Android实现旋转动画的两种方式案例详解 Android实现旋转动画的两种方式

练习案例
效果展示
前期准备
自定义 View java代码编写

方法一
方法二

易错点总结：

练习案例视差动画 - 雅虎新闻摘要加载

效果展示

文章图片

前期准备第一步：准备好颜色数组 res => values => colors.xml

#FF9600#02D1AC#FFD200#00C6FF#00E099#FF3891 @color/orange@color/aqua@color/yellow@color/bule@color/green@color/pink

【Android实现旋转动画的两种方式案例详解】

文章图片

自定义 View java代码编写
方法一
关键思想：属性动画 + 计算圆心

文章图片

package com.wust.mydialog; import android.animation.ObjectAnimator; import android.animation.ValueAnimator; import android.content.Context; import android.graphics.Canvas; import android.graphics.Paint; import android.util.AttributeSet; import android.view.View; import android.view.animation.LinearInterpolator; import androidx.annotation.Nullable; /** * ClassName: com.wust.mydialog.MyRotateView
* Description:
* date: 2021/8/7 12:13
* * @author yiqi
* @QQ 1820762465 * @微信 yiqiideallife * @技术交流QQ群 928023749 */public class MyRotateView extends View { //设置旋转间隔时间private int SPLASH_CIRCLE_ROTATE_TIME = 3000; //设置中心圆半径private float CENTER_CIRCLE_RADIUS; private float SMALL_CIRCLE_RADIUS; private float mCurrentSingle = 0f; private int[] mColorArray; private Paint mCirclePaint; private ValueAnimator va; public MyRotateView(Context context) {super(context); } public MyRotateView(Context context, @Nullable AttributeSet attrs) {super(context, attrs); } public MyRotateView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr); } @Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {int width = MeasureSpec.getSize(widthMeasureSpec); int height = MeasureSpec.getSize(heightMeasureSpec); //初始化参数initParams(width,height); setMeasuredDimension(width,height); } private void initParams(int w, int h) {//设置中心圆半径CENTER_CIRCLE_RADIUS = 1/4.0f * w; //设置小圆的半径SMALL_CIRCLE_RADIUS = 1/25.0f * w; //获取小球颜色mColorArray = getResources().getIntArray(R.array.splash_circle_colors); //初始化画笔mCirclePaint = new Paint(); mCirclePaint.setDither(true); mCirclePaint.setAntiAlias(true); } @Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas); //绘制圆drawSplashCircle(canvas); } private void drawSplashCircle(Canvas canvas) {//设置属性动画，让小圆转起来//这里得注意，是个坑，你如果不判断那球就不会动因为会陷入死循环值动画将值设置为0 -> invalidate()重绘 -> 执行draw 又将值设为0if (va == null){va = ObjectAnimator.ofFloat(0f, 2 * (float) Math.PI); va.setDuration(SPLASH_CIRCLE_ROTATE_TIME); va.setRepeatCount(ValueAnimator.INFINITE); va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {@Overridepublic void onAnimationUpdate(ValueAnimator animation) {mCurrentSingle = (float) animation.getAnimatedValue(); //System.out.println("mCurrentSingle ->" + mCurrentSingle); invalidate(); }}); va.setInterpolator(new LinearInterpolator()); va.start(); } //计算每个小球的间隔double spaceAngle = Math.PI*2/mColorArray.length; for (int i = 0; i < mColorArray.length; i++) {//为每个球画笔设置颜色mCirclePaint.setColor(mColorArray[i]); //利用勾股定理计算小圆中心点float cx = getWidth()/2 + (float) (CENTER_CIRCLE_RADIUS*Math.cos(spaceAngle*i+mCurrentSingle)); float cy = getHeight()/2 + (float) (CENTER_CIRCLE_RADIUS*Math.sin(spaceAngle*i+mCurrentSingle)); canvas.drawCircle(cx,cy,SMALL_CIRCLE_RADIUS,mCirclePaint); }}}

方法二
关键思想：旋转画布法

package com.wust.mydialog; import android.animation.ObjectAnimator; import android.animation.ValueAnimator; import android.content.Context; import android.graphics.Canvas; import android.graphics.Paint; import android.util.AttributeSet; import android.view.View; import android.view.animation.LinearInterpolator; import androidx.annotation.Nullable; /** * ClassName: com.wust.mydialog.MyRotateView
* Description:
* date: 2021/8/7 12:13
* * @author yiqi
* @QQ 1820762465 * @微信 yiqiideallife * @技术交流QQ群 928023749 */public class MyRotateView extends View { //设置旋转间隔时间private int SPLASH_CIRCLE_ROTATE_TIME = 3000; //设置中心圆半径private float CENTER_CIRCLE_RADIUS; private float SMALL_CIRCLE_RADIUS; private float mCurrentSingle = 0f; private int[] mColorArray; private Paint mCirclePaint; private ValueAnimator va; public MyRotateView(Context context) {super(context); } public MyRotateView(Context context, @Nullable AttributeSet attrs) {super(context, attrs); } public MyRotateView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr); } @Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {int width = MeasureSpec.getSize(widthMeasureSpec); int height = MeasureSpec.getSize(heightMeasureSpec); //初始化参数initParams(width,height); setMeasuredDimension(width,height); } private void initParams(int w, int h) {//设置中心圆半径CENTER_CIRCLE_RADIUS = 1/4.0f * w; //设置小圆的半径SMALL_CIRCLE_RADIUS = 1/25.0f * w; //获取小球颜色mColorArray = getResources().getIntArray(R.array.splash_circle_colors); //初始化画笔mCirclePaint = new Paint(); mCirclePaint.setDither(true); mCirclePaint.setAntiAlias(true); } @Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas); //绘制圆drawSplashCircle(canvas); } private void drawSplashCircle(Canvas canvas) {//设置属性动画，让小圆转起来//这里得注意，是个坑，你如果不判断那球就不会动因为会陷入死循环值动画将值设置为0 -> invalidate()重绘 -> 执行draw 又将值设为0if (va == null){//va = ObjectAnimator.ofFloat(0f, 2 * (float) Math.PI); va = ObjectAnimator.ofFloat(0f, 360.0f); va.setDuration(SPLASH_CIRCLE_ROTATE_TIME); va.setRepeatCount(ValueAnimator.INFINITE); va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {@Overridepublic void onAnimationUpdate(ValueAnimator animation) {mCurrentSingle = (float) animation.getAnimatedValue(); //System.out.println("mCurrentSingle ->" + mCurrentSingle); invalidate(); }}); va.setInterpolator(new LinearInterpolator()); va.start(); } //计算每个小球的间隔//double spaceAngle = Math.PI*2/mColorArray.length; double spaceAngle = 360.0d/mColorArray.length; System.out.println("spaceAngle -> " + spaceAngle); //利用旋转画布法canvas.save(); canvas.rotate(mCurrentSingle,getWidth()/2,getHeight()/2); for (int i = 0; i < mColorArray.length; i++) {canvas.rotate((float) spaceAngle,getWidth()/2,getHeight()/2); //为每个球画笔设置颜色mCirclePaint.setColor(mColorArray[i]); //利用勾股定理计算小圆中心点//float cx = getWidth()/2 + (float) (CENTER_CIRCLE_RADIUS*Math.cos(spaceAngle*i+mCurrentSingle)); //float cy = getHeight()/2 + (float) (CENTER_CIRCLE_RADIUS*Math.sin(spaceAngle*i+mCurrentSingle)); //利用旋转画布法float cx = getWidth()/2 + CENTER_CIRCLE_RADIUS; float cy = getHeight()/2; canvas.drawCircle(cx,cy,SMALL_CIRCLE_RADIUS,mCirclePaint); }canvas.restore(); }}

易错点总结： 1、canvas.rotate(mCurrentSingle,getWidth()/2,getHeight()/2); 中第一个参数传的是角度（360度的那种），而 Math.cos(); 中参数传的是一个弧度（2π的那种）
2、canvas.rotate() 函数执行之后对后续画布上的操作都是有影响的，所以，得配合 canvas.save(); 和 canvas.restore(); 使用。因此，里面的canvas.rotate((float) spaceAngle,getWidth()/2,getHeight()/2); 中spaceAngle不能乘 i 。
3、画布的旋转除了 canvas.rotate() 函数可以实现外，还可以利用矩阵。代码如下：

//创建矩阵private Matrix mSpaceMatrix; //初始化旋转矩阵mSpaceMatrix = new Matrix(); //初始化旋转矩阵mSpaceMatrix.reset(); mSpaceMatrix.postRotate((float) spaceAngle,getWidth()/2,getHeight()/2); //画布旋转角度canvas.concat(mSpaceMatrix);

完整代码

package com.wust.mydialog; import android.animation.ObjectAnimator; import android.animation.ValueAnimator; import android.content.Context; import android.graphics.Canvas; import android.graphics.Matrix; import android.graphics.Paint; import android.util.AttributeSet; import android.view.View; import android.view.animation.LinearInterpolator; import androidx.annotation.Nullable; /** * ClassName: com.wust.mydialog.MyRotateView
* Description:
* date: 2021/8/7 12:13
* * @author yiqi
* @QQ 1820762465 * @微信 yiqiideallife * @技术交流QQ群 928023749 */public class MyRotateView extends View { //设置旋转间隔时间private int SPLASH_CIRCLE_ROTATE_TIME = 3000; //设置中心圆半径private float CENTER_CIRCLE_RADIUS; private float SMALL_CIRCLE_RADIUS; private float mCurrentSingle = 0f; private int[] mColorArray; private Paint mCirclePaint; private ValueAnimator va; private Matrix mSpaceMatrix; public MyRotateView(Context context) {super(context); } public MyRotateView(Context context, @Nullable AttributeSet attrs) {super(context, attrs); } public MyRotateView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr); } @Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {int width = MeasureSpec.getSize(widthMeasureSpec); int height = MeasureSpec.getSize(heightMeasureSpec); //初始化参数initParams(width,height); setMeasuredDimension(width,height); } private void initParams(int w, int h) {//设置中心圆半径CENTER_CIRCLE_RADIUS = 1/4.0f * w; //设置小圆的半径SMALL_CIRCLE_RADIUS = 1/25.0f * w; //获取小球颜色mColorArray = getResources().getIntArray(R.array.splash_circle_colors); //初始化画笔mCirclePaint = new Paint(); mCirclePaint.setDither(true); mCirclePaint.setAntiAlias(true); //初始化旋转矩阵mSpaceMatrix = new Matrix(); } @Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas); //绘制圆drawSplashCircle(canvas); } private void drawSplashCircle(Canvas canvas) {//设置属性动画，让小圆转起来//这里得注意，是个坑，你如果不判断那球就不会动因为会陷入死循环值动画将值设置为0 -> invalidate()重绘 -> 执行draw 又将值设为0if (va == null){//va = ObjectAnimator.ofFloat(0f, 2 * (float) Math.PI); va = ObjectAnimator.ofFloat(0f, 360.0f); va.setDuration(SPLASH_CIRCLE_ROTATE_TIME); va.setRepeatCount(ValueAnimator.INFINITE); va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {@Overridepublic void onAnimationUpdate(ValueAnimator animation) {mCurrentSingle = (float) animation.getAnimatedValue(); //System.out.println("mCurrentSingle ->" + mCurrentSingle); invalidate(); }}); va.setInterpolator(new LinearInterpolator()); va.start(); } //计算每个小球的间隔//double spaceAngle = Math.PI*2/mColorArray.length; double spaceAngle = 360.0d/mColorArray.length; //初始化旋转矩阵mSpaceMatrix.reset(); mSpaceMatrix.postRotate((float) spaceAngle,getWidth()/2,getHeight()/2); //利用旋转画布法canvas.save(); canvas.rotate(mCurrentSingle,getWidth()/2,getHeight()/2); for (int i = 0; i < mColorArray.length; i++) {//canvas.rotate((float) spaceAngle,getWidth()/2,getHeight()/2); //System.out.println("spaceAngle -> " + spaceAngle); canvas.concat(mSpaceMatrix); //为每个球画笔设置颜色mCirclePaint.setColor(mColorArray[i]); //利用勾股定理计算小圆中心点//float cx = getWidth()/2 + (float) (CENTER_CIRCLE_RADIUS*Math.cos(spaceAngle*i+mCurrentSingle)); //float cy = getHeight()/2 + (float) (CENTER_CIRCLE_RADIUS*Math.sin(spaceAngle*i+mCurrentSingle)); //利用旋转画布法float cx = getWidth()/2 + CENTER_CIRCLE_RADIUS; float cy = getHeight()/2; canvas.drawCircle(cx,cy,SMALL_CIRCLE_RADIUS,mCirclePaint); }canvas.restore(); }}

注意事项：
1、canvas.concat(mSpaceMatrix); 对画布的操作也会对后面进行影响
2、Android中Matrix的set、pre、post的区别

说set、pre、post的区别之前，先说说Matrix。

Matrix包含一个3 X 3的矩阵，专门用于图像变换匹配。
Matrix提供了四种操作：

translate(平移)
rotate(旋转)
scale(缩放)
skew(倾斜)

也就是说这4种操作都是对这个3 X 3的矩阵设值来达到变换的效果。
Matrix没有结构体，它必须被初始化，通过reset或set方法。
OK，Matrix介绍完了，我们来看看set、pre、post的区别。
pre是在队列最前面插入，post是在队列最后面追加，而set先清空队列在添加（这也是上文提到的“Matrix没有结构体，它必须被初始化，通过reset或set方法”的原因）。
下面通过一些例子具体说明：