TOPIC:

I've tested what you told me then ,
as the code I wrote to test below ( please check the attachment ):

I just want to fill full of the screen width with the pdf file by the its page width when the pdf file is rendered in landscape mode.
Evidently, I should calculate the scale rate using the formula : scaleRate = screenWidth/pageWidth (this result is between minScale and maxScale),
but after I set the result to the method m_view.vSetScale(screenWidth/pageWidth , 0, 0) ,
it scales larger than what I expected, the final pdf view had beyonded the screen width.

Were there any codes I wrote wrong ?

the code I Wrote:

// to get current page width
final float f1 = m_doc.GetPageWidth(m_pageno);

// the landscape mode screen width(720x1280 screen size)
final float f2 = m_view.vGetPage(m_pageno).ToPDFSize(1280f);

// MaxScale= 2.1639342, MinScale= 0.72131145
Log.d("pdf", "MaxScale= " + m_view.vGetMaxScale() + ", MinScale= " + m_view.vGetMinScale());

// f1= 1190.55, f2= 1774.5455, getScale= 0.72131145
Log.d("pdf", "f1= " + f1 + ", f2= " + f2 + ", getScale= " + m_view.vGetScale());

// f2/f1= 1.49052580
m_view.vSetScale((f2 / f1), 0, 0);

Hi,
try to change this line:with this:

The issue still there,
I think it is not right to set the param f2 with value pageWidth, it should be set the value with screenWidth.

the method m_view.vGetWinW() is in proper:
final float f2 = m_view.vGetWinW()

but here comes another issue , the method of m_view.vTouchEvent ususlly lead the APP to collapse when I try to zoom in or out.

One more issue:
If I invoked m_view.vSetScale method once, it did do the right thing as this method defined,
when I invoked it for the second time , it crashed the APP and exited.

You can have a try with the PDFReader project....