碎片事务工作不正常

Question

在我的FragmentActivity类中，我有3个Fragmnet的Fragmnet Transaction。但我的onclick方法不正确。它只适用于一个if和else条件。我的另一个if条件不起作用。

我在这里做错了什么。。

public class Indi_Add_Details_menu extends FragmentActivity{
Fragment fragment;
Button btnFragment1, btnFragment2, btnFragment3, btnFragment4;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.add_detal_menu);
    btnFragment1 = (Button)findViewById(R.id.btn1);
    btnFragment2 = (Button)findViewById(R.id.btn2);
    btnFragment3 = (Button)findViewById(R.id.btn3);
    btnFragment4 = (Button)findViewById(R.id.btn4);
    btnFragment1.setBackgroundResource(R.drawable.add_sbutton_pressed);
    btnFragment2.setBackgroundResource(R.drawable.add_tbutton_pressed);
    btnFragment3.setBackgroundResource(R.drawable.add_pbutton_pressed);
    btnFragment4.setBackgroundResource(R.drawable.view_button_pressed);
    // get an instance of FragmentTransaction from your Activity
    FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    //add a fragment
    Fragment_addStudentDetails myFragment = new Fragment_addStudentDetails();
    fragmentTransaction.add(R.id.myfragment, myFragment);
    fragmentTransaction.commit();
    btnFragment1.setOnClickListener(btnFragmentOnClickListener);
    btnFragment2.setOnClickListener(btnFragmentOnClickListener);
    btnFragment3.setOnClickListener(btnFragmentOnClickListener);
    btnFragment4.setOnClickListener(btnFragmentOnClickListener);
}
Button.OnClickListener btnFragmentOnClickListener = new Button.OnClickListener(){
    @Override
    public void onClick(View v) {
        Fragment newFragment;
        // Create new fragment
        if(v == btnFragment1){
            newFragment = new Fragment_addStudentDetails();
        }if(v == btnFragment2){
            newFragment = new Group_Add_test();
        }else{
            newFragment = new ExpandableListFragment();
        }
        // Create new transaction
        FragmentTransaction transaction = getFragmentManager().beginTransaction();
        // Replace whatever is in the fragment_container view with this fragment,
        // and add the transaction to the back stack
        transaction.replace(R.id.myfragment, newFragment);
        transaction.addToBackStack(null);
        // Commit the transaction
        transaction.commit();
    }};
public void showDatePickerDialog(View v) {
    new DatePickerFragment((EditText) v).show(getFragmentManager(), "datePicker");
}
}

当我添加像这样的切换语句时

 switch (v.getId()){
            case R.id.btn1:
                newFragment = new Fragment_addStudentDetails();
                break;
            case R.id.btn2:
                newFragment = new Group_Add_test();
                break;
            case R.id.btn3:
                newFragment = new ExpandableListFragment();
                break;
            default:
                break;
        }

logcat说，

  Error:(80, 50) error: variable newFragment might not have been initialized

Answer 1

从您的代码中，我可以判断出每次newFragment=new ExpandableListFragment（）必须已执行。你在两个条件检查中都犯了错误如果（v==btnFragment1）。。。。不是检查视图是否被单击的正确方法。。。。因为它将比较参考文献。解决方案：如果（v.getId（）=btnFragment1.getId（

在切换案例Fragment newFragment;初始化您的片段

之前

此有效

 @Override
    public void onClick(View v) {
        Fragment newFragment;
        FragmentTransaction transaction = getFragmentManager().beginTransaction();
        switch (v.getId()){
            case R.id.btn1:
                newFragment = new Fragment_addStudentDetails();
                transaction.replace(R.id.myfragment, newFragment);
                transaction.addToBackStack(null);
                transaction.commit();
                break;
            case R.id.btn2:
                newFragment = new Group_Add_test();
                transaction.replace(R.id.myfragment, newFragment);
                transaction.addToBackStack(null);
                transaction.commit();
                break;
            case R.id.btn3:
                newFragment = new ExpandableListFragment();                  
                transaction.replace(R.id.myfragment, newFragment);
                transaction.addToBackStack(null);
                transaction.commit();
                break;
            default:
                break;
        }
    }};