Android open pdf file

As of API 24, sending a file:// URI to another app will throw a FileUriExposedException. Instead, use FileProvider to send a content:// URI:

public File getFile(Context context, String fileName) {
    if (!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
        return null;
    }

    File storageDir = context.getExternalFilesDir(null);
    return new File(storageDir, fileName);
}

public Uri getFileUri(Context context, String fileName) {
    File file = getFile(context, fileName);
    return FileProvider.getUriForFile(context, BuildConfig.APPLICATION_ID + ".provider", file);
}

You must also define the FileProvider in your manifest:

<provider
    android:name="android.support.v4.content.FileProvider"
    android:authorities="com.mydomain.fileprovider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/file_paths" />
</provider>

Example file_paths.xml:

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-files-path name="name" path="path" />
</paths>

Replace "name" and "path" as appropriate.

To give the PDF viewer access to the file, you also have to add the FLAG_GRANT_READ_URI_PERMISSION flag to the intent:

private void displayPdf(String fileName) {
    Uri uri = getFileUri(this, fileName);

    Intent intent = new Intent(Intent.ACTION_VIEW);
    intent.setDataAndType(uri, "application/pdf");

    // FLAG_GRANT_READ_URI_PERMISSION is needed on API 24+ so the activity opening the file can read it
    intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY | Intent.FLAG_GRANT_READ_URI_PERMISSION);

    if (intent.resolveActivity(getPackageManager()) == null) {
        // Show an error
    } else {
        startActivity(intent);
    }
}

See the FileProvider documentation for more details.

The problem is that there is no app installed to handle opening the PDF. You should use the Intent Chooser, like so:

File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() +"/"+ filename);
Intent target = new Intent(Intent.ACTION_VIEW);
target.setDataAndType(Uri.fromFile(file),"application/pdf");
target.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);

Intent intent = Intent.createChooser(target, "Open File");
try {
    startActivity(intent);
} catch (ActivityNotFoundException e) {
    // Instruct the user to install a PDF reader here, or something
}