我正在尝试在程序中访问两次文件。
首先我正在从文件中读取，运行正常。
第二次，我试图删除我读过的同一个文件。
奇怪的是第二次文件中没有记录。实际上，当我尝试运行命令file.exists时，它返回false。 为什么会这样？
以下是我的代码：
public class ControlLights extends AppCompatActivity {
private RoomListAdapter adapter;
private List<ROOM> mRoomList;
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
super.onCreateContextMenu(menu, v, menuInfo);
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.popup,menu);
}
public void filedel(int pos) {
Toast.makeText(getApplicationContext(), String.valueOf(pos), Toast.LENGTH_LONG).show();
File filemain = new File("roomdata.txt");
try {
File temp = File.createTempFile("file",".txt",filemain.getParentFile());
String charset = "UTF-8";
BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(temp), charset));
PrintWriter writer = new PrintWriter(new OutputStreamWriter(new FileOutputStream(temp), charset));
int p=0;
for(String line; (line=reader.readLine())!=null;) {
if(p == pos) {
line = line.replace(line,"");
writer.println(line);
}
writer.println(line);
}
reader.close();
writer.close();
filemain.delete();
temp.renameTo(filemain);
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public boolean onContextItemSelected(MenuItem item) {
AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
switch (item.getItemId()) {
case R.id.Edit:
return true;
case R.id.Delete:
filedel(info.position);
mRoomList.remove(info.position);
adapter.notifyDataSetChanged();
return true;
default:
return super.onContextItemSelected(item);
}
}
public void loadrooms() {
int block = 1024;
try {
boolean exists = (new File("roomdata.txt").exists());
Toast.makeText(getApplicationContext(), String.valueOf(exists), Toast.LENGTH_LONG).show();
FileInputStream fis = openFileInput("roomdata.txt");
InputStreamReader isr = new InputStreamReader(fis);
char[] data = new char[block];
String roomdata = "";
int size;
try {
while ((size = isr.read(data)) > 0) {
String read_data = String.copyValueOf(data, 0, size);
roomdata += read_data;
data = new char[block];
}
} catch (IOException e) {
e.printStackTrace();
}
String[] room_display = roomdata.split("\n");
String[] tempstring;
ListView lsv = (ListView) findViewById(R.id.Room_list);
mRoomList = new ArrayList<>();
for (int b = 0; b < room_display.length; b++) {
tempstring = room_display[b].split(":");
mRoomList.add(new ROOM(tempstring[0], tempstring[1], tempstring[2], tempstring[3], tempstring[4], tempstring[5], tempstring[6], tempstring[7], tempstring[8], tempstring[9]));
}
adapter = new RoomListAdapter(getApplicationContext(), mRoomList);
lsv.setAdapter(adapter);
registerForContextMenu(lsv);
int count = mRoomList.size();
final ArrayList<Integer> disabledpos = new ArrayList<Integer>();
for (int q = 0; q < count; q++) {
ROOM temp_room1 = mRoomList.get(q);
String IP = temp_room1.getRoom_IP_Address();
String online = null;
ConnectionTest CT = new ConnectionTest();
try {
online = CT.execute(IP, "a", "b").get();
Boolean b1 = Boolean.valueOf(online);
if (!b1) {
disabledpos.add(q);
}
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
try {
isr.reset();
isr.close();
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
if (new File("roomdata.txt").delete()) {
Toast.makeText(getApplicationContext(), "deleted", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getApplicationContext(), "not deleted", Toast.LENGTH_LONG).show();
// Not deleted
}
lsv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
int temp_position = position;
Intent p = new Intent(ControlLights.this, Electrical_equipment_list.class);
if (!(disabledpos.contains(position))) {
ROOM temp_room = mRoomList.get(temp_position);
p.putExtra("EE1", temp_room.getEE1());
p.putExtra("EE2", temp_room.getEE2());
p.putExtra("EE3", temp_room.getEE3());
p.putExtra("EE4", temp_room.getEE4());
p.putExtra("EE5", temp_room.getEE5());
p.putExtra("EE6", temp_room.getEE6());
p.putExtra("EE7", temp_room.getEE7());
p.putExtra("EE8", temp_room.getEE8());
p.putExtra("IPaddress", temp_room.getRoom_IP_Address());
startActivity(p);
}
}
});
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_control_lights);
loadrooms();
}
public class ConnectionTest extends AsyncTask<String, String, String> {
@Override
protected String doInBackground(String... params) {
Boolean online;
String tempstring = null;
try {
InetAddress roomaddress = InetAddress.getByName(params[0]);
online = roomaddress.isReachable(100);
tempstring = String.valueOf(online);
} catch (IOException e) {
e.printStackTrace();
}
return tempstring;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
}
}
}
答案 0 :(得分：0)
将File作为班级成员保留，因为它是班级的重要组成部分
将内部逻辑和文件引用初始化移至onStart()
公共类ControlLights扩展AppCompatActivity { 私人RoomListAdapter适配器; private List mRoomList; private file filemain; ...
public void filedel(int pos) {
Toast.makeText(getApplicationContext(), String.valueOf(pos), Toast.LENGTH_LONG).show();
try {
File temp = File.createTempFile("file",".txt", filemain.getParentFile());
...
}
}
public void loadrooms() {
int block = 1024;
try {
boolean exists = filemain.exists();
...
if (filemain.delete()) {
Toast.makeText(getApplicationContext(), "deleted", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getApplicationContext(), "not deleted", Toast.LENGTH_LONG).show();
// Not deleted
}
} ...
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_control_lights);
}
@Override
protected void onStart() {
super.onStart();
filemain = new File("roomdata.txt");
loadrooms();
}
}
脚注
我为可怕的代码格式道歉，但显然他们将解析算法更改为必须在此处再次手动键入所有代码而不是只能复制粘贴它。欢迎任何人进行相应的编辑。