当我从我的应用程序点击后退按钮时工作正常，但是当我从我的Android设备点击后退按钮并再次点击主页上的按钮时，我的应用就会停止。
主要活动 -
public class MainActivity extends Activity implements LoginResponse {
LoginThread login;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
login = new LoginThread(this);
login.delegate=this;
//function to execute when login button is pressed
login.execute(); // if login button is pressed
}
@Override
public void processFinish(RequestToken output) {
if(output!=null)
{
try {
startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(output.getAuthenticationURL())));
} catch (Exception e) {
// TODO: handle exception
Log.e("Error!!!", e.toString());
}
}
else
{
Intent i= new Intent(this,UserClass.class);
startActivity(i);
}
}
LoginThread类 -
public class LoginThread extends AsyncTask<Void, Void, RequestToken> {
public LoginThread(Context context)
{
this.context= context;
}
protected void onPreExecute()
{
// Shared Preferences
mSharedPreferences = context.getSharedPreferences("MyPref", 0);
try{
super.onPreExecute();
pDialog = new ProgressDialog(context);
pDialog.setMessage(Html.fromHtml("<b>Logging In</b><br/>Please wait..."));
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
catch (Exception ex)
{
Log.e("Error", "I got error", ex);
}
}
protected RequestToken doInBackground(Void... urls)
{
if(!isTwitterLoggedInAlready())
{
try
{
//Uri uri = ((Activity) context).getIntent().getData();
Log.e("Hello","sff");
Editor e= mSharedPreferences.edit();
e.putBoolean(PREF_KEY_TWITTER_LOGIN, true);
e.commit(); // save changes
ConfigurationBuilder builder = new ConfigurationBuilder();
builder.setOAuthConsumerKey(TWITTER_CONSUMER_KEY);
builder.setOAuthConsumerSecret(TWITTER_CONSUMER_SECRET);
Configuration configuration = builder.build();
TwitterFactory factory = new TwitterFactory(configuration);
twitter = factory.getInstance();
return requestToken = twitter.getOAuthRequestToken(TWITTER_CALLBACK_URL);
}
catch (TwitterException ex)
{
ex.printStackTrace();
return null;
}
}
else
{
return null;
}
}
protected void onPostExecute(RequestToken result)
{
pDialog.dismiss();
requestToken=result;
delegate.processFinish(requestToken);
}
/**
* Check user already logged in your application using twitter Login flag is
* fetched from Shared Preferences
* */
private boolean isTwitterLoggedInAlready() {
// return twitter login status from Shared Preferences
return mSharedPreferences.getBoolean(PREF_KEY_TWITTER_LOGIN, false);
}
的logcat -
03-13 10:04:44.623: D/AndroidRuntime(17352): Shutting down VM
03-13 10:04:44.623: W/dalvikvm(17352): threadid=1: thread exiting with uncaught exception (group=0x41a4a700)
03-13 10:04:44.638: E/AndroidRuntime(17352): FATAL EXCEPTION: main
03-13 10:04:44.638: E/AndroidRuntime(17352): java.lang.IllegalStateException: Could not execute method of the activity
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.view.View$1.onClick(View.java:3838)
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.view.View.performClick(View.java:4475)
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.view.View$PerformClick.run(View.java:18784)
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.os.Handler.handleCallback(Handler.java:730)
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.os.Handler.dispatchMessage(Handler.java:92)
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.os.Looper.loop(Looper.java:137)
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.app.ActivityThread.main(ActivityThread.java:5414)
03-13 10:04:44.638: E/AndroidRuntime(17352): at java.lang.reflect.Method.invokeNative(Native Method)
03-13 10:04:44.638: E/AndroidRuntime(17352): at java.lang.reflect.Method.invoke(Method.java:525)
03-13 10:04:44.638: E/AndroidRuntime(17352): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
03-13 10:04:44.638: E/AndroidRuntime(17352): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
03-13 10:04:44.638: E/AndroidRuntime(17352): at dalvik.system.NativeStart.main(Native Method)
03-13 10:04:44.638: E/AndroidRuntime(17352): Caused by: java.lang.reflect.InvocationTargetException
03-13 10:04:44.638: E/AndroidRuntime(17352): at java.lang.reflect.Method.invokeNative(Native Method)
03-13 10:04:44.638: E/AndroidRuntime(17352): at java.lang.reflect.Method.invoke(Method.java:525)
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.view.View$1.onClick(View.java:3833)
03-13 10:04:44.638: E/AndroidRuntime(17352): ... 11 more
03-13 10:04:44.638: E/AndroidRuntime(17352): Caused by: java.lang.IllegalStateException: Cannot execute task: the task has already been executed (a task can be executed only once)
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:578)
03-13 10:04:44.638: E/AndroidRuntime(17352): at android.os.AsyncTask.execute(AsyncTask.java:534)
03-13 10:04:44.638: E/AndroidRuntime(17352): at pack.locationinfo.MainActivity.TwitterLogin(MainActivity.java:75)
03-13 10:04:44.638: E/AndroidRuntime(17352): ... 14 more
答案 0 :(得分：0)
我得到了答案..感谢@Gaurav Gupta ..问题是我每次在主Activity类中都没有创建LoginThread类的新对象
这是主要活动类
的修改代码 @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LoginThread login;
/**
* Reference to this activity
*/
login = new LoginThread(this);
/**
* login interface
*/
login.delegate=this;
login.execute();
}
我错误地全局声明了LoginThread类的对象