Uri转路径 Uri转文件

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  8. How to get the Full file path from URI | Newbedev
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  11. android - Get filename and path from URI from mediastore - Stack Overflow

验证

1. 通过Uri -> FileDescriptor -> FileInputStream -> FileChannel

实在是想获取别的进程用FileProvider传过来的Uri对应的路径，
那就通过int fd = getContentResolver().openFileDescriptor().getFd()方法获取文件描述符，
然后获取/proc/{pid}/fd/{fd}文件的getCanonicalPath()，
或者是native中用readklink()方法，可以拿到Uri对应文件的绝对路径

java\io\FileInputStream.java
public FileChannel getChannel() {
    synchronized (this) {
        if (channel == null) {
            channel = FileChannelImpl.open(fd, path, true, false, this);
        }
        return channel;
    }
}

try {
    var f1: File = File(it.path)
    var f2: File = File(it.toString())
    LogUtils.d(TagConstants.URI_TO_FILE, "f1 correct:" + f1.exists() + " ; f2 correct:" + f2.exists())
    LogUtils.d(TagConstants.URI_TO_FILE, "f1 correct:" + f1.absolutePath + " ; f2 correct:" + f2.absolutePath)
} catch (e: Exception) {
    LogUtils.d(TagConstants.URI_TO_FILE, "gain file error. err:" + e.message)
}
try {
    LogUtils.d(TagConstants.URI_TO_FILE, "gain fd.");
    var fd: FileDescriptor? =  contentResolver.openFileDescriptor(it,"r")?.fileDescriptor
    var fi: FileInputStream? = null;
    if(fd != null){
        LogUtils.d(TagConstants.URI_TO_FILE, "gain fi.")
        fi = FileInputStream(fd)
        LogUtils.d(TagConstants.URI_TO_FILE, "gain fc.")
        var fc:FileChannel =  fi.channel
        if(fc == null){
            LogUtils.d(TagConstants.URI_TO_FILE, "gain fc. fc is null.")
        }else{
            LogUtils.d(TagConstants.URI_TO_FILE, "gain fc. fc is not null.")
        }
    }else{
        LogUtils.d(TagConstants.URI_TO_FILE, "gain fc. fd is null.")
    }
} catch (e: Exception) {
    LogUtils.d(TagConstants.URI_TO_FILE, "gain fc. err:" + e.message)
    e.printStackTrace()
}

2021-09-16 01:14:08.324 15897-15897 D/TagUriToFile: f1 correct:false ; f2 correct:false
2021-09-16 01:14:08.324 15897-15897 D/TagUriToFile: f1 correct:/2/352 ; f2 correct:/content:/com.google.android.apps.nbu.files.provider/2/352
2021-09-16 01:14:08.324 15897-15897 D/TagUriToFile: gain fd.
2021-09-16 01:14:08.331 15897-15897 D/TagUriToFile: gain fi.
2021-09-16 01:14:08.331 15897-15897 D/TagUriToFile: gain fc.
2021-09-16 01:14:08.331 15897-15897 D/TagUriToFile: gain fc. fc is not null.
2021-09-16 01:14:08.347 15897-15897 D/TagUriToFile: f1 correct:false ; f2 correct:false
2021-09-16 01:14:08.347 15897-15897 D/TagUriToFile: f1 correct:/2/36 ; f2 correct:/content:/com.google.android.apps.nbu.files.provider/2/36
2021-09-16 01:14:08.347 15897-15897 D/TagUriToFile: gain fd.
2021-09-16 01:14:08.350 15897-15897 D/TagUriToFile: gain fi.
2021-09-16 01:14:08.350 15897-15897 D/TagUriToFile: gain fc.
2021-09-16 01:14:08.350 15897-15897 D/TagUriToFile: gain fc. fc is not null.
2021-09-16 01:14:08.363 15897-15897 D/TagUriToFile: f1 correct:false ; f2 correct:false
2021-09-16 01:14:08.363 15897-15897 D/TagUriToFile: f1 correct:/2/29 ; f2 correct:/content:/com.google.android.apps.nbu.files.provider/2/29
2021-09-16 01:14:08.363 15897-15897 D/TagUriToFile: gain fd.
2021-09-16 01:14:08.366 15897-15897 D/TagUriToFile: gain fi.
2021-09-16 01:14:08.366 15897-15897 D/TagUriToFile: gain fc.
2021-09-16 01:14:08.366 15897-15897 D/TagUriToFile: gain fc. fc is not null.
2021-09-16 01:14:08.378 15897-15897 D/TagUriToFile: f1 correct:false ; f2 correct:false
2021-09-16 01:14:08.379 15897-15897 D/TagUriToFile: f1 correct:/2/28 ; f2 correct:/content:/com.google.android.apps.nbu.files.provider/2/28
2021-09-16 01:14:08.379 15897-15897 D/TagUriToFile: gain fd.
2021-09-16 01:14:08.382 15897-15897 D/TagUriToFile: gain fi.
2021-09-16 01:14:08.383 15897-15897 D/TagUriToFile: gain fc.
2021-09-16 01:14:08.383 15897-15897 D/TagUriToFile: gain fc. fc is not null.

2. 验证直接通过Uri获取InputStream和Uri->FileDescriptor->FileInputStream,两者读取效率差异

  • 从log看两者读取效率无明显差异.
//1: 
// FileDescriptor fd = contentResolver.openFileDescriptor(uri,"r").getFileDescriptor();
// FileInputStream fi = new FileInputStream(fd);
2021-09-24 17:00:59.331 28244-28283 D/TagUriPath: getFileSize. FileInputStream.curr: 1048576
2021-09-24 17:01:08.795 28244-28283 D/TagUriPath: getFileSize. FileInputStream.curr: 7181312198
2021-09-24 17:01:08.796 28244-28283 D/TagUriPath: getFileSize. FileInputStream <= -1. break.

//2: testIs = context.getApplicationContext().getContentResolver().openInputStream(uri);
2021-09-24 17:03:31.378 28639-28639 D/TagUriPath: getFileSize. fileSize:7181312198
2021-09-24 17:03:31.388 28639-28639 D/TagUriPath: getFileSize. is.start. FileInputStream.total: 0
2021-09-24 17:03:42.381 28639-28639 D/TagUriPath: getFileSize. is.end. FileInputStream.total: 7181312198

从log上,可见读取7G左右的文件,直接使用InputStream和得到FileDescriptor再转FileInputStream,读取效率很接近.
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