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我正在做android平臺的解密任務。起初，我創建了一個名爲RunDecrypt的方法。當我按下我的UI中的按鈕時，它工作正常。下面所示的方法：Android異步任務運行時異常錯誤。
public void runDecrypt() throws IOException{
EditText editText = (EditText) findViewById(R.id.fileName);
EditText editText2 = (EditText) findViewById(R.id.keyName);
String fileName = editText.getText().toString();
String keyName = editText2.getText().toString();
File sdcard = Environment.getExternalStorageDirectory();
File file = new File(sdcard , fileName);
File key = new File(sdcard, keyName);
BufferedReader brFile;
String Cipher = null;
try{
//Read file line by line and concat each line of string in file with space character.
FileInputStream fstream = new FileInputStream(file);
brFile = new BufferedReader(new InputStreamReader(fstream));
String tempString;
while((tempString = brFile.readLine()) != null){
if(Cipher == null){
Cipher = tempString;
}else{
Cipher = Cipher.concat(" ");
Cipher = Cipher.concat(tempString);
}
}
}catch(Exception e){
//messageBox("Decrypt", e.getMessage());
}
BufferedReader brKey;
String DecKey = null;
try{
FileInputStream fstream = new FileInputStream(key);
brKey = new BufferedReader(new InputStreamReader(fstream));
DecKey = brKey.readLine();
}catch(Exception e){
//messageBox("Decrypt", e.getMessage());
}
try{
byte[] cipherByte = DES.parseBytes(Cipher);
String decKey = DES.convertStringToHex(DecKey);
byte[] keyByte = DES.parseBytes(decKey);
String decryptResult = DES.hex(DES.decryptCBC(cipherByte, keyByte));
String temp = decryptResult.replace(" ", "");
String finalDecrypt = temp.substring(0, (temp.length() - DES.getConcatCount()));
String finResult = DES.convertHexToString(finalDecrypt);
TextView FinalResult = (TextView)findViewById(R.id.decryptText);
FinalResult.setText(finResult);
}catch(Exception e){
messageBox("Decrypt", "Please Upload File Properly");
}
}
由於它的做工精細，我嘗試實施這種方法與異步任務運行我的工作背景。
private class runDecrypt extends AsyncTask <URL , Integer, Long> {
private final ProgressDialog dialog = new ProgressDialog(Homepage.this);
AlertDialog.Builder builder = new AlertDialog.Builder(Homepage.this);
@SuppressWarnings("resource")
@Override
protected Long doInBackground(URL... params) {
EditText editText = (EditText) findViewById(R.id.fileName);
EditText editText2 = (EditText) findViewById(R.id.keyName);
String fileName = editText.getText().toString();
String keyName = editText2.getText().toString();
File sdcard = Environment.getExternalStorageDirectory();
File file = new File(sdcard , fileName);
File key = new File(sdcard, keyName);
BufferedReader brFile;
String Cipher = null;
try{
//Read file line by line and concat each line of string in file with space character.
FileInputStream fstream = new FileInputStream(file);
brFile = new BufferedReader(new InputStreamReader(fstream));
String tempString;
try {
while((tempString = brFile.readLine()) != null){
if(Cipher == null){
Cipher = tempString;
}else{
Cipher = Cipher.concat(" ");
Cipher = Cipher.concat(tempString);
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}catch(java.io.FileNotFoundException e){
System.out.println("File could not be found.");
}
BufferedReader brKey;
String DecKey = null;
try{
FileInputStream fstream = new FileInputStream(key);
brKey = new BufferedReader(new InputStreamReader(fstream));
try {
DecKey = brKey.readLine();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}catch(java.io.FileNotFoundException e){
System.out.println("Key file could not be found.");
}
String decKey = DES.convertStringToHex(DecKey);
byte[] cipherByte = DES.parseBytes(Cipher);
byte[] keyByte = DES.parseBytes(decKey);
String decryptResult = DES.hex(DES.decryptCBC(cipherByte, keyByte));
String temp = decryptResult.replace(" ", "");
String finalDecrypt = temp.substring(0, (temp.length() - DES.getConcatCount()));
String finResult = DES.convertHexToString(finalDecrypt);
TextView FinalResult = (TextView)findViewById(R.id.decryptText);
FinalResult.setText(finResult);
return null;
}
protected void onPreExecute() {
this.dialog.setMessage("Decrypting...");
this.dialog.show();
}
protected void onPostExecute(Long result) {
if (this.dialog.isShowing()) {
this.dialog.dismiss();
}
builder.setMessage("Decryption Completed");
builder.show();
}
protected void onProgressUpdate(int progress) {
setProgress(progress * 100);
}
}
我的onClick方法：即實現的顯示在下面的類
public void onClick (View v){
Intent browse = new Intent(this, Browse.class);
switch (v.getId()){
case R.id.browseFile:
browse.putExtra("browse","file");
startActivityForResult(browse, 1);
break;
case R.id.browseKey:
browse.putExtra("browse", "key");
startActivityForResult(browse, 1);
break;
case R.id.decrypt:
new runDecrypt().execute();
break;
default:
break;
}
}
我的logcat如下圖所示： 
任何人都可以請幫助？謝謝你，感謝！
'doInBackground（）'在後臺線程上被調用。從UI讀取應該在UI線程調用的'onPreExecute（）'方法內完成。 –