Plugin implementation for Android

README.md

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+# cordova-plugin-save-dialog
+
+This Cordova plugin for Android displays the native Save dialog which allows users to store a file in the selected location. The plugin utilizes the Storage Access Framework to save a file in a user-selected location as described in the [Android developer guide](https://developer.android.com/training/data-storage/shared/documents-files#create-file). Platforms other than Android are not supported currently.
+
+## Installation
+
+```
+cordova plugin add cordova-plugin-save-dialog --save
+```
+
+## API
+
+The plugin’s functionality is accessible through the object `cordova.plugins.saveDialog`.
+
+### saveFile
+
+Call this method to open the Save dialog and store raw contents in a file. The method accepts two arguments:
+
+* file contents as a Blob instance,
+* optional file name to display on default (the user may change it manually though).
+
+To construct a Blob representation for a file contents, either use the [Blob constructor](https://developer.mozilla.org/en-US/docs/Web/API/Blob/Blob) directly:
+
+```javascript
+let blob = new Blob(["file contents"], {type: "text/plain"});
+let fileName = "my-file.txt";
+cordova.plugins.saveDialog.saveFile(blob, fileName).then(() => {
+    console.info("The file has been successfully saved");
+}).catch(reason => {
+    console.warn(reason);
+});
+```
+
+or apply other methods of blob generation (such as [Response.blob()](https://developer.mozilla.org/en-US/docs/Web/API/Response/blob) for a network-fetched content):
+
+```javascript
+try {
+    let response = await fetch(`https://avatars.dicebear.com/api/avataaars/${Math.random()}.svg`);
+    let blob = await response.blob();
+    await cordova.plugins.saveDialog.saveFile(blob, "random-avatar.svg");
+} catch (e) {
+    console.error(e);
+}
+```

package.json

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+{
+  "name": "cordova-plugin-save-dialog",
+  "version": "0.1.0",
+  "description": "Cordova plugin for Android to display the native Save dialog and store a file in the selected location",
+  "main": "index.js",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/Amphiluke/cordova-plugin-save-dialog.git"
+  },
+  "keywords": [
+    "ecosystem:cordova",
+    "cordova-android",
+    "save",
+    "dialog"
+  ],
+  "author": "Amphiluke",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/Amphiluke/cordova-plugin-save-dialog/issues"
+  },
+  "homepage": "https://github.com/Amphiluke/cordova-plugin-save-dialog#readme"
+}

plugin.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<plugin xmlns="http://apache.org/cordova/ns/plugins/1.0" id="cordova-plugin-save-dialog" version="0.1.0">
+    <name>Save Dialog</name>
+    <description>Cordova plugin for Android to display the native Save dialog and store a file in the selected location</description>
+    <license>MIT</license>
+    <keywords>cordova,save,dialog</keywords>
+    <js-module src="www/save-dialog.js" name="SaveDialog">
+        <clobbers target="cordova.plugins.saveDialog" />
+    </js-module>
+
+    <platform name="android">
+        <config-file target="res/xml/config.xml" parent="/*">
+            <feature name="SaveDialog" >
+                <param name="android-package" value="io.github.amphiluke.SaveDialog"/>
+            </feature>
+        </config-file>
+        <source-file src="src/android/SaveDialog.java" target-dir="src/io/github/amphiluke" />
+    </platform>
+</plugin>

src/android/SaveDialog.java

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+package io.github.amphiluke;
+
+import android.app.Activity;
+import android.content.Intent;
+import android.net.Uri;
+import android.os.Bundle;
+import android.os.ParcelFileDescriptor;
+// import android.provider.DocumentsContract;
+import android.util.Base64;
+
+import org.apache.cordova.CallbackContext;
+import org.apache.cordova.CordovaPlugin;
+
+import org.json.JSONArray;
+import org.json.JSONException;
+
+import java.io.FileOutputStream;
+
+public class SaveDialog extends CordovaPlugin {
+    private static final int LOCATE_FILE = 1;
+
+    private CallbackContext callbackContext;
+
+    @Override
+    public boolean execute(String action, JSONArray args, CallbackContext callbackContext) throws JSONException {
+        this.callbackContext = callbackContext;
+        if (action.equals("locateFile")) {
+            this.locateFile(args.getString(0), args.getString(1));
+        } else if (action.equals("saveFile")) {
+            this.saveFile(Uri.parse(args.getString(0)), args.getString(1));
+        } else {
+            return false;
+        }
+        return true;
+    }
+
+    private void locateFile(String type, String name) {
+        Intent intent = new Intent(Intent.ACTION_CREATE_DOCUMENT);
+        intent.addCategory(Intent.CATEGORY_OPENABLE);
+        intent.setType(type);
+        intent.putExtra(Intent.EXTRA_TITLE, name);
+        // TODO Optionally, specify a URI for the directory that should be opened in
+        // the system file picker when your app creates the document.
+        // intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, pickerInitialUri);
+        cordova.startActivityForResult(this, intent, SaveDialog.LOCATE_FILE);
+    }
+
+    @Override
+    public void onActivityResult(int requestCode, int resultCode, Intent resultData) {
+        if (requestCode == SaveDialog.LOCATE_FILE && this.callbackContext != null) {
+            if (resultCode == Activity.RESULT_CANCELED) {
+                this.callbackContext.error("The dialog has been cancelled");
+            } else if (resultCode == Activity.RESULT_OK && resultData != null) {
+                Uri uri = resultData.getData();
+                this.callbackContext.success(uri.toString());
+            } else {
+                this.callbackContext.error("Unknown error");
+            }
+        }
+    }
+
+    public void onRestoreStateForActivityResult(Bundle state, CallbackContext callbackContext) {
+        this.callbackContext = callbackContext;
+    }
+
+    private void saveFile(Uri uri, String data) {
+        try {
+            byte[] rawData = Base64.decode(data, Base64.DEFAULT);
+            ParcelFileDescriptor pfd = cordova.getActivity().getContentResolver().openFileDescriptor(uri, "w");
+            FileOutputStream fileOutputStream = new FileOutputStream(pfd.getFileDescriptor());
+            try {
+                fileOutputStream.write(rawData);
+                this.callbackContext.success();
+            } catch (Exception e) {
+                this.callbackContext.error(e.getMessage());
+                e.printStackTrace();
+            } finally {
+                fileOutputStream.close();
+                pfd.close();
+            }
+        } catch (Exception e) {
+            this.callbackContext.error(e.getMessage());
+            e.printStackTrace();
+        }
+    }
+}

www/save-dialog.js

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+let exec = require("cordova/exec");
+let moduleMapper = require("cordova/modulemapper");
+let FileReader = moduleMapper.getOriginalSymbol(window, "FileReader") || window.FileReader;
+
+module.exports = {
+    saveFile(blob, name = "") {
+        return new Promise((resolve, reject) => {
+            exec(resolve, reject, "SaveDialog", "locateFile", [blob.type || "application/octet-stream", name]);
+        }).then(uri => {
+            let reader = new FileReader();
+            reader.onload = () => {
+                exec(resolve, reject, "SaveDialog", "saveFile", [uri, reader.result]);
+            };
+            reader.onerror = () => {
+                reject(reader.error);
+            };
+            reader.onabort = () => {
+                reject("Blob reading has been aborted");
+            };
+            reader.readAsArrayBuffer(blob);
+        });
+    }
+};