feature(ios): Add screenshot and screen capture block

Signed-off-by: Mohamed Javid <19339952+smohamedjavid@users.noreply.github.com>

modules/react-native-status/ios/RCTStatus/EncryptionUtils.m

@@ -3,6 +3,7 @@
 #import "React/RCTEventDispatcher.h"
 #import "Statusgo.h"
 #import "Utils.h"
+#import "UIHelper.h"
 
 @implementation EncryptionUtils
 
@@ -101,6 +102,13 @@ RCT_EXPORT_METHOD(setBlankPreviewFlag:(BOOL *)newValue)
     [userDefaults setBool:newValue forKey:@"BLANK_PREVIEW"];
 
     [userDefaults synchronize];
+    
+    if (newValue) {
+        [UIHelper addScreenshotBlock];
+    } else {
+        [UIHelper removeScreenshotBlock];
+    }
+    
 }
 
 RCT_EXPORT_METHOD(hashTransaction:(NSString *)txArgsJSON

modules/react-native-status/ios/RCTStatus/UIHelper.h

@@ -5,4 +5,7 @@
 
 @interface UIHelper : NSObject <RCTBridgeModule>
 
++ (void)addScreenshotBlock;
++ (void)removeScreenshotBlock;
+
 @end

modules/react-native-status/ios/RCTStatus/UIHelper.m

@@ -8,6 +8,9 @@ RCT_EXPORT_MODULE();
 
 #pragma mark - only android methods
 
+UITextField *textField;
+UIView *guardView;
+
 RCT_EXPORT_METHOD(setSoftInputMode: (NSInteger) i) {
 #if DEBUG
     NSLog(@"setSoftInputMode() works only on Android");
@@ -35,5 +38,75 @@ RCT_EXPORT_METHOD(clearStorageAPIs) {
     }
 }
 
++ (void) addScreenshotBlock {
+    // create new secure text field and append to the window layer to prevent screenshot
+    if (textField == nil) {
+        UIWindow *window = [UIApplication sharedApplication].keyWindow;
+
+        textField = [[UITextField alloc] initWithFrame:window.frame];
+        textField.translatesAutoresizingMaskIntoConstraints = NO;
+        
+        [textField setTextAlignment:NSTextAlignmentCenter];
+        [textField setUserInteractionEnabled: NO];
+        
+        [window makeKeyAndVisible];
+        [window.layer.superlayer addSublayer:textField.layer];
+
+        if (textField.layer.sublayers.firstObject) {
+            [textField.layer.sublayers.firstObject addSublayer: window.layer];
+        }
+    }
+    [textField setSecureTextEntry: TRUE];
+    [textField setBackgroundColor: [UIColor blackColor]];
+    
+    // create event listener for screen captures and add a view to prevent the app content from exposed if recorded
+    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
+    NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];
+    [center removeObserver:self
+                      name:UIScreenCapturedDidChangeNotification
+                    object:nil];
+    [center addObserverForName:UIScreenCapturedDidChangeNotification
+                        object:nil
+                         queue:mainQueue
+                    usingBlock:^(NSNotification *notification) {
+            if (UIScreen.mainScreen.captured){
+                UIWindow *window = [UIApplication sharedApplication].keyWindow;
+                if (guardView == nil) {
+                    guardView = [[UIView alloc]initWithFrame:window.frame];
+                    guardView.backgroundColor = [UIColor blackColor];
+                    guardView.alpha = 0;
+                }
+                   
+                [window addSubview:guardView];
+                [window bringSubviewToFront:guardView];
+                [UIView animateWithDuration:0.5 animations:^{
+                    guardView.alpha = 1;
+                }];
+            } else {
+                [UIView animateWithDuration:0.5 animations:^{
+                    guardView.alpha = 0;
+                } completion:^(BOOL finished) {
+                    [guardView removeFromSuperview];
+                }];
+            }
+       }];
+}
+
++ (void) removeScreenshotBlock {
+    UIWindow *window = [UIApplication sharedApplication].keyWindow;
+    if (textField != nil) {
+        [textField setSecureTextEntry: FALSE];
+        [textField setBackgroundColor: [UIColor clearColor]];
+        CALayer *textFieldLayer = textField.layer.sublayers.firstObject;
+        if ([window.layer.superlayer.sublayers containsObject:textFieldLayer]) {
+            [textFieldLayer removeFromSuperlayer];
+        }
+    }
+    
+    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
+    [center removeObserver:self
+                      name:UIScreenCapturedDidChangeNotification
+                    object:nil];
+}
 
 @end