Question

为什么不起作用？编辑：添加了新版本的代码＆amp;日志：

    private void savePhotoFromCacheToFolder(Uri uri) {

    File goodPhoto = album.setUpPhotoFile(); //new empty JPG
    File currentPhoto = new File(uri.getPath()); //JPG from camera in cache

    Log.v(TAG, "\ngoodPhoto Path " + goodPhoto);
    Log.v(TAG, "\ncurrentPhoto Path " + currentPhoto);

    FileInputStream source = null;
    FileOutputStream destination = null;

    try {
        source = new FileInputStream(currentPhoto);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
        Log.v(TAG, "\ncurrentPhoto not found ");
    }

    try {
        destination = new FileOutputStream(goodPhoto);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
        Log.v(TAG, "\ngoodPhoto not found  ");
    }

    FileChannel sourceFileChannel = source.getChannel();
    FileChannel destinationFileChannel = destination.getChannel();

    long size = 0;
    try {
        size = sourceFileChannel.size();
        sourceFileChannel.transferTo(0, size, destinationFileChannel);
    } catch (IOException e) {
        e.printStackTrace();
        Log.v(TAG, "\nshit happens ");
    }

}

日志：

V/MainActivity: goodPhoto Path /storage/emulated/0/Pictures/Good photos/IMG_20170222_113700_-913025224.jpg
V/MainActivity: currentPhoto Path /cache/photo.jpg
V/MainActivity: currentPhoto not found 
java.lang.NullPointerException: Attempt to invoke virtual method 'java.nio.channels.FileChannel java.io.FileInputStream.getChannel()' on a null object reference

看起来Uri不正确，但这个Uri是由相机应用程序返回的。或者我可能无法访问缓存文件夹，但之前我使用此Uri预览了照片。

Answer 1

我们已经创建了一个输入流和一个输出流对象。输入流指向当前java文件，输出流指向Output.java。对于这个Output.java，我们希望传输文件的内容。如前所述，文件对象与文件通道对象相关联。因此，我们使用以下代码

获取输入和输出流的文件通道对象

public copyFile( String filePath ){


        FileInputStream source = new FileInputStream(filePath );
        FileOutputStream destination = new FileOutputStream("Output.java");

        FileChannel sourceFileChannel = source.getChannel();
        FileChannel destinationFileChannel = destination.getChannel();

        long size = sourceFileChannel.size();
        sourceFileChannel.transferTo(0, size, destinationFileChannel);
    }

将您的代码与上面的代码进行比较，传输数据的方法有所不同，而这里没有使用。

如何通过Uri复制JPG文件

1 个答案: