我是android平台的新手。我需要在android中创建一个文本文件。请告诉我如何在android中执行此任务。我编写了一个在java中工作正常但在android中没有的代码。请帮助我....我写的示例代码是： -
try
{
DataOutputStream dos = new DataOutputStream(new FileOutputStream("test.txt", true));
dos.writeBytes(dataLine);
dos.close();
}
catch (FileNotFoundException ex) {}
上面的代码片段在java中工作正常，但在android：（
谢谢， Ashish
答案 0 :(得分：2)
Android开发指南explains it nicely：
String FILENAME = "hello_file";
String string = "hello world!";
FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
fos.write(string.getBytes());
fos.close();
如果您希望所创建的文件对外界可见，请使用external storage。但正如我在评论中所说，确保你“成为一个好公民”。即使用户卸载了您的应用，这些文件仍然存在。
答案 1 :(得分：0)
试试这个
final File sdcard=Environment.getExternalStorageDirectory();
button.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View arg0) {
File path=new File(sdcard,"textfile.txt");
try {
BufferedWriter wr=new BufferedWriter(new FileWriter(path));
wr.write("Your Text Here");
wr.close();
} catch (IOException e) {
e.printStackTrace();
}
}
此外，您还需要向清单文件添加以下权限
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
答案 2 :(得分：0)
import android.os.Environment;
import android.util.Log;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
/**
* Static methods used for common file operations.
*
* @author Carl Hartung (carlhartung@gmail.com)
*/
public class FileUtils {
private final static String t = "FileUtils";
// Used to validate and display valid form names.
public static final String VALID_FILENAME = "[ _\\-A-Za-z0-9]*.x[ht]*ml";
// Storage paths
public static final String FORMS_PATH = Environment.getExternalStorageDirectory() + "/odk/forms/";
public static final String INSTANCES_PATH = Environment.getExternalStorageDirectory() + "/odk/instances/";
public static final String CACHE_PATH = Environment.getExternalStorageDirectory() + "/odk/.cache/";
public static final String TMPFILE_PATH = CACHE_PATH + "tmp.jpg";
public static ArrayList<String> getValidFormsAsArrayList(String path) {
ArrayList<String> formPaths = new ArrayList<String>();
File dir = new File(path);
if (!storageReady()) {
return null;
}
if (!dir.exists()) {
if (!createFolder(path)) {
return null;
}
}
File[] dirs = dir.listFiles();
for (int i = 0; i < dirs.length; i++) {
// skip all the directories
if (dirs[i].isDirectory())
continue;
String formName = dirs[i].getName();
formPaths.add(dirs[i].getAbsolutePath());
}
return formPaths;
}
public static ArrayList<String> getFoldersAsArrayList(String path) {
ArrayList<String> mFolderList = new ArrayList<String>();
File root = new File(path);
if (!storageReady()) {
return null;
}
if (!root.exists()) {
if (!createFolder(path)) {
return null;
}
}
if (root.isDirectory()) {
File[] children = root.listFiles();
for (File child : children) {
boolean directory = child.isDirectory();
if (directory) {
mFolderList.add(child.getAbsolutePath());
}
}
}
return mFolderList;
}
public static boolean deleteFolder(String path) {
// not recursive
if (path != null && storageReady()) {
File dir = new File(path);
if (dir.exists() && dir.isDirectory()) {
File[] files = dir.listFiles();
for (File file : files) {
if (!file.delete()) {
Log.i(t, "Failed to delete " + file);
}
}
}
return dir.delete();
} else {
return false;
}
}
public static boolean createFolder(String path) {
if (storageReady()) {
boolean made = true;
File dir = new File(path);
if (!dir.exists()) {
made = dir.mkdirs();
}
return made;
} else {
return false;
}
}
public static boolean deleteFile(String path) {
if (storageReady()) {
File f = new File(path);
return f.delete();
} else {
return false;
}
}
public static byte[] getFileAsBytes(File file) {
byte[] bytes = null;
InputStream is = null;
try {
is = new FileInputStream(file);
// Get the size of the file
long length = file.length();
if (length > Integer.MAX_VALUE) {
Log.e(t, "File " + file.getName() + "is too large");
return null;
}
// Create the byte array to hold the data
bytes = new byte[(int) length];
// Read in the bytes
int offset = 0;
int read = 0;
try {
while (offset < bytes.length && read >= 0) {
read = is.read(bytes, offset, bytes.length - offset);
offset += read;
}
} catch (IOException e) {
Log.e(t, "Cannot read " + file.getName());
e.printStackTrace();
return null;
}
// Ensure all the bytes have been read in
if (offset < bytes.length) {
try {
throw new IOException("Could not completely read file " + file.getName());
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
return bytes;
} catch (FileNotFoundException e) {
Log.e(t, "Cannot find " + file.getName());
e.printStackTrace();
return null;
} finally {
// Close the input stream
try {
is.close();
} catch (IOException e) {
Log.e(t, "Cannot close input stream for " + file.getName());
e.printStackTrace();
return null;
}
}
}
public static boolean storageReady() {
String cardstatus = Environment.getExternalStorageState();
if (cardstatus.equals(Environment.MEDIA_REMOVED)
|| cardstatus.equals(Environment.MEDIA_UNMOUNTABLE)
|| cardstatus.equals(Environment.MEDIA_UNMOUNTED)
|| cardstatus.equals(Environment.MEDIA_MOUNTED_READ_ONLY)) {
return false;
} else {
return true;
}
}
public static String getMd5Hash(File file) {
try {
// CTS (6/15/2010) : stream file through digest instead of handing it the byte[]
MessageDigest md = MessageDigest.getInstance("MD5");
int chunkSize = 256;
byte[] chunk = new byte[chunkSize];
// Get the size of the file
long lLength = file.length();
if (lLength > Integer.MAX_VALUE) {
Log.e(t, "File " + file.getName() + "is too large");
return null;
}
int length = (int) lLength;
InputStream is = null;
is = new FileInputStream(file);
int l = 0;
for (l = 0; l + chunkSize < length; l += chunkSize) {
is.read(chunk, 0, chunkSize);
md.update(chunk, 0, chunkSize);
}
int remaining = length - l;
if (remaining > 0) {
is.read(chunk, 0, remaining);
md.update(chunk, 0, remaining);
}
byte[] messageDigest = md.digest();
BigInteger number = new BigInteger(1, messageDigest);
String md5 = number.toString(16);
while (md5.length() < 32)
md5 = "0" + md5;
is.close();
return md5;
} catch (NoSuchAlgorithmException e) {
Log.e("MD5", e.getMessage());
return null;
} catch (FileNotFoundException e) {
Log.e("No Cache File", e.getMessage());
return null;
} catch (IOException e) {
Log.e("Problem reading from file", e.getMessage());
return null;
}
}
}