SpringAnimation使用示例

前言

SpringAnimation是由com.android.support:support-dynamic-animation支持包提供的弹性动画方案。SpringAnimation是由Springforce驱动的动画。弹簧力定义弹簧的刚度、阻尼比以及静止位置。一旦启动SpringAnimation，在每个帧上，弹簧力将更新动画的值和速度。动画将继续运行，直到弹簧力达到平衡。如果动画中使用的弹簧没有阻尼，动画将永远不会达到平衡，它将永远振荡。官方文档1；官方文档2

动画代码实例

Activity文件

package com.xol.viewpagerfragment;

import android.os.Bundle;
import android.support.animation.DynamicAnimation;
import android.support.animation.SpringAnimation;
import android.support.animation.SpringForce;
import android.support.annotation.FloatRange;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewTreeObserver;
import android.widget.Toast;

public class ActivityForSpringAnim1 extends AppCompatActivity {

    float STIFFNESS = SpringForce.STIFFNESS_MEDIUM;//硬度
    float DAMPING_RATIO = SpringForce.DAMPING_RATIO_HIGH_BOUNCY;//阻尼
    boolean isMove;

    SpringAnimation xAnimation;//x方向
    SpringAnimation yAnimation;//y方向

    View movingView;//图片

    int lastX = 0;
    int lastY = 0;
    private static final String TAG = "ActivityForSpringAnim1";

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_for_spring1);

        movingView = findViewById(R.id.movingView);

        // 以图片的初始位置创建动画对象
        movingView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                xAnimation = createSpringAnimation(
                        movingView, SpringAnimation.X, movingView.getX(), STIFFNESS, DAMPING_RATIO);
                yAnimation = createSpringAnimation(
                        movingView, SpringAnimation.Y, movingView.getY(), STIFFNESS, DAMPING_RATIO);
                //初始位置确定，移除监听
                movingView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
            }
        });

        movingView.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View view, MotionEvent event) {
                int x = (int) event.getX();
                int y = (int) event.getY();
                switch (event.getActionMasked()) {
                    case MotionEvent.ACTION_DOWN:
                        isMove = false;
                        lastX = x;
                        lastY = y;
                        // 取消动画以便按住图片
                        xAnimation.cancel();
                        yAnimation.cancel();
                        break;
                    case MotionEvent.ACTION_MOVE:

                        int offX = x - lastX;
                        int offY = y - lastY;
                        movingView.offsetLeftAndRight(offX);
                        movingView.offsetTopAndBottom(offY);
                        isMove = true;
                        break;
                    case MotionEvent.ACTION_UP:
                        xAnimation.start();
                        yAnimation.start();
                        //没有移动是点击事件
                        if (!isMove) {
                            Toast.makeText(ActivityForSpringAnim1.this,
                                    "click", Toast.LENGTH_LONG).show();
                        }
                        break;
                }
                return true;
            }
        });

    }

    /**
     * 创建弹性动画
     *
     * @param view          动画关联的控件
     * @param property      动画作用的属性
     * @param finalPosition 动画结束的位置
     * @param stiffness     硬度
     * @param dampingRatio  阻尼
     * @return
     */
    SpringAnimation createSpringAnimation(View view,
                                          DynamicAnimation.ViewProperty property,
                                          Float finalPosition,
                                          @FloatRange(from = 0.0) Float stiffness,
                                          @FloatRange(from = 0.0) Float dampingRatio) {
        //创建弹性动画类SpringAnimation
        SpringAnimation animation = new SpringAnimation(view, property);

        SpringForce spring = new SpringForce(finalPosition);
        spring.setStiffness(stiffness);
        spring.setDampingRatio(dampingRatio);
        //关联弹性特质
        animation.setSpring(spring);
        return animation;
    }

}

activity_for_spring1.xml布局文件

效果展示

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