[android开发]手写签名系统的设计与实现之实现解析pdf文件（二）

上一篇文章，我们介绍了如何去实现读取手机文件及文件夹，并以列表的形式显示出来，今天我们将说说如何读取pdf文件。先看效果图：

选择pdf文件 显示pdf文件主界面

一、实现原理：

手机端解析pdf的实例并不是很多，android系统本身没有解析的类，就需要第三方开发库，现在常用的两种方式：一种是利用动态链接库libmupdf.so；另一种是利用动态链接库libvudroid.so。两者各有自己的优缺点，前者解析速度快，但是比较耗内存；后者省内存，但是解析比较慢。本项目是利用前者动态库来解析pdf的，这两个在网上都可以下载，也有一个相关的实例。本人感觉，前者比较简单，后者实现的相对复杂，之前有人说前者动态库是在后者的基础上写的，等待求证。下面我们就介绍libmupdf.so动态库：MUPDF是一个轻量级pdf显示阅读器，大家需要把limupdf.so导入到项目中，建立一个包名为com.artifex.mupdf，目录结构如下：

在com.artifex.mupdf包中新建这几个类，我们重点介绍MuPDFActivity、ReaderView、PageView、MuPDFCore。

在MuPDFActivity类中获取要读取的pdf地址，传给MuPDFCore对象：

/**	 * 功能：根据获取的文件路径，解析pdf，并返回core	 * @param path	 * @return core	 */	private MuPDFCore openFile(String path)	{				PATH = path;		int lastSlashPos = path.lastIndexOf('/');		mFileName = new String(lastSlashPos == -1					? path					: path.substring(lastSlashPos+1));		System.out.println("Trying to open "+path);		try		{			core = new MuPDFCore(path);			// New file: drop the old outline data		}		catch (Exception e)		{			System.out.println(e);			return null;		}		return core;	}

private ReaderView   mDocView;

mDocView = new ReaderView(this) {			private boolean showButtonsDisabled;			public boolean onSingleTapUp(MotionEvent e) {				if (e.getX() < super.getWidth()/TAP_PAGE_MARGIN) {					super.moveToPrevious();				} else if (e.getX() > super.getWidth()*(TAP_PAGE_MARGIN-1)/TAP_PAGE_MARGIN) {					super.moveToNext();				} else if (!showButtonsDisabled) {					int linkPage = -1;					if (mLinkState != LinkState.INHIBIT) {						MuPDFPageView pageView = (MuPDFPageView) mDocView.getDisplayedView();						if (pageView != null) {// XXX							linkPage = pageView.hitLinkPage(e.getX(), e.getY());						}					}					if (linkPage != -1) {						mDocView.setDisplayedViewIndex(linkPage);					} else {						if (!mButtonsVisible) {							showButtons();						} else {							hideButtons();						}					}				}				return super.onSingleTapUp(e);			}			public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {				if (!showButtonsDisabled)					hideButtons();				return super.onScroll(e1, e2, distanceX, distanceY);			}			public boolean onScaleBegin(ScaleGestureDetector d) {				showButtonsDisabled = true;				return super.onScaleBegin(d);			}			public boolean onTouchEvent(MotionEvent event) {				if (event.getActionMasked() == MotionEvent.ACTION_DOWN){					showButtonsDisabled = false;				}				return super.onTouchEvent(event);			}			protected void onChildSetup(int i, View v) {				((PageView)v).setLinkHighlighting(mLinkState == LinkState.HIGHLIGHT);			}			protected void onMoveToChild(int i) {				if (core == null)					return;				mPageNumberView.setText(String.format("%d/%d", i+1, core.countPages()));				mPageSlider.setMax(core.countPages()-1);				mPageSlider.setProgress(i);			}			protected void onSettle(View v) {				// When the layout has settled ask the page to render				// in HQ				((PageView)v).addHq();			}			protected void onUnsettle(View v) {				// When something changes making the previous settled view				// no longer appropriate, tell the page to remove HQ				((PageView)v).removeHq();			}		};				mDocView.setAdapter(new MuPDFPageAdapter(this, core));

MuPDFPageView pageView = (MuPDFPageView) mDocView.getDisplayedView();

ReaderView包含了对pdf文件的相关操作，比如页面放大缩小、翻页等相关手势：

/**	 * 用户轻触触摸屏，由1个MotionEvent ACTION_DOWN触发	 * */	public boolean onDown(MotionEvent arg0) {		mScroller.forceFinished(true);		//Log.e("info", "-->onDown");		return true;	}	/*	 * 用户按下触摸屏、快速移动后松开，	 * 由1个MotionEvent ACTION_DOWN, 	 * 多个ACTION_MOVE, 1个ACTION_UP触发	 * */	public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,			float velocityY) {		if (mScrollDisabled)			return true;		View v = mChildViews.get(mCurrent);		if (v != null) {			Rect bounds = getScrollBounds(v);			switch(directionOfTravel(velocityX, velocityY)) {			case MOVING_LEFT:				if (bounds.left >= 0) {					// Fling off to the left bring next view onto screen					View vl = mChildViews.get(mCurrent+1);					if (vl != null) {						slideViewOntoScreen(vl);						return true;					}				}				break;			case MOVING_RIGHT:				if (bounds.right <= 0) {					// Fling off to the right bring previous view onto screen					View vr = mChildViews.get(mCurrent-1);					if (vr != null) {						slideViewOntoScreen(vr);						return true;					}				}				break;			}			mScrollerLastX = mScrollerLastY = 0;						Rect expandedBounds = new Rect(bounds);			expandedBounds.inset(-FLING_MARGIN, -FLING_MARGIN);			if(withinBoundsInDirectionOfTravel(bounds, velocityX, velocityY)					&& expandedBounds.contains(0, 0)) {				mScroller.fling(0, 0, (int)velocityX, (int)velocityY, bounds.left, bounds.right, bounds.top, bounds.bottom);				post(this);			}		}		return true;	}	/**	 * 用户长按触摸屏，由多个MotionEvent ACTION_DOWN触发 	 * */	public void onLongPress(MotionEvent e) {	}	/**	 * 功能：扑捉屏幕手势滑动动作	 * 用户按下触摸屏，并拖动，由1个MotionEvent ACTION_DOWN, 	 * 多个ACTION_MOVE触发。	 * */	public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,			float distanceY) {				//Log.e("info", "-->onScroll");		//这里控制pdf文件翻页		if (!mScrollDisabled) {			mXScroll -= distanceX;			mYScroll -= distanceY;			requestLayout();		}				return true;	}				/**	 * 用户轻触触摸屏，尚未松开或拖动，由一个1个MotionEvent ACTION_DOWN触发	 * 注意和onDown()的区别，强调的是没有松开或者拖动的状态 .	 * */	public void onShowPress(MotionEvent e) {		//Log.e("info", "-->onShowPress");	}	/**	 * 用户（轻触触摸屏后）松开，由一个1个MotionEvent ACTION_UP触发	 * */	public boolean onSingleTapUp(MotionEvent e) {		return false;	}	/**	 * 处理对屏幕的缩放比例	 * */	public boolean onScale(ScaleGestureDetector detector) {		//截屏视图不显示时，手势操作可以进行			float previousScale = mScale;			mScale = Math.min(Math.max(mScale * detector.getScaleFactor(), MIN_SCALE), MAX_SCALE);			scalingFactor = mScale/previousScale;//缩放比例			//Log.e("info", "--->scalingFactor="+scalingFactor);			View v = mChildViews.get(mCurrent);			if (v != null) {				// Work out the focus point relative to the view top left				int viewFocusX = (int)detector.getFocusX() - (v.getLeft() + mXScroll);				int viewFocusY = (int)detector.getFocusY() - (v.getTop() + mYScroll);				// Scroll to maintain the focus point				mXScroll += viewFocusX - viewFocusX * scalingFactor;				mYScroll += viewFocusY - viewFocusY * scalingFactor;				requestLayout();		}		return true;	}	public boolean onScaleBegin(ScaleGestureDetector detector) {		mScaling = true;		// Ignore any scroll amounts yet to be accounted for: the		// screen is not showing the effect of them, so they can		// only confuse the user		mXScroll = mYScroll = 0;		// Avoid jump at end of scaling by disabling scrolling		// until the next start of gesture		mScrollDisabled = true;		return true;//一定要返回true才会进入onScale()这个函数	}	public void onScaleEnd(ScaleGestureDetector detector) {		mScaling = false;	}		/*      * 在onTouch()方法中，我们调用GestureDetector的onTouchEvent()方法，将捕捉到的MotionEvent交给GestureDetector      * 来分析是否有合适的callback函数来处理用户的手势      */  	@Override	public boolean onTouch(View v, MotionEvent event) {		// TODO Auto-generated method stub		return mGestureDetector.onTouchEvent(event); 	}	@Override	public boolean onTouchEvent(MotionEvent event) {				mScaleGestureDetector.onTouchEvent(event);		if (!mScaling)			mGestureDetector.onTouchEvent(event);		if (event.getActionMasked() == MotionEvent.ACTION_DOWN) {			mUserInteracting = true;		}		if (event.getActionMasked() == MotionEvent.ACTION_UP) {			mScrollDisabled = false;			mUserInteracting = false;									if(event.getAction() == MotionEvent.ACTION_UP){				View v = mChildViews.get(mCurrent);				if (v != null) {					if (mScroller.isFinished()) {						slideViewOntoScreen(v);					}						if (mScroller.isFinished()) {						postSettle(v);						}					}			}		}		requestLayout();		return true;	}

这些完成之后，我们就要在FileActivity类中调用MuPDFActivity：

					Intent intent = new Intent(getApplicationContext(), MuPDFActivity.class);					intent.setAction(Intent.ACTION_VIEW);					intent.setData(uri);					startActivity(intent);

【android开发】手写签名系统的设计与实现之实现解析pdf文件（二）