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我在網上搜索了在應用程序中顯示PDF文檔的示例。此外，我搜索了一個Downloader類，因爲我想從互聯網上加載PDF。執行後它只顯示空白的PDF頁面。在應用程序中下載和顯示PDF的應用程序僅返回空白內容
MainActivity.java僅僅發送PDF鏈接DisplayPDF.java活動：
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會在緩存目錄中的文件夾和PDF。然後它啓動帶有pdf鏈接和目錄的Downloader。最後，它應該只是顯示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連接到PDF頁面和PDF下載從給定的鏈接到需要的目錄：
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;
}
}
最有可能的，你是crashi ng與'NetworkOnMainThreadException'。檢查LogCat以查看您正在記錄的異常情況。 – CommonsWare
將解決方案分爲兩部分，以瞭解問題實際存在的地方：1）將下載的文件存儲在公共目錄中，並使用標準pdf閱讀器打開它，以查看文件是否損壞2）嘗試打開現有的pdf文件你的文件系統，以確保你可以顯示你知道有效的PDF文件 – SimoV8