViewGroup.LayoutParams generateLayoutParams(
AttributeSet attrs)
return new LayoutParams(getContext(), attrs);
@Override
protected android.view.ViewGroup.LayoutParams generateLayoutParams(
android.view.ViewGroup.LayoutParams p)
return new LayoutParams(p);
public static class LayoutParams extends MarginLayoutParams
public int gravity = -1;
public LayoutParams(Context c, AttributeSet attrs)
super(c, attrs);
TypedArray ta = c.obtainStyledAttributes(attrs,
R.styleable.MyViewGroup);
gravity = ta.getInt(R.styleable.MyViewGroup_gravity, -1);
ta.recycle();
public LayoutParams(int width, int height)
this(width, height, -1);
public LayoutParams(int width, int height, int gravity)
super(width, height);
this.gravity = gravity;
public LayoutParams(android.view.ViewGroup.LayoutParams source)
super(source);
public LayoutParams(MarginLayoutParams source)
super(source);
public int getOrientation()
return mOrientation;
public void setOrientation(int orientation)
this.mOrientation = orientation;
if (getParent() instanceof MyViewGroup)
sameDirection = ((MyViewGroup) getParent()).getOrientation() == orientation;
requestLayout();
//------------------------我是快乐的分割线------------------------------------------------------
@Override
public boolean onInterceptTouchEvent(MotionEvent ev)
int action = ev.getAction();
if (action == MotionEvent.ACTION_DOWN)
downX = lastX = ev.getX();
downY = lastY = ev.getY();
else if (action == MotionEvent.ACTION_MOVE)
//拦截move事件
return true;
return false;
@Override
public boolean onTouchEvent(MotionEvent event)
obtainVelocityTracker(event);
int action = event.getAction();
float x = event.getX();
float y = event.getY();
if (action == MotionEvent.ACTION_DOWN)
if (!mScroller.isFinished())
mScroller.abortAnimation();
mPointerId = event.getPointerId(0);
lastX = x;
lastY = y;
getParent().requestDisallowInterceptTouchEvent(true);
else if (action == MotionEvent.ACTION_MOVE)
if (isFirst)
lastX = x;
lastY = y;
isFirst = false;
if (mOrientation == HORIZONTAL)
touchMoveHorizontal(event);
else
touchMoveVertical(event);
if (scrollChangeListener != null) //滚动距离的回调
scrollChangeListener.onScrollChange(getScrollX(), getScrollY());
mScrollState = SCROLLING;
else if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_CANCEL)
//计算1000ms的速度
mVelocityTracker.computeCurrentVelocity(1000, mMaxVelocity);
//获取x，y在mPointerId上的的速度
final float velocityX = mVelocityTracker.getXVelocity(mPointerId);
final float velocityY = mVelocityTracker.getYVelocity(mPointerId);
if (mOrientation == HORIZONTAL)
if (getScrollX() < 0) //超出起始边界，弹回起始位置
mScroller.startScroll(getScrollX(), 0, -getScrollX(), 0, 300);
else if (getScrollX() + getWidth() > childWidth) //超过结尾边界同理
mScroller.startScroll(getScrollX(), 0, (int) -(getScrollX() + getWidth() - childWidth), 0, 300);
else //中间时候，按最后的瞬时速度抛出，不超过剩下的距离
mScroller.fling(getScrollX(), 0, (int) -velocityX, 0, 0, childWidth - getWidth() + 100, 0, 0);
else
if (getScrollY() < 0)
mScroller.startScroll(0, getScrollY(), 0, -getScrollY(), 300);
else if (getScrollY() + getHeight() > childHeight)
mScroller.startScroll(0, getScrollY(), 0, (int) -(getScrollY() + getHeight() - childHeight), 300);
else
mScroller.fling(0, getScrollY(), 0, (int) -velocityY, 0, 0, 0, childHeight - getHeight() + 100);
isFirst = true;
recycleVelocityTracker();
postInvalidate();//调用重绘才会调用computeScroll方法，形成动画
return true;
/**
* 水平滚动
*/
private void touchMoveHorizontal(MotionEvent event)
float x = event.getX();
int offsetX = 0;
moveX = x;
//超出界限时，增加阻力
if (getScrollX() < 0 || getScrollX() + getWidth() > childWidth)
offsetX = (int) ((moveX - lastX) / 2.5);
else
offsetX = (int) (moveX - lastX);
if (!sameDirection)
// 不同向
if (Math.abs(x - downX) + mTouchSlop > Math.abs(event.getY() - downY) && childWidth > getWidth())
getParent().requestDisallowInterceptTouchEvent(true);
else
getParent().requestDisallowInterceptTouchEvent(false);
else
// 同向
if (lastX >= downX)
if (getScrollX() <= 0)
getParent().requestDisallowInterceptTouchEvent(false);
else
getParent().requestDisallowInterceptTouchEvent(true);
else
if (getScrollX() >= childWidth - getWidth())
getParent().requestDisallowInterceptTouchEvent(false);
else
getParent().requestDisallowInterceptTouchEvent(true);
if (Math.abs(downX - x) > mTouchSlop)
scrollBy(-offsetX, 0);
lastX = moveX;
/**
* 垂直滚动
*/
private void touchMoveVertical(MotionEvent event)
float y = event.getY();
int offsetY = 0;
moveY = y;
//超出界限时，增加阻力
if (getScrollY() < 0 || getScrollY() + getHeight() > childHeight)
offsetY = (int) ((moveY - lastY) / 2.5);
else
offsetY = (int) (moveY - lastY);
Logg.e(sameDirection);
if (!sameDirection)
// 不同向
if (Math.abs(event.getX() - downX) < Math.abs(y - downY) + mTouchSlop && childHeight > getHeight())
getParent().requestDisallowInterceptTouchEvent(true);
else
getParent().requestDisallowInterceptTouchEvent(false);
else
// 同向
if (lastY >= downY)
if (getScrollY() <= 0)
getParent().requestDisallowInterceptTouchEvent(false);
else
getParent().requestDisallowInterceptTouchEvent(true);
else
if (getScrollY() >= childHeight - getHeight())
getParent().requestDisallowInterceptTouchEvent(false);
else
getParent().requestDisallowInterceptTouchEvent(true);
//有效滑动，滚动-offsetY距离
if (Math.abs(downY - y) > mTouchSlop)
scrollBy(0, -offsetY);
lastY = moveY;
/**
* 创建新的速度监视对象
*
* @param event 滑动事件
*/
private void obtainVelocityTracker(MotionEvent event)
if (null == mVelocityTracker)
mVelocityTracker = VelocityTracker.obtain();
mVelocityTracker.addMovement(event);
/**
* 释放资源
*/
private void recycleVelocityTracker()
if (null != mVelocityTracker)
mVelocityTracker.clear();
mVelocityTracker.recycle();
mVelocityTracker = null;
@Override
public void computeScroll()
super.computeScroll();
if (mScroller.computeScrollOffset())
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
postInvalidate();//当没滚动到需要的位置时，不断的重绘，形成动画
mScrollState = SCROLLING;
else
mScrollState = IDLE;
/**
* 滚动距离监听器
*/
interface ScrollChangeListener
void onScrollChange(int scrollX, int scrollY);
private ScrollChangeListener scrollChangeListener;
/**
* 设置滚动监听
*
* @param l 回调
*/
public void setScrollChangeListener(ScrollChangeListener l)
this.scrollChangeListener = l;
private int mScrollState;
public static final int IDLE = 0;//闲置状态
public static final int SCROLLING = 1;//滚动状态
/**
* @return 当前滚动状态
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