android文件转化为字符串,java-Android文件到字符串

我想在Android中读取文件并以字符串形式获取内容.然后,我想将其发送到服务器.但是为了进行测试,我只是在设备上创建一个文件,然后将内容放入其中：

InputStream stream = getContentResolver().openInputStream(fileUri);

BufferedReader reader = new BufferedReader(new InputStreamReader(stream));

File dir = new File (Environment.getExternalStorageDirectory() + "/Android/data/" + getPackageName());

if(!dir.exists())

dir.mkdirs();

File file = new File(dir, "output."+format); // format is "txt", "png" or sth like that

if(!file.exists())

file.createNewFile();

BufferedWriter writer = null;

writer = new BufferedWriter(new FileWriter(file));

String line = reader.readLine();

while (line != null)

{

writer.write(line);

line = reader.readLine();

if(line != null)

writer.write("

");

}

writer.flush();

writer.close();

stream.close();

这适用于txt文件,但是例如当我尝试复制pdf文件时,它是可打开的,但只有白色.

谁能帮我？

谢谢