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 <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 = 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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