我有一个登录活动与标签。一个用于登录，另一个用于注册。我想继续检查网络连接，所以我编写了一个线程。我想在没有连接的情况下显示一个对话框，说明检查你的网络连接然后重试，并且有一个按钮可以再次尝试。
这是我的代码：
package com.geniboys.sosyaaal;
import java.util.Locale;
import android.app.ActionBar;
import android.app.AlertDialog;
import android.app.FragmentTransaction;
import android.content.Context;
import android.content.DialogInterface;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
public class Logger extends FragmentActivity implements ActionBar.TabListener {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
* will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;
static boolean isBoxOpen = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_logger);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setTitle("Sosyaaal");
actionBar.setBackgroundDrawable(getResources().getDrawable(R.drawable.action_bar));
Thread connectivity = new Thread(){
public void run(){
try {
while(!isBoxOpen)
{
if( !isOnline() )
{
isBoxOpen = true;
// display error
new AlertDialog.Builder(Logger.this)
.setTitle("Bağlantı Sorunu")
.setMessage("İnternet bağlantısını kontrol edip tekrar deneyin")
.setCancelable(false)
.setPositiveButton(R.string.yeniden, new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
Logger.isBoxOpen = false;// Try Again
}
})
.show();
}
}
} catch (Exception e) {
}
}
};
connectivity.start();
// Create the adapter that will return a fragment for each of the three
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager
.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.logger, menu);
return true;
}
public boolean isOnline() {
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnectedOrConnecting()) {
return true;
}
return false;
}
@Override
public void onTabSelected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabReselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
// Top Rated fragment activity
return new GirisFragment();
case 1:
// Games fragment activity
return new KayitFragment();
}
return null;
}
@Override
public int getCount() {
// Show 2 total pages.
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
}
return null;
}
}
/**
* A dummy fragment representing a section of the app, but that simply
* displays dummy text.
*/
public static class GirisFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
public GirisFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_giris,
container, false);
return rootView;
}
}
public static class KayitFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
public KayitFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_kayit,
container, false);
return rootView;
}
}
}
这里是logcat：
01-31 15:21:33.414: W/dalvikvm(7688): threadid=12: thread exiting with uncaught exception (group=0x4104cae0)
01-31 15:21:33.414: E/AndroidRuntime(7688): FATAL EXCEPTION: Thread-608
01-31 15:21:33.414: E/AndroidRuntime(7688): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
01-31 15:21:33.414: E/AndroidRuntime(7688): at android.os.Handler.<init>(Handler.java:197)
01-31 15:21:33.414: E/AndroidRuntime(7688): at android.os.Handler.<init>(Handler.java:111)
01-31 15:21:33.414: E/AndroidRuntime(7688): at android.app.Dialog.<init>(Dialog.java:114)
01-31 15:21:33.414: E/AndroidRuntime(7688): at android.app.AlertDialog.<init>(AlertDialog.java:121)
01-31 15:21:33.414: E/AndroidRuntime(7688): at android.app.AlertDialog$Builder.create(AlertDialog.java:945)
01-31 15:21:33.414: E/AndroidRuntime(7688): at android.app.AlertDialog$Builder.show(AlertDialog.java:965)
01-31 15:21:33.414: E/AndroidRuntime(7688): at com.geniboys.sosyaaal.Logger$1.run(Logger.java:74)
01-31 15:21:35.434: I/Process(7688): Sending signal. PID: 7688 SIG: 9
01-31 15:21:37.844: W/dalvikvm(8023): threadid=11: thread exiting with uncaught exception (group=0x4104cae0)
01-31 15:21:37.844: E/AndroidRuntime(8023): FATAL EXCEPTION: Thread-643
01-31 15:21:37.844: E/AndroidRuntime(8023): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
01-31 15:21:37.844: E/AndroidRuntime(8023): at android.os.Handler.<init>(Handler.java:197)
01-31 15:21:37.844: E/AndroidRuntime(8023): at android.os.Handler.<init>(Handler.java:111)
01-31 15:21:37.844: E/AndroidRuntime(8023): at android.app.Dialog.<init>(Dialog.java:114)
01-31 15:21:37.844: E/AndroidRuntime(8023): at android.app.AlertDialog.<init>(AlertDialog.java:121)
01-31 15:21:37.844: E/AndroidRuntime(8023): at android.app.AlertDialog$Builder.create(AlertDialog.java:945)
01-31 15:21:37.844: E/AndroidRuntime(8023): at android.app.AlertDialog$Builder.show(AlertDialog.java:965)
01-31 15:21:37.844: E/AndroidRuntime(8023): at com.geniboys.sosyaaal.Logger$1.run(Logger.java:74)
答案 0 :(得分：2)
你必须在UI线程中创建AlertDialog，否则它永远不会工作。您可以使用MessageHandler或runOnUiThread(using runnable)在内部创建对话框。
示例：
runOnUiThread(new Runnable() {
public void run() {
new AlertDialog.Builder(Logger.this)
.setTitle("Bağlantı Sorunu")
.setMessage("İnternet bağlantısını kontrol edip tekrar deneyin")
.setCancelable(false)
.setPositiveButton(R.string.yeniden, new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
Logger.isBoxOpen = false;// Try Again
}
})
.show();
}
});