Add fastInit option in document initialization

Using this option it can be decided whether to initialize the text stripper engine on Android immediately or at the first text read.

Author: AlessioLuciani

android/src/main/kotlin/dev/aluc/pdf_text/PdfTextPlugin.kt

@@ -63,7 +63,8 @@ public class PdfTextPlugin: FlutterPlugin, MethodCallHandler {
             val args = call.arguments as Map<String, Any>
             val path = args["path"] as String
             val password = args["password"] as String
-            initDoc(result, path, password)
+            val fastInit = args["fastInit"] as Boolean
+            initDoc(result, path, password, fastInit)
           }
           "getDocPageText" -> {
             val args = call.arguments as Map<String, Any>
@@ -93,8 +94,8 @@ public class PdfTextPlugin: FlutterPlugin, MethodCallHandler {
   /**
     Initializes the PDF document and returns some information into the channel.
    */
-  private fun initDoc(result: Result, path: String, password: String) {
-    val doc = getDoc(result, path, password) ?: return
+  private fun initDoc(result: Result, path: String, password: String, fastInit: Boolean) {
+    val doc = getDoc(result, path, password, !fastInit) ?: return
     // Getting the length of the PDF document in pages.
     val length = doc.numberOfPages
 
@@ -173,8 +174,10 @@ public class PdfTextPlugin: FlutterPlugin, MethodCallHandler {
 
   /**
   Gets a PDF document, given its path.
+  Initializes the text stripper engine if initTextStripper is true.
    */
-  private fun getDoc(result: Result, path: String, password: String = ""): PDDocument? {
+  private fun getDoc(result: Result, path: String, password: String = "",
+    initTextStripper: Boolean = true): PDDocument? {
     // Checking for cached document
     if (cachedDoc != null && cachedDocPath == path) {
       return cachedDoc
@@ -183,7 +186,9 @@ public class PdfTextPlugin: FlutterPlugin, MethodCallHandler {
       val doc = PDDocument.load(File(path), password)
       cachedDoc = doc
       cachedDocPath = path
-      initTextStripperEngine(doc)
+      if (initTextStripper) {
+        initTextStripperEngine(doc)
+      }
       doc
     } catch (e: Exception) {
       Handler(Looper.getMainLooper()).post {

lib/pdf_text.dart

@@ -19,14 +19,20 @@ class PDFDoc {
   PDFDoc._internal();
 
   /// Creates a [PDFDoc] object with a [File] instance.
-  /// Optionally, takes a password for encrypted PDF documents.
-  static Future<PDFDoc> fromFile(File file, {String password = ""}) async {
+  /// Optionally, takes a [password] for encrypted PDF documents.
+  /// If [fastInit] is true, the initialization of the document will
+  /// be faster on Android. In that case, the text stripper engine
+  /// will not be initialized with this call, but later when some text
+  /// is read. This means that the first text read will take some time
+  /// but the document data can be accessed immediately.
+  static Future<PDFDoc> fromFile(File file,
+      {String password = "", bool fastInit = false}) async {
     var doc = PDFDoc._internal();
     doc._file = file;
     Map data;
     try {
-      data = await _CHANNEL
-          .invokeMethod('initDoc', {"path": file.path, "password": password});
+      data = await _CHANNEL.invokeMethod('initDoc',
+          {"path": file.path, "password": password, "fastInit": fastInit});
     } on Exception catch (e) {
       return Future.error(e);
     }
@@ -39,16 +45,28 @@ class PDFDoc {
   }
 
   /// Creates a [PDFDoc] object with a file path.
-  /// Optionally, takes a password for encrypted PDF documents.
-  static Future<PDFDoc> fromPath(String path, {String password = ""}) async {
-    return await fromFile(File(path), password: password);
+  /// Optionally, takes a [password] for encrypted PDF documents.
+  /// If [fastInit] is true, the initialization of the document will
+  /// be faster on Android. In that case, the text stripper engine
+  /// will not be initialized with this call, but later when some text
+  /// is read. This means that the first text read will take some time
+  /// but the document data can be accessed immediately.
+  static Future<PDFDoc> fromPath(String path,
+      {String password = "", bool fastInit = false}) async {
+    return await fromFile(File(path), password: password, fastInit: fastInit);
   }
 
   /// Creates a [PDFDoc] object with a URL.
-  /// Optionally, takes a password for encrypted PDF documents.
+  /// Optionally, takes a [password] for encrypted PDF documents.
+  /// If [fastInit] is true, the initialization of the document will
+  /// be faster on Android. In that case, the text stripper engine
+  /// will not be initialized with this call, but later when some text
+  /// is read. This means that the first text read will take some time
+  /// but the document data can be accessed immediately.
   /// It downloads the PDF file located in the given URL and saves it
   /// in the app's temporary directory.
-  static Future<PDFDoc> fromURL(String url, {String password = ""}) async {
+  static Future<PDFDoc> fromURL(String url,
+      {String password = "", bool fastInit = false}) async {
     File file;
     try {
       String tempDirPath = (await getTemporaryDirectory()).path;
@@ -62,7 +80,7 @@ class PDFDoc {
     } on Exception catch (e) {
       return Future.error(e);
     }
-    return await fromFile(file, password: password);
+    return await fromFile(file, password: password, fastInit: fastInit);
   }
 
   /// Gets the page of the document at the given page number.