Switching fragments via getActivity ()

Question

There is a class MainActivity

public class MainActivity extends FragmentActivity { final int DIALOG_EXIT = 1; FragmentTransaction ft; FirstFragment ff = new FirstFragment(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); ff = new FirstFragment(); getSupportFragmentManager().beginTransaction().add(R.id.frame, ff) .commit(); } @Override public void onBackPressed() { // TODO Auto-generated method stub if (getSupportFragmentManager().getBackStackEntryCount() > 0) { super.onBackPressed(); } else { new AlertDialog.Builder(this).setIcon(android.R.drawable.ic_dialog_alert).setTitle("EXIT").setMessage("Уверен что хочешь выйти?^^").setPositiveButton("Да", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialogInterface, int i) { finish(); } }).setNegativeButton("Нет", null).show(); } }}

And also three identical fragments

 public class FirstFragment extends Fragment { FragmentTransaction ft; SecondFragment sf; ThirdFragment tf; Button next1; Button back1; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View v = inflater.inflate(R.layout.first, null); sf = new SecondFragment(); tf = new ThirdFragment(); Button next1 = (Button) v.findViewById(R.id.next1); Button back1 = (Button) v.findViewById(R.id.back1); next1.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { ft = getFragmentManager().beginTransaction(); switch (v.getId()) { case R.id.next1: ft.replace(R.id.frame, sf).addToBackStack(null); break; default: break; } ft.commit(); } }); back1.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { ft = getFragmentManager().beginTransaction(); switch (v.getId()) { case R.id.back1: //((Button)getActivity().findViewById(R.id.back1)); //getActivity() //(MainActivity()getActivity()). ft.replace(R.id.frame, tf).addToBackStack(null); break; default: break; } ft.commit(); } }); return v; }}

Fragments are switched inside of themselves, how to make switching through ((MainActivity) getActivity ())?

Accepted Answer · 2014-01-15T16:20:02

I advise you to do it through callback.
those. describe the interface of the fragment

 public interface DoSomesingListener { public void doSomesing(); }

and you make a private field for a fragment (for all fragments) or for one basic fragment and inherit all fragments from it. with inheritance is preferable, because there will be no repetition of the code

 private DoSomesingListener doSomesingListener;

and setter to him

 public void setDoSomesingListener(final DoSomesingListener doSomesingListener) { this.doSomesingListener = doSomesingListener; }

Then, in the necessary activity, implement this interface and send to the fragments where these actions are to be performed, via setDoSomesingListener

I hope clearly described his thought.

But you can and as you suggested, but I would not do that.

UPD: it turned out pretty massive, I advise you to compare written above, with the code below

 public class MainActivity extends FragmentActivity implements BaseFragment.OnFragmentChangeListener { private OneFragment oneFragment; private TwoFragment twoFragment; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); //предварительно переменный oneFragment и twoFragment //должны быть инициализированны //далее посылаем слушателя в каждый фрагмент oneFragment.setOnFragmentChangeListener(this); twoFragment.setOnFragmentChangeListener(this); } @Override public void onFragmentChange() { //тут происходит переключение фрагментов, //логику уж не знаю, придется делать самому } } public class BaseFragment extends Fragment { //тут происходит всякая инициализация и другой код public interface OnFragmentChangeListener { //методо может иметь входные параметры(так, для справки) public void onFragmentChange(); } protected OnFragmentChangeListener onFragmentChangeListener; public void setOnFragmentChangeListener(final OnFragmentChangeListener onFragmentChangeListener) { this.onFragmentChangeListener = onFragmentChangeListener; } //этот метод не обязателен, так как поле onFragmentChangeListener с модификатором protected, // а значит все наследники класса имеют к нему доступ // написал на всякий случай public OnFragmentChangeListener getOnFragmentChangeListener() { return this.onFragmentChangeListener } } public class OneFragment extends BaseFragment { //тут происходит всякая инициализация и другой код private void wantChangeFragment() { if (onFragmentChangeListener!=null) onFragmentChangeListener.onFragmentChangeListener(); } } public class TwoFragment extends BaseFragment { //тут происходит всякая инициализация и другой код private void wantChangeFragment() { if (onFragmentChangeListener!=null) onFragmentChangeListener.onFragmentChangeListener(); } }

until tomorrow I propose to think :) today I can not do anything.

Switching fragments via getActivity ()

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