最近看到了好多高端、大气、上档次的动画效果，如果给你的项目中加上这些动画，相信你的app一定很优秀，今天给大家分析一下来自yalantis的一个超好看的下拉刷新动画。
首先我们看一下效果如何：
怎么样？是不是很高大上？接下来我们看一下代码：
一、首先我们需要自定义刷新的动态refreshview（也就是下拉时候的头）
1.初始化头所占用的dimens
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private void initiatedimens() {
mscreenwidth = mcontext.getresources().getdisplaymetrics().widthpixels;
mjettopoffset = mparent.gettotaldragdistance() * 0.5f;
mtop = -mparent.gettotaldragdistance();
}
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2.为头填充图片，设置图片的大小
分别为左边的云彩，右边的云彩，中间的云彩还有中间的飞机，飞机是带有动画的，下面会介绍飞机的动画
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private void createbitmaps() {
mleftclouds = bitmapfactory.decoderesource(mcontext.getresources(), r.drawable.clouds_left);
mrightclouds = bitmapfactory.decoderesource(mcontext.getresources(), r.drawable.clouds_right);
mfrontclouds = bitmapfactory.decoderesource(mcontext.getresources(), r.drawable.clouds_center);
mjet = bitmapfactory.decoderesource(mcontext.getresources(), r.drawable.airplane);
mjetwidthcenter = mjet.getwidth() / 2;
mjetheightcenter = mjet.getheight() / 2;
mfrontcloudwidthcenter = mfrontclouds.getwidth() / 2;
mfrontcloudheightcenter = mfrontclouds.getheight() / 2;
mrightcloudswidthcenter = mrightclouds.getwidth() / 2;
mrightcloudsheightcenter = mrightclouds.getheight() / 2;
mleftcloudswidthcenter = mleftclouds.getwidth() / 2;
mleftcloudsheightcenter = mleftclouds.getheight() / 2;
}
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3.然后我们来画这个头
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public void draw(@nonnull canvas canvas) {
final int savecount = canvas.save();
// draw background.
canvas.drawcolor(mcontext.getresources().getcolor(r.color.sky_background));
if (isrefreshing) {
// set up new set of wind
while (mwinds.size() < wind_set_amount) {
float y = (float) (mparent.gettotaldragdistance() / (math.random() * random_y_coefficient));
float x = random(min_wind_x_offset, max_wind_x_offset);
// magic with checking interval between winds
if (mwinds.size() > 1) {
y = 0;
while (y == 0) {
float tmp = (float) (mparent.gettotaldragdistance() / (math.random() * random_y_coefficient));
for (map.entry<float, float> wind : mwinds.entryset()) {
// we want that interval will be greater than fifth part of draggable distance
if (math.abs(wind.getkey() - tmp) > mparent.gettotaldragdistance() / random_y_coefficient) {
y = tmp;
} else {
y = 0;
break;
}
}
}
}
mwinds.put(y, x);
drawwind(canvas, y, x);
}
// draw current set of wind
if (mwinds.size() >= wind_set_amount) {
for (map.entry<float, float> wind : mwinds.entryset()) {
drawwind(canvas, wind.getkey(), wind.getvalue());
}
}
// we should to create new set of winds
if (minversedirection && mnewwindset) {
mwinds.clear();
mnewwindset = false;
mwindlinewidth = random(min_wind_line_width, max_wind_line_width);
}
// needed for checking direction
mlastanimationtime = mloadinganimationtime;
}
drawjet(canvas);
drawsideclouds(canvas);
drawcenterclouds(canvas);
canvas.restoretocount(savecount);
}
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/**
* draw wind on loading animation
*
* @param canvas - area where we will draw
* @param y - y position fot one of lines
* @param xoffset - x offset for on of lines
*/
private void drawwind(canvas canvas, float y, float xoffset) {
/* we should multiply current animation time with this coefficient for taking all screen width in time
removing slowing of animation with dividing on {@link #slow_down_animation_coefficient}
and we should don't forget about distance that should "fly" line that depend on screen of device and x offset
*/
float cof = (mscreenwidth + xoffset) / (loading_animation_coefficient / slow_down_animation_coefficient);
float time = mloadinganimationtime;
// horrible hack for revers animation that should work like restart animation
if (mlastanimationtime - mloadinganimationtime > 0) {
minversedirection = true;
// take time from 0 to end of animation time
time = (loading_animation_coefficient / slow_down_animation_coefficient) - mloadinganimationtime;
} else {
mnewwindset = true;
minversedirection = false;
}
// taking current x position of drawing wind
// for fully disappearing of line we should subtract wind line width
float x = (mscreenwidth - (time * cof)) + xoffset - mwindlinewidth;
float xend = x + mwindlinewidth;
canvas.drawline(x, y, xend, y, mwindpaint);
}
private void drawsideclouds(canvas canvas) {
matrix matrixleftclouds = mmatrix;
matrix matrixrightclouds = madditionalmatrix;
matrixleftclouds.reset();
matrixrightclouds.reset();
// drag percent will newer get more then 1 here
float dragpercent = math.min(1f, math.abs(mpercent));
boolean overdrag = false;
// but we check here for overdrag
if (mpercent > 1.0f) {
overdrag = true;
}
float scale;
float scalepercentdelta = dragpercent - scale_start_percent;
if (scalepercentdelta > 0) {
float scalepercent = scalepercentdelta / (1.0f - scale_start_percent);
scale = side_clouds_initial_scale + (side_clouds_final_scale - side_clouds_initial_scale) * scalepercent;
} else {
scale = side_clouds_initial_scale;
}
// current y position of clouds
float dragyoffset = mparent.gettotaldragdistance() * (1.0f - dragpercent);
// position where clouds fully visible on screen and we should drag them with content of listview
int cloudsvisibleposition = mparent.gettotaldragdistance() / 2 - mleftcloudsheightcenter;
boolean needmovecloudswithcontent = false;
if (dragyoffset < cloudsvisibleposition) {
needmovecloudswithcontent = true;
}
float offsetrightx = mscreenwidth - mrightclouds.getwidth();
float offsetrighty = (needmovecloudswithcontent
? mparent.gettotaldragdistance() * dragpercent - mleftclouds.getheight()
: dragyoffset)
+ (overdrag ? mtop : 0);
float offsetleftx = 0;
float offsetlefty = (needmovecloudswithcontent
? mparent.gettotaldragdistance() * dragpercent - mleftclouds.getheight()
: dragyoffset)
+ (overdrag ? mtop : 0);
// magic with animation on loading process
if (isrefreshing) {
if (checkcurrentanimationpart(animationpart.first)) {
offsetlefty += getanimationpartvalue(animationpart.first) / y_side_clouds_slow_down_cof;
offsetrightx -= getanimationpartvalue(animationpart.first) / x_side_clouds_slow_down_cof;
} else if (checkcurrentanimationpart(animationpart.second)) {
offsetlefty += getanimationpartvalue(animationpart.second) / y_side_clouds_slow_down_cof;
offsetrightx -= getanimationpartvalue(animationpart.second) / x_side_clouds_slow_down_cof;
} else if (checkcurrentanimationpart(animationpart.third)) {
offsetlefty -= getanimationpartvalue(animationpart.third) / y_side_clouds_slow_down_cof;
offsetrightx += getanimationpartvalue(animationpart.third) / x_side_clouds_slow_down_cof;
} else if (checkcurrentanimationpart(animationpart.fourth)) {
offsetlefty -= getanimationpartvalue(animationpart.fourth) / x_side_clouds_slow_down_cof;
offsetrightx += getanimationpartvalue(animationpart.fourth) / y_side_clouds_slow_down_cof;
}
}
matrixrightclouds.postscale(scale, scale, mrightcloudswidthcenter, mrightcloudsheightcenter);
matrixrightclouds.posttranslate(offsetrightx, offsetrighty);
matrixleftclouds.postscale(scale, scale, mleftcloudswidthcenter, mleftcloudsheightcenter);
matrixleftclouds.posttranslate(offsetleftx, offsetlefty);
canvas.drawbitmap(mleftclouds, matrixleftclouds, null);
canvas.drawbitmap(mrightclouds, matrixrightclouds, null);
}
private void drawcenterclouds(canvas canvas) {
matrix matrix = mmatrix;
matrix.reset();
float dragpercent = math.min(1f, math.abs(mpercent));
float scale;
float overdragpercent = 0;
boolean overdrag = false;
if (mpercent > 1.0f) {
overdrag = true;
// here we want know about how mach percent of over drag we done
overdragpercent = math.abs(1.0f - mpercent);
}
float scalepercentdelta = dragpercent - scale_start_percent;
if (scalepercentdelta > 0) {
float scalepercent = scalepercentdelta / (1.0f - scale_start_percent);
scale = center_clouds_initial_scale + (center_clouds_final_scale - center_clouds_initial_scale) * scalepercent;
} else {
scale = center_clouds_initial_scale;
}
float parallaxpercent = 0;
boolean parallax = false;
// current y position of clouds
float dragyoffset = mparent.gettotaldragdistance() * dragpercent;
// position when should start parallax scrolling
int startparallaxheight = mparent.gettotaldragdistance() - mfrontcloudheightcenter;
if (dragyoffset > startparallaxheight) {
parallax = true;
parallaxpercent = dragyoffset - startparallaxheight;
}
float offsetx = (mscreenwidth / 2) - mfrontcloudwidthcenter;
float offsety = dragyoffset
- (parallax ? mfrontcloudheightcenter + parallaxpercent : mfrontcloudheightcenter)
+ (overdrag ? mtop : 0);
float sx = overdrag ? scale + overdragpercent / 4 : scale;
float sy = overdrag ? scale + overdragpercent / 2 : scale;
if (isrefreshing && !overdrag) {
if (checkcurrentanimationpart(animationpart.first)) {
sx = scale - (getanimationpartvalue(animationpart.first) / loading_animation_coefficient) / 8;
} else if (checkcurrentanimationpart(animationpart.second)) {
sx = scale - (getanimationpartvalue(animationpart.second) / loading_animation_coefficient) / 8;
} else if (checkcurrentanimationpart(animationpart.third)) {
sx = scale + (getanimationpartvalue(animationpart.third) / loading_animation_coefficient) / 6;
} else if (checkcurrentanimationpart(animationpart.fourth)) {
sx = scale + (getanimationpartvalue(animationpart.fourth) / loading_animation_coefficient) / 6;
}
sy = sx;
}
matrix.postscale(sx, sy, mfrontcloudwidthcenter, mfrontcloudheightcenter);
matrix.posttranslate(offsetx, offsety);
canvas.drawbitmap(mfrontclouds, matrix, null);
}
private void drawjet(canvas canvas) {
matrix matrix = mmatrix;
matrix.reset();
float dragpercent = mpercent;
float rotateangle = 0;
// check overdrag
if (dragpercent > 1.0f && !mendofrefreshing) {
rotateangle = (dragpercent % 1) * 10;
dragpercent = 1.0f;
}
float offsetx = ((mscreenwidth * dragpercent) / 2) - mjetwidthcenter;
float offsety = mjettopoffset
+ (mparent.gettotaldragdistance() / 2)
* (1.0f - dragpercent)
- mjetheightcenter;
if (isrefreshing) {
if (checkcurrentanimationpart(animationpart.first)) {
offsety -= getanimationpartvalue(animationpart.first);
} else if (checkcurrentanimationpart(animationpart.second)) {
offsety -= getanimationpartvalue(animationpart.second);
} else if (checkcurrentanimationpart(animationpart.third)) {
offsety += getanimationpartvalue(animationpart.third);
} else if (checkcurrentanimationpart(animationpart.fourth)) {
offsety += getanimationpartvalue(animationpart.fourth);
}
}
matrix.settranslate(offsetx, offsety);
if (dragpercent == 1.0f) {
matrix.prerotate(rotateangle, mjetwidthcenter, mjetheightcenter);
}
canvas.drawbitmap(mjet, matrix, null);
}
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动画效果已经画好了，下面我们来看看怎么结合下拉刷新来调用吧？
二、我们还需要自定义一个pulltorefreshview（下拉刷新）
1.我们的pulltorefreshview这里需要继承viewgroup
我们先把刚才定义的刷新时的动画加进来
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private refreshview mrefreshview;
<pre name="code" class="java">private imageview mrefreshimageview;
<pre name="code" class="java">mrefreshimageview = new imageview(context);
mrefreshview = new refreshview(getcontext(), this);
mrefreshimageview.setimagedrawable(mrefreshview);
addview(mrefreshimageview);
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2.然后我们设置ontouchevent()事件
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@override
public boolean ontouchevent(@nonnull motionevent ev) {
if (!misbeingdragged) {
return super.ontouchevent(ev);
}
final int action = motioneventcompat.getactionmasked(ev);
switch (action) {
case motionevent.action_move: {
final int pointerindex = motioneventcompat.findpointerindex(ev, mactivepointerid);
if (pointerindex < 0) {
return false;
}
final float y = motioneventcompat.gety(ev, pointerindex);
final float ydiff = y - minitialmotiony;
final float scrolltop = ydiff * drag_rate;
mcurrentdragpercent = scrolltop / mtotaldragdistance;
if (mcurrentdragpercent < 0) {
return false;
}
float boundeddragpercent = math.min(1f, math.abs(mcurrentdragpercent));
float extraos = math.abs(scrolltop) - mtotaldragdistance;
float slingshotdist = mtotaldragdistance;
float tensionslingshotpercent = math.max(0,
math.min(extraos, slingshotdist * 2) / slingshotdist);
float tensionpercent = (float) ((tensionslingshotpercent / 4) - math.pow(
(tensionslingshotpercent / 4), 2)) * 2f;
float extramove = (slingshotdist) * tensionpercent / 2;
int targety = (int) ((slingshotdist * boundeddragpercent) + extramove);
mrefreshview.setpercent(mcurrentdragpercent);
settargetoffsettop(targety - mcurrentoffsettop, true);
break;
}
case motioneventcompat.action_pointer_down:
final int index = motioneventcompat.getactionindex(ev);
mactivepointerid = motioneventcompat.getpointerid(ev, index);
break;
case motioneventcompat.action_pointer_up:
onsecondarypointerup(ev);
break;
case motionevent.action_up:
case motionevent.action_cancel: {
if (mactivepointerid == invalid_pointer) {
return false;
}
final int pointerindex = motioneventcompat.findpointerindex(ev, mactivepointerid);
final float y = motioneventcompat.gety(ev, pointerindex);
final float overscrolltop = (y - minitialmotiony) * drag_rate;
misbeingdragged = false;
if (overscrolltop > mtotaldragdistance) {
setrefreshing(true, true);
} else {
mrefreshing = false;
animateoffsettoposition(manimatetostartposition);
}
mactivepointerid = invalid_pointer;
return false;
}
}
return true;
}
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三、最后我们看怎样在activity中使用这个下拉刷新控件
1.先看一下布局文件
这里是我们的下拉刷新空间嵌套着我们的listview，然后我们再给listview填充数据即可
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<relativelayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".pulltorefreshactivity">
<com.hankkin.animationpulltorefreshdemo.pulltorefreshview
android:id="@+id/pull_to_refresh"
android:layout_width="match_parent"
android:layout_height="match_parent">
<listview
android:id="@+id/list_view"
android:divider="@null"
android:dividerheight="0dp"
android:fadingedge="none"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</com.hankkin.animationpulltorefreshdemo.pulltorefreshview>
</relativelayout>
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2.为listview填充数据
为了我们的效果比较好看，这里我们给listview的每一个item填充不同的颜色，看起来会比较高大上。
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map<string, integer> map;
list<map<string, integer>> samplelist = new arraylist<map<string, integer>>();
int[] colors = {
r.color.saffron,
r.color.eggplant,
r.color.sienna};
int[] tripnames = {
r.string.trip_to_india,
r.string.trip_to_italy,
r.string.trip_to_indonesia};
for (int i = 0; i < tripnames.length; i++) {
map = new hashmap<string, integer>();
map.put(sampleadapter.key_name, tripnames[i]);
map.put(sampleadapter.key_color, colors[i]);
samplelist.add(map);
}
listview listview = (listview) findviewbyid(r.id.list_view);
listview.setadapter(new sampleadapter(this, r.layout.list_item, samplelist));
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3.最后，我们再设置一下下拉刷新的监听事件就ok了
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mpulltorefreshview = (pulltorefreshview) findviewbyid(r.id.pull_to_refresh);
mpulltorefreshview.setonrefreshlistener(new pulltorefreshview.onrefreshlistener() {
@override
public void onrefresh() {
mpulltorefreshview.postdelayed(new runnable() {
@override
public void run() {
mpulltorefreshview.setrefreshing(false);
}
}, refresh_delay);
}
});
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怎么样？有没有很高大上啊？
大家可以动手实践一下，希望对大家的学习有所帮助。