当手机上的wifi超出范围时，我有一个崩溃的应用程序。它主要从在线txt获取字符串，并且在完成后我确实断开了HTTPURLConnection，所以我没想到崩溃。以下是相关代码;
要检查网络可用性（首先检查使用互联网连接的所有代码）：
public boolean isNetworkAvailable() {
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnectedOrConnecting()) {
//if (netInfo != null && netInfo.isConnected()) {
return true;
}
return false;
}
我在onResume上运行的checkForPromptPassword asynctask：
private class CheckForPromptPasswordAgain extends AsyncTask<Void, Void, Boolean>
{
// ProgressDialog pdLoading = new ProgressDialog(MainScreenActivity.this);
@Override
protected void onPreExecute() {
super.onPreExecute();
//this method will be running on UI thread
// pdLoading.setMessage("\tFetching Database...");
// pdLoading.show();
}
@Override
protected Boolean doInBackground(Void... params) {
//this method will be running on background thread so don't update UI frome here
//do your long running http tasks here,you dont want to pass argument and u can access the parent class' variable url over here
//view GONE by default of update button
if (isNetworkAvailable()){
if (PromptForPasswordAgain()){
//TODO: //show update button or dialog
return true;
}else{
//TODO: //proceed as normal
return false;
}
}
return false;
}
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
//this method will be running on UI thread
if (result==true){
promptForPassword();
}else{
// showDialog("string", "string",0);
}
// pdLoading.dismiss();
}
}
我在onResume（）上运行的checkForUpdate AsyncTask：
Private class CheckForUpdate extends AsyncTask<Void, Void, Boolean>
{
// ProgressDialog pdLoading = new ProgressDialog(MainScreenActivity.this);
@Override
protected void onPreExecute() {
super.onPreExecute();
//this method will be running on UI thread
// pdLoading.setMessage("\t string.");
// pdLoading.show();
}
@Override
protected Boolean doInBackground(Void... params) {
//this method will be running on background thread so don't update UI frome here
//do your long running http tasks here,you dont want to pass argument and u can access the parent class' variable url over here
//view GONE by default of update button
if (fileExistance("data.txt")){
try {
if (isNetworkAvailable()){
if (isDatabaseContentDifferent()){
//TODO: //show update button or dialog
return true;
}else{
//TODO: //proceed as normal
return false;
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}else{
Log.i("error","file data.txt does not exist in internal");
return false;
}
return false;
}
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
//this method will be running on UI thread
Button updateButton = (Button) findViewById(R.id.UpdateDatabase);
updateButton.setVisibility(View.GONE);
if (result==true){
showDialog("Database Updated On Server", "The Database App has detected a change in the database, press \"Update Database\" to account for the change(s). ",0);
updateButton.setVisibility(View.VISIBLE);
}else{
updateButton.setVisibility(View.GONE);
// showDialog("No Update Detected", "The Database App has detected a change in the database, press \"Update Database\" to account for the change(s). ",0);
}
// pdLoading.dismiss();
}
}
我正在使用的HTTPURLClient的示例，许多函数，但这是基本结构：
public boolean isDatabaseContentDifferent() throws IOException{
String page = null;
try{
URL url = new URL(_data);
HttpURLConnection.setFollowRedirects(true);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setDoOutput(false);
con.setReadTimeout(20000);
con.setRequestProperty("Connection", "keep-alive");
//get etag for update check
//String etag= "";
con.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/20100101 Firefox/16.0");
((HttpURLConnection) con).setRequestMethod("GET");
//System.out.println(con.getContentLength()) ;
con.setConnectTimeout(5000);
BufferedInputStream in = new BufferedInputStream(con.getInputStream());
//make seperate function for etag it doesn't work with GET
//String etag = con.getHeaderField("etag");
int responseCode = con.getResponseCode();
if (responseCode == HttpURLConnection.HTTP_OK) {
System.out.println(responseCode);
}
StringBuffer buffer = new StringBuffer();
int chars_read;
//int total = 0;
while ((chars_read = in.read()) != -1)
{
char g = (char) chars_read;
buffer.append(g);
}
page = buffer.toString();
//create password.txt to internal
//TODO: checkkk
con.disconnect();
}catch(Exception e){
showDialog("Database Fetch Failure","Unable to Fetch Password Database, check your internet" +
" connection and try again later.",0);
Log.i("Page", "Error in isDatabaseContentDifferent()");
return false;
}
if (fileExistance("data.txt")){
if (isTextInFileDifferent(page,"data.txt")){
return true;
}else{
return false;
}
}else{
Log.i("Page","file data.txt does not exist IN isDatabaseContentDifferent()");
return false;
}
}
任何帮助都将受到高度赞赏。感谢。