Android Support Design库之FloatingActionButton

FloatingActionButton(以下简称FAB)是继承自ImageView，所以FAB拥有ImageView的所有属性。CoordinatorLayout可以用来配合FAB浮动按钮，设置app：layout_anchor和app:layout_anchorGravity构建出特定的位置与效果的FloatingActionButton。

1.引入design库的支持

//版本可以修改为自己对应的版本
compile 'com.android.support:design:24.0.0-beta1'

2.使用也非常简单

<android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:layout_marginBottom="36dp"
        android:layout_marginRight="@dimen/activity_horizontal_margin"
        android:src="@drawable/favorites"
        app:elevation="20dp"
        app:layout_behavior="com.zsy.fab.ScrollAwareFABBehaviorDefault" />

3.FAB的一些属性

• app:backgroundTint - 设置FAB的背景颜色。
• app:rippleColor - 设置FAB点击时的背景颜色。
• app:borderWidth - 该属性尤为重要，如果不设置0dp，那么在4.1- 的sdk上FAB会显示为正方形，而且在5.0以后的sdk没有阴影效果。所以设置为borderWidth=”0dp”。
• app:elevation - 默认状态下FAB的阴影大小。
• app:pressedTranslationZ - 点击时候FAB的阴影大小。
• app:fabSize - 设置FAB的大小，该属性有两个值，分别为normal和mini，对应的FAB大小分别为56dp和40dp。
• src - 设置FAB的图标，Google建议符合Design设计的该图标大小为24dp。
• app:layout_anchor - 设置FAB的锚点，即以哪个控件为参照点设置位置。
• app:layout_anchorGravity - 设置FAB相对锚点的位置，值有 bottom、center、right、left、top等

4.这里使用了app:layout_behavior对它进行动态显示隐藏来看下效果

效果一：通过继承FloatingActionButton.Behavior自定义behavior

ScrollAwareFABBehaviorDefault.class

public class ScrollAwareFABBehaviorDefault extends FloatingActionButton.Behavior {

    public ScrollAwareFABBehaviorDefault(Context context, AttributeSet attrs) {
        super();
    }

    @Override
    public boolean onStartNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
                                       final View directTargetChild, final View target, final int nestedScrollAxes) {
        // Ensure we react to vertical scrolling
        return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL
                || super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
    }

    @Override
    public void onNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
                               final View target, final int dxConsumed, final int dyConsumed,
                               final int dxUnconsumed, final int dyUnconsumed) {
        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
        if (dyConsumed > 0 && child.getVisibility() == View.VISIBLE) {
            // User scrolled down and the FAB is currently visible -> hide the FAB
            child.hide();
        } else if (dyConsumed < 0 && child.getVisibility() != View.VISIBLE) {
            // User scrolled up and the FAB is currently not visible -> show the FAB
            child.show();
        }
    }
}

第二种效果:

ScrollAwareFABBehavior.class

public class ScrollAwareFABBehavior extends FloatingActionButton.Behavior {
    private static final Interpolator INTERPOLATOR = new FastOutSlowInInterpolator();
    private boolean mIsAnimatingOut = false;

    public ScrollAwareFABBehavior(Context context, AttributeSet attrs) {
        super();
    }

    @Override
    public boolean onStartNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
                                       final View directTargetChild, final View target, final int nestedScrollAxes) {
        // Ensure we react to vertical scrolling
        return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL
                || super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
    }

    @Override
    public void onNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
                               final View target, final int dxConsumed, final int dyConsumed,
                               final int dxUnconsumed, final int dyUnconsumed) {
        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
        if (dyConsumed > 0 && !this.mIsAnimatingOut && child.getVisibility() == View.VISIBLE) {
            // User scrolled down and the FAB is currently visible -> hide the FAB
            animateOut(child);
        } else if (dyConsumed < 0 && child.getVisibility() != View.VISIBLE) {
            // User scrolled up and the FAB is currently not visible -> show the FAB
            animateIn(child);
        }
    }

    // Same animation that FloatingActionButton.Behavior uses to hide the FAB when the AppBarLayout exits
    private void animateOut(final FloatingActionButton button) {
        if (Build.VERSION.SDK_INT >= 14) {
            ViewCompat.animate(button).translationY(button.getHeight() + getMarginBottom(button)).setInterpolator(INTERPOLATOR).withLayer()
                    .setListener(new ViewPropertyAnimatorListener() {
                        public void onAnimationStart(View view) {
                            ScrollAwareFABBehavior.this.mIsAnimatingOut = true;
                        }

                        public void onAnimationCancel(View view) {
                            ScrollAwareFABBehavior.this.mIsAnimatingOut = false;
                        }

                        public void onAnimationEnd(View view) {
                            ScrollAwareFABBehavior.this.mIsAnimatingOut = false;
                            view.setVisibility(View.GONE);
                        }
                    }).start();
        } else {

        }
    }

    // Same animation that FloatingActionButton.Behavior uses to show the FAB when the AppBarLayout enters
    private void animateIn(FloatingActionButton button) {
        button.setVisibility(View.VISIBLE);
        if (Build.VERSION.SDK_INT >= 14) {
            ViewCompat.animate(button).translationY(0)
                    .setInterpolator(INTERPOLATOR).withLayer().setListener(null)
                    .start();
        } else {

        }
    }

    private int getMarginBottom(View v) {
        int marginBottom = 0;
        final ViewGroup.LayoutParams layoutParams = v.getLayoutParams();
        if (layoutParams instanceof ViewGroup.MarginLayoutParams) {
            marginBottom = ((ViewGroup.MarginLayoutParams) layoutParams).bottomMargin;
        }
        return marginBottom;
    }
}