今天周日，不适合出门，太冷了，俗说：一九二九不出手，三九四九零来走。。
我们的应用也可以有一些冬天的效果, 教大家做一个下雪的动画效果, 参考.
主要
(1) 隐藏status bar, 全屏显示图片.
(2) 绘制多个点, 实现移动效果.
(3) 回收点, 避免重复创建.
我喜欢用注释说话, 请大家多关注代码中的注释.
github下载地址
1. 雪花类
雪花的属性包含: 随机量, 位置, 增量, 大小, 角度, 画笔.
绘画的过程中, 使用角度会移动点的位置, 每次速率都不同.
当雪花移出屏幕时, 会重新使用, 在屏幕的顶端重新落下.
算法参考.
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/*** 雪花的类, 移动, 移出屏幕会重新设置位置.* <p/>* created by wangchenlong on 16/1/24.*/public class snowflake {// 雪花的角度private static final float ange_range = 0.1f; // 角度范围private static final float half_angle_range = ange_range / 2f; // 一般的角度private static final float half_pi = (float) math.pi / 2f; // 半piprivate static final float angle_seed = 25f; // 角度随机种子private static final float angle_divisor = 10000f; // 角度的分母// 雪花的移动速度private static final float increment_lower = 2f;private static final float increment_upper = 4f;// 雪花的大小private static final float flake_size_lower = 7f;private static final float flake_size_upper = 20f;private final randomgenerator mrandom; // 随机控制器private final point mposition; // 雪花位置private float mangle; // 角度private final float mincrement; // 雪花的速度private final float mflakesize; // 雪花的大小private final paint mpaint; // 画笔private snowflake(randomgenerator random, point position, float angle, float increment, float flakesize, paint paint) {mrandom = random;mposition = position;mincrement = increment;mflakesize = flakesize;mpaint = paint;mangle = angle;}public static snowflake create(int width, int height, paint paint) {randomgenerator random = new randomgenerator();int x = random.getrandom(width);int y = random.getrandom(height);point position = new point(x, y);float angle = random.getrandom(angle_seed) / angle_seed * ange_range + half_pi - half_angle_range;float increment = random.getrandom(increment_lower, increment_upper);float flakesize = random.getrandom(flake_size_lower, flake_size_upper);return new snowflake(random, position, angle, increment, flakesize, paint);}// 绘制雪花public void draw(canvas canvas) {int width = canvas.getwidth();int height = canvas.getheight();move(width, height);canvas.drawcircle(mposition.x, mposition.y, mflakesize, mpaint);}// 移动雪花private void move(int width, int height) {double x = mposition.x + (mincrement * math.cos(mangle));double y = mposition.y + (mincrement * math.sin(mangle));mangle += mrandom.getrandom(-angle_seed, angle_seed) / angle_divisor; // 随机晃动mposition.set((int) x, (int) y);// 移除屏幕, 重新开始if (!isinside(width, height)) {reset(width);}}// 判断是否在其中private boolean isinside(int width, int height) {int x = mposition.x;int y = mposition.y;return x >= -mflakesize - 1 && x + mflakesize <= width && y >= -mflakesize - 1 && y - mflakesize < height;}// 重置雪花private void reset(int width) {mposition.x = mrandom.getrandom(width);mposition.y = (int) (-mflakesize - 1); // 最上面mangle = mrandom.getrandom(angle_seed) / angle_seed * ange_range + half_pi - half_angle_range;}}随机数生成器, 包含区间随机和上界随机./*** 随机生成器* <p/>* created by wangchenlong on 16/1/24.*/public class randomgenerator {private static final random random = new random();// 区间随机public float getrandom(float lower, float upper) {float min = math.min(lower, upper);float max = math.max(lower, upper);return getrandom(max - min) + min;}// 上界随机public float getrandom(float upper) {return random.nextfloat() * upper;}// 上界随机public int getrandom(int upper) {return random.nextint(upper);}} |
2. 雪花视图
雪花视图, delay时间重绘, 绘制num_snowflakes个雪花.
初始化在onsizechanged中进行, 绘制在ondraw中进行.
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/*** 雪花视图, delay时间重绘, 绘制num_snowflakes个雪花* <p/>* created by wangchenlong on 16/1/24.*/public class snowview extends view {private static final int num_snowflakes = 150; // 雪花数量private static final int delay = 5; // 延迟private snowflake[] msnowflakes; // 雪花public snowview(context context) {super(context);}public snowview(context context, attributeset attrs) {super(context, attrs);}public snowview(context context, attributeset attrs, int defstyleattr) {super(context, attrs, defstyleattr);}@targetapi(21)public snowview(context context, attributeset attrs, int defstyleattr, int defstyleres) {super(context, attrs, defstyleattr, defstyleres);}@override protected void onsizechanged(int w, int h, int oldw, int oldh) {super.onsizechanged(w, h, oldw, oldh);if (w != oldw || h != oldh) {initsnow(w, h);}}private void initsnow(int width, int height) {paint paint = new paint(paint.anti_alias_flag); // 抗锯齿paint.setcolor(color.white); // 白色雪花paint.setstyle(paint.style.fill); // 填充;msnowflakes = new snowflake[num_snowflakes];for (int i = 0; i < num_snowflakes; ++i) {msnowflakes[i] = snowflake.create(width, height, paint);}}@override protected void ondraw(canvas canvas) {super.ondraw(canvas);for (snowflake s : msnowflakes) {s.draw(canvas);}// 隔一段时间重绘一次, 动画效果gethandler().postdelayed(runnable, delay);}// 重绘线程private runnable runnable = new runnable() {@overridepublic void run() {invalidate();}};} |
使用gethandler().postdelayed(runnable, delay);刷新页面.
3. 全屏布局
全屏布局
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<?xml version="1.0" encoding="utf-8"?><android.support.design.widget.collapsingtoolbarlayoutxmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"><framelayoutandroid:layout_width="match_parent"android:layout_height="match_parent"><imageviewandroid:layout_width="match_parent"android:layout_height="match_parent"android:contentdescription="@null"android:scaletype="centercrop"android:src="@drawable/christmas"/><me.chunyu.spike.wcl_snowfall_demo.views.snowviewandroid:layout_width="match_parent"android:layout_height="match_parent"/></framelayout></android.support.design.widget.collapsingtoolbarlayout> |
status bar默认是不会被透明化的, 需要使用collapsingtoolbarlayout,
替换status bar的样式, 否则会留有一定高度, 即使透明也不会填充.
样式
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<?xml version="1.0" encoding="utf-8"?><resources><style name="apptheme.nostatusbar"><item name="android:windowtranslucentstatus">true</item></style></resources> |
