嗨，我是android的初学者，希望我能为您提供详细的帮助
我使用AsyncTask建立了与MySQL数据库的连接，这一切都很好，它可以很好地连接数据库，并且可以从数据库中获取数据，但是问题是当我关闭数据库（数据库处于关闭状态）时，我的应用程序强制关闭，并且出现此错误：java。 util.concurrent.timeoutexception
我将把AsyncTask代码放在下面
private void get_banners(final int pages) {
AsyncHttpPost post = new AsyncHttpPost("http://192.168.1.102/soton/new.php");
post.setTimeout(5000);
MultipartFormDataBody body = new MultipartFormDataBody();
body.addStringPart("City", MainActivity.sp.getString("City", ""));
body.addStringPart("Page", String.valueOf(pages));
body.addStringPart("Cate", "all");
post.setBody(body);
AsyncHttpClient.getDefaultInstance().executeString(post, new AsyncHttpClient.StringCallback() {
@Override
public void onCompleted(final Exception e, AsyncHttpResponse source, final String result) {
if (e != null) {
MainActivity.activity.runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.activity, e.toString(), Toast.LENGTH_LONG).show();
e.printStackTrace();
mSwipeRefreshLayout.setRefreshing(false);
}
});
}
if (!result.equals("")) {
MainActivity.activity.runOnUiThread(new Runnable() {
@Override
public void run() {
//you can toast the result here
//Toast.makeText(MainActivity.activity, result,Toast.LENGTH_LONG).show();
if (page == 0) {
hash_all.clear();
}
items.clone();
try {
JSONArray jsonArray = new JSONArray(result);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject object = jsonArray.getJSONObject(i);
HashMap<String, Object> hash_add = new HashMap<>();
hash_add.put("ID", object.getString("ID"));
hash_add.put("Username", object.getString("Username"));
hash_add.put("Title", object.getString("Title"));
hash_add.put("Description", object.getString("Description"));
hash_add.put("Price", object.getString("Price"));
hash_add.put("Tell", object.getString("Tell"));
hash_add.put("Email", object.getString("Email"));
hash_add.put("City", object.getString("City"));
hash_add.put("Cate", object.getString("Cate"));
hash_add.put("Img1", object.getString("Img1"));
hash_add.put("Img2", object.getString("Img2"));
hash_add.put("Img3", object.getString("Img3"));
hash_add.put("Date", object.getString("Date"));
hash_all.add(hash_add);
items = new String[hash_all.size()];
}
ad.notifyDataSetChanged();
mSwipeRefreshLayout.setRefreshing(false);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
else {
Toast.makeText(MainActivity.activity,result,Toast.LENGTH_LONG).show();
}
}
});
}
更新：堆栈跟踪
FATAL EXCEPTION: AsyncServer
Process: com.morteza.newproject, PID: 3211
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
at com.morteza.newproject.Frag_banners_all$3.onCompleted(Frag_banners_all.java:145)
at com.morteza.newproject.Frag_banners_all$3.onCompleted(Frag_banners_all.java:130)
at com.koushikdutta.async.http.AsyncHttpClient.invokeWithAffinity(AsyncHttpClient.java:527)
at com.koushikdutta.async.http.AsyncHttpClient.access$800(AsyncHttpClient.java:51)
at com.koushikdutta.async.http.AsyncHttpClient$7.run(AsyncHttpClient.java:534)
at com.koushikdutta.async.AsyncServer.lockAndRunQueue(AsyncServer.java:740)
at com.koushikdutta.async.AsyncServer.runLoop(AsyncServer.java:758)
at com.koushikdutta.async.AsyncServer.run(AsyncServer.java:658)
at com.koushikdutta.async.AsyncServer.access$800(AsyncServer.java:44)
at com.koushikdutta.async.AsyncServer$14.run(AsyncServer.java:600)
W / System.err：java.util.concurrent.TimeoutException
W / System.err：at com.koushikdutta.async.http.AsyncHttpClient $ 2.run（AsyncHttpClient.java:246）
W / System.err：位于com.koushikdutta.async.AsyncServer.lockAndRunQueue（AsyncServer.java:740）
W / System.err：位于com.koushikdutta.async.AsyncServer.runLoop（AsyncServer.java:758）
W / System.err：位于com.koushikdutta.async.AsyncServer.run（AsyncServer.java:658）
W / System.err：at com.koushikdutta.async.AsyncServer.access $ 800（AsyncServer.java:44）
W / System.err：at com.koushikdutta.async.AsyncServer $ 14.run（AsyncServer.java:600）
申请已终止。
最佳答案
问题解决了，我在代码中仅添加了一个else来解决它，下面是正确的代码
private void get_banners(final int pages) {
AsyncHttpPost post = new AsyncHttpPost("http://192.168.1.102/soton/new.php");
post.setTimeout(5000);
MultipartFormDataBody body = new MultipartFormDataBody();
body.addStringPart("City", MainActivity.sp.getString("City", ""));
body.addStringPart("Page", String.valueOf(pages));
body.addStringPart("Cate", "all");
post.setBody(body);
try {
AsyncHttpClient.getDefaultInstance().executeString(post, new AsyncHttpClient.StringCallback() {
@Override
public void onCompleted(final Exception e, AsyncHttpResponse source, final String result) {
if (e != null) {
MainActivity.activity.runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.activity, "server is offline", Toast.LENGTH_LONG).show();
e.printStackTrace();
mSwipeRefreshLayout.setRefreshing(false);
}
});
}
//this is the answer
else {
if (!result.equals("")) {
MainActivity.activity.runOnUiThread(new Runnable() {
@Override
public void run() {
//you can toast the result here
//Toast.makeText(MainActivity.activity, result,Toast.LENGTH_LONG).show();
if (page == 0) {
hash_all.clear();
}
items.clone();
try {
JSONArray jsonArray = new JSONArray(result);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject object = jsonArray.getJSONObject(i);
HashMap<String, Object> hash_add = new HashMap<>();
hash_add.put("ID", object.getString("ID"));
hash_add.put("Username", object.getString("Username"));
hash_add.put("Title", object.getString("Title"));
hash_add.put("Description", object.getString("Description"));
hash_add.put("Price", object.getString("Price"));
hash_add.put("Tell", object.getString("Tell"));
hash_add.put("Email", object.getString("Email"));
hash_add.put("City", object.getString("City"));
hash_add.put("Cate", object.getString("Cate"));
hash_add.put("Img1", object.getString("Img1"));
hash_add.put("Img2", object.getString("Img2"));
hash_add.put("Img3", object.getString("Img3"));
hash_add.put("Date", object.getString("Date"));
hash_all.add(hash_add);
items = new String[hash_all.size()];
}
ad.notifyDataSetChanged();
mSwipeRefreshLayout.setRefreshing(false);
} catch (Exception e) {
e.printStackTrace();
}
}
});
} else {
Toast.makeText(MainActivity.activity, result, Toast.LENGTH_LONG).show();
}
}
}
});
}catch (Exception e){
e.printStackTrace();
}
}