Complete saving after Cordova Activity relaunch

README.md

@@ -38,6 +38,7 @@ 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");
+    console.info("The file has been successfully saved");
 } catch (e) {
     console.error(e);
 }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "cordova-plugin-save-dialog",
-  "version": "0.1.0",
+  "version": "0.1.1",
   "description": "Cordova plugin for Android to display the native Save dialog and store a file in the selected location",
   "main": "index.js",
   "repository": {
@@ -10,6 +10,7 @@
   "keywords": [
     "ecosystem:cordova",
     "cordova-android",
+    "file",
     "save",
     "dialog"
   ],

plugin.xml

@@ -1,12 +1,14 @@
 <?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">
+<plugin xmlns="http://apache.org/cordova/ns/plugins/1.0" id="cordova-plugin-save-dialog" version="0.1.1">
     <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">
+    <js-module src="www/SaveDialog.js" name="SaveDialog">
         <clobbers target="cordova.plugins.saveDialog" />
     </js-module>
+    <js-module src="www/BlobKeeper.js" name="BlobKeeper">
+    </js-module>
 
     <platform name="android">
         <config-file target="res/xml/config.xml" parent="/*">

www/BlobKeeper.js

@@ -0,0 +1,61 @@
+let moduleMapper = require("cordova/modulemapper");
+let indexedDB = moduleMapper.getOriginalSymbol(window, "indexedDB") || window.indexedDB;
+
+function openDB() {
+    if (!indexedDB) {
+        return Promise.reject("indexedDB is not supported");
+    }
+    if (openDB._db) {
+        return Promise.resolve(openDB._db);
+    }
+    return new Promise((resolve, reject) => {
+        let openRequest = indexedDB.open("CordovaPluginSaveDialog");
+        openRequest.onupgradeneeded = () => {
+            openRequest.result.createObjectStore("blobs");
+        };
+        openRequest.onsuccess = () => {
+            openDB._db = openRequest.result;
+            resolve(openDB._db);
+        };
+        openRequest.onerror = () => {
+            openDB._db = null;
+            reject(openRequest.error);
+        };
+    });
+}
+
+function writeBlob(blob) {
+    return openDB().then(db => new Promise((resolve, reject) => {
+        let objectStore = db.transaction(["blobs"], "readwrite").objectStore("blobs");
+        let putRequest = blob ? objectStore.put(blob, 0) : objectStore.clear();
+        putRequest.onsuccess = () => {
+            resolve();
+        };
+        putRequest.onerror = () => {
+            reject(putRequest.error);
+        };
+    }));
+}
+
+function getBlob() {
+    return openDB().then(db => new Promise((resolve, reject) => {
+        let objectStore = db.transaction(["blobs"], "readonly").objectStore("blobs");
+        let getRequest = objectStore.get(0);
+        getRequest.onsuccess = () => {
+            resolve(getRequest.result);
+        };
+        getRequest.onerror = () => {
+            reject(getRequest.error);
+        };
+    }));
+}
+
+function warn(reason) {
+    console.warn("[SaveDialog]", reason);
+}
+
+module.exports = {
+    keep: blob => writeBlob(blob).catch(warn),
+    get: () => getBlob().catch(warn),
+    clear: () => writeBlob(null).catch(warn)
+};

www/SaveDialog.js

@@ -0,0 +1,61 @@
+let exec = require("cordova/exec");
+let {keep: keepBlob, get: getBlob, clear: clearBlob} = require("./BlobKeeper");
+let moduleMapper = require("cordova/modulemapper");
+let FileReader = moduleMapper.getOriginalSymbol(window, "FileReader") || window.FileReader;
+
+let locateFile = (type, name) => new Promise((resolve, reject) => {
+    exec(resolve, reject, "SaveDialog", "locateFile", [type || "application/octet-stream", name]);
+});
+
+let saveFile = (uri, blob) => new Promise((resolve, reject) => {
+    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);
+});
+
+module.exports = {
+    saveFile(blob, name = "") {
+        if (window.cordova.platformId !== "android") {
+            return Promise.reject("Unsupported platform");
+        }
+        return keepBlob(blob) // see the “resume” event handler below
+            .then(() => locateFile(blob.type, name))
+            .then(uri => saveFile(uri, blob))
+            .then(() => {
+                clearBlob();
+            })
+            .catch(reason => {
+                clearBlob();
+                return Promise.reject(reason);
+            });
+    }
+};
+
+// If Android OS has destroyed the Cordova Activity in background, try to complete the Save operation
+// using the URI passed in the payload of the “resume” event and the blob stored by the BlobKeeper.
+// https://cordova.apache.org/docs/en/10.x/guide/platforms/android/plugin.html#launching-other-activities
+document.addEventListener("resume", ({pendingResult = {}}) => {
+    if (pendingResult.pluginServiceName !== "SaveDialog") {
+        return;
+    }
+    if (pendingResult.pluginStatus !== "OK" || !pendingResult.result) {
+        clearBlob();
+        return;
+    }
+    getBlob().then(blob => {
+        if (blob instanceof Blob) {
+            saveFile(pendingResult.result, blob).catch(reason => {
+                console.warn("[SaveDialog]", reason);
+            });
+        }
+        clearBlob();
+    });
+}, false);