标签：lex googl boolean needed images anim cell specific 回调
原文地址：https://github.com/Rowandjj/my_awesome_blog/blob/master/fab_anlysis/README.md
FloatingActionButton（下文以fab代替）是android support design组件库中提供的一个视图控件，是material design设计中fab的官方实现。
此控件的官方介绍如下：
Floating action buttons are used for a promoted action. They are distinguished by a circled icon floating above the UI and have motion behaviors that include morphing, launching, and a transferring anchor point.
关于该控件的设计规范及使用场景请参考文档：
http://www.google.com/design/spec/components/buttons-floating-action-button.html#
如果你还不了解design组件库，请参考官方博客:
http://android-developers.blogspot.hk/2015/05/android-design-support-library.html
源码版本:23.3.0
fab间接继承自ImageView（ImageButton是ImageView的子类），因而拥有ImageView的大部分特性。但是其内部还是做了很多定制，我们一一来看。
从构造器开始：
public FloatingActionButton(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); //检查是否使用Theme.Appcompat主题 ThemeUtils.checkAppCompatTheme(context); //拿到自定义属性并赋值 TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.FloatingActionButton, defStyleAttr, R.style.Widget_Design_FloatingActionButton); ... a.recycle(); final int maxImageSize = (int) getResources().getDimension(R.dimen.design_fab_image_size); mImagePadding = (getSizeDimension() - maxImageSize) / 2; //背景着色 getImpl().setBackgroundDrawable(mBackgroundTint, mBackgroundTintMode, mRippleColor, mBorderWidth); //绘制阴影 getImpl().setElevation(elevation); ... }
构造器中主要是拿到用户设置的自定义属性，比如着色、波纹颜色、大小等等,一共有以下几个属性可以定义。
<declare-styleable name="FloatingActionButton">
<attr name="backgroundTint"/>
<attr name="backgroundTintMode"/>
<attr format="color" name="rippleColor"/>
<attr name="fabSize">
<enum name="normal" value="0"/>
<enum name="mini" value="1"/>
</attr>
<attr name="elevation"/>
<attr format="dimension" name="pressedTranslationZ"/>
<attr format="dimension" name="borderWidth"/>
<attr format="boolean" name="useCompatPadding"/>
</declare-styleable>
属性的默认值定义如下：
<style name="Widget.Design.FloatingActionButton" parent="android:Widget">
<item name="android:background">@drawable/design_fab_background</item>
<item name="backgroundTint">?attr/colorAccent</item>
<item name="fabSize">normal</item>
<item name="elevation">@dimen/design_fab_elevation</item>
<item name="pressedTranslationZ">@dimen/design_fab_translation_z_pressed</item>
<item name="rippleColor">?attr/colorControlHighlight</item>
<item name="borderWidth">@dimen/design_fab_border_width</item>
</style>
需要注意的是android:background属性，这里指定了background为design_fab_background,并且不允许改变:
@Override public void setBackgroundDrawable(Drawable background) { Log.i(LOG_TAG, "Setting a custom background is not supported."); }
那么我们来看下这个background长啥样：
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="oval">
<solid android:color="@android:color/white" />
</shape>
很显然，fab的形状固定为圆形都是因为这个background。那么这里指定了背景色为白色，那是不是fab只能是白色背景呢？当然不是，还有我们牛逼的backgroundTint(即背景着色)，tint是android 5.x引进的一个新特性，可以动态地给drawable资源着色，其原理就是通过给控件设置colorFilter:
drawable.java
public void setColorFilter(@ColorInt int color, @NonNull PorterDuff.Mode mode) { setColorFilter(new PorterDuffColorFilter(color, mode)); }
默认的着色模式为SRC_IN(取交集、显示上层，故底层白色会被忽略)：
static final PorterDuff.Mode DEFAULT_TINT_MODE = PorterDuff.Mode.SRC_IN;
在fab构造的时候，会指定着色为？attr/colorAccent，即当前主题的colorAccent属性值。 然后执行如下代码，进行着色。
getImpl().setBackgroundDrawable(mBackgroundTint, mBackgroundTintMode,
mRippleColor, mBorderWidth);
因为不同版本间的实现略有不同，所以这里会根据不同版本创建不同的FloatingActionButtonImpl实现类：
private FloatingActionButtonImpl createImpl() { final int sdk = Build.VERSION.SDK_INT; if (sdk >= 21) { return new FloatingActionButtonLollipop(this, new ShadowDelegateImpl()); } else if (sdk >= 14) { return new FloatingActionButtonIcs(this, new ShadowDelegateImpl()); } else { return new FloatingActionButtonEclairMr1(this, new ShadowDelegateImpl()); } }
以5.x为例，其setBackgroundDrawable实现代码如下:
先创建着色的背景drawable。
GradientDrawable createShapeDrawable() { GradientDrawable d = new GradientDrawable(); d.setShape(GradientDrawable.OVAL); d.setColor(Color.WHITE); return d; }
再对此drawable设置tint：
@Override void setBackgroundDrawable(ColorStateList backgroundTint, PorterDuff.Mode backgroundTintMode, int rippleColor, int borderWidth) { // Now we need to tint the shape background with the tint mShapeDrawable = DrawableCompat.wrap(createShapeDrawable()); //着色，这里会其实就是设置了下colorFilter DrawableCompat.setTintList(mShapeDrawable, backgroundTint); if (backgroundTintMode != null) { DrawableCompat.setTintMode(mShapeDrawable, backgroundTintMode); } final Drawable rippleContent; if (borderWidth > 0) { mBorderDrawable = createBorderDrawable(borderWidth, backgroundTint); rippleContent = new LayerDrawable(new Drawable[]{mBorderDrawable, mShapeDrawable}); } else { mBorderDrawable = null; rippleContent = mShapeDrawable; } mRippleDrawable = new RippleDrawable(ColorStateList.valueOf(rippleColor), rippleContent, null); mContentBackground = mRippleDrawable; mShadowViewDelegate.setBackgroundDrawable(mRippleDrawable); }
经过着色，fab就呈现出我们想要的颜色啦。
再来看fab的大小，fab有两种大小，一种是NORMAL，一种是MINI，实际大小分别是56dp和40dp，其定义可以在design库的values.xml中看到。
fab如何控制控件大小只有这两种规格呢(这样说不准确，事实上你可以通过设置fab的layout_width/layout_height指定为任意大小，但是我们最好按照MD规范来)?必然是通过复写onMeasure啦:
@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { //我们希望的大小 final int preferredSize = getSizeDimension(); //最终测量的大小 final int w = resolveAdjustedSize(preferredSize, widthMeasureSpec); final int h = resolveAdjustedSize(preferredSize, heightMeasureSpec); //取小值，保证最后绘制的是圆形 final int d = Math.min(w, h); // We add the shadow‘s padding to the measured dimension setMeasuredDimension( d + mShadowPadding.left + mShadowPadding.right, d + mShadowPadding.top + mShadowPadding.bottom); }
其中getSizeDimension方法计算出来的是我们期望的大小:
final int getSizeDimension() { switch (mSize) { case SIZE_MINI: return getResources().getDimensionPixelSize(R.dimen.design_fab_size_mini);//40dp case SIZE_NORMAL: default: return getResources().getDimensionPixelSize(R.dimen.design_fab_size_normal);//56dp } }
但是最终的值还是得看我们设置的LayoutParams。关于控件测量相关内容不在此文介绍范围内，大家可以自行google。
fab还支持fab以动画的方式显现/隐藏，通常和AppBarLayout一起使用，可以通过hide()/show()两个方法控制。
那么动画是如何实现的呢:
private void show(OnVisibilityChangedListener listener, boolean fromUser) { getImpl().show(wrapOnVisibilityChangedListener(listener), fromUser); } private void hide(@Nullable OnVisibilityChangedListener listener, boolean fromUser) { getImpl().hide(wrapOnVisibilityChangedListener(listener), fromUser); }
这里因为要兼容不同版本，所以具体实现也交给了不同的fab实现类。3.x之后很好办，直接使用属性动画，如果是3.x之前的话，那么只能使用传统的Animation了
以hide()为例，使用属性动画较为简单，直接使用View#animate()即可链式调用。
@Override void hide(@Nullable final InternalVisibilityChangedListener listener, final boolean fromUser) { if (mIsHiding || mView.getVisibility() != View.VISIBLE) { // A hide animation is in progress, or we‘re already hidden. Skip the call if (listener != null) { listener.onHidden(); } return; } if (!ViewCompat.isLaidOut(mView) || mView.isInEditMode()) { // If the view isn‘t laid out, or we‘re in the editor, don‘t run the animation mView.internalSetVisibility(View.GONE, fromUser); if (listener != null) { listener.onHidden(); } } else { mView.animate().cancel(); mView.animate() .scaleX(0f) .scaleY(0f) .alpha(0f) .setDuration(SHOW_HIDE_ANIM_DURATION) .setInterpolator(AnimationUtils.FAST_OUT_LINEAR_IN_INTERPOLATOR) .setListener(new AnimatorListenerAdapter() { private boolean mCancelled; @Override public void onAnimationStart(Animator animation) { mIsHiding = true; mCancelled = false; mView.internalSetVisibility(View.VISIBLE, fromUser); } @Override public void onAnimationCancel(Animator animation) { mIsHiding = false; mCancelled = true; } @Override public void onAnimationEnd(Animator animation) { mIsHiding = false; if (!mCancelled) { mView.internalSetVisibility(View.GONE, fromUser); if (listener != null) { listener.onHidden(); } } } }); } }
如果使用传统动画的话，则先在xml中定义好动画，然后构造Animation实例，启动动画。
@Override void hide(@Nullable final InternalVisibilityChangedListener listener, final boolean fromUser) { if (mIsHiding || mView.getVisibility() != View.VISIBLE) { // A hide animation is in progress, or we‘re already hidden. Skip the call if (listener != null) { listener.onHidden(); } return; } Animation anim = android.view.animation.AnimationUtils.loadAnimation( mView.getContext(), R.anim.design_fab_out); anim.setInterpolator(AnimationUtils.FAST_OUT_LINEAR_IN_INTERPOLATOR); anim.setDuration(SHOW_HIDE_ANIM_DURATION); anim.setAnimationListener(new AnimationUtils.AnimationListenerAdapter() { @Override public void onAnimationStart(Animation animation) { mIsHiding = true; } @Override public void onAnimationEnd(Animation animation) { mIsHiding = false; mView.internalSetVisibility(View.GONE, fromUser); if (listener != null) { listener.onHidden(); } } }); mView.startAnimation(anim); }
这块内容因为与
CoordinatorLayout/CoordinatorLayout#Behavior有很大关联，如果不熟悉，请先google相关资料。本文假设读者对这块内容已经有一定理解。
fab并不直接与CoordinatorLayout联系，而是通过CoordinatorLayout#Behavior作为桥梁。CoordinatorLayout类通过CoordinatorLayout#Behavior可以间接控制其直系子View的行为，能控制什么行为？View测量、布局、touch事件拦截、监听、NestedScroll等等。是不是很屌。
fab内部实现了CoordinatorLayout#Behavior抽象类。该抽象类有如下接口:
public static abstract class Behavior<V extends View> { ... public boolean onInterceptTouchEvent(CoordinatorLayout parent, V child, MotionEvent ev) { return false; } public boolean onTouchEvent(CoordinatorLayout parent, V child, MotionEvent ev) { return false; } ... /** * Determine whether the supplied child view has another specific sibling view as a * layout dependency. * * <p>This method will be called at least once in response to a layout request. If it * returns true for a given child and dependency view pair, the parent CoordinatorLayout * will:</p> * <ol> * <li>Always lay out this child after the dependent child is laid out, regardless * of child order.</li> * <li>Call {@link #onDependentViewChanged} when the dependency view‘s layout or * position changes.</li> * </ol> */ public boolean layoutDependsOn(CoordinatorLayout parent, V child, View dependency) { return false; } /** * Respond to a change in a child‘s dependent view * * <p>This method is called whenever a dependent view changes in size or position outside * of the standard layout flow. A Behavior may use this method to appropriately update * the child view in response.</p> * * <p>A view‘s dependency is determined by * {@link #layoutDependsOn(CoordinatorLayout, android.view.View, android.view.View)} or * if {@code child} has set another view as it‘s anchor.</p> * * <p>Note that if a Behavior changes the layout of a child via this method, it should * also be able to reconstruct the correct position in * {@link #onLayoutChild(CoordinatorLayout, android.view.View, int) onLayoutChild}. * <code>onDependentViewChanged</code> will not be called during normal layout since * the layout of each child view will always happen in dependency order.</p> * * <p>If the Behavior changes the child view‘s size or position, it should return true. * The default implementation returns false.</p> * */ public boolean onDependentViewChanged(CoordinatorLayout parent, V child, View dependency) { return false; } ... /** * Called when the parent CoordinatorLayout is about the lay out the given child view. * * <p>This method can be used to perform custom or modified layout of a child view * in place of the default child layout behavior. The Behavior‘s implementation can * delegate to the standard CoordinatorLayout measurement behavior by calling * {@link CoordinatorLayout#onLayoutChild(android.view.View, int) * parent.onLayoutChild}.</p> * * <p>If a Behavior implements * {@link #onDependentViewChanged(CoordinatorLayout, android.view.View, android.view.View)} * to change the position of a view in response to a dependent view changing, it * should also implement <code>onLayoutChild</code> in such a way that respects those * dependent views. <code>onLayoutChild</code> will always be called for a dependent view * <em>after</em> its dependency has been laid out.</p> * */ public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) { return false; } ... public void onNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) { // Do nothing } }
看到这个抽象类，有两点需要注意:
fab实现此抽象类:
public static class Behavior extends CoordinatorLayout.Behavior<FloatingActionButton> {}
有选择性地实现了三个方法:
public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton child, View dependency); public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton child, View dependency); public boolean onLayoutChild(CoordinatorLayout parent, FloatingActionButton child, int layoutDirection);
fab为啥要实现Behavior?主要是为了配合其他控件完成一些复杂的交互，比较经典的像这个:
fab需要在snackBar弹出的时候自动向上平移，这就得知道SnackBar的状态了，实现Behavior让fab有机会监听到其他CoordinatorLayout子View的状态，并根据状态更新自己。
复写layoutDependsOn方法可以告诉CoordinatorLayout我对哪个View感兴趣，
这里当然是SnackBar了。（注意哦，SnackBar最终展现的是SnackbarLayout，SnackBar本身并不是View）
private static final boolean SNACKBAR_BEHAVIOR_ENABLED = Build.VERSION.SDK_INT >= 11; @Override public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton child, View dependency) { // We‘re dependent on all SnackbarLayouts (if enabled) return SNACKBAR_BEHAVIOR_ENABLED && dependency instanceof Snackbar.SnackbarLayout; }
为什么API LEVEL要大于11呢？因为google偷懒想直接使用属性动画。
前面告诉了CoordinatorLayoutfab对SnackBar比较感兴趣,那么当SnackBar状态改变的时候，CoordinatorLayout就会通过onDependentViewChanged回调通知fab:
fab就可以更新自己的UI拉（这里当然是平移喽）:
@Override public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton child, View dependency) { if (dependency instanceof Snackbar.SnackbarLayout) { updateFabTranslationForSnackbar(parent, child, dependency); } else if (dependency instanceof AppBarLayout) { // If we‘re depending on an AppBarLayout we will show/hide it automatically // if the FAB is anchored to the AppBarLayout updateFabVisibility(parent, (AppBarLayout) dependency, child); } return false; }
如果是SnackBar状态变化了，那么fab就会根据情况进行平移：
private void updateFabTranslationForSnackbar(CoordinatorLayout parent, final FloatingActionButton fab, View snackbar) { final float targetTransY = getFabTranslationYForSnackbar(parent, fab); if (mFabTranslationY == targetTransY) { // We‘re already at (or currently animating to) the target value, return... return; } final float currentTransY = ViewCompat.getTranslationY(fab); // Make sure that any current animation is cancelled if (mFabTranslationYAnimator != null && mFabTranslationYAnimator.isRunning()) { mFabTranslationYAnimator.cancel(); } if (fab.isShown() && Math.abs(currentTransY - targetTransY) > (fab.getHeight() * 0.667f)) { // If the FAB will be travelling by more than 2/3 of it‘s height, let‘s animate // it instead if (mFabTranslationYAnimator == null) { mFabTranslationYAnimator = ViewUtils.createAnimator(); mFabTranslationYAnimator.setInterpolator( AnimationUtils.FAST_OUT_SLOW_IN_INTERPOLATOR); mFabTranslationYAnimator.setUpdateListener( new ValueAnimatorCompat.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimatorCompat animator) { ViewCompat.setTranslationY(fab, animator.getAnimatedFloatValue()); } }); } mFabTranslationYAnimator.setFloatValues(currentTransY, targetTransY); mFabTranslationYAnimator.start(); } else { // Now update the translation Y ViewCompat.setTranslationY(fab, targetTransY); } mFabTranslationY = targetTransY; }
代码里的注释很多，我就不解释了。
前面说到AppBarLayout和fab一起使用可以完成另一个效果，即AppBarLayout伸缩时，fab也可以以动画的形式显现、隐藏，其实现如下：
private boolean updateFabVisibility(CoordinatorLayout parent, AppBarLayout appBarLayout, FloatingActionButton child) { final CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) child.getLayoutParams(); //注意到我们必须为fab指定layout_anchor为appBarLayout if (lp.getAnchorId() != appBarLayout.getId()) { // The anchor ID doesn‘t match the dependency, so we won‘t automatically // show/hide the FAB return false; } if (child.getUserSetVisibility() != VISIBLE) { // The view isn‘t set to be visible so skip changing it‘s visibility return false; } if (mTmpRect == null) { mTmpRect = new Rect(); } // First, let‘s get the visible rect of the dependency final Rect rect = mTmpRect; ViewGroupUtils.getDescendantRect(parent, appBarLayout, rect); if (rect.bottom <= appBarLayout.getMinimumHeightForVisibleOverlappingContent()) { // If the anchor‘s bottom is below the seam, we‘ll animate our FAB out child.hide(null, false); } else { // Else, we‘ll animate our FAB back in child.show(null, false); } return true; }
除此之外，fab#Behavior还实现了onLayoutChild,主要是为了根据AppBarLayout的当前状态来判断自己是否需要隐藏。
@Override public boolean onLayoutChild(CoordinatorLayout parent, FloatingActionButton child, int layoutDirection) { // First, lets make sure that the visibility of the FAB is consistent final List<View> dependencies = parent.getDependencies(child); for (int i = 0, count = dependencies.size(); i < count; i++) { final View dependency = dependencies.get(i); if (dependency instanceof AppBarLayout && updateFabVisibility(parent, (AppBarLayout) dependency, child)) { break; } } // Now let the CoordinatorLayout lay out the FAB parent.onLayoutChild(child, layoutDirection); // Now offset it if needed offsetIfNeeded(parent, child); return true; }
此方法会在CoordinatorLayout对孩子布局的时候进行调用(即CoordinatorLayout#onLayout)，CoordinatorLayout会检查所有的直系孩子，是否设置了Behavior，如果设置了，那么就执行其onLayoutChild方法:
CoordinatorLayout#onLayout
@Override protected void onLayout(boolean changed, int l, int t, int r, int b) { final int layoutDirection = ViewCompat.getLayoutDirection(this); final int childCount = mDependencySortedChildren.size(); for (int i = 0; i < childCount; i++) { final View child = mDependencySortedChildren.get(i); final LayoutParams lp = (LayoutParams) child.getLayoutParams(); final Behavior behavior = lp.getBehavior(); if (behavior == null || !behavior.onLayoutChild(this, child, layoutDirection)) { onLayoutChild(child, layoutDirection); } } }
如果该Behavior实现了OnLayoutChild，并且返回了true，那么将不会执行CoordinatorLayout #onLayoutChild,否则执行默认的布局方案。 最后一点，这里的Behavior如何生效的呢？通过注解：
@CoordinatorLayout.DefaultBehavior(FloatingActionButton.Behavior.class) public class FloatingActionButton extends VisibilityAwareImageButton {
CoordinatorLayout在解析孩子的LayoutParams时，会check有无注解：
LayoutParams getResolvedLayoutParams(View child) { final LayoutParams result = (LayoutParams) child.getLayoutParams(); if (!result.mBehaviorResolved) { Class<?> childClass = child.getClass(); DefaultBehavior defaultBehavior = null; while (childClass != null && (defaultBehavior = childClass.getAnnotation(DefaultBehavior.class)) == null) { childClass = childClass.getSuperclass(); } if (defaultBehavior != null) { try { result.setBehavior(defaultBehavior.value().newInstance()); } catch (Exception e) { Log.e(TAG, "Default behavior class " + defaultBehavior.value().getName() + " could not be instantiated. Did you forget a default constructor?", e); } } result.mBehaviorResolved = true; } return result; }
至此fab解析完毕，谢谢观看！
标签：lex googl boolean needed images anim cell specific 回调
原文地址：http://www.cnblogs.com/anni-qianqian/p/6761302.html
