Android实现旋转动画的两种方式案例详解

目录

• 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

前期准备

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

 <color name="orange">#FF9600</color>
    <color name="aqua">#02D1AC</color>
    <color name="yellow">#FFD200</color>
    <color name="bule">#00C6FF</color>
    <color name="green">#00E099</color>
    <color name="pink">#FF3891</color>

    <array name="splash_circle_colors">
        <item>@color/orange</item>
        <item>@color/aqua</item>
        <item>@color/yellow</item>
        <item>@color/bule</item>
        <item>@color/green</item>
        <item>@color/pink</item>
    </array>

自定义 View java代码编写

方法一

关键思想： 属性动画 + 计算圆心

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 <br/>
 * Description: <br/>
 * date: 2021/8/7 12:13<br/>
 *
 * @author yiqi<br />
 * @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);
    }

    @Override
    protected 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);

    }

    @Override
    protected 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0
        if (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() {
                @Override
                public 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 <br/>
 * Description: <br/>
 * date: 2021/8/7 12:13<br/>
 *
 * @author yiqi<br />
 * @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);
    }

    @Override
    protected 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);

    }

    @Override
    protected 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0
        if (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() {
                @Override
                public 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 <br/>
 * Description: <br/>
 * date: 2021/8/7 12:13<br/>
 *
 * @author yiqi<br />
 * @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);
    }

    @Override
    protected 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();
    }

    @Override
    protected 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0
        if (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() {
                @Override
                public 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：

1. matrix.preScale(2f,1f);
2. matrix.preTranslate(5f, 0f);
3. matrix.postScale(0.2f, 1f);
4. matrix.postTranslate(0.5f, 0f);

执行顺序：translate(5, 0) -> scale(2f, 1f) -> scale(0.2f, 1f) -> translate(0.5f, 0f)

1. matrix.postTranslate(2f, 0f);
2. matrix.preScale(0.2f, 1f);
3. matrix.setScale(1f, 1f);
4. matrix.postScale(5f, 1f);
5. matrix.preTranslate(0.5f, 0f);

执行顺序：translate(0.5f, 0f) -> scale(1f, 1f) -> scale(5f, 1)

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