代码修改自该处(开源 Android pdf 阅读器开发总结)作者分享到Google code的代码,经仔细阅读后整理出读取PDF文档的主要部分(vudroid so库的使用),原作者应该也是在vudroid项目下稍微进行了修改,代码有点乱,所以我整理了下,把关键地方抽了出来,项目中没有提供vudroid so库的源码,所以知道的接口只有那几个,想完整了解vudroid库接口的建议去下载vudroid官方源码,再自行通过ndk编译.(源码下载依然在最后)

import android.os.Bundle;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.RectF;
import android.view.Menu;
import android.view.MotionEvent;
import android.widget.ImageView;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.FloatMath;

import org.vudroid.pdfdroid.codec.*;


public class MainActivity extends Activity {
    private PdfContext pdf_conext;
    private ImageView view;
    
    private float screen_width = 800;
    private float screen_height = 1280;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        view = (ImageView)findViewById(R.id.imageView1);
        
        pdf_conext = new PdfContext();
        PdfDocument d = pdf_conext.openDocument("/sdcard/test.pdf");
        
        PdfPage vuPage = d.getPage(1);
        RectF rf = new RectF();
        rf.bottom = rf.right = (float)1.0;
        //参数一二为生成图片的宽高,参数三Rect的top,left,bottom,right为截取部分在该页中的百分比位置
        //例如top=0.5,left=0.5,right=1.0,1.0则截取右下角四分之一的部分
        Bitmap bitmap = vuPage.renderBitmap((int)screen_width, (int)screen_height, rf);
        view.setImageBitmap(bitmap);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
    
    Matrix matrix = new Matrix();
    Matrix savedMatrix = new Matrix();   
    static final int NONE = 0;   
    static final int DRAG = 1;   
    static final int ZOOM = 2;   
    int mode = NONE;   
    PointF start = new PointF();   
    PointF mid = new PointF();   
    float oldDist = 1f;   
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            matrix.set(view.getImageMatrix());
            savedMatrix.set(matrix);
            start.set(event.getX(), event.getY());
            mode = DRAG;

            break;
        case MotionEvent.ACTION_POINTER_DOWN:
            oldDist = spacing(event);
            if (oldDist > 10f) {
                savedMatrix.set(matrix);
                midPoint(mid, event);
                mode = ZOOM;
            }
            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_POINTER_UP:
            mode = NONE;
            break;
        case MotionEvent.ACTION_MOVE:
            if (mode == DRAG) {
                matrix.set(savedMatrix);
                matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);
                
                keepInSight(matrix);
                
            } else if (mode == ZOOM) {
                float newDist = spacing(event);
                if (newDist > 10f) {
                    matrix.set(savedMatrix);
                    float scale = newDist / oldDist;
                    matrix.postScale(scale, scale, mid.x, mid.y);
                    
                    keepInSight(matrix);
                }
            }
            break;
        }
        view.setImageMatrix(matrix);
        return true;
    }

    private float spacing(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return FloatMath.sqrt(x * x + y * y);
    }

    private void midPoint(PointF point, MotionEvent event) {
        float x = event.getX(0) + event.getX(1);
        float y = event.getY(0) + event.getY(1);
        point.set(x / 2, y / 2);
    }

    private void keepInSight(Matrix m){
        float f[] = new float[9];
        m.getValues(f);
        if(f[0]<1) f[0]=1;
        if(f[4]<1) f[4]=1;
        
        if(f[2]>0) f[2]=0;
        if(f[5]>0) f[5]=0;
        
        float l = screen_width-screen_width*f[0];
        if(f[2]<l) f[2] = l;
            
        float t = screen_height-screen_height*f[0];
        if(f[5]<t) f[5] = t;
        
        m.setValues(f);
    }
}

源码下载:

http://dl.vmall.com/c0x4dky4py