[英]Android thread error - Can't create handler inside thread that has not called Looper.prepare()
[英]Android Waiting progress bar Can't create handler inside thread that has not called Looper.prepare() error
在我的android應用程序中,我將一些數據從服務器數據庫復制到本地數據庫,這可能需要15分鍾以上的時間。 對於較慢的連接,可能會超過該值。 所以我想顯示一個等待進度條。
該代碼發布在下面。
refresh.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
final ProgressDialog progressDialog = ProgressDialog.show(login.this, "", "Please wait...");
new Thread() {
public void run() {
try{
mySQLiteAdapter.openToWrite();
mySQLiteAdapter.deleteAll();
radapter.openToWrite();
radapter.deleteAll();
uadapter.openToWrite();
uadapter.deleteAll();
try
{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://xxxxxxxxxxxxxxxxxxxxx");
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Toast.makeText(getBaseContext(), e.toString(), Toast.LENGTH_LONG).show();
}
try {
jObj = new JSONObject(json);
contacts = jObj.getJSONArray("get");
for(int i = 0; i < contacts.length(); i++){
JSONObject c = contacts.getJSONObject(i);
if(!c.isNull("rname"))// || c.getString("rcode").equals(null))
{
rname = c.getString("rname");
rcode = c.getString("rcode");
radapter.insert(rcode, rname);
}
else
{
rname = "";
rcode = c.getString("rcode");
radapter.insert(rcode, rname);
}
}
Toast.makeText(getBaseContext(), " Ryot BackUp completed", Toast.LENGTH_SHORT).show();
} catch (JSONException e) {
Toast.makeText(getBaseContext(), "Error"+e.toString(), Toast.LENGTH_LONG).show();
}
progressDialog.dismiss();
}
}.start();
adapter.deleteAll();
oadapter.deleteAll();
e2.setText("Back Up completed");
}
catch (Exception e) {
Log.e("tag", e.getMessage());
}
progressDialog.dismiss();
}
}.start();
}
});
當我運行我的應用程序時,進度條僅顯示幾秒鍾,並且執行了Catch塊,顯示logcat錯誤為
Logcat:
02-26 14:26:07.151: E/tag(301): Can't create handler inside thread that has not called Looper.prepare()
有人可以解釋我的代碼中的錯誤是什么以及如何解決它
Toast.makeText(getBaseContext(), " Ryot BackUp completed", Toast.LENGTH_SHORT).show();
問題是由上面的代碼引起的,此方法將更改UI,您不能在非UI線程中更新UI。 因此,您需要從主ui線程調用它。
由於這是一項耗時的工作,因此我強烈建議您在Android中使用AsyncTask 。
但是,如果您只想對現有代碼進行一些更改,請嘗試使用
context.runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(...).show();
}
});
或處理程序,您可以查看Android中處理程序的工作方式 。 一個基本的例子:
public Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
//show toast here
}
}
protected void startLongRunningOperation() {
Thread t = new Thread() {
public void run() {
//do something here
//update the result
mHandler.postDelayed(mUpdateResults, 200);}
mHandler.post(mUpdateResults);
}
};
t.start();
}
而不是創建新的線程,而是創建一個HandlerThread- http://developer.android.com/reference/android/os/HandlerThread.html
只需將“ new Thread()”替換為“ new HandlerThread(“ any string”)“,它就可以工作。
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