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Merged
xroche merged 2 commits into from
Oct 31, 2026
Merged

Scan the file chooser's directories off the UI thread #267

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2540b9c
Scan the file chooser's directories off the UI thread
xroche Oct 31, 2026
ab426bc
Make a UI-thread listing impossible rather than merely untested
xroche Oct 31, 2026
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108 changes: 108 additions & 0 deletions app/src/main/java/com/httrack/android/DirScanner.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,108 @@
package com.httrack.android;

import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicInteger;

/**
* Lists directories for the file chooser off the UI thread. A stat() per entry blows past the ANR
* budget on a large or slow directory. Only the newest scan is drawn, because a slower one started
* earlier would otherwise draw over it.
*/
final class DirScanner {
private static final File ROOT = new File("/");

/** Holds what one scan found. */
static final class Listing {
/** Where the "up one level" entry leads, the filesystem root when there is nothing above. */
final File parent;

/** The visible sub-directories, in the order the filesystem listed them. */
final List<File> subdirectories;

Listing(final File parent, final List<File> subdirectories) {
this.parent = parent;
this.subdirectories = subdirectories;
}
}

/** Takes the listing of the newest scan, on the UI executor. */
interface Sink {
void onListing(Listing listing);
}

private final Executor worker;
private final Executor ui;

/** Counts the scans asked for, so a scan can tell whether it is still the newest. */
private final AtomicInteger newest = new AtomicInteger();

DirScanner(final Executor worker, final Executor ui) {
this.worker = worker;
this.ui = ui;
}

/**
* Scan a directory and hand the result to a sink.
*
* @param dir the directory to list, as the chooser currently has it, never null
* @param fallback listed instead when dir is gone, never null
* @param sink called on the UI executor, unless a later scan has superseded this one
*/
void scan(final File dir, final File fallback, final Sink sink) {
final int ticket = newest.incrementAndGet();
worker.execute(new Runnable() {
@Override
public void run() {
if (ticket != newest.get()) {
return;
}
final Listing listing = list(dir, fallback);
ui.execute(new Runnable() {
@Override
public void run() {
if (ticket == newest.get()) {
sink.onListing(listing);
}
}
});
}
});
}

/**
* Read the parent and the visible sub-directories of a directory. Private, so that the UI thread
* can reach a listing only through scan().
*
* @param dir the directory to list, which may be gone
* @param fallback listed instead when dir is gone, which leaves the parent at the root, because
* a path that no longer exists says nothing about where it sat
* @return what the chooser must show
*/
private static Listing list(final File dir, final File fallback) {
final boolean usable = dir.exists();
return new Listing(usable ? parentOf(dir) : ROOT, subdirectoriesOf(usable ? dir : fallback));
}

/** Returns the directory above dir, or the filesystem root when there is nothing above it. */
private static File parentOf(final File dir) {
final File parent = dir.getParentFile();
return parent != null ? parent : ROOT;
}

/** Returns the sub-directories of dir the chooser offers, which excludes the hidden ones. */
private static List<File> subdirectoriesOf(final File dir) {
final List<File> dirs = new ArrayList<File>();
final File[] list = dir.listFiles();
if (list != null) {
for (final File file : list) {
if (file.isDirectory() && !file.isHidden()) {
dirs.add(file);
}
}
}
return dirs;
}
}
140 changes: 75 additions & 65 deletions app/src/main/java/com/httrack/android/FileChooserActivity.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executor;

import android.os.Bundle;
import android.os.Handler;
Expand Down Expand Up @@ -33,6 +34,19 @@ public class FileChooserActivity extends Activity implements
// Handler to execute code in UI thread
private final Handler handlerUI = new Handler();

/** Lists the directories to offer on a worker thread, then draws them through handlerUI. */
private final DirScanner scanner = new DirScanner(new Executor() {
@Override
public void execute(final Runnable command) {
new Thread(command).start();
}
}, new Executor() {
@Override
public void execute(final Runnable command) {
handlerUI.post(command);
}
});

/*
* Convert dp (Density-independent Pixels) to px (pixel)
*/
Expand All @@ -51,84 +65,80 @@ private void setFile(final File file) {
}

/*
* Create all tabs for main options menu.
* Ask for the current directory's listing. showDir draws it once it arrives.
*/
private void refreshDir() {
// Clear list
files.clear();
scanner.scan(projectRootFile, defaultRootFile, new DirScanner.Sink() {
@Override
public void onListing(final DirScanner.Listing listing) {
showDir(listing);
}
});
}

// Find parent
final File parent = projectRootFile != null && projectRootFile.exists() ? projectRootFile.getParentFile() : null;
if (parent != null && projectRootFile != null && !parent.getAbsolutePath().equals(projectRootFile.getAbsolutePath())) {
files.add(new Pair<String, File>(getString(R.string.ellipsis), parent));
Log.d("httrack", "found parent of " + projectRootFile.getAbsolutePath() + ": " + parent.getAbsolutePath());
} else {
files.add(new Pair<String, File>(getString(R.string.ellipsis), new File("/")));
Log.d("httrack", "could not find found parent of " + projectRootFile.getAbsolutePath() + ", using /");
/** Draws the listing as one button per entry. */
private void showDir(final DirScanner.Listing listing) {
if (isDestroyed()) {
return;
}

// List directory
final File[] list = projectRootFile != null && projectRootFile.exists() ? projectRootFile
.listFiles() : defaultRootFile.listFiles();
if (list != null) {
for (final File file : list) {
if (file.isDirectory() && !file.isHidden() /* && file.canWrite() */) {
files.add(new Pair<String, File>(file.getName(), file));
}
}
// Clear list
files.clear();

// Up one level, then the sub-directories
files.add(new Pair<String, File>(getString(R.string.ellipsis), listing.parent));
for (final File dir : listing.subdirectories) {
files.add(new Pair<String, File>(dir.getName(), dir));
}

if (files != null) {
// Create tabs
final LinearLayout scroll = LinearLayout.class
.cast(findViewById(R.id.layout));
scroll.removeAllViews();

// Add all buttons linking to options
for (int i = 0; i < files.size(); i++) {
// Add separator
if (borderless && i != 0) {
final View line = new View(this, null, R.style.DividerLineHorizontal);

// FIXME TODO: why in hell isn't my shiny style NOT working ?
final LinearLayout.MarginLayoutParams layout = new LinearLayout.MarginLayoutParams(
LayoutParams.FILL_PARENT, dpToPx(1));
layout.bottomMargin = dpToPx(8);
layout.topMargin = dpToPx(8);
line.setLayoutParams(layout);
line.setBackgroundColor(getResources().getColor(R.color.black));

// Add line
scroll.addView(line);
}
// Create tabs
final LinearLayout scroll = LinearLayout.class
.cast(findViewById(R.id.layout));
scroll.removeAllViews();

// Add all buttons linking to options
for (int i = 0; i < files.size(); i++) {
// Add separator
if (borderless && i != 0) {
final View line = new View(this, null, R.style.DividerLineHorizontal);

// FIXME TODO: why in hell isn't my shiny style NOT working ?
final LinearLayout.MarginLayoutParams layout = new LinearLayout.MarginLayoutParams(
LayoutParams.FILL_PARENT, dpToPx(1));
layout.bottomMargin = dpToPx(8);
layout.topMargin = dpToPx(8);
line.setLayoutParams(layout);
line.setBackgroundColor(getResources().getColor(R.color.black));

// Add line
scroll.addView(line);
}

// Next tab class
final Pair<String, File> entry = files.get(i);
final String title = entry.first;

// Create a flat button ; see
// <http://developer.android.com/guide/topics/ui/controls/button.html#Borderless>
// Added in API level 11
final Button button = borderless ? new Button(this, null,
android.R.attr.borderlessButtonStyle) : new Button(this);
if (borderless) {
// Left-aligned text
button.setGravity(Gravity.LEFT | Gravity.CENTER_VERTICAL);
}
// Next tab class
final Pair<String, File> entry = files.get(i);
final String title = entry.first;

// Create a flat button ; see
// <http://developer.android.com/guide/topics/ui/controls/button.html#Borderless>
// Added in API level 11
final Button button = borderless ? new Button(this, null,
android.R.attr.borderlessButtonStyle) : new Button(this);
if (borderless) {
// Left-aligned text
button.setGravity(Gravity.LEFT | Gravity.CENTER_VERTICAL);
}

// Title
button.setText(title);
// Title
button.setText(title);

// Set listener
button.setOnClickListener(this);
// Set listener
button.setOnClickListener(this);

// Set tag to our index
button.setTag(i);
// Set tag to our index
button.setTag(i);

// And finally add button
scroll.addView(button);
}
// And finally add button
scroll.addView(button);
}
}

Expand Down
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