即使获得 read/write 权限,也无法从外部存储读取或创建文件
Failure to read or create a file from external storage even though given read/write permissions
这是清单文件:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
...
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<application
android:requestLegacyExternalStorage="true"
android:allowBackup="true"
...
</manifest>
我使用了 tedpermission。
按日期命名的文本文件(例如:2020_10_23.txt)
来自外部存储(例如:storage/emulated/0/myDiary/2020_10_23.txt)
对于 i/o 操作。
这里是mainactivity中的核心代码:
PermissionListener permissionlistener = new PermissionListener() {
@Override
public void onPermissionGranted() {
Toast.makeText(MainActivity.this, "Permission granted", Toast.LENGTH_SHORT).show();
}
@Override
public void onPermissionDenied(List<String> deniedPermissions) {
Toast.makeText(MainActivity.this, "Permission denied\n" + deniedPermissions.toString(), Toast.LENGTH_SHORT).show();
}
};
@RequiresApi(api = Build.VERSION_CODES.R)
@Override
public void onCreate(Bundle savedInstanceState) {
TedPermission.with(this)
.setPermissionListener(permissionlistener)
.setDeniedMessage("External Storage READ/WRITE Denied")
.setPermissions(Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE)
.check();
...
final String sdPath = Environment.getExternalStorageDirectory().getAbsolutePath();
final File myDir = new File(sdPath + "/myDiary");
string fileName = Integer.toString(year) + "_"
+ Integer.toString(monthOfYear + 1) + "_"
+ Integer.toString(dayOfMonth) + ".txt";
...
btnWrite.setOnClickListener(new View.OnClickListener() {
@RequiresApi(api = Build.VERSION_CODES.O)
public void onClick(View v) {
try {
//openFileoutput Methods does not allow path delimiters.
File current_file = new File(myDir + "/" + fileName);
if (!current_file.getParentFile().exists()) {
if (!current_file.getParentFile().mkdirs()) {
Toast.makeText(getApplicationContext(),
"Failed to create folder : " + myDir, Toast.LENGTH_SHORT).show();
}
}
if (!current_file.exists()) {
if (!current_file.createNewFile()) {
Toast.makeText(getApplicationContext(),
"Failed to create file : " + myDir + "/" + fileName, Toast.LENGTH_SHORT).show();
}
}
FileOutputStream outFs = new FileOutputStream(new File(String.valueOf(current_file)));
String str = edtDiary.getText().toString();
outFs.write(str.getBytes());
outFs.close();
Toast.makeText(getApplicationContext(),
fileName + " is saved", Toast.LENGTH_SHORT).show();
} catch (IOException e) {
Toast.makeText(getApplicationContext(),
"Failed to save file : " + myDir + "/" + fileName, Toast.LENGTH_SHORT).show();
e.printStackTrace();
}
}
});
...
//read text file from external storage
String readDiary(String fName) {
String diaryStr = null;
FileInputStream inFs;
try {
inFs = new FileInputStream(new File(fName));
byte[] txt = new byte[500];
inFs.read(txt);
inFs.close();
diaryStr = (new String(txt)).trim();
btnWrite.setText("modify");
} catch (IOException e) {
edtDiary.setHint("no existing diary");
btnWrite.setText("new save");
}
return diaryStr;
}
Android版本:11
应用权限:
这是logcat:
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: java.io.IOException: No such file or directory
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: at java.io.UnixFileSystem.createFileExclusively0(Native Method)
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: at java.io.UnixFileSystem.createFileExclusively(UnixFileSystem.java:317)
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: at java.io.File.createNewFile(File.java:1008)
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: at com.cookandroid.project8_1.MainActivity.onClick(MainActivity.java:102)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.view.View.performClick(View.java:7448)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.view.View.performClickInternal(View.java:7425)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.view.View.access00(View.java:810)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.view.View$PerformClick.run(View.java:28305)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.os.Handler.handleCallback(Handler.java:938)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.os.Handler.dispatchMessage(Handler.java:99)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.os.Looper.loop(Looper.java:223)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.app.ActivityThread.main(ActivityThread.java:7656)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at java.lang.reflect.Method.invoke(Native Method)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
无法在 storage/emulated/0 上创建文件夹 'myDiary'
我尽力了。为什么即使我给了外部存储 I/O 权限也无法创建文件夹和文件?
使用这个
public class Folder
{
private final File appDataFolder;
public Folder()
{
File file = Environment.getExternalStorageDirectory();
appDataFolder = new File(file, "AppDataFolder");
if (!appDataFolder.exists()) appDataFolder.mkdir();
}
public String getMainFolder()
{
return appDataFolder.getAbsolutePath();
}
public void deleteMainFolder()
{
if (appDataFolder.isDirectory())
{
String[] children = appDataFolder.list();
for (String child : children)
{
new File(appDataFolder, child).delete();
}
}
new Folder();
}
public void createNewFolder(String folderName)
{
File file = new File(appDataFolder, folderName);
if (!file.exists()) file.mkdir();
}
public void createChildFolder(String parentName, String childName)
{
String path = appDataFolder.getAbsolutePath() + File.separator + parentName;
File parent = new File(path);
File file = new File(parent, childName);
if (!file.exists()) file.mkdir();
}
}
并在 activity
PermissionListener permissionlistener = new PermissionListener() {
@Override
public void onPermissionGranted() {
new Folder().createNewFolder("myDiary");
Toast.makeText(MainActivity.this, "Permission granted", Toast.LENGTH_SHORT).show();
}
@Override
public void onPermissionDenied(List<String> deniedPermissions) {
Toast.makeText(MainActivity.this, "Permission denied\n" + deniedPermissions.toString(), Toast.LENGTH_SHORT).show();
}
};
在 Android 11 您无法访问外部存储的根。
您不能在 /storage/emulated/0 中创建文件或文件夹。
但是..您可以写入 /storage/emulated/0 上的常用 public 文件夹,例如
Download, Documents, DCIM, Pictures, Alarms, a.s.o.
查看您的设备上已有哪些文件夹,您可以将它们大部分用于读取和/或写入操作。
这是清单文件:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
...
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<application
android:requestLegacyExternalStorage="true"
android:allowBackup="true"
...
</manifest>
我使用了 tedpermission。 按日期命名的文本文件(例如:2020_10_23.txt) 来自外部存储(例如:storage/emulated/0/myDiary/2020_10_23.txt) 对于 i/o 操作。
这里是mainactivity中的核心代码:
PermissionListener permissionlistener = new PermissionListener() {
@Override
public void onPermissionGranted() {
Toast.makeText(MainActivity.this, "Permission granted", Toast.LENGTH_SHORT).show();
}
@Override
public void onPermissionDenied(List<String> deniedPermissions) {
Toast.makeText(MainActivity.this, "Permission denied\n" + deniedPermissions.toString(), Toast.LENGTH_SHORT).show();
}
};
@RequiresApi(api = Build.VERSION_CODES.R)
@Override
public void onCreate(Bundle savedInstanceState) {
TedPermission.with(this)
.setPermissionListener(permissionlistener)
.setDeniedMessage("External Storage READ/WRITE Denied")
.setPermissions(Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE)
.check();
...
final String sdPath = Environment.getExternalStorageDirectory().getAbsolutePath();
final File myDir = new File(sdPath + "/myDiary");
string fileName = Integer.toString(year) + "_"
+ Integer.toString(monthOfYear + 1) + "_"
+ Integer.toString(dayOfMonth) + ".txt";
...
btnWrite.setOnClickListener(new View.OnClickListener() {
@RequiresApi(api = Build.VERSION_CODES.O)
public void onClick(View v) {
try {
//openFileoutput Methods does not allow path delimiters.
File current_file = new File(myDir + "/" + fileName);
if (!current_file.getParentFile().exists()) {
if (!current_file.getParentFile().mkdirs()) {
Toast.makeText(getApplicationContext(),
"Failed to create folder : " + myDir, Toast.LENGTH_SHORT).show();
}
}
if (!current_file.exists()) {
if (!current_file.createNewFile()) {
Toast.makeText(getApplicationContext(),
"Failed to create file : " + myDir + "/" + fileName, Toast.LENGTH_SHORT).show();
}
}
FileOutputStream outFs = new FileOutputStream(new File(String.valueOf(current_file)));
String str = edtDiary.getText().toString();
outFs.write(str.getBytes());
outFs.close();
Toast.makeText(getApplicationContext(),
fileName + " is saved", Toast.LENGTH_SHORT).show();
} catch (IOException e) {
Toast.makeText(getApplicationContext(),
"Failed to save file : " + myDir + "/" + fileName, Toast.LENGTH_SHORT).show();
e.printStackTrace();
}
}
});
...
//read text file from external storage
String readDiary(String fName) {
String diaryStr = null;
FileInputStream inFs;
try {
inFs = new FileInputStream(new File(fName));
byte[] txt = new byte[500];
inFs.read(txt);
inFs.close();
diaryStr = (new String(txt)).trim();
btnWrite.setText("modify");
} catch (IOException e) {
edtDiary.setHint("no existing diary");
btnWrite.setText("new save");
}
return diaryStr;
}
Android版本:11
应用权限:
这是logcat:
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: java.io.IOException: No such file or directory
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: at java.io.UnixFileSystem.createFileExclusively0(Native Method)
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: at java.io.UnixFileSystem.createFileExclusively(UnixFileSystem.java:317)
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: at java.io.File.createNewFile(File.java:1008)
2020-10-23 15:40:00.986 6178-6178/com.cookandroid.project8_1 W/System.err: at com.cookandroid.project8_1.MainActivity.onClick(MainActivity.java:102)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.view.View.performClick(View.java:7448)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.view.View.performClickInternal(View.java:7425)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.view.View.access00(View.java:810)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.view.View$PerformClick.run(View.java:28305)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.os.Handler.handleCallback(Handler.java:938)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.os.Handler.dispatchMessage(Handler.java:99)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.os.Looper.loop(Looper.java:223)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at android.app.ActivityThread.main(ActivityThread.java:7656)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at java.lang.reflect.Method.invoke(Native Method)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
2020-10-23 15:40:00.987 6178-6178/com.cookandroid.project8_1 W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
无法在 storage/emulated/0 上创建文件夹 'myDiary' 我尽力了。为什么即使我给了外部存储 I/O 权限也无法创建文件夹和文件?
使用这个
public class Folder
{
private final File appDataFolder;
public Folder()
{
File file = Environment.getExternalStorageDirectory();
appDataFolder = new File(file, "AppDataFolder");
if (!appDataFolder.exists()) appDataFolder.mkdir();
}
public String getMainFolder()
{
return appDataFolder.getAbsolutePath();
}
public void deleteMainFolder()
{
if (appDataFolder.isDirectory())
{
String[] children = appDataFolder.list();
for (String child : children)
{
new File(appDataFolder, child).delete();
}
}
new Folder();
}
public void createNewFolder(String folderName)
{
File file = new File(appDataFolder, folderName);
if (!file.exists()) file.mkdir();
}
public void createChildFolder(String parentName, String childName)
{
String path = appDataFolder.getAbsolutePath() + File.separator + parentName;
File parent = new File(path);
File file = new File(parent, childName);
if (!file.exists()) file.mkdir();
}
}
并在 activity
PermissionListener permissionlistener = new PermissionListener() {
@Override
public void onPermissionGranted() {
new Folder().createNewFolder("myDiary");
Toast.makeText(MainActivity.this, "Permission granted", Toast.LENGTH_SHORT).show();
}
@Override
public void onPermissionDenied(List<String> deniedPermissions) {
Toast.makeText(MainActivity.this, "Permission denied\n" + deniedPermissions.toString(), Toast.LENGTH_SHORT).show();
}
};
在 Android 11 您无法访问外部存储的根。
您不能在 /storage/emulated/0 中创建文件或文件夹。
但是..您可以写入 /storage/emulated/0 上的常用 public 文件夹,例如
Download, Documents, DCIM, Pictures, Alarms, a.s.o.
查看您的设备上已有哪些文件夹,您可以将它们大部分用于读取和/或写入操作。