Vâng, tôi quản lý để đặt lại với nhau một ví dụ đơn giản của thanh cuộn trong đơn giản bằng cách sử dụng Xem OverScroller:
package net.project.experimental;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PointF;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.widget.OverScroller;
public class WorksheetView extends View
{
protected static final int OVERSCROLL_DISTANCE = 10;
protected static final int INVALID_POINTER_ID = -1;
private int fWorksheetWidth = 2000;
private int fWorksheetHeight = 2000;
private OverScroller fScroller;
private VelocityTracker fVelocityTracker = null;
private int fMinimumVelocity;
// The ‘active pointer’ is the one currently moving our object.
private int fTranslatePointerId = INVALID_POINTER_ID;
private PointF fTranslateLastTouch = new PointF();
private boolean fInteracting = false;
public WorksheetView(Context context, AttributeSet attrs)
{
super(context, attrs);
this.initView(context, attrs);
}
public WorksheetView(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
this.initView(context, attrs);
}
protected void initView(Context context, AttributeSet attrs)
{
fScroller = new OverScroller(this.getContext());
this.setOverScrollMode(OVER_SCROLL_ALWAYS);
final ViewConfiguration configuration = ViewConfiguration.get(getContext());
//fTouchSlop = configuration.getScaledTouchSlop();
fMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
}
@Override
public boolean onTouchEvent(MotionEvent event)
{
if (fVelocityTracker == null)
{
fVelocityTracker = VelocityTracker.obtain();
}
fVelocityTracker.addMovement(event);
final int action = event.getAction();
switch (action & MotionEvent.ACTION_MASK)
{
case MotionEvent.ACTION_DOWN:
{
if (!fScroller.isFinished())
fScroller.abortAnimation();
final float x = event.getX();
final float y = event.getY();
fTranslateLastTouch.set(x, y);
fTranslatePointerId = event.getPointerId(0);
this.startInteracting();
break;
}
case MotionEvent.ACTION_MOVE:
{
final int pointerIndexTranslate = event.findPointerIndex(fTranslatePointerId);
if (pointerIndexTranslate >= 0)
{
float translateX = event.getX(pointerIndexTranslate);
float translateY = event.getY(pointerIndexTranslate);
this.overScrollBy(
(int) (fTranslateLastTouch.x - translateX),
(int) (fTranslateLastTouch.y - translateY),
this.getScrollX(),
this.getScrollY(),
fWorksheetWidth - this.getWidth(),
fWorksheetHeight - this.getHeight(),
OVERSCROLL_DISTANCE,
OVERSCROLL_DISTANCE,
true);
fTranslateLastTouch.set(translateX, translateY);
this.invalidate();
}
break;
}
case MotionEvent.ACTION_UP:
{
final VelocityTracker velocityTracker = fVelocityTracker;
velocityTracker.computeCurrentVelocity(1000);
//velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int initialXVelocity = (int) velocityTracker.getXVelocity();
int initialYVelocity = (int) velocityTracker.getYVelocity();
if ((Math.abs(initialXVelocity) + Math.abs(initialYVelocity) > fMinimumVelocity))
{
this.fling(-initialXVelocity, -initialYVelocity);
}
else
{
if (fScroller.springBack(this.getScrollX(), this.getScrollY(), 0, fWorksheetWidth - this.getWidth(), 0, fWorksheetHeight - this.getHeight()))
this.invalidate();
this.stopInteracting();
}
if (fVelocityTracker != null)
{
fVelocityTracker.recycle();
fVelocityTracker = null;
}
fTranslatePointerId = INVALID_POINTER_ID;
break;
}
case MotionEvent.ACTION_POINTER_DOWN:
{
break;
}
case MotionEvent.ACTION_POINTER_UP:
{
final int pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = event.getPointerId(pointerIndex);
if (pointerId == fTranslatePointerId)
{
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
fTranslateLastTouch.set(event.getX(newPointerIndex), event.getY(newPointerIndex));
fTranslatePointerId = event.getPointerId(newPointerIndex);
}
break;
}
case MotionEvent.ACTION_CANCEL:
{
if (fScroller.springBack(this.getScrollX(), this.getScrollY(), 0, fWorksheetWidth - this.getWidth(), 0, fWorksheetHeight - this.getHeight()))
this.invalidate();
fTranslatePointerId = INVALID_POINTER_ID;
break;
}
}
return true;
}
private void fling(int velocityX, int velocityY)
{
int x = this.getScrollX();
int y = this.getScrollY();
this.startInteracting();
//fScroller.setFriction(ViewConfiguration.getScrollFriction());
fScroller.fling(x, y, velocityX, velocityY, 0, fWorksheetWidth - this.getWidth(), 0, fWorksheetHeight - this.getHeight());
this.invalidate();
}
private void startInteracting()
{
fInteracting = true;
}
private void stopInteracting()
{
fInteracting = false;
}
@Override
public void computeScroll()
{
if (fScroller != null && fScroller.computeScrollOffset())
{
int oldX = this.getScrollX();
int oldY = this.getScrollY();
int x = fScroller.getCurrX();
int y = fScroller.getCurrY();
if (oldX != x || oldY != y)
{
this.overScrollBy(
x - oldX,
y - oldY,
oldX,
oldY,
fWorksheetWidth - this.getWidth(),
fWorksheetHeight - this.getHeight(),
OVERSCROLL_DISTANCE,
OVERSCROLL_DISTANCE,
false);
}
if (fScroller.isFinished())
this.stopInteracting();
this.postInvalidate();
}
}
@Override
protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY)
{
// Treat animating scrolls differently; see #computeScroll() for why.
if (!fScroller.isFinished())
{
super.scrollTo(scrollX, scrollY);
if (clampedX || clampedY)
{
fScroller.springBack(this.getScrollX(), this.getScrollY(), 0, fWorksheetWidth - this.getWidth(), 0, fWorksheetHeight - this.getHeight());
}
}
else
{
super.scrollTo(scrollX, scrollY);
}
awakenScrollBars();
}
@Override
protected int computeHorizontalScrollExtent()
{
return this.getWidth();
}
@Override
protected int computeHorizontalScrollRange()
{
return fWorksheetWidth;
}
@Override
protected int computeHorizontalScrollOffset()
{
return this.getScrollX();
}
@Override
protected int computeVerticalScrollExtent()
{
return this.getHeight();
}
@Override
protected int computeVerticalScrollRange()
{
return fWorksheetHeight;
}
@Override
protected int computeVerticalScrollOffset()
{
return this.getScrollY();
}
@Override
protected void onDraw(Canvas canvas)
{
canvas.drawColor(Color.BLACK);
Paint paint = new Paint();
if (fInteracting)
;
paint.setColor(Color.WHITE);
canvas.drawRect(0, 0, fWorksheetWidth, fWorksheetHeight, paint);
paint.setColor(Color.RED);
for (int i = 0; i < 1500; i += 10)
{
canvas.drawLine(i, 0, i + 100, 500, paint);
}
canvas.drawRect(fWorksheetWidth - 50, 0, fWorksheetWidth, fWorksheetHeight, paint);
canvas.drawRect(0, fWorksheetHeight - 50, fWorksheetWidth, fWorksheetHeight, paint);
}
}