Android Scroller 简单示例

Question

谁能给我一个关于 Scroller 类的简单例子？据我了解，它封装了滚动，所以我需要开始计算，然后手动更新必须 ScrollView 到新位置。所以我只是尝试

 Scroller scroller = new Scroller(getApplicationContext());
    scroller.startScroll(0, 0, 10, 10, 500);
    for (int i = 0; i < 100; i++) {
        Log.d("scroller", scroller.getCurrX()+" "+ scroller.getCurrY());
    }

我的输出只有零。我的错在哪里？

Answer 1

private class Flinger implements Runnable {
    private final Scroller scroller;

    private int lastX = 0;

    Flinger() {
        scroller = new Scroller(getActivity());
    }

    void start(int initialVelocity) {
        int initialX = scrollingView.getScrollX();
        int maxX = Integer.MAX_VALUE; // or some appropriate max value in your code
        scroller.fling(initialX, 0, initialVelocity, 0, 0, maxX, 0, 10);
        Log.i(TAG, "starting fling at " + initialX + ", velocity is " + initialVelocity + "");

        lastX = initialX;
        getView().post(this);
    }

    public void run() {
        if (scroller.isFinished()) {
            Log.i(TAG, "scroller is finished, done with fling");
            return;
        }

        boolean more = scroller.computeScrollOffset();
        int x = scroller.getCurrX();
        int diff = lastX - x;
        if (diff != 0) {
            scrollingView.scrollBy(diff, 0);
            lastX = x;
        }

        if (more) {
            getView().post(this);
        }
    }

    boolean isFlinging() {
        return !scroller.isFinished();
    }

    void forceFinished() {
        if (!scroller.isFinished()) {
            scroller.forceFinished(true);
        }
    }
}

取自https://stackoverflow.com/a/6219382/1351347

Answer 2

startScroll() 中的最后一个参数是持续时间。 可能你的for-loop 在滚动条完成之前完成:) 你也应该打电话给computeScrollOffset() 试试这个代码，它可以工作：

Scroller scroller = new Scroller(getApplicationContext());
scroller.startScroll(0, 0, 100, 100, 500);
while (!scroller.isFinished()) {
    Log.d("scroller", scroller.getCurrX() + " " + scroller.getCurrY());
    scroller.computeScrollOffset();
}