Question

美好的一天，我在android studio＆gt;上几乎是pdf渲染器的新手。 api 21，我发现了一个简单的代码来读取assets文件夹上的pdf。我的问题是，当它加载时，文件的第一页没有显示，除非我按下一个按钮。我的申请旨在阅读用户手册pdf。

username error: Username must be at least 6 charachers long
password error: Password msut be at least 8 charachers long

Answer 1

REQ_WIDTH和REQ_HEIGHT为0.尝试添加与屏幕尺寸相关的值

Answer 2

你可以尝试这个代码我只是稍微清理了一下

import android.app.AlertDialog;
import android.content.Context;
import android.content.res.AssetManager;
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.Rect;
import android.graphics.pdf.PdfRenderer;
import android.os.ParcelFileDescriptor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class UsersManual extends AppCompatActivity {

    private ImageView imageView;
    private int currentPage = 0;
    private Button next, previous;
    private PdfRenderer renderer;
    int REQ_WIDTH = imageView.getWidth();
    int REQ_HEIGHT = imageView.getHeight();
    private int count;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_users_manual);

        next = (Button) findViewById(R.id.next);
        previous = (Button) findViewById(R.id.previous);
        render();
        display();
        next.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                currentPage++;
                display();
            }
        });

        previous.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                currentPage--;
                display();
            }
        });


    }

    private void render() {
        try {
            imageView = (ImageView) findViewById(R.id.image);
            REQ_WIDTH = imageView.getWidth();
            REQ_HEIGHT = imageView.getHeight();

            File f = new File(getFilesDir() + "/Learning Python 5th Ed 2013.pdf");
            renderer = new PdfRenderer(ParcelFileDescriptor.open(f, ParcelFileDescriptor.MODE_READ_ONLY));
            count = renderer.getPageCount();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void display(){

        if (currentPage <= 0) {
            currentPage = 0;
        } else if (currentPage > count) {
            currentPage = renderer.getPageCount() - 1;
        }

        Bitmap bitmap = Bitmap.createBitmap(REQ_WIDTH, REQ_HEIGHT, Bitmap.Config.ARGB_8888);

        Matrix m = imageView.getImageMatrix();
        Rect rect = new Rect(0, 0, REQ_WIDTH, REQ_HEIGHT);
        renderer.openPage(currentPage).render(bitmap, rect, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
        imageView.setImageMatrix(m);
        imageView.setImageBitmap(bitmap);
        imageView.invalidate();
    }


}

启动时不显示第一页

2 个答案: