fix apk file open fails in some cases

android/src/main/java/vn/hunghd/flutterdownloader/DownloadWorker.java

@@ -276,8 +276,8 @@ private void downloadFile(Context context, String fileURL, String savedDir, Stri
                 int storage = ContextCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.WRITE_EXTERNAL_STORAGE);
                 PendingIntent pendingIntent = null;
                 if (status == DownloadStatus.COMPLETE && clickToOpenDownloadedFile && storage == PackageManager.PERMISSION_GRANTED) {
-                    Intent intent = IntentUtils.getOpenFileIntent(getApplicationContext(), saveFilePath, contentType);
-                    if (IntentUtils.validateIntent(getApplicationContext(), intent)) {
+                    Intent intent = IntentUtils.validatedFileIntent(getApplicationContext(), saveFilePath, contentType);
+                    if (intent != null) {
                         Log.d(TAG, "Setting an intent to open the file " + saveFilePath);
                         pendingIntent = PendingIntent.getActivity(getApplicationContext(), 0, intent, PendingIntent.FLAG_CANCEL_CURRENT);
                     } else {

android/src/main/java/vn/hunghd/flutterdownloader/FlutterDownloaderPlugin.java

@@ -295,8 +295,8 @@ private void open(MethodCall call, MethodChannel.Result result) {
                     filename = fileURL.substring(fileURL.lastIndexOf("/") + 1, fileURL.length());
                 }
                 String saveFilePath = savedDir + File.separator + filename;
-                Intent intent = IntentUtils.getOpenFileIntent(context, saveFilePath, task.mimeType);
-                if (IntentUtils.validateIntent(context, intent)) {
+                Intent intent = IntentUtils.validatedFileIntent(context, saveFilePath, task.mimeType);
+                if (intent!=null) {
                     context.startActivity(intent);
                     result.success(true);
                 } else {

android/src/main/java/vn/hunghd/flutterdownloader/IntentUtils.java

@@ -5,35 +5,73 @@
 import android.content.pm.PackageManager;
 import android.content.pm.ResolveInfo;
 import android.net.Uri;
+import android.os.Build;
+
 import androidx.core.content.FileProvider;
 
+import java.io.BufferedInputStream;
 import java.io.File;
+import java.io.FileInputStream;
+import java.net.URLConnection;
 import java.util.List;
 
-import android.util.Log;
-import android.os.Build;
-
 public class IntentUtils {
-
-    public static synchronized Intent getOpenFileIntent(Context context, String path, String contentType) {
-        File file = new File(path);
+
+    private static Intent buildIntent(Context context, File file, String mime){
         Intent intent = new Intent(Intent.ACTION_VIEW);
-
-        if (Build.VERSION.SDK_INT >= 24) {
-            Uri uri = FileProvider.getUriForFile(
-                    context,
-                    context.getPackageName() + ".flutter_downloader.provider", file);
-            intent.setDataAndType(uri, contentType);
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+            Uri uri = FileProvider.getUriForFile(context, context.getPackageName() + ".flutter_downloader.provider", file);
+            intent.setDataAndType(uri, mime);
         } else {
-            intent.setDataAndType(Uri.fromFile(file), contentType);
+            intent.setDataAndType(Uri.fromFile(file), mime);
         }
-
         intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
         intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
         return intent;
     }
 
-    public static synchronized boolean validateIntent(Context context, Intent intent) {
+    public static synchronized Intent validatedFileIntent(Context context, String path, String contentType) {
+        File file = new File(path);
+        Intent intent = buildIntent(context,file,contentType);
+        if(validateIntent(context, intent))
+            return intent;
+        String mime = null;
+        try {
+            FileInputStream inputFile = new FileInputStream(path);
+            mime = URLConnection.guessContentTypeFromStream(inputFile);//does not work in some target sdk version
+            if(mime==null){
+                mime = URLConnection.guessContentTypeFromName(path);//works fine
+
+            }
+        } catch (Exception ignored){
+
+        }
+        if(mime!=null) {
+            intent = buildIntent(context,file,mime);
+            if(validateIntent(context, intent))
+                return intent;
+        }
+        return null;
+    }
+
+//     public static synchronized Intent getOpenFileIntent(Context context, String path, String contentType) {
+//         File file = new File(path);
+//         Intent intent = new Intent(Intent.ACTION_VIEW);
+//         if (Build.VERSION.SDK_INT >= 24) {
+//             Uri uri = FileProvider.getUriForFile(
+//                     context,
+//                     context.getPackageName() + ".flutter_downloader.provider", file);
+//             intent.setDataAndType(uri, contentType);
+//         } else {
+//             intent.setDataAndType(Uri.fromFile(file), contentType);
+//         }
+
+//         intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+//         intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
+//         return intent;
+//     }
+
+    private static boolean validateIntent(Context context, Intent intent) {
         PackageManager manager = context.getPackageManager();
         List<ResolveInfo> infos = manager.queryIntentActivities(intent, 0);
         if (infos.size() > 0) {