docs: 批量博文

2026-05-25 04:17:17 +00:00 · 2020-02-25 17:46:51 +08:00
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+
+# 长按UIWebView上的图片保存到相册
+
+> 不知道各位对于这个需求要如何解决？
+>
+> 可能有些人会想到js与原生交互，js监听图片点击事件，然后将图片的url传递给原生App端，然后原生App将图片保存到相册，这样子麻烦吗？超麻烦。（1）、js监听图片长按事件；（2）、js将图片url传递给原生；（3）、原生通过图片的url生成UIImage；（4）、保存UIImage到系统相册，巨麻烦啊，大哥，我很懒的好不好
+
+#### 那么问题跑出来了，怎么办最简单？
+
+* 鉴于个人道行尚浅，我就将自己的想法说出来
+
+* 有个js的api：`Document.elementFromPoint()`
+
+> The`elementFromPoint()`method of the[`Document`](https://developer.mozilla.org/en-US/docs/Web/API/Document)interface returns the topmost element at the specified coordinates.
+
+所以根据这个提示，我们完全可以只在App原生端做一些代码开发，实现这个需求
+
+#### 开发步骤
+
+*给UIWebView添加长按手势
+*监听手势动作，拿到坐标点(x,y)
+*UIWebView注入js:Document.elementFromPoint(x,y).src拿到img标签的src
+*判断拿到的src是否有值，有值则代表点击的网页上的img标签，此时弹出对话框，是否保存到相册。如果src为空，则代表点击网页上的非img标签，则不需要弹出对话框。
+*拿到图片的url，生成UIImage。再将图片保存到相册
+
+#### 有巨坑
+
+* 长按手势事件不能每次都响应，据我猜测UIWebView本身就有很多事件，所以实现下UIGestureRecognizerDelegate代理方法。长按手势准确率100%
+
+```
+- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
+    return YES;
+}
+```
+
+
+```
+//
+//  ViewController.m
+//  WebView长按图片保存到相册
+//
+//  Created by 杭城小刘 on 2017/8/2.
+//  Copyright © 2017年 杭城小刘. All rights reserved.
+//
+
+#import "ViewController.h"
+
+@interface ViewController ()<UIGestureRecognizerDelegate,NSURLSessionDelegate>
+@property (weak, nonatomic) IBOutlet UIWebView *webView;
+
+@end
+
+@implementation ViewController
+
+#pragma mark -- life cycle
+- (void)viewDidLoad{
+    [super viewDidLoad];
+    
+    NSString *htmlURL = [[NSBundle mainBundle] pathForResource:@"saveImage" ofType:@"html"];
+    [self.webView loadRequest:[NSURLRequest requestWithURL:[NSURL fileURLWithPath:htmlURL]]];
+    //给UIWebView添加手势
+    UILongPressGestureRecognizer* longPressed = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressed:)];
+    longPressed.delegate = self;
+    [self.webView addGestureRecognizer:longPressed];
+}
+
+#pragma mark -- UIGestureRecognizerDelegate
+- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
+    UIActivityTypeAddToReadingList
+    return YES;
+}
+
+- (void)longPressed:(UILongPressGestureRecognizer*)recognizer{
+    if (recognizer.state != UIGestureRecognizerStateBegan) {
+        return;
+    }
+    CGPoint touchPoint = [recognizer locationInView:self.webView];
+    NSString *imgURL = [NSString stringWithFormat:@"document.elementFromPoint(%f, %f).src", touchPoint.x, touchPoint.y];
+    NSString *urlToSave = [self.webView stringByEvaluatingJavaScriptFromString:imgURL];
+    if (urlToSave.length == 0) {
+        return;
+    }
+    
+    UIAlertController *alertVC =  [UIAlertController alertControllerWithTitle:@"大宝贝儿" message:@"你真的要保存图片到相册吗？" preferredStyle:UIAlertControllerStyleAlert];
+    UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"真的啊" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
+            [self saveImageToDiskWithUrl:urlToSave];
+    }];
+    UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"大哥，我点错了，不好意思" style:UIAlertActionStyleDefault handler:nil];
+    [alertVC addAction:okAction];
+    [alertVC addAction:cancelAction];
+    [self presentViewController:alertVC animated:YES completion:nil];
+}
+
+#pragma mark - private method
+- (void)saveImageToDiskWithUrl:(NSString *)imageUrl{
+    NSURL *url = [NSURL URLWithString:imageUrl];
+    
+    NSURLSessionConfiguration * configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
+    
+    NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:[NSOperationQueue new]];
+    
+    NSURLRequest *imgRequest = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:30.0];
+    
+    NSURLSessionDownloadTask  *task = [session downloadTaskWithRequest:imgRequest completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
+        if (error) {
+            return ;
+        }
+        NSData * imageData = [NSData dataWithContentsOfURL:location];
+        dispatch_async(dispatch_get_main_queue(), ^{
+            
+            UIImage * image = [UIImage imageWithData:imageData];
+            UIImageWriteToSavedPhotosAlbum(image, self, @selector(imageSavedToPhotosAlbum:didFinishSavingWithError:contextInfo:), NULL);
+        });
+    }];
+    [task resume];
+}
+
+#pragma mark 保存图片后的回调
+- (void)imageSavedToPhotosAlbum:(UIImage*)image didFinishSavingWithError:  (NSError*)error contextInfo:(id)contextInfo{
+    NSString*message =@"嘿嘿";
+    if(!error) {
+        UIAlertController *alertControl = [UIAlertController alertControllerWithTitle:@"提示" message:@"成功保存到相册" preferredStyle:UIAlertControllerStyleAlert];
+        
+        UIAlertAction *action = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDestructive handler:nil];
+        [alertControl addAction:action];
+        [self presentViewController:alertControl animated:YES completion:nil];
+    }else{
+        message = [error description];
+        UIAlertController *alertControl = [UIAlertController alertControllerWithTitle:@"提示" message:message preferredStyle:UIAlertControllerStyleAlert];
+        UIAlertAction *action = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleCancel handler:nil];
+        [alertControl addAction:action];
+        [self presentViewController:alertControl animated:YES completion:nil];
+    }
+}
+
+@end
+```
+
+附上关键的js官方文档：[Document.elementFromPoint()](https://developer.mozilla.org/en-US/docs/Web/API/Document/elementFromPoint)
+
+附上Demo：[Demo](https://github.com/FantasticLBP/BlogDemos)