对于Android片段我是相当新的，并且我试图制作一个用户点击“提交”按钮后加载新片段的应用。单击“提交”按钮时，我想要发生的是，为正在显示的现有片段交换新片段。 LogCat显示调用commit（）方法时发生的错误。有关为何抛出此错误的任何解释？
MainActivity.java
package com.example.flightfragmenttest;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Spinner;
import android.widget.AdapterView.OnItemSelectedListener;
public class MainActivity extends ActionBarActivity {
Spinner modelInputSpinner, specInputSpinner;
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
GensetFragment genFrag = new GensetFragment();
ResultsFragment resFrag = new ResultsFragment();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (findViewById(R.id.fragmentContainer) != null) {
if (savedInstanceState != null) {
return;
}
transaction.add(R.id.fragmentContainer, genFrag).commit();
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public void search(View v) {
modelInputSpinner = (Spinner) findViewById(R.id.modelSpinner);
specInputSpinner = (Spinner) findViewById(R.id.specSpinner);
addModelItemSelectedListener();
addSpecItemSelectedListener();
genFrag.search(modelInputSpinner, specInputSpinner);
transaction.replace(R.id.fragmentContainer, resFrag);
transaction.addToBackStack(null);
transaction.commit();
}
private void addSpecItemSelectedListener() {
specInputSpinner
.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent,
View view, int position, long id) {
//
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub
}
});
}
private void addModelItemSelectedListener() {
modelInputSpinner
.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent,
View view, int position, long id) {
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub
}
});
}
}
第一个片段
package com.example.flightfragmenttest;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Spinner;
public class GensetFragment extends Fragment {
Genset userInput = new Genset();
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_genset, container,
false);
return rootView;
}
public void search(Spinner model, Spinner spec) {
userInput.setModelNumber(model.getSelectedItem()
.toString());
userInput.setSpecNumber(spec.getSelectedItem()
.toString());
System.out.println(userInput.getModelNumber() + " " + userInput.getSpecNumber());
}
}
第二片段
package com.example.flightfragmenttest;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class ResultsFragment extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
System.out.println("Step in to results");
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_results, container, false);
System.out.println("Step in to results");
return rootView;
}
}
logcat的
06-09 11:36:00.494: E/AndroidRuntime(2982): FATAL EXCEPTION: main
06-09 11:36:00.494: E/AndroidRuntime(2982): Process: com.example.flightfragmenttest, PID: 2982
06-09 11:36:00.494: E/AndroidRuntime(2982): java.lang.IllegalStateException: Could not execute method of the activity
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.view.View$1.onClick(View.java:3823)
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.view.View.performClick(View.java:4438)
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.view.View$PerformClick.run(View.java:18422)
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.os.Handler.handleCallback(Handler.java:733)
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.os.Handler.dispatchMessage(Handler.java:95)
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.os.Looper.loop(Looper.java:136)
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.app.ActivityThread.main(ActivityThread.java:5017)
06-09 11:36:00.494: E/AndroidRuntime(2982): at java.lang.reflect.Method.invokeNative(Native Method)
06-09 11:36:00.494: E/AndroidRuntime(2982): at java.lang.reflect.Method.invoke(Method.java:515)
06-09 11:36:00.494: E/AndroidRuntime(2982): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
06-09 11:36:00.494: E/AndroidRuntime(2982): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
06-09 11:36:00.494: E/AndroidRuntime(2982): at dalvik.system.NativeStart.main(Native Method)
06-09 11:36:00.494: E/AndroidRuntime(2982): Caused by: java.lang.reflect.InvocationTargetException
06-09 11:36:00.494: E/AndroidRuntime(2982): at java.lang.reflect.Method.invokeNative(Native Method)
06-09 11:36:00.494: E/AndroidRuntime(2982): at java.lang.reflect.Method.invoke(Method.java:515)
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.view.View$1.onClick(View.java:3818)
06-09 11:36:00.494: E/AndroidRuntime(2982): ... 11 more
06-09 11:36:00.494: E/AndroidRuntime(2982): Caused by: java.lang.IllegalStateException: commit already called
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:582)
06-09 11:36:00.494: E/AndroidRuntime(2982): at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:574)
06-09 11:36:00.494: E/AndroidRuntime(2982): at com.example.flightfragmenttest.MainActivity.search(MainActivity.java:61)
06-09 11:36:00.494: E/AndroidRuntime(2982): ... 14 more
答案 0 :(得分：2)
您无法重复使用片段事务。致电beginTransaction()创建一个新的。
此外，仅在onCreate()或稍后的活动生命周期中访问片段管理器可能更好。
答案 1 :(得分：1)
不要将FragmentTransaction作为您活动的班级成员。每次要更改片段时都会获得一个新的FragmentTransaction，例如
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragmentContainer, resFrag);
.addToBackStack(null);
.commit();