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[path_provider] started supporting background platform channels #4443

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Oct 28, 2021
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[path_provider] started supporting background platform channels #4443

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9705580
[path_provider] started supporting background platform channels
gaaclarke Oct 21, 2021
367b458
added docstrings
gaaclarke Oct 27, 2021
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5 changes: 5 additions & 0 deletions packages/path_provider/path_provider/CHANGELOG.md
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@@ -1,3 +1,8 @@
## 2.0.6

* Added support for Background Platform Channels on Android when it is
available.

## 2.0.5

* Update minimum Flutter SDK to 2.5 and iOS deployment target to 9.0.
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196 changes: 152 additions & 44 deletions ...th_provider/android/src/main/java/io/flutter/plugins/pathprovider/PathProviderPlugin.java
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Expand Up @@ -9,51 +9,183 @@
import android.os.Build.VERSION_CODES;
import android.os.Handler;
import android.os.Looper;
import android.util.Log;
import androidx.annotation.NonNull;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.SettableFuture;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import io.flutter.embedding.engine.plugins.FlutterPlugin;
import io.flutter.plugin.common.BinaryMessenger;
import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
import io.flutter.plugin.common.MethodChannel.Result;
import io.flutter.plugin.common.MethodCodec;
import io.flutter.plugin.common.StandardMethodCodec;
import io.flutter.util.PathUtils;
import java.io.File;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

public class PathProviderPlugin implements FlutterPlugin, MethodCallHandler {

static final String TAG = "PathProviderPlugin";
private Context context;
private MethodChannel channel;
private final Executor uiThreadExecutor = new UiThreadExecutor();
private final Executor executor =
Executors.newSingleThreadExecutor(
new ThreadFactoryBuilder()
.setNameFormat("path-provider-background-%d")
.setPriority(Thread.NORM_PRIORITY)
.build());
private PathProviderImpl impl;

/**
* An abstraction over how to access the paths in a thread-safe manner.
*
* <p>We need this so on versions of Flutter that support Background Platform Channels this plugin
* can take advantage of it.
*
* <p>This can be removed after https://github.com/flutter/engine/pull/29147 becomes available on
* the stable branch.
*/
private interface PathProviderImpl {
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nit: *Impl is usually used for the implementation of an interface.

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Added docstring to clarify its purpose.

void getTemporaryDirectory(@NonNull Result result);

void getApplicationDocumentsDirectory(@NonNull Result result);

void getStorageDirectory(@NonNull Result result);

void getExternalCacheDirectories(@NonNull Result result);

void getExternalStorageDirectories(@NonNull String directoryName, @NonNull Result result);

void getApplicationSupportDirectory(@NonNull Result result);
}

/** The implementation for getting system paths that executes from the platform */
private class PathProviderPlatformThread implements PathProviderImpl {
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If this is the shim, could it have a name that is easier to map to the reason why this class exists?

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Added docstring to clarify its purpose. I couldn't pack all that information into a name. This is something that exists temporarily so between the documentation and the good enough name, hopefully that's satisfactory.

private final Executor uiThreadExecutor = new UiThreadExecutor();
private final Executor executor =
Executors.newSingleThreadExecutor(
new ThreadFactoryBuilder()
.setNameFormat("path-provider-background-%d")
.setPriority(Thread.NORM_PRIORITY)
.build());

public void getTemporaryDirectory(@NonNull Result result) {
executeInBackground(() -> getPathProviderTemporaryDirectory(), result);
}

public void getApplicationDocumentsDirectory(@NonNull Result result) {
executeInBackground(() -> getPathProviderApplicationDocumentsDirectory(), result);
}

public void getStorageDirectory(@NonNull Result result) {
executeInBackground(() -> getPathProviderStorageDirectory(), result);
}

public void getExternalCacheDirectories(@NonNull Result result) {
executeInBackground(() -> getPathProviderExternalCacheDirectories(), result);
}

public void getExternalStorageDirectories(
@NonNull String directoryName, @NonNull Result result) {
executeInBackground(() -> getPathProviderExternalStorageDirectories(directoryName), result);
}

public void getApplicationSupportDirectory(@NonNull Result result) {
executeInBackground(() -> PathProviderPlugin.this.getApplicationSupportDirectory(), result);
}

private <T> void executeInBackground(Callable<T> task, Result result) {
final SettableFuture<T> future = SettableFuture.create();
Futures.addCallback(
future,
new FutureCallback<T>() {
public void onSuccess(T answer) {
result.success(answer);
}

public void onFailure(Throwable t) {
result.error(t.getClass().getName(), t.getMessage(), null);
}
},
uiThreadExecutor);
executor.execute(
() -> {
try {
future.set(task.call());
} catch (Throwable t) {
future.setException(t);
}
});
}
}

/** The implementation for getting system paths that executes from a background thread. */
private class PathProviderBackgroundThread implements PathProviderImpl {
public void getTemporaryDirectory(@NonNull Result result) {
result.success(getPathProviderTemporaryDirectory());
}

public void getApplicationDocumentsDirectory(@NonNull Result result) {
result.success(getPathProviderApplicationDocumentsDirectory());
}

public void getStorageDirectory(@NonNull Result result) {
result.success(getPathProviderStorageDirectory());
}

public void getExternalCacheDirectories(@NonNull Result result) {
result.success(getPathProviderExternalCacheDirectories());
}

public void getExternalStorageDirectories(
@NonNull String directoryName, @NonNull Result result) {
result.success(getPathProviderExternalStorageDirectories(directoryName));
}

public void getApplicationSupportDirectory(@NonNull Result result) {
result.success(PathProviderPlugin.this.getApplicationSupportDirectory());
}
}

public PathProviderPlugin() {}

private void setup(BinaryMessenger messenger, Context context) {
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Please remember when naming methods that "setup" is a noun, and "set up" is a verb, so a method (which should be named with a verb) should be called "setUp". I'm aware that Pigeon has this issue, but we shouldn't spread it beyond there.

String channelName = "plugins.flutter.io/path_provider";
// TODO(gaaclarke): Remove reflection guard when https://github.com/flutter/engine/pull/29147
// becomes available on the stable branch.
try {
Class methodChannelClass = Class.forName("io.flutter.plugin.common.MethodChannel");
Class taskQueueClass = Class.forName("io.flutter.plugin.common.BinaryMessenger$TaskQueue");
Method makeBackgroundTaskQueue = messenger.getClass().getMethod("makeBackgroundTaskQueue");
Object taskQueue = makeBackgroundTaskQueue.invoke(messenger);
Constructor<MethodChannel> constructor =
methodChannelClass.getConstructor(
BinaryMessenger.class, String.class, MethodCodec.class, taskQueueClass);
channel =
constructor.newInstance(messenger, channelName, StandardMethodCodec.INSTANCE, taskQueue);
impl = new PathProviderBackgroundThread();
Log.d(TAG, "Use TaskQueues.");
} catch (Exception ex) {
channel = new MethodChannel(messenger, channelName);
impl = new PathProviderPlatformThread();
Log.d(TAG, "Don't use TaskQueues.");
}
this.context = context;
channel.setMethodCallHandler(this);
}

@SuppressWarnings("deprecation")
public static void registerWith(io.flutter.plugin.common.PluginRegistry.Registrar registrar) {
PathProviderPlugin instance = new PathProviderPlugin();
instance.channel = new MethodChannel(registrar.messenger(), "plugins.flutter.io/path_provider");
instance.context = registrar.context();
instance.channel.setMethodCallHandler(instance);
instance.setup(registrar.messenger(), registrar.context());
}

@Override
public void onAttachedToEngine(@NonNull FlutterPluginBinding binding) {
channel = new MethodChannel(binding.getBinaryMessenger(), "plugins.flutter.io/path_provider");
context = binding.getApplicationContext();
channel.setMethodCallHandler(this);
setup(binding.getBinaryMessenger(), binding.getApplicationContext());
}

@Override
Expand All @@ -62,52 +194,28 @@ public void onDetachedFromEngine(@NonNull FlutterPluginBinding binding) {
channel = null;
}

private <T> void executeInBackground(Callable<T> task, Result result) {
final SettableFuture<T> future = SettableFuture.create();
Futures.addCallback(
future,
new FutureCallback<T>() {
public void onSuccess(T answer) {
result.success(answer);
}

public void onFailure(Throwable t) {
result.error(t.getClass().getName(), t.getMessage(), null);
}
},
uiThreadExecutor);
executor.execute(
() -> {
try {
future.set(task.call());
} catch (Throwable t) {
future.setException(t);
}
});
}

@Override
public void onMethodCall(MethodCall call, @NonNull Result result) {
switch (call.method) {
case "getTemporaryDirectory":
executeInBackground(() -> getPathProviderTemporaryDirectory(), result);
impl.getTemporaryDirectory(result);
break;
case "getApplicationDocumentsDirectory":
executeInBackground(() -> getPathProviderApplicationDocumentsDirectory(), result);
impl.getApplicationDocumentsDirectory(result);
break;
case "getStorageDirectory":
executeInBackground(() -> getPathProviderStorageDirectory(), result);
impl.getStorageDirectory(result);
break;
case "getExternalCacheDirectories":
executeInBackground(() -> getPathProviderExternalCacheDirectories(), result);
impl.getExternalCacheDirectories(result);
break;
case "getExternalStorageDirectories":
final Integer type = call.argument("type");
final String directoryName = StorageDirectoryMapper.androidType(type);
executeInBackground(() -> getPathProviderExternalStorageDirectories(directoryName), result);
impl.getExternalStorageDirectories(directoryName, result);
break;
case "getApplicationSupportDirectory":
executeInBackground(() -> getApplicationSupportDirectory(), result);
impl.getApplicationSupportDirectory(result);
break;
default:
result.notImplemented();
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2 changes: 1 addition & 1 deletion packages/path_provider/path_provider/pubspec.yaml
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Expand Up @@ -2,7 +2,7 @@ name: path_provider
description: Flutter plugin for getting commonly used locations on host platform file systems, such as the temp and app data directories.
repository: https://github.com/flutter/plugins/tree/master/packages/path_provider/path_provider
issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+path_provider%22
version: 2.0.5
version: 2.0.6
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This will need a higher version constraint on Flutter SDK. I'm not sure if that means it also needs a minor or major version bump.

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Ahh I see, you're using reflection for this.

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It should really have been a minor version update anyway, since this is a change to "add functionality in a backwards compatible manner" (the semver spec description for when to make a minor change), rather than a bug fix.


environment:
sdk: ">=2.14.0 <3.0.0"
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