Android Scroller的使用方法

public void scrollTo(int x, int y) {
    if (mScrollX != x || mScrollY != y) {
        int oldX = mScrollX;
        int oldY = mScrollY;
        mScrollX = x;
        mScrollY = y;
        invalidateParentCaches();
        onScrollChanged(mScrollX, mScrollY, oldX, oldY);
        if (!awakenScrollBars()) {
            postInvalidateOnAnimation();
        }
    }
}


public void scrollBy(int x, int y) {
    scrollTo(mScrollX + x, mScrollY + y);
}

int sx = 0;
int sy = 0;
if (!drawingWithRendernode) {
    computeScroll();
    sx = mScrollX;
    sy = mScrollY;
}

...

if (offsetForScroll) {
    canvas.translate(mLeft - sx, mTop - sy);
}

public void computeScroll() {
}

class ScrollableLinearLayout @JVMOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : LinearLayout(context, attrs, defStyleAttr) {
    private val scroller = Scroller(context, BounceInterpolator())

    override fun computeScroll() {
        if(scroller.computeScrollOffset()) {
            // 真正实现滚动操作的地方
            scrollTo(scroller.currX, scroller.currY)

            // 刷新
            invalidate()
        }
    }

    fun scroll() {
        // 调用Scroller的startScroll
        if(scrollX == 0) {
            scroller.startScroll(scrollX, scrollY,  -500,  0,  300)
        } else {
            scroller.startScroll(scrollX, scrollY, 500, 0, 300)
        }

        // 刷新
        invalidate()
    }

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="Http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".scroller.activity.ScrollerSampleActivity">

    <com.sahooz.customviewdemo.scroller.view.ScrollableLinearLayout
        android:id="@+id/sll"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:gravity="center_vertical"
        android:orientation="vertical"
        android:background="#FFAAAA">

        <Button
            android:id="@+id/btnScroll"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Scroll" />

    </com.sahooz.customviewdemo.scroller.view.ScrollableLinearLayout>

</LinearLayout>

class ScrollerSampleActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_scroller_sample)

        val btnScroll = findViewById<Button>(R.id.btnScroll)
        btnScroll.setOnClickListener {
            findViewById<ScrollableLinearLayout>(R.id.sll).scroll()
        }
    }
}