javascript - When using html input file on an Android phone, the file type and file name cannot be obtained

Question

On some Android phones, the file information cannot be obtained by input file. What's going on?

Decode name as follows:

There are experts abroad who can read and obtain file streams. Is this the only way?
http://stackoverflow.com/ques...

Answer 1

It seems that this problem is still difficult to solve, so I will solve it myself

Since the file.type read directly is an empty string, the file header information can only be read from the file stream.

Refer to the link scheme in the question, it is optimized here

function checkFileType(type, file, back) {
    /**
     * type png jpg mp4 ...
     * file input.change=> this.files[0]
     * back callback(boolean)
     */
    // http://www.garykessler.net/library/file_sigs.html
    var args = arguments;
    if (args.length != 3) {
        back(0);
    }
    var type = args[0]; // type = '(png|jpg)' , 'png'
    var file = args[1];
    var back = typeof args[2] == 'function' ? args[2] : function() {};
    if (file.type == '') {
        // 如果系统无法获取文件类型，则读取二进制流，对二进制进行解析文件类型
        var imgType = [
            'ff d8 ff', //jpg
            '89 50 4e', //png

            '0 0 0 14 66 74 79 70 69 73 6F 6D', //mp4
            '0 0 0 18 66 74 79 70 33 67 70 35', //mp4
            '0 0 0 0 66 74 79 70 33 67 70 35', //mp4
            '0 0 0 0 66 74 79 70 4D 53 4E 56', //mp4
            '0 0 0 0 66 74 79 70 69 73 6F 6D', //mp4

            '0 0 0 18 66 74 79 70 6D 70 34 32', //m4v
            '0 0 0 0 66 74 79 70 6D 70 34 32', //m4v

            '0 0 0 14 66 74 79 70 71 74 20 20', //mov
            '0 0 0 0 66 74 79 70 71 74 20 20', //mov
            '0 0 0 0 6D 6F 6F 76', //mov

            '4F 67 67 53 0 02', //ogg
            '1A 45 DF A3', //ogg
        ];
        var typeName = [
            'jpg',
            'png',
            'mp4',
            'mp4',
            'mp4',
            'mp4',
            'mp4',
            'm4v',
            'm4v',
            'mov',
            'mov',
            'mov',
            'ogg',
            'ogg',
        ];
        var sliceSize = /png|jpg|jpeg/.test(type) ? 3 : 12;
        var reader = new FileReader();
        reader.readAsArrayBuffer(file);
        reader.addEventListener("load", function(e) {
            var slice = e.target.result.slice(0, sliceSize);
            reader = null;
            if (slice && slice.byteLength == sliceSize) {
                var view = new Uint8Array(slice);
                var arr = [];
                view.forEach(function(v) {
                    arr.push(v.toString(16));
                });
                view = null;
                console.log(arr.join(' '));
                var idx = arr.join(' ').indexOf(imgType);
                if (idx > -1) {
                    back(typeName[idx]);
                    console.log(typeName[idx]);
                } else {
                    back(false);
                }
            } else {
                back(false);
            }

        });
    } else {
        var type = file.name.match(/\.(\w+)$/)[1];
        back(type);
    }
}

How to use:

input.addEventListener(function(){
    var file = this.files[0];
    if(file.type==''){
        // 第一个参数支持单类型，或多类型，多类型时用竖线分隔，用于生成正则式
        checkFileType('(png|jpg|jpeg|mp4|mov|m4v|ogg)',file,function(fileType){
            console.log(fileType);
            //'png'
        });
        checkFileType('jpg',file,function(fileType){
            console.log(fileType);
            //false
        });
    }
});

Only judge the common formats of png, jpg, jpeg, mp4, mov, m4v, ogg. For file header information of other file types, you can view it here:
http://www.garykessler.net/li.. .