问题描述
作为序言，我熟悉编码(在高中学习2年)，但是对于Android Studio(和Java)来说，是一个完全的新手.我一直在寻找解决方案，但是由于我的经验不足，我不知道如何为我的项目实施解决方案.
As a preface, I am familiar with coding (2 years in highschool) but am a complete novice when it comes to Android Studio (and Java, in general). I've been searching for solutions for my problem, but due to my inexperience I have no idea how to implement the solutions to my project.
简而言之，我需要从某些外部URL下载pdf，将其存储到外部存储中，并使用某些pdf-viewer应用程序进行显示.我遇到了错误:
In short, I need to download a pdf from some external URL, store it into external storage, and display it using some pdf-viewer application. I've been getting error:
android.os.FileUriExposedException:file:///storage/emulated/0/pdf/Read.pdf通过Intent.getData()在应用程序之外公开
android.os.FileUriExposedException: file:///storage/emulated/0/pdf/Read.pdf exposed beyond app through Intent.getData()
...
我一直在使用和上的此来源作为参考.
I've been using this source on using an intent to open a pdf-viewer and this source on "File Provider" as references.
以下是我到目前为止的内容:
Below is what I have so far:
public class Fire extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fire);
final TextView testButton = findViewById(R.id.testPDF);
// File file = getFilesDir();
testButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(Fire.this, pdfView.class);
startActivity(intent);
}
});
pdfView活动
public class pdfView extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_pdf_view);
String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
File folder = new File(extStorageDirectory, "pdf");
folder.mkdir();
File file = new File(folder, "Read.pdf");
try {
file.createNewFile();
} catch (IOException e1) {
e1.printStackTrace();
}
Downloader.DownloadFile(__PDF_URL___, file);
showPdf();
}
public void showPdf()
{
File file = new File(Environment.getExternalStorageDirectory()+"/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 = Uri.fromFile(file);
intent.setDataAndType(uri, "application/pdf");
startActivity(intent);
}
下载器类
public class Downloader {
public static void DownloadFile(String fileURL, File directory) {
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;
while ((len1 = in.read(buffer)) > 0) {
f.write(buffer, 0, len1);
}
f.close();
} catch (Exception e) {
e.printStackTrace();
}
}
从我的研究看来，我的问题似乎源于我对URI的使用而不是文件提供者".同样，似乎实现了文件提供者"的解决方案被称为文件提供者".使用某种形式的 Context ，我对上下文的目的和实现方式感到困惑.
From my research, it seems that my problem stems from my usage of URI instead of a "File provider." Also, it seems the solution that implements a "File Provider" uses Context in some form or another, and I'm confused on what the purpose of context is and how to implement it.
如果您没有答案，那很好.关于如何弄清楚甚至理解这个概念的任何信息对我来说都是足够的.
If you do not have answers that is fine. Any information on how to figure this out or even understand the concept is good enough for me.
推荐答案
如果您的targetSdkVersion> = 24，那么我们必须使用FileProvider类来授予对特定文件或文件夹的访问权限，以使其他应用程序可以访问它们.
If your targetSdkVersion >= 24, then we have to use FileProvider class to give access to the particular file or folder to make them accessible for other apps.
1)首先在AndroidManifest.xml中的标签下添加一个FileProvider标签，如下所示:
1) First Add a FileProvider tag in AndroidManifest.xml under tag as below:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
...
<application
...
<provider
android:name=".GenericFileProvider"
android:authorities="${applicationId}.my.package.name.provider"
android:exported="false"
android:grantUriPermissions="true">
<meta-data
android:name="android.support.FILE_PROVIDER_PATHS"
android:resource="@xml/provider_paths"/>
</provider>
</application>
</manifest>
2)然后在res/xml文件夹中创建provider_paths.xml文件.如果文件夹不存在，则可能需要创建该文件夹.
2) Then create a provider_paths.xml file in res/xml folder. Folder may be needed to created if it doesn't exist.
<paths>
<external-path name="external_files" path="."/>
</paths>
3)现在创建PdfDownload.java类文件并粘贴以下代码:
3) Now create PdfDownload.java class file and paste below code:
public class PdfDownload extends Activity {
TextView tv_loading;
Context context;
int downloadedSize = 0, totalsize;
float per = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
isStoragePermissionGranted();
super.onCreate(savedInstanceState);
tv_loading = new TextView(this);
tv_loading.setGravity(Gravity.CENTER);
tv_loading.setTypeface(null, Typeface.BOLD);
setContentView(tv_loading);
downloadAndOpenPDF();
}
public static String getLastBitFromUrl(final String url) {
return url.replaceFirst(".*/([^/?]+).*", "$1");
}
void downloadAndOpenPDF() {
final String download_file_url = getIntent().getStringExtra("url");
new Thread(new Runnable() {
public void run() {
Uri path = Uri.fromFile(downloadFile(download_file_url));
try {
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
Uri uri = FileProvider.getUriForFile(PdfDownload.this, BuildConfig.APPLICATION_ID, downloadFile(download_file_url));
intent.setDataAndType(uri, "application/pdf");
startActivity(intent);
finish();
} catch (ActivityNotFoundException e) {
tv_loading
.setError("PDF Reader application is not installed in your device");
}
}
}).start();
}
File downloadFile(String dwnload_file_path) {
File file = null;
try {
URL url = new URL(dwnload_file_path);
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
urlConnection.connect();
String test = getLastBitFromUrl(dwnload_file_path);
String dest_file_path = test.replace("%20", "_");
// set the path where we want to save the file
File SDCardRoot = Environment.getExternalStorageDirectory();
// // create a new file, to save the downloaded file
file = new File(SDCardRoot, dest_file_path);
if (file.exists()) {
return file;
}
FileOutputStream fileOutput = new FileOutputStream(file);
// Stream used for reading the data from the internet
InputStream inputStream = urlConnection.getInputStream();
// this is the total size of the file which we are
// downloading
totalsize = urlConnection.getContentLength();
setText("Starting PDF download...");
// create a buffer...
byte[] buffer = new byte[1024 * 1024];
int bufferLength = 0;
while ((bufferLength = inputStream.read(buffer)) > 0) {
fileOutput.write(buffer, 0, bufferLength);
downloadedSize += bufferLength;
per = ((float) downloadedSize / totalsize) * 100;
if ((totalsize / 1024) <= 1024) {
setText("Total PDF File size : " + (totalsize / 1024)
+ " KB\n\nDownloading PDF " + (int) per + "% complete");
} else {
setText("Total PDF File size : " + (totalsize / 1024) / 1024
+ " MB\n\nDownloading PDF " + (int) per + "% complete");
}
// setText("configuring your book pleease wait a moment");
}
// close the output stream when complete //
fileOutput.close();
// setText("Download Complete. Open PDF Application installed in the device.");
setText("configuaration is completed now your book is ready to read");
} catch (final MalformedURLException e) {
setTextError("Some error occured. Press back and try again.",
Color.RED);
} catch (final IOException e) {
setTextError("Some error occured. Press back and try again.",
Color.RED);
} catch (final Exception e) {
setTextError(
"Failed to download image. Please check your internet connection.",
Color.RED);
}
return file;
}
void setTextError(final String message, final int color) {
runOnUiThread(new Runnable() {
public void run() {
tv_loading.setTextColor(color);
tv_loading.setText(message);
}
});
}
void setText(final String txt) {
runOnUiThread(new Runnable() {
public void run() {
tv_loading.setText(txt);
}
});
}
private static final String TAG = "MyActivity";
public boolean isStoragePermissionGranted() {
if (Build.VERSION.SDK_INT >= 23) {
if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
== PackageManager.PERMISSION_GRANTED) {
Log.v(TAG, "Permission is granted");
return true;
} else {
Log.v(TAG, "Permission is revoked");
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
return false;
}
} else { //permission is automatically granted on sdk<23 upon installation
Log.v(TAG, "Permission is granted");
return true;
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
Log.v(TAG, "Permission: " + permissions[0] + "was " + grantResults[0]);
}
}
}
这篇关于下载PDF并显示它(FileUriExposedException)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！