Android开发：小球往左飞带有拖影的动画有示例代码吗

以下是一个实现小球往左飞带有拖影的动画的示例代码：

首先，创建一个名为ShadowBallAnimation的类，继承自Animation类：

import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Point;

public class ShadowBallAnimation extends Animation {
    private Paint ballPaint;
    private Paint shadowPaint;
    private int radius;
    private int shadowOffset;
    private int startX;
    private int startY;
    private int endX;
    private int endY;
    private int shadowAlpha;
    private Path shadowPath;

    public ShadowBallAnimation(int startX, int startY, int endX, int endY, int radius, int shadowOffset, int shadowAlpha) {
        this.startX = startX;
        this.startY = startY;
        this.endX = endX;
        this.endY = endY;
        this.radius = radius;
        this.shadowOffset = shadowOffset;
        this.shadowAlpha = shadowAlpha;

        ballPaint = new Paint();
        ballPaint.setColor(0xFF0000FF); // 设置小球颜色为蓝色

        shadowPaint = new Paint();
        shadowPaint.setColor(0x80000000); // 设置拖影颜色为半透明黑色

        shadowPath = new Path();
    }

    @Override
    public void applyTransformation(float interpolatedTime, Canvas canvas) {
        float currentX = startX + (endX - startX) * interpolatedTime;
        float currentY = startY + (endY - startY) * interpolatedTime;
        float shadowX = currentX - shadowOffset;

        // 绘制拖影
        shadowPath.reset();
        shadowPath.moveTo(shadowX + radius, currentY);
        shadowPath.lineTo(currentX + radius, currentY);
        shadowPath.lineTo(currentX - radius, currentY);
        shadowPath.lineTo(shadowX - radius, currentY);
        shadowPath.close();
        shadowPaint.setAlpha((int) (shadowAlpha * (1 - interpolatedTime)));
        canvas.drawPath(shadowPath, shadowPaint);

        // 绘制小球
        canvas.drawCircle(currentX, currentY, radius, ballPaint);
    }
}

然后，在你的Activity中使用这个动画：

import android.animation.Animator;
import android.animation.ObjectAnimator;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    private View ballView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ballView = findViewById(R.id.ball);

        Button startButton = findViewById(R.id.start_button);
        startButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startAnimation();
            }
        });
    }

    private void startAnimation() {
        int startX = ballView.getLeft();
        int startY = ballView.getTop();
        int endX = ballView.getLeft() - 800;
        int endY = ballView.getTop();
        int radius = ballView.getWidth() / 2;
        int shadowOffset = 50;
        int shadowAlpha = 200;

        ShadowBallAnimation animation = new ShadowBallAnimation(startX, startY, endX, endY, radius, shadowOffset, shadowAlpha);
        animation.setDuration(2000);

        ObjectAnimator animator = ObjectAnimator.ofFloat(ballView, View.ALPHA, 0f, 1f);
        animator.setDuration(2000);

        AnimatorSet animatorSet = new AnimatorSet();
        animatorSet.playTogether(animation, animator);
        animatorSet.start();
    }
}

在上面的代码中，ballView是一个显示小球的View，你可以根据你的需求替换成你的小球View。

这样，当点击"Start"按钮时，就会开始执行小球往左飞带有拖影的动画