我在SO上阅读了很多关于如何请求访问SD卡和删除文件的问题，但我仍然无法使用我的应用程序。 我试图在用户尝试删除SD卡上的文件时请求访问权限，然后在获得权限后删除该文件。
这是我尝试过的：
public static boolean permissiongranted = true;
public static boolean deletebuttonclicked =false;
button3.setOnClickListener(
new View.OnClickListener() {
public void onClick(View view) {
AlertDialog.Builder builder1 = new AlertDialog.Builder(SDCard.this);
builder1.setMessage("Are you sure you want to delete it ?");
builder1.setCancelable(true);
builder1.setPositiveButton(
"Yes",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
if(permissiongranted){
Log.v(TAG,"here");
deletebuttonclicked=true;
access();
}
}
});
builder1.setNegativeButton(
"No",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
AlertDialog alert11 = builder1.create();
alert11.show();
}
});
private void access(){
Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
startActivityForResult(intent, 42);
}
public void onActivityResult(int requestCode, int resultCode, Intent resultData) {
if (resultCode == RESULT_OK) {
Uri treeUri = resultData.getData();
DocumentFile pickedDir = DocumentFile.fromTreeUri(this, treeUri);
// List all existing files inside picked directory
for (DocumentFile file : pickedDir.listFiles()) {
Log.d(TAG, "Found file " + file.getName() + " with size " + file.length());
}
// Create a new file and write into it
DocumentFile newFile = pickedDir.createFile("text/plain", "My Novel");
if(deletebuttonclicked){
adapter.deleteItem();
Log.v(TAG,"executed");
}
try {
OutputStream out = getContentResolver().openOutputStream(newFile.getUri());
out.write("A long time ago...".getBytes());
out.close();
}catch (Exception e){
e.printStackTrace();
}
permissiongranted = false;
}
}
主要活动中的运行时权限：
private void buttonClicked(View view) {
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.READ_EXTERNAL_STORAGE) + ContextCompat
.checkSelfPermission(this,
Manifest.permission.INTERNET) + ContextCompat
.checkSelfPermission(this,
Manifest.permission.WRITE_EXTERNAL_STORAGE)
!= PackageManager.PERMISSION_GRANTED) {
Snackbar.make(view, "Permission not Granted, Requesting permission.", Snackbar.LENGTH_LONG).show();
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.READ_EXTERNAL_STORAGE) && ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
Snackbar.make(view, "We need permission to internal storage for displaying songs", Snackbar.LENGTH_LONG).show();
} else {
Snackbar.make(view, "Allow myapp3 to access this device's internal storage", Snackbar.LENGTH_LONG).show();
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.READ_EXTERNAL_STORAGE,Manifest.permission.WRITE_EXTERNAL_STORAGE},
MY_PERMISSIONS_REQUEST_READ_EXTERNAL_STORAGE);
// MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
// app-defined int constant. The callback method gets the
// result of the request.
}
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
switch (requestCode) {
case 1: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
Toast.makeText(Bacon1.this, "WRITE_CONTACTS granted", Toast.LENGTH_SHORT)
.show();
} else {
Toast.makeText(Bacon1.this, "WRITE_CONTACTS Denied", Toast.LENGTH_SHORT)
.show();
}
return;
}
// other 'case' lines to check for other
// permissions this app might request
}
}
清单文件中的权限：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_MEDIA_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.MEDIA_CONTENT_CONTROL" />
<uses-permission android:name="android.permission.INTERNET" />
删除适配器类中文件的方法：
protected void deleteItem() {
for (int i = 0; i < mSelected.size(); i++) {
Log.v(TAG, mSelected.get(i));
Log.v(TAG, mData2.get(Integer.parseInt(mSelected.get(i))));
File file = new File(mData2.get(Integer.parseInt(mSelected.get(i))));
if(file.isDirectory()){
String[] children = file.list();
for (int j = 0; j < children.length; j++)
{
new File(file, children[i]).delete();
mData2.remove(Integer.parseInt(mSelected.get(i)));
}
}
Log.v(TAG, file.toString());
file.delete();
mData2.remove(Integer.parseInt(mSelected.get(i)));
MediaScannerConnection.scanFile(context,new String[] { file.toString() }, null, new MediaScannerConnection.OnScanCompletedListener()
{
public void onScanCompleted(String path, Uri uri)
{
Log.i("ZAA", "Scanned " + path + ":");
Log.i("ZAA", "-> uri=" + uri);
}
});
}
notifyDataSetChanged();
}
LOGCAT：
02-19 16:09:18.700 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: 0
02-19 16:09:18.719 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: /storage/F2A7-15EE
02-19 16:09:26.042 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: 0 final size
02-19 16:09:26.042 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: 0 is the size
02-19 16:09:26.043 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: 1 this is size
02-19 16:09:29.751 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: here
02-19 16:09:41.380 23271-23271/com.example.dell_1.Myapp3 D/com.example.dell_1.myapp3.InternalMemory: Found file LOST.DIR with size 32768
02-19 16:09:41.404 23271-23271/com.example.dell_1.Myapp3 D/com.example.dell_1.myapp3.InternalMemory: Found file .android_secure with size 32768
02-19 16:09:42.470 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: 37
02-19 16:09:42.470 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: /storage/F2A7-15EE/My Novel (1).txt
02-19 16:09:42.471 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: /storage/F2A7-15EE/My Novel (1).txt
02-19 16:09:42.506 23271-23271/com.example.dell_1.Myapp3 V/com.example.dell_1.myapp3.InternalMemory: executed