Android实现雅虎新闻摘要加载视差动画效果

基础知识

继 Android实现旋转动画的两种方式我们了解了 Android实现旋转的两种基本方法之后，我们来写一个综合案例
效果展示

代码实现

实现思路
从效果中我们可以看到可以将其分为三个动画：
1、旋转动画（Android实现旋转动画的两种方式）
2、聚合动画
3、扩展动画
代码展示
package com.wust.mydialog; import android.animation.Animator;import android.animation.AnimatorListenerAdapter;import android.animation.ObjectAnimator;import android.animation.ValueAnimator;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Matrix;import android.graphics.Paint;import android.util.AttributeSet;import android.view.View;import android.view.WindowManager;import android.view.animation.AnticipateInterpolator;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 = 1000;    //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;     private LoadingState mLoadingState;    //当前中心圆半径    private float mCurCenterRadius;    private float mDiagonal;    private float mLineWidth;     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);                if (mLoadingState == null) {            mLoadingState = new RotateState();        }        mLoadingState.onDraw(canvas);    }     //定义 状态 抽象类    private abstract class LoadingState {        public abstract void onDraw(Canvas canvas);    }     //旋转动画    private class RotateState extends LoadingState {         public RotateState() {            //计算每个小球的间隔            double spaceAngle = 360.0d / mColorArray.length;            //初始化旋转矩阵            mSpaceMatrix.reset();            mSpaceMatrix.postRotate((float) spaceAngle, getWidth() / 2, getHeight() / 2);             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();                    invalidate();                }            });            va.setInterpolator(new LinearInterpolator());            va.start();        }         @Override        public void onDraw(Canvas canvas) {            //绘制背景            canvas.drawColor(Color.WHITE);            //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.concat(mSpaceMatrix);                //为 每个球 画笔 设置颜色                mCirclePaint.setColor(mColorArray[i]);                //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();        }    }     //聚合动画    private class ScaleState extends LoadingState {         public ScaleState() {            va = ObjectAnimator.ofFloat(CENTER_CIRCLE_RADIUS,0);            va.setDuration(SPLASH_CIRCLE_ROTATE_TIME);            va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {                @Override                public void onAnimationUpdate(ValueAnimator animation) {                    mCurCenterRadius = (float) animation.getAnimatedValue();                    invalidate();                }            });            va.addListener(new AnimatorListenerAdapter() {                @Override                public void onAnimationEnd(Animator animation) {                    mLoadingState = new ExtentState();                }            });            va.setInterpolator(new AnticipateInterpolator());            va.start();        }         @Override        public void onDraw(Canvas canvas) {            //绘制背景            canvas.drawColor(Color.WHITE);            //绘制小圆            canvas.save();            //这句话也不能调，要不然不连贯            canvas.rotate(mCurrentSingle,getWidth()/2,getHeight()/2);            for (int i = 0; i < mColorArray.length; i++) {                mCirclePaint.setColor(mColorArray[i]);                canvas.concat(mSpaceMatrix);                canvas.drawCircle(mCurCenterRadius+getWidth()/2,getHeight()/2,SMALL_CIRCLE_RADIUS,mCirclePaint);            }            canvas.restore();        }    }     //扩展动画    public class ExtentState extends LoadingState{         public ExtentState() {            //初始化对角线            float cx = getWidth()/2.0f;            float cy = getHeight()/2.0f;            mDiagonal = (float) Math.sqrt(Math.pow(cx,2)+Math.pow(cy,2));             va = ObjectAnimator.ofFloat(mDiagonal,0);            va.setDuration(3000);            va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {                @Override                public void onAnimationUpdate(ValueAnimator animation) {                    mLineWidth = (float) animation.getAnimatedValue();                    invalidate();                }            });            va.setInterpolator(new LinearInterpolator());            va.start();        }         @Override        public void onDraw(Canvas canvas) {            mCirclePaint.setColor(Color.WHITE);            mCirclePaint.setStrokeWidth(mLineWidth*2);//元的半径只会到达线宽的中间，所以要乘2            mCirclePaint.setStyle(Paint.Style.STROKE);            canvas.drawCircle(getWidth()/2,getHeight()/2,mDiagonal,mCirclePaint);        }    }     public void dismiss() {        if (mLoadingState instanceof RotateState){            //取消旋转值动画            va.cancel();            //创建缩放动画            mLoadingState = new ScaleState();            //刷新布局、可以写也可以不写//            invalidate();        }    }}
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基础知识

效果展示

代码实现

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