android 阻尼效果(图片下拉变大)_增大下拉阻尼

import android.widget.Scroller;

/** * 阻尼效果的scrollview */

public class DampView extends ScrollView { private static final int LEN = 0xc8; private static final int DURATION = 500; private static final int MAX_DY = 200; private Scroller mScroller; TouchTool tool; int left, top; float startX, startY, currentX, currentY; int imageViewH; int rootW, rootH; ImageView imageView; boolean scrollerType;

public DampView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);

}

public DampView(Context context, AttributeSet attrs) {
    super(context, attrs);
    mScroller = new Scroller(context);
}

public DampView(Context context) {
    super(context);

}

public void setImageView(ImageView imageView) {
    this.imageView = imageView;
}

@Override
protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) {

    return 0;
}

private int[] li = new int[2];
private int[] li2 = new int[2];
private float lastLy;
private boolean startIsTop = true;

@Override
public boolean dispatchTouchEvent(MotionEvent event) {
    super.dispatchTouchEvent(event);
    int action = event.getAction();
    if (!mScroller.isFinished()) {
        return super.onTouchEvent(event);
    }
    currentX = event.getX();
    currentY = event.getY();
    imageView.getLocationInWindow(li);
    getLocationOnScreen(li2);
    imageView.getTop();
    switch (action) {
    case MotionEvent.ACTION_DOWN:
        if (li[1] != li2[1]) {// 判断开始触摸时，imageview和窗口顶部对齐没
            startIsTop = false;
        }
        left = imageView.getLeft();
        top = imageView.getBottom();
        rootW = getWidth();
        rootH = getHeight();
        imageViewH = imageView.getHeight();
        startX = currentX;
        startY = currentY;
        tool = new TouchTool(imageView.getLeft(), imageView.getBottom(), imageView.getLeft(),
                imageView.getBottom() + LEN);
        break;
    case MotionEvent.ACTION_MOVE:
        if (!startIsTop && li[1] == li2[1]) {
            startY = currentY;
            startIsTop = true;
        } 
        if (imageView.isShown() && imageView.getTop() >= 0) {
            if (tool != null) {
                int t = tool.getScrollY(currentY - startY);
                if (!scrollerType && currentY < lastLy && imageView.getHeight() > imageViewH) {
                    scrollTo(0, 0);
                    imageView.getLocationInWindow(li);
                    getLocationOnScreen(li2);
                    android.view.ViewGroup.LayoutParams params = imageView.getLayoutParams();
                    params.height = t;
                    imageView.setLayoutParams(params);
                    if (imageView.getHeight() == imageViewH && li[1] == li2[1]) {
                        scrollerType = true;
                    }
                    if (startIsTop && li[1] != li2[1]) {
                        startIsTop = false;
                    }
                }
                if (t >= top && t <= imageView.getBottom() + LEN && li[1] == li2[1] && currentY > lastLy) {
                    android.view.ViewGroup.LayoutParams params = imageView.getLayoutParams();
                    params.height = t;
                    imageView.setLayoutParams(params);
                }
            }
            scrollerType = false;
        }

        lastLy = currentY;
        break;
    case MotionEvent.ACTION_UP:
        if (li[1] == li2[1]) {
            scrollerType = true;
            mScroller.startScroll(imageView.getLeft(), imageView.getBottom(), 0 - imageView.getLeft(),
                    imageViewH - imageView.getBottom(), DURATION);
            invalidate();
        }
        startIsTop = true;
        break;
    }

    return true;
}

@Override
public void computeScroll() {
    super.computeScroll();
    if (mScroller.computeScrollOffset()) {
        int x = mScroller.getCurrX();
        int y = mScroller.getCurrY();
        imageView.layout(0, 0, x + imageView.getWidth(), y);
        invalidate();
        if (!mScroller.isFinished() && scrollerType && y > MAX_DY) {
            android.view.ViewGroup.LayoutParams params = imageView.getLayoutParams();
            params.height = y;
            imageView.setLayoutParams(params);
        }
    }
}

public class TouchTool {

    private int startX, startY;

    public TouchTool(int startX, int startY, int endX, int endY) {
        super();
        this.startX = startX;
        this.startY = startY;
    }

    public int getScrollX(float dx) {
        int xx = (int) (startX + dx / 2.5F);
        return xx;
    }

    public int getScrollY(float dy) {
        int yy = (int) (startY + dy / 2.5F);
        return yy;
    }
}

}

### 应用与布局文件: 不贴代码了 贴图 特别简单


![这里写图片描述](https://p3-xtjj-sign.byteimg.com/tos-cn-i-73owjymdk6/cca4fd195fcb48e8830d47bcb58df8d1~tplv-73owjymdk6-jj-mark-v1:0:0:0:0:5o6Y6YeR5oqA5pyv56S-5Yy6IEAg5L2c6ICFdmlwMTAyNGPkuqTmtYE=:q75.awebp?rk3s=f64ab15b&x-expires=1771030314&x-signature=7jbYgNd9m36t5%2FrRRDCoez0aUis%3D)


### 代码配置(最后一步 也是最重要的一步) 提示: