我正在编写一个Android应用程序（使用Java），该应用程序使用OCR将手写内容转换为数字文本。我试图在代码中使用OCR函数生成的String并将其写入文本文件（OCR部分当前正在工作）。然后，我想创建一个文件夹（在手机的外部存储中，例如Samsung上的“我的文件”），然后将文本文件添加到该文件夹中，该文件夹仅包含用户创建的文件（用户应该可以访问和共享） ）。
我已经进行了一些有关写手机外部存储的研究（包括其他StackOverflow问题），但是没有一个教程对我有用。
/* Checks if external storage is available for read and write */
public boolean isExternalStorageWritable() {
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
return true;
}
return false;
}
public File writeFolder ()
{
File file = null;
if (isExternalStorageWritable())
{
// Get the directory for the user's public directory.
file = new File(Environment.getExternalStorageDirectory() + File.separator + "OCR Documents");
}
if (!file.mkdirs())
Log.e(LOG_TAG, "Directory not created");
else
System.out.println(file.getAbsolutePath());
return file;
}
上面的代码是我所拥有的，但是在测试之后，AbsolutePath为null。它似乎没有在电话的外部存储上创建文件夹。我将如何处理以便创建文件夹并可以将文件添加到该文件夹？
答案 0 :(得分：0)
您创建目录的代码很好。
但是由于新版本的Android需要征得用户同意才能将文件写入外部存储，因此您可能会失去权限。
首先，请确保您在Manifest.xml中具有此权限：
<manifest ...>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
...
</manifest>
然后，由于WRITE_EXTERNAL_STORAGE被列为危险许可，如https://developer.android.com/guide/topics/permissions/overview#normal-dangerous所示，因此，您还需要显式请求用户许可。
最后，请求许可：
// Here, thisActivity is the current activity
if (ContextCompat.checkSelfPermission(thisActivity,
Manifest.permission.READ_CONTACTS)
!= PackageManager.PERMISSION_GRANTED) {
// Permission is not granted
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(thisActivity,
Manifest.permission.READ_CONTACTS)) {
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
} else {
// No explanation needed; request the permission
ActivityCompat.requestPermissions(thisActivity,
new String[]{Manifest.permission.READ_CONTACTS},
MY_PERMISSIONS_REQUEST_READ_CONTACTS);
// MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
// app-defined int constant. The callback method gets the
// result of the request.
}
} else {
// Permission has already been granted
}
您还需要处理请求的响应：
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_READ_CONTACTS: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// permission was granted, yay! Do the
// contacts-related task you need to do.
} else {
// permission denied, boo! Disable the
// functionality that depends on this permission.
}
return;
}
// other 'case' lines to check for other
// permissions this app might request.
}
}
上面的代码是从https://developer.android.com/training/permissions/requesting
复制而来的您应该更彻底地阅读该链接，因为它可以很好地说明您需要向用户解释的内容，因为当Apps要求修改存储中文件的权限时，用户通常会非常警惕。
答案 1 :(得分：0)
您可以尝试一下，
private void getWirtePermissionAndCreateDir() {
if (Build.VERSION.SDK_INT < 23) {
createDir();
} else {
final String[] PERMISSIONS_STORAGE = {Manifest.permission.WRITE_EXTERNAL_STORAGE};
//Asking request Permissions
ActivityCompat.requestPermissions(MainActivity.this, PERMISSIONS_STORAGE, 9);
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
boolean writeAccepted = false;
switch (requestCode) {
case 9:
writeAccepted = grantResults[0] == PackageManager.PERMISSION_GRANTED;
break;
}
if (writeAccepted) {
createDir();
} else {
Toast.makeText(MainActivity.this, "You don't assign permission.", Toast.LENGTH_LONG).show();
}
}
private void createDir(){
File file = new File(Environment.getExternalStorageDirectory() + File.separator + "OCR Documents");
file.mkdirs();
Toast.makeText(MainActivity.this, file.getAbsolutePath(), Toast.LENGTH_LONG).show();
}
您必须在活动正文中添加getWirtePermissionAndCreateDir()而不是writeFolder()。
答案 2 :(得分：0)
以下功能将创建文件夹，然后在该文件夹中创建文件，如果文件夹已存在，则只需创建文件。
private FileOutputStream fos;
//Function: create a file in a folder
private boolean createFileInFolder(String fileName, String folderName) {
if (isExternalStorageWritable()) {
String path = Environment.getExternalStorageDirectory() + "/" + folderName;
File folder = new File(path);
if (!folder.exists()) {
folder.mkdirs();
}
txtFile = new File(path, fileName);
try {
fos = new FileOutputStream(txtFile);
return true;
} catch (IOException e) {
Toast.makeText(this, e.toString(), Toast.LENGTH_SHORT).show();
return false;
}
} else
return false;
}
//Function: IsExternalStorageWritable?
public boolean isExternalStorageWritable() {
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
return true;
}
return false;
}
您可能需要检查权限，然后定义这些功能。
private boolean permission;
private final int MY_PERMISSIONS_REQUEST = 10;
//Function: checkPermission
private void checkPermission() {
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.WRITE_EXTERNAL_STORAGE)
!= PackageManager.PERMISSION_GRANTED) {
// No explanation needed, we can request the permission.
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
MY_PERMISSIONS_REQUEST);
} else {
permission = true;
}
}
//Function: Permission Request Results
@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
permission = true;
} else {
permission = false;
}
return;
}
}
}
在清单文件中，不要忘记添加此行。
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />