Android实现跳动的小球加载动画效果

先来看看效果图

跳动的小球做这个动画,需掌握:

     1、属性动画

     2、Path类、Canvas类

     3、贝塞尔曲线

     4、SurfaceView用法

     5、自定义attr属性

     6 、架构: 状态模式,控制器

     7 、自由落体,抛物线等概念

不多说了,直接上码

1.DancingView.java

public class DancingView extends SurfaceView implements SurfaceHolder.Callback {
  public static final int STATE_DOWN = 1;//向下状态
  public static final int STATE_UP = 2;//向上状态
  public static final int DEFAULT_POINT_RADIUS = 10;
  public static final int DEFAULT_BALL_RADIUS = 13;
  public static final int DEFAULT_LINE_WIDTH = 200;
  public static final int DEFAULT_LINE_HEIGHT = 2;
  public static final int DEFAULT_LINE_COLOR = Color.parseColor("#FF9800");
  public static final int DEFAULT_POINT_COLOR = Color.parseColor("#9C27B0");
  public static final int DEFAULT_BALL_COLOR = Color.parseColor("#FF4081");
  public static final int DEFAULT_DOWN_DURATION = 600;//ms
  public static final int DEFAULT_UP_DURATION = 600;//ms
  public static final int DEFAULT_FREEDOWN_DURATION = 1000;//ms
  public static final int MAX_OFFSET_Y = 50;//水平下降最大偏移距离
  public int PONIT_RADIUS = DEFAULT_POINT_RADIUS;//小球半径
  public int BALL_RADIUS = DEFAULT_BALL_RADIUS;//小球半径
  private Paint mPaint;
  private Path mPath;
  private int mLineColor;
  private int mPonitColor;
  private int mBallColor;
  private int mLineWidth;
  private int mLineHeight;
  private float mDownDistance;
  private float mUpDistance;
  private float freeBallDistance;
  private ValueAnimator mDownController;//下落控制器
  private ValueAnimator mUpController;//上弹控制器
  private ValueAnimator mFreeDownController;//自由落体控制器
  private AnimatorSet animatorSet;
  private int state;
  private boolean ismUpControllerDied = false;
  private boolean isAnimationShowing = false;
  private boolean isBounced = false;
  private boolean isBallFreeUp = false;
  public DancingView(Context context) {
    super(context);
    init(context, null);
  }
  public DancingView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context, attrs);
  }
  public DancingView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init(context, attrs);
  }
  private void init(Context context, AttributeSet attrs) {
    initAttributes(context, attrs);
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setStrokeWidth(mLineHeight);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPath = new Path();
    getHolder().addCallback(this);
    initController();
  }
  private void initAttributes(Context context, AttributeSet attrs) {
    TypedArray typeArray = context.obtainStyledAttributes(attrs, R.styleable.DancingView);
    mLineColor = typeArray.getColor(R.styleable.DancingView_lineColor, DEFAULT_LINE_COLOR);
    mLineWidth = typeArray.getDimensionPixelOffset(R.styleable.DancingView_lineWidth, DEFAULT_LINE_WIDTH);
    mLineHeight = typeArray.getDimensionPixelOffset(R.styleable.DancingView_lineHeight, DEFAULT_LINE_HEIGHT);
    mPonitColor = typeArray.getColor(R.styleable.DancingView_pointColor, DEFAULT_POINT_COLOR);
    mBallColor = typeArray.getColor(R.styleable.DancingView_ballColor, DEFAULT_BALL_COLOR);
    typeArray.recycle();
  }
  private void initController() {
    mDownController = ValueAnimator.ofFloat(0, 1);
    mDownController.setDuration(DEFAULT_DOWN_DURATION);
    mDownController.setInterpolator(new DecelerateInterpolator());
    mDownController.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
      @Override
      public void onAnimationUpdate(ValueAnimator animation) {
        mDownDistance = MAX_OFFSET_Y * (float) animation.getAnimatedValue();
        postInvalidate();
      }
    });
    mDownController.addListener(new Animator.AnimatorListener() {
      @Override
      public void onAnimationStart(Animator animation) {
        state = STATE_DOWN;
      }
      @Override
      public void onAnimationEnd(Animator animation) {
      }
      @Override
      public void onAnimationCancel(Animator animation) {
      }
      @Override
      public void onAnimationRepeat(Animator animation) {
      }
    });
    mUpController = ValueAnimator.ofFloat(0, 1);
    mUpController.setDuration(DEFAULT_UP_DURATION);
    mUpController.setInterpolator(new DancingInterpolator());
    mUpController.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
      @Override
      public void onAnimationUpdate(ValueAnimator animation) {
        mUpDistance = MAX_OFFSET_Y * (float) animation.getAnimatedValue();
        if (mUpDistance >= MAX_OFFSET_Y) {
          //进入自由落体状态
          isBounced = true;
          if (!mFreeDownController.isRunning() && !mFreeDownController.isStarted() && !isBallFreeUp) {
            mFreeDownController.start();
          }
        }
        postInvalidate();
      }
    });
    mUpController.addListener(new Animator.AnimatorListener() {
      @Override
      public void onAnimationStart(Animator animation) {
        state = STATE_UP;
      }
      @Override
      public void onAnimationEnd(Animator animation) {
        ismUpControllerDied = true;
      }
      @Override
      public void onAnimationCancel(Animator animation) {
      }
      @Override
      public void onAnimationRepeat(Animator animation) {
      }
    });
    mFreeDownController = ValueAnimator.ofFloat(0, 8f);
    mFreeDownController.setDuration(DEFAULT_FREEDOWN_DURATION);
    mFreeDownController.setInterpolator(new DecelerateInterpolator());
    mFreeDownController.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
      @Override
      public void onAnimationUpdate(ValueAnimator animation) {
        //该公式解决上升减速 和 下降加速
        float t = (float) animation.getAnimatedValue();
        freeBallDistance = 40 * t - 5 * t * t;
        if (ismUpControllerDied) {//往上抛,到临界点
          postInvalidate();
        }
      }
    });
    mFreeDownController.addListener(new Animator.AnimatorListener() {
      @Override
      public void onAnimationStart(Animator animation) {
        isBallFreeUp = true;
      }
      @Override
      public void onAnimationEnd(Animator animation) {
        isAnimationShowing = false;
        //循环第二次
        startAnimations();
      }
      @Override
      public void onAnimationCancel(Animator animation) {
      }
      @Override
      public void onAnimationRepeat(Animator animation) {
      }
    });
    animatorSet = new AnimatorSet();
    animatorSet.play(mDownController).before(mUpController);
    animatorSet.addListener(new Animator.AnimatorListener() {
      @Override
      public void onAnimationStart(Animator animation) {
        isAnimationShowing = true;
      }
      @Override
      public void onAnimationEnd(Animator animation) {
      }
      @Override
      public void onAnimationCancel(Animator animation) {
      }
      @Override
      public void onAnimationRepeat(Animator animation) {
      }
    });
  }
  
  public void startAnimations() {
    if (isAnimationShowing) {
      return;
    }
    if (animatorSet.isRunning()) {
      animatorSet.end();
      animatorSet.cancel();
    }
    isBounced = false;
    isBallFreeUp = false;
    ismUpControllerDied = false;
    animatorSet.start();
  }
  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    // 一条绳子用左右两部分的二阶贝塞尔曲线组成
    mPaint.setColor(mLineColor);
    mPath.reset();
    //起始点
    mPath.moveTo(getWidth() / 2 - mLineWidth / 2, getHeight() / 2);
    if (state == STATE_DOWN) {//下落
      
      //左部分 的贝塞尔
      mPath.quadTo((float) (getWidth() / 2 - mLineWidth / 2 + mLineWidth * 0.375), getHeight() / 2 + mDownDistance,
          getWidth() / 2, getHeight() / 2 + mDownDistance);
      //右部分 的贝塞尔
      mPath.quadTo((float) (getWidth() / 2 + mLineWidth / 2 - mLineWidth * 0.375), getHeight() / 2 + mDownDistance,
          getWidth() / 2 + mLineWidth / 2, getHeight() / 2);
      mPaint.setStyle(Paint.Style.STROKE);
      canvas.drawPath(mPath, mPaint);
      
      
      mPaint.setStyle(Paint.Style.FILL);
      mPaint.setColor(mBallColor);
      canvas.drawCircle(getWidth() / 2, getHeight() / 2 + mDownDistance - BALL_RADIUS, BALL_RADIUS, mPaint);
      
    } else if (state == STATE_UP) { //向上弹
      
      //左部分的贝塞尔
      mPath.quadTo((float) (getWidth() / 2 - mLineWidth / 2 + mLineWidth * 0.375), getHeight() / 2 + 50 - mUpDistance,
          getWidth() / 2,
          getHeight() / 2 + (50 - mUpDistance));
      //右部分的贝塞尔
      mPath.quadTo((float) (getWidth() / 2 + mLineWidth / 2 - mLineWidth * 0.375), getHeight() / 2 + 50 - mUpDistance,
          getWidth() / 2 + mLineWidth / 2,
          getHeight() / 2);
      mPaint.setStyle(Paint.Style.STROKE);
      canvas.drawPath(mPath, mPaint);
      
      mPaint.setStyle(Paint.Style.FILL);
      mPaint.setColor(mBallColor);
      //弹性小球,自由落体
      if (!isBounced) {
        //上升
        canvas.drawCircle(getWidth() / 2, getHeight() / 2 + (MAX_OFFSET_Y - mUpDistance) - BALL_RADIUS, BALL_RADIUS, mPaint);
      } else {
        //自由落体
        canvas.drawCircle(getWidth() / 2, getHeight() / 2 - freeBallDistance - BALL_RADIUS, BALL_RADIUS, mPaint);
      }
    }
    mPaint.setColor(mPonitColor);
    mPaint.setStyle(Paint.Style.FILL);
    canvas.drawCircle(getWidth() / 2 - mLineWidth / 2, getHeight() / 2, PONIT_RADIUS, mPaint);
    canvas.drawCircle(getWidth() / 2 + mLineWidth / 2, getHeight() / 2, PONIT_RADIUS, mPaint);
  }
  @Override
  public void surfaceCreated(SurfaceHolder holder) {
    Canvas canvas = holder.lockCanvas();//锁定整个SurfaceView对象,获取该Surface上的Canvas.
    draw(canvas);
    holder.unlockCanvasAndPost(canvas);//释放画布，提交修改
  }
  @Override
  public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
  }
  @Override
  public void surfaceDestroyed(SurfaceHolder holder) {
  }
}

2.DancingInterpolator.java

 public class DancingInterpolator implements Interpolator {
  @Override
  public float getInterpolation(float input) {
    return (float) (1 - Math.exp(-3 * input) * Math.cos(10 * input));
  }
}

3.自定义属性 styles.xml

<declare-styleable name="DancingView">
    <attr name="lineWidth" format="dimension" />
    <attr name="lineHeight" format="dimension" />
    <attr name="pointColor" format="reference|color" />
    <attr name="lineColor" format="reference|color" />
    <attr name="ballColor" format="reference|color" />
</declare-styleable>

注意：颜色、尺寸、参数可以自己测试，调整。

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