title: 自定义ViewGroup
tags: ViewGroup,Android,自定义View
初始化
- 重写构造函数——三个
- 通过this调用
- init来获取自定义的属性
public SwipeLayout(Context context) {
this(context,null);
}
public SwipeLayout(Context context, AttributeSet attrs) {
this(context, attrs,0);
}
public SwipeLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context, attrs, defStyleAttr);
}
获取自定义属性
布局文件 attr.xml
<declare-styleable name="SwipeLayout">
<attr name="leftView" format="reference"/>
<attr name="rightView" format="reference"/>
<attr name="contentView1" format="reference"/>
<attr name="canRightSwipe1" format="boolean" />
<attr name="canLeftSwipe1" format="boolean" />
<attr name="fraction1" format="float" />
</declare-styleable>
获取属性
TypedArray typedArray = context.obtainStyledAttributes(attrs,R.styleable.SwipeLayout);
leftViewId = typedArray.getResourceId(R.styleable.SwipeLayout_leftView,-1);
rightViewId = typedArray.getResourceId(R.styleable.SwipeLayout_rightView,-1);
contentViewId = typedArray.getResourceId(R.styleable.SwipeLayout_contentView1,-1);
canLeftSwipe = typedArray.getBoolean(R.styleable.SwipeLayout_canLeftSwipe1,true);
canRightSwipe = typedArray.getBoolean(R.styleable.SwipeLayout_canRightSwipe1,true);
mFraction = typedArray.getFloat(R.styleable.SwipeLayout_fraction1,0.5f);
typedArray.recycle();
onMeasure
思路
- View是match_parent 的特殊处理，其他的正常处理
- 正常的最终需要调用 setMeasuredDimension 方法，需要的参数 宽高、宽高的spec以及state
- match_parent 的最终需要调用 measure方法，需要参数widthMeasureSpec, heightMeasureSpec
- onMeasure前面所做的事情都是来获取这些参数
setMeasuredDimension(resolveSizeAndState(maxWidth,widthMeasureSpec,childState)
,resolveSizeAndState(maxHeight,heightMeasureSpec,childState << MEASURED_HEIGHT_STATE_SHIFT));
view.measure(childWidthMeasureSpec,childHeightMeasureSpec);
步骤
- 获取子View的数量
代码
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
//1. 获取childView的个数
setClickable(true);
int count = getChildCount();
//参考frameLayout测量代码
final boolean measureMatchParentChildren =
MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.EXACTLY ||
MeasureSpec.getMode(heightMeasureSpec) != MeasureSpec.EXACTLY;
mMatchParentChildren.clear();
int maxHeight = 0;
int maxWidth = 0;
int childState = 0;
//遍历childViews
for (int i = 0; i < count; i++) {
View child = getChildAt(i);
if (child.getVisibility() != GONE) {
measureChildWithMargins(child,widthMeasureSpec,0,heightMeasureSpec,0);
final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
maxHeight = Math.max(maxHeight,child.getMeasuredHeight()+lp.leftMargin+lp.rightMargin);
maxWidth = Math.max(maxWidth,child.getMeasuredWidth()+lp.topMargin+lp.bottomMargin);
childState = combineMeasuredStates(childState, child.getMeasuredState());
if (measureMatchParentChildren){
if ( lp.width == LayoutParams.MATCH_PARENT || lp.height == LayoutParams.MATCH_PARENT) {
mMatchParentChildren.add(child);
}
}
}
}
//宽度和高度还要考虑背景的大小
maxHeight = Math.max(maxHeight,getSuggestedMinimumHeight());
maxWidth = Math.max(maxWidth,getSuggestedMinimumWidth());
// 设置具体宽高
setMeasuredDimension(resolveSizeAndState(maxWidth,widthMeasureSpec,childState)
,resolveSizeAndState(maxHeight,heightMeasureSpec,childState << MEASURED_HEIGHT_STATE_SHIFT));
count = mMatchParentChildren.size();
if (count > 1) {
for (int i = 0; i < count; i++) {
View view = mMatchParentChildren.get(i);
MarginLayoutParams lp = (MarginLayoutParams) view.getLayoutParams();
final int childWidthMeasureSpec;
if ( lp.width == LayoutParams.MATCH_PARENT) {
int width = Math.max(0,getMeasuredWidth()
- lp.leftMargin - lp.rightMargin);
childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width,MeasureSpec.EXACTLY);
}else {
childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,lp.leftMargin+lp.rightMargin
,lp.width);
}
final int childHeightMeasureSpec;
if ( lp.height == LayoutParams.MATCH_PARENT) {
int height = Math.max(0,getMeasuredHeight()
- lp.topMargin - lp.bottomMargin);
childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height,MeasureSpec.EXACTLY);
}else{
childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec,lp.topMargin+lp.bottomMargin
,lp.height);
}
view.measure(childWidthMeasureSpec,childHeightMeasureSpec);
}
}
}
onLayout
思路
- 调用layout方法，需要四个参数
view.layout(rLeft,rTop,rRight,rBottom)
padding——内边距
margin——外边距
代码
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
// 1. 先找到布局中的View
int count = getChildCount();
int left = 0 + getPaddingLeft();
int right = 0 + getPaddingLeft();
int top = 0 + getPaddingTop();
int bottom = 0 + getPaddingTop();
for (int i = 0; i < count; i++) {
View child = getChildAt(i);
if (mLeftView == null && child.getId() == leftViewId) {
mLeftView = child;
mLeftView.setClickable(true);
}else if (mRightView == null && child.getId() == rightViewId){
mRightView = child;
mRightView.setClickable(true);
}else if (mContentView == null && child.getId() == contentViewId){
mContentView = child;
mContentView.setClickable(true);
}
}
//2. 设置放置的位置
if (mContentView != null) {
mContentViewLp = (MarginLayoutParams) mContentView.getLayoutParams();
int cTop = mContentViewLp.topMargin + top;
int cLeft = mContentViewLp.leftMargin + left;
int cRight = cLeft + mContentView.getMeasuredWidth();
//TODO 此处能不能使用 ??? mContentViewLp.height
int cBottom = cTop + mContentView.getMeasuredHeight();
mContentView.layout(cLeft, cTop, cRight, cBottom);
}
if (mLeftView != null) {
MarginLayoutParams leftViewLp = (MarginLayoutParams) mLeftView.getLayoutParams();
int cTop = leftViewLp.topMargin + top;
int cRight = 0 - leftViewLp.rightMargin ;
int cLeft = 0 - mLeftView.getMeasuredWidth() + leftViewLp.rightMargin + leftViewLp.leftMargin;
int cBottom = top + mLeftView.getMeasuredHeight() + leftViewLp.bottomMargin;
mLeftView.layout(cLeft,cTop,cRight,cBottom);
}
if (mRightView != null) {
MarginLayoutParams rightViewLp = (MarginLayoutParams) mRightView.getLayoutParams();
int rTop = rightViewLp.topMargin + top;
int rLeft = rightViewLp.leftMargin + mContentView.getRight() + mContentViewLp.rightMargin;
int rRight = rLeft + mRightView.getMeasuredWidth();
int rBottom = rTop + mRightView.getMeasuredHeight();;
mRightView.layout(rLeft,rTop,rRight,rBottom);
}
}
几个常用函数
getX() 是表示Widget相对于自身左上角的x坐标
getRawX() 是表示相对于屏幕左上角的x坐标值
理解 getScrollX()
image
1是手机屏幕，在此区域内的人眼可以看见
2是幕布
3是内容
getScrollX 其实获取的值，就是这块幕布在窗口左边界时候的值了，而幕布上面哪个点是原点（0，0）呢？就是初始化时内容显示的位置。
- 将幕布往右推动的时候，幕布在窗口左边界的值就会在0的左边（-100）
- 向左推动，则其值会是在0的右边（100）
scrollTo()和scrollBy(x,y)
scrollTo(int x, int y) 是将View中内容滑动到相应的位置，参考的坐标系原点为parent View的左上角。
- 参数为正的，右移
- 参数为负值，左移
scrollTo()指的是移动到指定的(x,y)位置
而scrollBy(x,y)指的是，在当前位置在移动(x,y)个位置
阻止父层的View截获touch事件
调用getParent().requestDisallowInterceptTouchEvent(true);方法。一旦底层View收到touch的action后调用这个方法那么父层View就不会再调用onInterceptTouchEvent了，也无法截获以后的action
ViewGroup generateLayoutParams() 方法的作用
父容器生成 子view 的布局LayoutParams;
如果一个View想要被添加到这个容器中，这个view可以调用此方法生成和容器类匹配的布局LayoutParams，
这个方法主要是用于父容器添加子View时调用。
用于生成和此容器类型相匹配的布局参数类
startScroll方法
第一个参数是起始移动的x坐标值，第二个是起始移动的y坐标值，第三个第四个参数都是移到某点的坐标值，而duration 当然就是执行移动的时间
computeScroll方法
当startScroll执行过程中即在duration时间内，computeScrollOffset 方法会一直返回false，但当动画执行完成后会返回返加true.
@Override
public void computeScroll() {
//判断Scroller是否执行完毕：
if (mScroller.computeScrollOffset()) {
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
//通知View重绘-invalidate()->onDraw()->computeScroll()
invalidate();
}
}
onDetachedFromWindow()
销毁View的时候调用这个方法，我们可以在里面做一些清理工作（做一些收尾工作）如：取消广播注册等等
