实际效果只有二级页面的TabLayout能够粘在顶部，而一级页面是不会有联动的。
解决方案：自定义NestedCoordinatorLayout，替换二级页面的CoordinatorLayout。
NestedCoordinatorLayout代码如下，
import android.content.Context;
import android.support.annotation.IntDef;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.annotation.Size;
import android.support.design.widget.CoordinatorLayout;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
/**
* A {@link CoordinatorLayout} that implements {@link NestedScrollingChild}.
* This means it can act as a nested scrolling child, and thus forward scroll events to parents.
*
* This is useful for nested Coordinators, e.g. for inner fragments in a parent activity. If this is used,
* scrolls to the inner fragment will trigger scroll animations (e.g. {@code AppBarLayout}s, fabs, ...)
* to the parent activity as well.
*
* This works by *not* reinventing the wheel and reusing the same nested scrolling logic implemented
* by behaviors. There is a dummy view inside the sheet that is capable of getting nested scrolling
* callbacks, and forward them to the *outer* behavior that they normally would never reach.
*/
public class NestedScrollCoordinatorLayout extends CoordinatorLayout implements NestedScrollingChild {
private static final String TAG = NestedScrollCoordinatorLayout.class.getSimpleName();
/**
* Constant for {@link #setPassMode(int)}. When this is selected, scroll events are
* passed to the parent stream and, at the same time, to this Coordinator childs.
*/
public static final int PASS_MODE_BOTH = 0;
/**
* Constant for {@link #setPassMode(int)}. When this is selected, scroll events are
* passed to the parent stream and, if not consumed, they go on to this Coordinator childs.
*/
public static final int PASS_MODE_PARENT_FIRST = 1;
@Retention(RetentionPolicy.SOURCE)
@IntDef({PASS_MODE_BOTH, PASS_MODE_PARENT_FIRST})
public @interface PassMode {}
private NestedScrollingChildHelper helper;
private DummyBehavior dummyBehavior;
public NestedScrollCoordinatorLayout(Context context) {
super(context); i();
}
public NestedScrollCoordinatorLayout(Context context, AttributeSet attrs) {
super(context, attrs); i();
}
public NestedScrollCoordinatorLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr); i();
}
private void i() {
helper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
// Add a dummy view that will receive inner touch events.
View dummyView = new View(getContext());
dummyBehavior = new DummyBehavior();
// I *think* this is needed for dummyView to be identified as "topmost" and receive events
// before any other view.
ViewCompat.setElevation(dummyView, ViewCompat.getElevation(this));
// Make sure it does not fit windows, or it will consume insets before the AppBarLayout.
dummyView.setFitsSystemWindows(false);
LayoutParams params = new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
params.setBehavior(dummyBehavior);
addView(dummyView, params);
}
/**
* Sets the pass mode for this coordinator.
* @see #PASS_MODE_BOTH
* @see #PASS_MODE_PARENT_FIRST
*
* @param mode desired pass mode for scroll events.
*/
public void setPassMode(@PassMode int mode) {
if (dummyBehavior != null) dummyBehavior.setPassMode(mode);
}
@Override
public void setNestedScrollingEnabled(boolean enabled) {
helper.setNestedScrollingEnabled(enabled);
}
@Override
public boolean isNestedScrollingEnabled() {
return helper.isNestedScrollingEnabled();
}
@Override
public boolean startNestedScroll(int axes) {
return helper.startNestedScroll(axes);
}
@Override
public void stopNestedScroll() {
helper.stopNestedScroll();
}
@Override
public boolean hasNestedScrollingParent() {
return helper.hasNestedScrollingParent();
}
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, @Nullable @Size(value = 2) int[] offsetInWindow) {
return helper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
}
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable @Size(value = 2) int[] consumed, @Nullable @Size(value = 2) int[] offsetInWindow) {
return helper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
}
@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
return helper.dispatchNestedFling(velocityX, velocityY, consumed);
}
@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
return helper.dispatchNestedPreFling(velocityX, velocityY);
}
/**
* This behavior is assigned to our dummy, MATCH_PARENT view inside this bottom sheet layout.
* Through this behavior the dummy view can listen to touch/scroll events.
* Our goal is to propagate them to the parent stream.
*
* It has to be done manually because by default CoordinatorLayouts don't propagate scroll events
* to their parent. This is bad for CoordinatorLayouts inside other CoordinatorLayouts, since
* the coordination works relies heavily on scroll events.
*
* @param <DummyView> make sure it's not a nested-scrolling-enabled view or this will break.
*/
private static class DummyBehavior<DummyView extends View> extends Behavior<DummyView> {
@PassMode private int mode = PASS_MODE_PARENT_FIRST;
private final int[] cache = new int[2];
DummyBehavior() {}
void setPassMode(@PassMode int mode) {
this.mode = mode;
}
@Override
public boolean onStartNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull DummyView child, @NonNull View directTargetChild, @NonNull View target, int axes, int type) {
NestedScrollCoordinatorLayout sheet = (NestedScrollCoordinatorLayout) coordinatorLayout;
// If we want to catch, catch.
return sheet.startNestedScroll(axes);
}
@Override
public void onStopNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull DummyView child, @NonNull View target, int type) {
NestedScrollCoordinatorLayout sheet = (NestedScrollCoordinatorLayout) coordinatorLayout;
sheet.stopNestedScroll();
}
@Override
// When moving the finger up, dy is > 0.
public void onNestedPreScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull DummyView child, @NonNull View target, int dx, int dy, @NonNull int[] consumed, int type) {
NestedScrollCoordinatorLayout sheet = (NestedScrollCoordinatorLayout) coordinatorLayout;
if (mode == PASS_MODE_PARENT_FIRST) {
sheet.dispatchNestedPreScroll(dx, dy, consumed, null);
} else if (mode == PASS_MODE_BOTH) {
// Don't let sheet consume the original int.
cache[0] = consumed[0];
cache[1] = consumed[1];
sheet.dispatchNestedPreScroll(dx, dy, cache, null);
}
}
@Override
public boolean onNestedPreFling(@NonNull CoordinatorLayout coordinatorLayout, @NonNull DummyView child, @NonNull View target, float velocityX, float velocityY) {
NestedScrollCoordinatorLayout sheet = (NestedScrollCoordinatorLayout) coordinatorLayout;
boolean s = sheet.dispatchNestedPreFling(velocityX, velocityY);
if (mode == PASS_MODE_PARENT_FIRST) {
return s;
}
return false;
}
// onNestedScroll and onNestedFling are not needed.
}
}另外要注意CollapsingToolbarLayout属性的设置：
第一层：
第二层：
参考链接：
https://stackoverflow.com/questions/34181372/coordinatorlayout-inside-another-coordinatorlayout