开始布局时,方法回调顺序:
1:StickBehavior([context, attrs])->
2:onAttachedToLayoutParams([params])->
3:layoutDependsOn([parent,child,dependency])->//当dependency是你需要监听的View时,需要返回true, 否则dependency View位置改变, 或者大小改变不会有onDependentViewChanged回调.
4:onMeasureChild([parent,child,parentWidthMeasureSpec,widthUsed,parentHeightMeasureSpec,heightUsed])->
5:layoutDependsOn([parent,child,dependency])->
6:onMeasureChild([parent,child,parentWidthMeasureSpec,widthUsed,parentHeightMeasureSpec,heightUsed])->
7:layoutDependsOn([parent,child,dependency])->
8:onMeasureChild([parent,child,parentWidthMeasureSpec,widthUsed,parentHeightMeasureSpec,heightUsed])->
9:layoutDependsOn([parent,child,dependency])->
10:onMeasureChild([parent,child,parentWidthMeasureSpec,widthUsed,parentHeightMeasureSpec,heightUsed])->
11:onLayoutChild([parent,child,layoutDirection])->
12:onDependentViewChanged([parent, child, dependency])-> //当layoutDependsOn返回true时, 才会有这个回调开始滚动子View时, 方法回调顺序
1:onStartNestedScroll([coordinatorLayout, child, directTargetChild, target, nestedScrollAxes])-> //此方法必须返回true, 否则之后的滚动事件将没有回调
2:onNestedScrollAccepted([coordinatorLayout, child, directTargetChild, target, nestedScrollAxes])->
3:onNestedPreScroll([coordinatorLayout, child, target, dx, dy, consumed])->
4:onNestedScroll([coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed])->
//当快速滑动的时候, 才会触发fling回调
//4.1:onNestedPreFling([coordinatorLayout, child, target, velocityX, velocityY])->
//4.2:onNestedFling([coordinatorLayout, child, target, velocityX, velocityY, consumed])->
5:onStopNestedScroll([coordinatorLayout, child, target])->public class StickBehavior<V extends View> extends CoordinatorLayout.Behavior<V> {
View mTargetView;
/**
* 悬停区域的高度 px
*/
int stickHeight = 0;
/**
* 为了保存已经偏移的距离
*/
int lastTop = 0;
public StickBehavior() {
}
public StickBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
/**
* 当CoordinatorLayout在layout的时候, 会回调此方法, 告诉你,
* 是否需要得到dependency View的位置大小改变的监听,如果你需要, 那么必须返回true
*/
@Override
public boolean layoutDependsOn(CoordinatorLayout parent, V child, View dependency) {
if (mTargetView == null) {
lastTop = 0;
}
if (dependency instanceof StickLayout) {
//StickLayout只是用来判断是否是目标的标识, 没有任何不同支持,
//你也可以通过getId判断id是否相等, 来处理
mTargetView = dependency;
stickHeight = (int) (40 * child.getContext().getResources().getDisplayMetrics().density);
return true;
}
return super.layoutDependsOn(parent, child, dependency);
}
/**
* 只有当layoutDependsOn返回true时, 才会回调.
* 当dependency对应的View, 发生了改变, 就会回调此方法.
* 你可以在此更新child的位置
*/
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, V child, View dependency) {
lastTop = dependency.getTop();
child.setTop(dependency.getBottom());
return true;
}
/**
* 测量child的大小, 和自定义view的套路一样
*/
@Override
public boolean onMeasureChild(CoordinatorLayout parent, V child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) {
child.measure(View.MeasureSpec.makeMeasureSpec(parent.getMeasuredWidth(), View.MeasureSpec.EXACTLY),
View.MeasureSpec.makeMeasureSpec(parent.getMeasuredHeight() - stickHeight, View.MeasureSpec.EXACTLY));
return true;
}
/**
* 布局child的位置, 和自定义view的套路一样
*/
@Override
public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) {
if (mTargetView != null) {
ViewCompat.offsetTopAndBottom(mTargetView, lastTop);
int top = mTargetView.getBottom();// - Math.abs(lastTop);
child.layout(0, top, child.getMeasuredWidth(), top + child.getMeasuredHeight());
return true;
}
return super.onLayoutChild(parent, child, layoutDirection);
}
/**
* 必须返回true, 否则你收不到子View滚动的事件
*/
@Override
public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, V child, View directTargetChild, View target, int nestedScrollAxes) {
return true;
}
/**
* 当子View开始滚动之前, 你可以通过此方法消耗掉滚动事件, 并偏移child的位置
*/
@Override
public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dx, int dy, int[] consumed) {
if (dy == 0 || (dy < 0 && ViewCompat.canScrollVertically(target, -1))) {
return;
}
int offsetMax = mTargetView.getMeasuredHeight() - stickHeight;
int top = mTargetView.getTop();
int offset = 0;
if (dy > 0) {
//上滑
offset = Math.min(dy, offsetMax + top);
} else if (dy < 0) {
//下滑
offset = Math.max(dy, top);
}
ViewCompat.offsetTopAndBottom(mTargetView, -offset);
consumed[1] = offset;
}
/**
* 用来处理快速滑动
*/
@Override
public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY) {
L.e("call: onNestedPreFling([coordinatorLayout, child, target, velocityX, velocityY])-> ");
if (velocityY < 0 && ViewCompat.canScrollVertically(target, -1)) {
return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
}
int offsetMax = mTargetView.getMeasuredHeight() - stickHeight;
if (velocityY > offsetMax) {
mTargetView.setTop(-offsetMax);
//mTargetView.setBottom(mTargetView.getMeasuredHeight() - offsetMax);
animToBottom(mTargetView.getMeasuredHeight() - offsetMax);
} else if (velocityY < -offsetMax) {
mTargetView.setTop(0);
//mTargetView.setBottom(mTargetView.getMeasuredHeight());
animToBottom(mTargetView.getMeasuredHeight());
}
return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
}
void animToBottom(int bottom) {
ValueAnimator animator = ObjectAnimator.ofInt(mTargetView.getBottom(), bottom);
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
mTargetView.setBottom((Integer) animation.getAnimatedValue());
}
});
animator.setInterpolator(new LinearInterpolator());
animator.setDuration(100);
animator.start();
}
}
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