如何使用URL检查ALAsset是否仍然存在 [英] How to check if an ALAsset still exists using a URL

问题描述

我有一个包含ALAsset url的数组（不是完整的ALAsset对象）
因此，每次启动我的应用程序时，我都想检查我的数组以查看它是否仍然是最新的...

I've got an array containing ALAsset urls (not full ALAsset objects) So each time I start my application I want to check my array to see if it's still up to date...

所以我尝试了

NSData *assetData = [[NSData alloc] initWithContentsOfFile:@"assets-library://asset/asset.PNG?id=1000000001&ext=PNG"];

但是assetData始终为零

but assetData is allways nil

thx寻求帮助

推荐答案

请改用ALAssetsLibrary的assetForURL：resultBlock：failureBlock：方法从其URL获取资产。

Use assetForURL:resultBlock:failureBlock: method of ALAssetsLibrary instead to get the asset from its URL.

// Create assets library
ALAssetsLibrary *library = [[[ALAssetsLibrary alloc] init] autorelease];

// Try to load asset at mediaURL
[library assetForURL:mediaURL resultBlock:^(ALAsset *asset) {
    // If asset exists
    if (asset) {
        // Type your code here for successful
    } else {
        // Type your code here for not existing asset
    }
} failureBlock:^(NSError *error) {
    // Type your code here for failure (when user doesn't allow location in your app)
}];

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