SnackBar源码解析及封装

废话不多说，先看效果图，没有效果图就等于扯淡。

因为上传大小有限制，并且GIF有卡顿。所以大家下载源码可以看到更多效果

SnackBar

前两天创建新项目的activity的时候，不小心选择了ScrollingActivity，打开一看里面有一个SnackBar来显示出吐司。感觉跟Toast一样，于是研究了一番。先来简单的介绍一下SnackBar，Snackbar 是 Android 5.0 新特性——Material Design 中的一个控件，用来代替 Toast ，Snackbar与Toast的主要区别是：Snackbar可以滑动退出，也可以处理用户交互（点击）事件。总之Toast能做的它也可以做，而且部分功能做的更好。比如显示时长，Toast最多3s，SnackBar可以自定义时长。这一点比Toast强大很多。

Snackbar特性

屏幕上同时最多只能显示一个Snackbar；
可以在Snackbar中添加一个按钮，处理用户点击事件；
Snackbar一般需要CoordinatorLayout来作为父容器，CoordinatorLayout保证Snackbar可以右滑退出；
出现时不会阻碍用户在屏幕上的输入；
可以自定义显示时长；
可以监听显示隐藏事件，便于用户操作更多。

扩展功能

因为SnackBar并不能完全支撑我们的开发需要，所以这里通过修改源码拓展了一些功能

SnackBar展示位置（SnackBar默认只能在底部显示，并且动画也只是根据底部弹出的，所以如果想要在其他位置显示，需要通过修改源码在修改；具体代码在BaseTransientBottomBar.java中的445行设置，如果想要拓展的，可以直接修改此类）
SnackBar展示动画（跟上面一样，动画默认是底部弹出。如果需要修改，可以在源码MySnackBar.java中的256行通过setGravity()方法来追踪，具体都有注释，想必不难理解。）

这里的拓展功能是我根据我当前项目需要，就只修改了这两处的源码。大家可以根据项目需求自行拓展

我修改的源码

1.MySnackBar.java（这个类没有修改，新增了一个方法，用来调用）

 /*** 自定义SnackBar显示位置* @param type*/public void setGravity(int type) {BaseTransientBottomBar.DISPLAY_LOCATION_TYPE = type;}

2.BaseTransientBottomBar.java（这个类里面修改了两处，一个是显示位置，一个是显示动画）

这里是显示位置修改的代码

 final void showView() {if (mView.getParent() == null) {final ViewGroup.LayoutParams lp = mView.getLayoutParams();if (lp instanceof CoordinatorLayout.LayoutParams) {// If our LayoutParams are from a CoordinatorLayout, we'll setup our Behaviorfinal CoordinatorLayout.LayoutParams clp = (CoordinatorLayout.LayoutParams) lp;final Behavior behavior = new Behavior();behavior.setStartAlphaSwipeDistance(0.1f);behavior.setEndAlphaSwipeDistance(0.6f);behavior.setSwipeDirection(SwipeDismissBehavior.SWIPE_DIRECTION_START_TO_END);behavior.setListener(new SwipeDismissBehavior.OnDismissListener() {@Overridepublic void onDismiss(View view) {view.setVisibility(View.GONE);dispatchDismiss(BaseCallback.DISMISS_EVENT_SWIPE);}@Overridepublic void onDragStateChanged(int state) {switch (state) {case SwipeDismissBehavior.STATE_DRAGGING:case SwipeDismissBehavior.STATE_SETTLING:// If the view is being dragged or settling, pause the timeoutSnackBarManager.getInstance().pauseTimeout(mManagerCallback);break;case SwipeDismissBehavior.STATE_IDLE:// If the view has been released and is idle, restore the timeoutSnackBarManager.getInstance().restoreTimeoutIfPaused(mManagerCallback);break;}}});clp.setBehavior(behavior);// Also set the inset edge so that views can dodge the bar correctlyclp.insetEdge = Gravity.BOTTOM;}//SnackBar源码为 mTargetParent.addView(mView)，但是为了兼容动态显示的位置，这里使用了动态布局加载包裹，可以实现自由切换底部还是顶部LinearLayout.LayoutParams param = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);//此处相当于布局文件中的Android:layout_gravity属性if(DISPLAY_LOCATION_TYPE == 1){param.gravity = Gravity.TOP;} else if(DISPLAY_LOCATION_TYPE == 2){param.gravity = Gravity.BOTTOM;} else if(DISPLAY_LOCATION_TYPE == 3){param.gravity = Gravity.CENTER;}mView.setLayoutParams(param);LinearLayout linear = new LinearLayout(mContext);//注意，对于LinearLayout布局来说，设置横向还是纵向是必须的！否则就看不到效果了。linear.setOrientation(LinearLayout.HORIZONTAL);linear.addView(mView);mTargetParent.addView(linear);}mView.setOnAttachStateChangeListener(new View.OnAttachStateChangeListener() {@Overridepublic void onViewAttachedToWindow(View view) {}@Overridepublic void onViewDetachedFromWindow(View view) {if (isShownOrQueued()) {// If we haven't already been dismissed then this event is coming from a// non-user initiated action. Hence we need to make sure that we callback// and keep our state up to date. We need to post the call since// removeView() will call through to onDetachedFromWindow and thus overflow.sHandler.post(new Runnable() {@Overridepublic void run() {onViewHidden(BaseCallback.DISMISS_EVENT_MANUAL);}});}}});if (ViewCompat.isLaidOut(mView)) {if (shouldAnimate()) {// If animations are enabled, animate it inanimateViewIn();} else {// Else if anims are disabled just call back nowonViewShown();}} else {// Otherwise, add one of our layout change listeners and show it in when laid outmView.setOnLayoutChangeListener(new View.OnLayoutChangeListener() {@Overridepublic void onLayoutChange(View view, int i, int i1, int i2, int i3, int i4, int i5, int i6, int i7) {mView.setOnLayoutChangeListener(null);if (shouldAnimate()) {// If animations are enabled, animate it inanimateViewIn();} else {// Else if anims are disabled just call back nowonViewShown();}}});}}

这里是显示动画修改的代码

 /*** 动画开始方法*/void animateViewIn() {if (Build.VERSION.SDK_INT >= 12) {final int viewHeight;if(DISPLAY_LOCATION_TYPE == 1){//顶部显示viewHeight = -mView.getHeight();}else{//底部显示viewHeight = mView.getHeight();}if (USE_OFFSET_API) {ViewCompat.offsetTopAndBottom(mView, viewHeight);} else {mView.setTranslationY(viewHeight);}final ValueAnimator animator = new ValueAnimator();animator.setIntValues(viewHeight, 0);animator.setInterpolator(FAST_OUT_SLOW_IN_INTERPOLATOR);animator.setDuration(ANIMATION_DURATION);animator.addListener(new AnimatorListenerAdapter() {@Overridepublic void onAnimationStart(Animator animator) {mContentViewCallback.animateContentIn(ANIMATION_DURATION - ANIMATION_FADE_DURATION,ANIMATION_FADE_DURATION);}@Overridepublic void onAnimationEnd(Animator animator) {onViewShown();}});animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {private int mPreviousAnimatedIntValue = viewHeight;@Overridepublic void onAnimationUpdate(ValueAnimator animator) {int currentAnimatedIntValue = (int) animator.getAnimatedValue();if (USE_OFFSET_API) {ViewCompat.offsetTopAndBottom(mView,currentAnimatedIntValue - mPreviousAnimatedIntValue);} else {mView.setTranslationY(currentAnimatedIntValue);}mPreviousAnimatedIntValue = currentAnimatedIntValue;}});animator.start();} else {final Animation anim = android.view.animation.AnimationUtils.loadAnimation(mView.getContext(),R.anim.design_snackbar_in);anim.setInterpolator(FAST_OUT_SLOW_IN_INTERPOLATOR);anim.setDuration(ANIMATION_DURATION);anim.setAnimationListener(new Animation.AnimationListener() {@Overridepublic void onAnimationEnd(Animation animation) {onViewShown();}@Overridepublic void onAnimationStart(Animation animation) {}@Overridepublic void onAnimationRepeat(Animation animation) {}});mView.startAnimation(anim);}}/*** 动画结束方法* @param event*/private void animateViewOut(final int event) {if (Build.VERSION.SDK_INT >= 12) {final ValueAnimator animator = new ValueAnimator();if(DISPLAY_LOCATION_TYPE == 1){//改成0，顶部显示才会生效（design_layout_snackbar.xml里的layout_gravity由bottom改为top）//如果要底部显示（注释这一行即可）mView.setTranslationY(0);//顶部显示animator.setIntValues(0, -mView.getHeight());}else{//底部显示animator.setIntValues(0, mView.getHeight());}animator.setInterpolator(FAST_OUT_SLOW_IN_INTERPOLATOR);animator.setDuration(ANIMATION_DURATION);animator.addListener(new AnimatorListenerAdapter() {@Overridepublic void onAnimationStart(Animator animator) {mContentViewCallback.animateContentOut(0, ANIMATION_FADE_DURATION);}@Overridepublic void onAnimationEnd(Animator animator) {onViewHidden(event);}});animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {private int mPreviousAnimatedIntValue = 0;@Overridepublic void onAnimationUpdate(ValueAnimator animator) {int currentAnimatedIntValue = (int) animator.getAnimatedValue();if (USE_OFFSET_API) {ViewCompat.offsetTopAndBottom(mView,currentAnimatedIntValue - mPreviousAnimatedIntValue);} else {mView.setTranslationY(currentAnimatedIntValue);}mPreviousAnimatedIntValue = currentAnimatedIntValue;}});animator.start();} else {final Animation anim = android.view.animation.AnimationUtils.loadAnimation(mView.getContext(),R.anim.design_snackbar_out);anim.setInterpolator(FAST_OUT_SLOW_IN_INTERPOLATOR);anim.setDuration(ANIMATION_DURATION);anim.setAnimationListener(new Animation.AnimationListener() {@Overridepublic void onAnimationEnd(Animation animation) {onViewHidden(event);}@Overridepublic void onAnimationStart(Animation animation) {}@Overridepublic void onAnimationRepeat(Animation animation) {}});mView.startAnimation(anim);}}

我修改的代码就上面这么多

以上就是所有的代码

附上demo源码。

源码：源码请点这里

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                                                                         ---财财亲笔