我在网上搜索了在应用中显示pdf文档的示例。另外，我搜索了一个Downloader类，因为我想从互联网上加载pdf。执行后，它只显示空白的PDF页面。
MainActivity.java只是将pdf链接发送到DisplayPDF.java活动：
package com.example.pdfviewevaluation;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
public class MainActivity extends AppCompatActivity {
public final static String EXTRA_MESSAGE = "com.example.pdfviewevaluation.MESSAGE";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent intent = new Intent(this, DisplayPDF.class);
String url = "pdf link";
intent.putExtra(EXTRA_MESSAGE, url);
startActivity(intent);
}
}
DisplayPDF.java在缓存目录中创建文件夹和PDF。然后它使用pdf链接和目录启动Downloader。最后它应该只显示pdf：
package com.example.pdfviewevaluation;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.concurrent.ExecutionException;
public class DisplayPDF extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_display_pdf);
String pdfURL = getIntent().getStringExtra(MainActivity.EXTRA_MESSAGE);
File folder = new File(this.getCacheDir(), "pdf");
folder.mkdir();
File file = new File(folder, "Read.pdf");
try {
file.createNewFile();
} catch (IOException e1) {
e1.printStackTrace();
}
Downloader dl = new Downloader(pdfURL, file);
try {
dl.execute().get();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
showPdf();
}
public void showPdf() {
File file = new File(this.getCacheDir()+"/pdf/Read.pdf");
PackageManager packageManager = getPackageManager();
Intent testIntent = new Intent(Intent.ACTION_VIEW);
testIntent.setType("application/pdf");
List list = packageManager.queryIntentActivities(testIntent, PackageManager.MATCH_DEFAULT_ONLY);
Intent intent = new Intent();
intent.setAction(Intent.ACTION_VIEW);
Uri uri = FileProvider.getUriForFile(this.getApplicationContext(), this.getApplicationContext().getPackageName() + ".provider", file);
intent.setDataAndType(uri, "application/pdf");
startActivity(intent);
}
}
Downloader.java连接到pdf页面并将pdf从给定链接下载到所需目录：
package com.example.pdfviewevaluation;
import android.os.AsyncTask;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class Downloader extends AsyncTask<Void,Void,Void> {
private String fileURL;
private File directory;
public Downloader(String fileURL, File directory)
{
this.fileURL = fileURL;
this.directory = directory;
}
protected Void doInBackground(Void... params) {
try {
FileOutputStream f = new FileOutputStream(directory);
URL u = new URL(fileURL);
HttpURLConnection c = (HttpURLConnection) u.openConnection();
c.setRequestMethod("GET");
c.setDoOutput(true);
c.connect();
InputStream in = c.getInputStream();
byte[] buffer = new byte[1024];
int len1 = 0;
int i = 0;
while ((len1 = in.read(buffer)) > 0) {
f.write(buffer, 0, len1);
}
f.close();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
答案 0 :(得分：0)
花了很多时间在我的问题上，我在YouTube上搜索了另一个解决方案。这些是显示解决方案：
的AndroidManifest.xml：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.downloadingfiles">
<uses-sdk android:minSdkVersion="21"
android:targetSdkVersion="22" />
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
MainActivity.java：
import android.app.DownloadManager;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.Rect;
import android.graphics.pdf.PdfRenderer;
import android.net.Uri;
import android.os.Environment;
import android.os.ParcelFileDescriptor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.webkit.MimeTypeMap;
import android.webkit.URLUtil;
import android.widget.ImageView;
import android.widget.Toast;
import java.io.File;
public class MainActivity extends AppCompatActivity {
String myUrl = "http://www.orimi.com/pdf-test.pdf";
private ImageView imageView;
private int currentPage = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
registerReceiver(onComplete, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(myUrl));
request.setTitle("File download.");
request.setDescription("File is being downloaded...");
request.allowScanningByMediaScanner();
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
String nameOfFile = URLUtil.guessFileName(myUrl, null, MimeTypeMap.getFileExtensionFromUrl(myUrl));
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, nameOfFile);
DownloadManager manager = (DownloadManager) this.getSystemService(Context.DOWNLOAD_SERVICE);
manager.enqueue(request);
}
BroadcastReceiver onComplete=new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
render();
}
};
/**Called when the user clicks the "Next" button defined in activity_main.xml */
public void nextPage(View view) {
currentPage++;
render();
}
/**Called when the user clicks the "Previous" button defined in activity_main.xml */
public void previousPage(View view) {
currentPage--;
render();
}
private void render(){
try{
imageView = (ImageView) findViewById(R.id.image);
int REQ_WIDTH = imageView.getWidth();
int REQ_HEIGHT = imageView.getHeight();
Bitmap bitmap = Bitmap.createBitmap(REQ_WIDTH, REQ_HEIGHT, Bitmap.Config.ARGB_4444);
String nameOfFile = URLUtil.guessFileName(myUrl, null, MimeTypeMap.getFileExtensionFromUrl(myUrl));
File file = new File("/sdcard/Download/"+nameOfFile);
PdfRenderer renderer = new PdfRenderer(ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY));
if(currentPage < 0){
currentPage = 0;
}else if(currentPage >= renderer.getPageCount()){
currentPage = renderer.getPageCount() - 1;
}
Matrix m = imageView.getImageMatrix();
Rect rect = new Rect(0, 0, REQ_WIDTH, REQ_HEIGHT);
renderer.openPage(currentPage).render(bitmap, rect, m, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
imageView.setImageMatrix(m);
imageView.setImageBitmap(bitmap);
imageView.invalidate();
} catch (Exception e){
e.printStackTrace();
}
}
}