<Android>自定义竖向seekbar

自定义竖向的seekbar（顶部在上），开始以为只要将画布翻转就可以，后来发现动作的操作也需要重新定义，移动由X轴转到Y轴，需要进行的操作有两步：

1.翻转画布，先顺时针转动90度。再右移动width宽度。

2.将X轴进行的动作搬到Y轴上。

此外用到的一种较好的设计模式是：

留接口处理seekListener，在内部预留接口使得外部调用的方法，是一种比较常见的封装方式。

代码如下，参考网络

public class VerticalSeekBar extends SeekBar
{
private boolean mIsDragging;
private float mTouchDownY;
private int mScaledTouchSlop;
private boolean isInScrollingContainer = false;

public interface OnSeekBarChangeListener
{
void onProgressChanged(VerticalSeekBar VerticalBar, int progress, boolean fromUser);
void onStartTrackingTouch(VerticalSeekBar VerticalBar);
void onStopTrackingTouch(VerticalSeekBar VerticalBar);
}

private OnSeekBarChangeListener mOnSeekBarChangeListener;

public void setOnSeekBarChangeListener(OnSeekBarChangeListener l)
{
mOnSeekBarChangeListener = l;
}

public boolean isInScrollingContainer()
{
return isInScrollingContainer;
}

public void setInScrollingContainer(boolean isInScrollingContainer)
{
this.isInScrollingContainer = isInScrollingContainer;
}

/**
* On touch, this offset plus the scaled value from the position of the
* touch will form the progress value. Usually 0.
*/
float mTouchProgressOffset;

public VerticalSeekBar(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
mScaledTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();

}

public VerticalSeekBar(Context context, AttributeSet attrs)
{
super(context, attrs);
}

public VerticalSeekBar(Context context)
{
super(context);
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh)
{

super.onSizeChanged(h, w, oldh, oldw);
}

@Override
protected synchronized void onMeasure(int widthMeasureSpec,
int heightMeasureSpec)
{
super.onMeasure(heightMeasureSpec, widthMeasureSpec);
setMeasuredDimension(getMeasuredHeight(), getMeasuredWidth());
}

@Override
protected synchronized void onDraw(Canvas canvas)
{
canvas.rotate(90);
canvas.translate(0, -getWidth());
super.onDraw(canvas);
}

@Override
public boolean onTouchEvent(MotionEvent event)
{
if (!isEnabled())
{
return false;
}

switch (event.getAction())
{
case MotionEvent.ACTION_DOWN:
if (isInScrollingContainer())
{

mTouchDownY = event.getY();
}
else
{
setPressed(true);
invalidate();
onStartTrackingTouch();
trackTouchEvent(event);
attemptClaimDrag();
onSizeChanged(getWidth(), getHeight(), 0, 0);
}
break;

case MotionEvent.ACTION_MOVE:
if (mIsDragging)
{
trackTouchEvent(event);

}
else
{
final float y = event.getY();
if (Math.abs(y - mTouchDownY) > mScaledTouchSlop)
{
setPressed(true);

invalidate();
onStartTrackingTouch();
trackTouchEvent(event);
attemptClaimDrag();

}
}
onSizeChanged(getWidth(), getHeight(), 0, 0);
break;

case MotionEvent.ACTION_UP:
if (mIsDragging)
{
trackTouchEvent(event);
onStopTrackingTouch();
setPressed(false);

}
else
{
// Touch up when we never crossed the touch slop threshold
// should
// be interpreted as a tap-seek to that location.
onStartTrackingTouch();
trackTouchEvent(event);
onStopTrackingTouch();

}
onSizeChanged(getWidth(), getHeight(), 0, 0);
invalidate();
break;
}
return true;

}

private void trackTouchEvent(MotionEvent event)
{
final int height = getHeight();
final int top = getPaddingTop();
final int bottom = getPaddingBottom();
final int available = height - top - bottom;

int y = (int) event.getY();

float scale;
float progress = 0;

if (y > height - bottom)
{
scale = 0.0f;
}
else if (y < top)
{
scale = 1.0f;
}
else
{
scale = (float) (y) / (float) available;
progress = mTouchProgressOffset;
}

final int max = getMax();
progress += scale * max;

setProgress((int) progress);

}

/**
* This is called when the user has started touching this widget.
*/
public void onStartTrackingTouch()
{
mIsDragging = true;
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onStartTrackingTouch(this);
}
}

/**
* This is called when the user either releases his touch or the touch is
* canceled.
*/
public void onStopTrackingTouch()
{
mIsDragging = false;
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onStopTrackingTouch(this);
}
}

private void attemptClaimDrag()
{
ViewParent p = getParent();
if (p != null)
{
p.requestDisallowInterceptTouchEvent(true);
}
}

@Override
public synchronized void setProgress(int progress)
{
super.setProgress(progress);
onSizeChanged(getWidth(), getHeight(), 0, 0);
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onProgressChanged(this, getProgress(), isPressed());
}
}

}