如何解决android中删除片段时出现的非法状态异常

我在android中动态添加和删除片段，同时删除片段。我遇到了这个异常。有人能告诉我如何删除片段吗

12-09 15:00:16.363: ERROR/AndroidRuntime(673): FATAL EXCEPTION: main
12-09 15:00:16.363: ERROR/AndroidRuntime(673): java.lang.IllegalStateException: commit already called
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at android.app.BackStackRecord.commitInternal(BackStackRecord.java:499)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at android.app.BackStackRecord.commit(BackStackRecord.java:491)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at com.gcm.fragment.GcmFragmentActivity.onClick(GcmFragmentActivity.java:50)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at android.view.View.performClick(View.java:3110)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at android.view.View$PerformClick.run(View.java:11928)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at android.os.Handler.handleCallback(Handler.java:587)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at android.os.Handler.dispatchMessage(Handler.java:92)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at android.os.Looper.loop(Looper.java:132)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at android.app.ActivityThread.main(ActivityThread.java:4025)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at java.lang.reflect.Method.invokeNative(Native Method)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at java.lang.reflect.Method.invoke(Method.java:491)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
12-09 15:00:16.363: ERROR/AndroidRuntime(673):     at dalvik.system.NativeStart.main(Native Method)

我的代码在下面

package com.gcm.fragment;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;

public class GcmFragmentActivity extends Activity implements OnClickListener {
    TextView txtIhaveIdea=null;
    boolean subMenu=false;
    Fragment fragOne = new SubFragment(); 
    FragmentManager fm = getFragmentManager(); 
    FragmentTransaction ft = fm.beginTransaction(); 

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        txtIhaveIdea=(TextView)findViewById(R.id.txtIhaveAnIdea);
        txtIhaveIdea.setOnClickListener(this);

        ; 
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        if(v.getId()==R.id.txtIhaveAnIdea)
        {
            if(!subMenu)
            {

                /*Bundle arguments = new Bundle(); 
                arguments.putBoolean("shouldYouCreateAChildFragment", true); 
                fragOne.setArguments(arguments); */
                //ft.show(fragOne);
                fm.beginTransaction(); 
                ft.add(R.id.main_frag_container, fragOne);              
                ft.commit();
                subMenu=true;
            }
            else if(subMenu)
            {
                fm.beginTransaction(); 
                ft.remove(fragOne);
                ft.commit();
                /*fm.beginTransaction(); 
                ft.replace(R.id.main_frag_container, null);                 
                ft.commit();*/
                subMenu=false;
                //ft.hide(fragOne);

                //ft.remove(fragOne);
                /*FragmentManager fm = getFragmentManager(); 
                FragmentTransaction ft = fm.beginTransaction(); 

                fm.beginTransaction(); 
                Fragment fragOne = new SubFragment(); 
                Bundle arguments = new Bundle(); 
                arguments.putBoolean("shouldYouCreateAChildFragment", true); 
                fragOne.setArguments(arguments); 
                ft.remove(fragOne); 
                ft.commit();    */
            }

        }

    }
}

/*FragmentManager fm = getFragmentManager(); 
FragmentTransaction ft = fm.beginTransaction(); 

fm.beginTransaction(); 
Fragment fragOne = new MyFragment(); 
Bundle arguments = new Bundle(); 
arguments.putBoolean("shouldYouCreateAChildFragment", true); 
fragOne.setArguments(arguments); 
ft.add(R.id.main_frag_container, fragOne); 
ft.commit(); 
*/

有人能告诉我如何解决这个问题吗

---

谢谢

让ft成为局部变量，而不是类级别变量

public class GcmFragmentActivity extends Activity implements OnClickListener {
    TextView txtIhaveIdea=null;
    boolean subMenu=false;
    Fragment fragOne = new SubFragment(); 
    FragmentManager fm = getFragmentManager(); 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        txtIhaveIdea=(TextView)findViewById(R.id.txtIhaveAnIdea);
        txtIhaveIdea.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        if(v.getId()==R.id.txtIhaveAnIdea){
        if(!subMenu){
            FragmentTransaction ft = fm.beginTransaction(); 
            ft.add(R.id.main_frag_container, fragOne);              
            ft.commit();
            subMenu=true;
        }else if(subMenu){
            FragmentTransaction ft = fm.beginTransaction();
            ft.remove(fragOne);
            ft.commit();
            subMenu=false;
        }
        }
    }
}

---

谢谢你的提示解决了我的问题。但是你能告诉我这背后的概念吗？或者任何可以帮助我的参考网站？好的。我发现类级变量FragmentTransaction已经执行了提交。转到另一个片段不会破坏此对象，再次调用commit会导致问题。对吗？所以每次我都需要设置自定义动画，对吗？