开发实用技巧 ​

UILabel *titleLab = [[UILabel alloc] initWithFrame:CGRectMake(0, 100, 200, 40)];
titleLab.numberOfLines = 2;
titleLab.lineBreakMode = NSLineBreakByTruncatingTail;

[self.tableView reloadData];
  [self.tableView layoutIfNeeded]; //这句是关键
  [self.tableView setContentOffset:CGPointMake(0,0) animated:NO];

#pragma mark - app保持后台静音播放声音
- (void)appKeepAVAudioActive {
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback withOptions:AVAudioSessionCategoryOptionAllowBluetooth error:nil];
    [[AVAudioSession sharedInstance] setActive:YES error:nil];
}

NSString *bundlePath = [[ NSBundle mainBundle] pathForResource:@"bundleName" ofType :@"bundle"];
NSBundle *bundle = [NSBundle bundleWithPath:bundlePath];
NSString *voicePath = [bundle pathForResource:[NSString stringWithFormat:@"mp3/%@",name] ofType:@"mp3"];
NSURL *filePath = [NSURL fileURLWithPath:voicePath isDirectory:NO];
NSError *error;
AVAudioPlayer *audioPlayer = = [[AVAudioPlayer alloc]initWithContentsOfURL:filePath error:&error];
if (error) return;
[audioPlayer prepareToPlay];
//获取系统音量
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
CGFloat volume = audioSession.outputVolume;
audioPlayer.volume = volume;
[audioPlayer play];

[[UIApplication sharedApplication] endReceivingRemoteControlEvents];

#pragma mark - app保持常亮
- (void)appKeepLight {
    [[UIApplication sharedApplication] setIdleTimerDisabled:YES];
    [[UIScreen mainScreen] setBrightness:0.5];
}

#pragma mark - app退出
-(void)appTerminate {
    [[UIApplication sharedApplication] setIdleTimerDisabled:NO];
}

#pragma mark - app保持后台
- (void)appKeepBackground {
    [[UIApplication sharedApplication] setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];
}

[[UIScreen mainScreen] setBrightness:0.5];

typedef NS_ENUM(NSUInteger,webviewLoadingStatus) {
 
    WebViewNormalStatus = 0, //正常
 
    WebViewErrorStatus, //白屏
 
    WebViewPendStatus, //待决
};
 
// 判断是否白屏
- (void)judgeLoadingStatus:(WKWebview *)webview  withBlock:(void (^)(webviewLoadingStatus status))completionBlock{
    webviewLoadingStatus __block status = WebViewPendStatus;
    if (@available(iOS 11.0, *)) {
        if (webview && [webview isKindOfClass:[WKWebView class]]) {
 
            CGFloat statusBarHeight =  [[UIApplication sharedApplication] statusBarFrame].size.height; //状态栏高度
            CGFloat navigationHeight = webview.viewController.navigationController.navigationBar.frame.size.height; //导航栏高度
            WKSnapshotConfiguration *shotConfiguration = [[WKSnapshotConfiguration alloc] init];
            shotConfiguration.rect = CGRectMake(0, statusBarHeight + navigationHeight, webview.bounds.size.width, (webview.bounds.size.height - navigationHeight - statusBarHeight)); //仅截图检测导航栏以下部分内容
            [webview takeSnapshotWithConfiguration:shotConfiguration completionHandler:^(UIImage * _Nullable snapshotImage, NSError * _Nullable error) {
                dispatch_async(dispatch_get_global_queue(0, 0), ^{
                  if (snapshotImage) {
                      // 对图片进行缩放
                      UIImage *scaleImage = [self scaleImage:snapshotImage];
                      // 白屏检测, 在主线程会卡线程
                      BOOL isWhiteScreen = [self searchEveryPixel:scaleImage rgb:rgb proportion:proportion];
                      if (isWhiteScreen) { // 白屏
                          status = WKWebViewErrorStatus;
                      }else{
                          status = WKWebViewNormalStatus;
                      }
                  }
                  dispatch_async(dispatch_get_main_queue(), ^{
                      //回到主线程，执行UI刷新操作
                      if (completionBlock) {
                        completionBlock(status);
                      }
                  });
              });
            }];
        }
    }
}
 
// 遍历像素点 白色像素占比大于95%认定为白屏
- (BOOL)searchEveryPixel:(UIImage *)image {
    CGImageRef cgImage = [image CGImage];
    size_t width = CGImageGetWidth(cgImage);
    size_t height = CGImageGetHeight(cgImage);
    size_t bytesPerRow = CGImageGetBytesPerRow(cgImage); //每个像素点包含r g b a 四个字节
    size_t bitsPerPixel = CGImageGetBitsPerPixel(cgImage);
 
    CGDataProviderRef dataProvider = CGImageGetDataProvider(cgImage);
    CFDataRef data = CGDataProviderCopyData(dataProvider);
    UInt8 * buffer = (UInt8*)CFDataGetBytePtr(data);
 
    int whiteCount = 0;
    int totalCount = 0;
 
    for (int j = 0; j < height; j ++ ) {
        for (int i = 0; i < width; i ++) {
            UInt8 * pt = buffer + j * bytesPerRow + i * (bitsPerPixel / 8);
            UInt8 red   = * pt;
            UInt8 green = *(pt + 1);
            UInt8 blue  = *(pt + 2);
//            UInt8 alpha = *(pt + 3);
 
            totalCount ++;
            if (red == 255 && green == 255 && blue == 255) {
                whiteCount ++;
            }
        }
    }
    float proportion = (float)whiteCount / totalCount ;
    NSLog(@"当前像素点数：%d,白色像素点数:%d , 占比: %f",totalCount , whiteCount , proportion );
    if (proportion > 0.95) {
        return YES;
    }else{
        return NO;
    }
}
 
//缩放图片
- (UIImage *)scaleImage: (UIImage *)image {
    CGFloat scale = 0.2;
    CGSize newsize;
    newsize.width = floor(image.size.width * scale);
    newsize.height = floor(image.size.height * scale);
    if (@available(iOS 10.0, *)) {
        UIGraphicsImageRenderer * renderer = [[UIGraphicsImageRenderer alloc] initWithSize:newsize];
          return [renderer imageWithActions:^(UIGraphicsImageRendererContext * _Nonnull rendererContext) {
                [image drawInRect:CGRectMake(0, 0, newsize.width, newsize.height)];
          }];
    }else{
        return image;
    }
}

dispatch_async(dispatch_get_global_queue(0, 0), ^{
    //执行耗时的异步操作..
    dispatch_async(dispatch_get_main_queue(), ^{
        //回到主线程，执行UI刷新操作
    });
});

NSString *basePath = [NSString stringWithFormat: @"%@/%@", [[NSBundle mainBundle] bundlePath], @"2.2.13"];
NSURL *baseUrl = [NSURL fileURLWithPath: basePath isDirectory: YES];
NSString *filePath = [NSString stringWithFormat: @"file://%@/index.html#/page", basePath];
NSURL *fileUrl = [NSURL URLWithString: filePath];
[self.webview loadFileURL: fileUrl allowingReadAccessToURL: baseUrl];