tdf#129833 android: Move reading file to separate thread

Reading the input file from the main thread is problematic
when that happens over the network.

For example, trying to opening a file in a NextCloud share
using the system file picker from within the LO Android Viewer
app (with NextCloud app 3.15.1 serving as DocumentsProvider
for the NextCloud share in the file chooser) previously
resulted in a crash, with this in ADB log:

I DownloadFileOperation: Download of /Documents/five_pages.odt to /storage/emulated/0/Android/media/com.nextcloud.client/nextcloud/<USERNAME>@demo2.nextcloud.com/Documents/five_pages.odt: Unexpected exception
E DocumentsStorageProvider: RemoteOperationResult(mSuccess=false, mHttpCode=-1, mHttpPhrase=null, mException=android.os.NetworkOnMainThreadException, mCode=HOST_NOT_AVAILABLE, message=null, getLogMessage=Unexpected exception)

Moving this to a separate thread fixes the
NetworkOnMainThreadException and made opening, editing
and saving the modified file back work successfully
for that scenario.
(Using a separate thread when writing back does not
seem to be necessary, but could be added in a similar
way.)

This just moves the IO to a new thread and then waits
for its completion.
For a better user experience in cases where the copy
operation may be slow, providing some additional
feedback in the UI might be useful.

Change-Id: I58e2c4bb1dcd2d59383fba0f216c9614f5d3e3a7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/112769
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

1 files changed, 44 insertions, 19 deletions

diff --git a/android/source/src/java/org/libreoffice/LibreOfficeMainActivity.java b/android/source/src/java/org/libreoffice/LibreOfficeMainActivity.java
index bf6108edc8af..368d19af1375 100644
--- a/android/source/src/java/org/libreoffice/LibreOfficeMainActivity.java
+++ b/android/source/src/java/org/libreoffice/LibreOfficeMainActivity.java
@@ -297,9 +297,7 @@ public class LibreOfficeMainActivity extends AppCompatActivity implements Settin
     }
 
     private boolean copyFileToTemp() {
-        ContentResolver contentResolver = getContentResolver();
-        FileChannel inputChannel = null;
-        FileChannel outputChannel = null;
+        final ContentResolver contentResolver = getContentResolver();
         // CSV files need a .csv suffix to be opened in Calc.
         String suffix = null;
         String intentType = getIntent().getType();
@@ -308,26 +306,53 @@ public class LibreOfficeMainActivity extends AppCompatActivity implements Settin
             suffix = ".csv";
 
         try {
+            mTempFile = File.createTempFile("LibreOffice", suffix, this.getCacheDir());
+            final FileChannel outputChannel = new FileOutputStream(mTempFile).getChannel();
             try {
-                AssetFileDescriptor assetFD = contentResolver.openAssetFileDescriptor(getIntent().getData(), "r");
-                if (assetFD == null) {
-                    Log.e(LOGTAG, "couldn't create assetfiledescriptor from " + getIntent().getDataString());
-                    return false;
-                }
-                inputChannel = assetFD.createInputStream().getChannel();
-                mTempFile = File.createTempFile("LibreOffice", suffix, this.getCacheDir());
+                // need to run copy operation in a separate thread, since network access is not
+                // allowed from main thread, but that may happen here when underlying
+                // DocumentsProvider (like the NextCloud one) does that
+                class CopyThread extends Thread {
+                    /** Whether copy operation was successful. */
+                    private boolean result = false;
 
-                outputChannel = new FileOutputStream(mTempFile).getChannel();
-                long bytesTransferred = 0;
-                // might not  copy all at once, so make sure everything gets copied...
-                while (bytesTransferred < inputChannel.size()) {
-                    bytesTransferred += outputChannel.transferFrom(inputChannel, bytesTransferred, inputChannel.size());
+                    @Override
+                    public void run() {
+                        result = false;
+                        try {
+                            final AssetFileDescriptor assetFD = contentResolver.openAssetFileDescriptor(getIntent().getData(), "r");
+                            if (assetFD == null) {
+                                Log.e(LOGTAG, "couldn't create assetfiledescriptor from " + getIntent().getDataString());
+                                return;
+                            }
+                            FileChannel inputChannel = assetFD.createInputStream().getChannel();
+                            long bytesTransferred = 0;
+                            // might not  copy all at once, so make sure everything gets copied...
+                            while (bytesTransferred < inputChannel.size()) {
+                                bytesTransferred += outputChannel.transferFrom(inputChannel, bytesTransferred, inputChannel.size());
+                            }
+                            Log.e(LOGTAG, "Success copying " + bytesTransferred + " bytes");
+                            inputChannel.close();
+                        } catch (IOException e) {
+                            e.printStackTrace();
+                            return;
+                        }
+                        result = true;
+                    }
+                };
+                CopyThread copyThread = new CopyThread();
+                copyThread.start();
+                try {
+                    // wait for copy operation to finish
+                    // NOTE: might be useful to add some indicator in UI for long copy operations involving network...
+                    copyThread.join();
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
                 }
-                Log.e(LOGTAG, "Success copying " + bytesTransferred + " bytes");
-                return true;
+
+                return copyThread.result;
             } finally {
-                if (inputChannel != null) inputChannel.close();
-                if (outputChannel != null) outputChannel.close();
+                outputChannel.close();
             }
         } catch (FileNotFoundException e) {
             return false;