类适配器不工作 [英] CLASS ADAPTER DOESN'T WORK

问题描述

我有选项卡;如果ia从选项卡PIZZA中选择一个复选框，之后，当我继续第三个选项卡BIRRE如果我点击按钮get_answer我想要在第一个选项卡中选中的复选框在第二个选项卡 TWO...但用我的代码，当我点击按钮get_answerIDE说我空指针异常行为（Planet p：plAdapter.getBox（））在THREE FRAGMENT ...我也使用共享首选项存储复选框，当我单击另一个选项卡，infact复选框存储....但它不工作...我不知道为什么....

现在我发布我的代码...

适应器：

  public abstract class PlanetAdapter extends ArrayAdapter< Planet> implements CompoundButton.OnCheckedChangeListener 
 
 {
 
 private List< Planet> planetList = null; 
 private Context context = null; 
 ArrayList< Birra>对象; 
 private HashMap< Integer，Planet> pizzaSelected = new HashMap<>（）; 
 public boolean Checked; 
 
 public PlanetAdapter（List< Planet> planetList，Context context）{
 
 super（context，R.layout.single_listview_item，planetList）; 
 this.planetList = planetList; 
 this.context = context; 
} 
 
 
 public class PlanetHolder {
 public TextView planetName; 
 public TextView distView; 
 public TextView valuta; 
 public CheckBox chkBox; 
 public EditText edit; 
 // public Stringquantità; 
 public boolean checked; 
 public TextView id; 
} 
 
 @Override 
 public int getCount（）{
 return planetList.size（）; 
} 
 
 @Override 
 public Planet getItem（int position）{
 return planetList.get（position）; 
} 
 
 @Override 
 public long getItemId（int position）{
 return planetList.get（position）.getId（）; 
} 
 
 
 @Override 
 public View getView（final int position，View convertView，ViewGroup parent）{
 
 View row = convertView ; 
 PlanetHolder holder = null; 
 
 if（row == null）{
 LayoutInflater inflater =（（Activity）context）.getLayoutInflater（）; 
 row = inflater.inflate（R.layout.single_listview_item，parent，false）; 
 holder = new PlanetHolder（）; 
 holder.planetName =（TextView）row.findViewById（R.id.name）; 
 holder.distView =（TextView）row.findViewById（R.id.dist）; 
 holder.valuta =（TextView）row.findViewById（R.id.valuta）; 
 holder.chkBox =（CheckBox）row.findViewById（R.id.chk_box）; 
 holder.edit =（EditText）row.findViewById（R.id.editText）; 
 holder.edit.setVisibility（View.GONE）; 
 holder.edit.setEnabled（false）; 
 // holder.id =（TextView）row.findViewById（R.id.id）; 
 
 
 row.setTag（holder）; 
 
} else {
 holder =（PlanetHolder）row.getTag（）; 
} 
 final Planet p = planetList.get（position）; 
 holder.planetName.setText（p.getName（））; 
 holder.distView.setText（+ p.getDistance（））; 
 holder.valuta.setText（+ p.getValuta（））; 
 holder.chkBox.setChecked（p.isSelected（））; 
 holder.chkBox.setTag（p）; 
 holder.edit.setEnabled（false）; 
 SharedPreferences states = getContext（）。getSharedPreferences（states，Context.MODE_PRIVATE）; 
 boolean isChecked = states.getBoolean（holder.chkBox+ holder.planetName.getText（）。toString（），false）; 
 System.out.println（isChecked）; 
 if（isChecked）{
 holder.chkBox.setChecked（true）; 
 holder.edit.setVisibility（View.VISIBLE）; 
 holder.edit.setEnabled（true）; 
 SharedPreferences statess = getContext（）。getSharedPreferences（states，Context.MODE_PRIVATE）; 
 String string = statess.getString（finalHolder.edit+ holder.planetName.getText（）。toString（），holder.edit.getText（）。toString（）。trim（））; 
 holder.edit.setText（string）; 
 
 
} else {
 holder.chkBox.setChecked（false）; 
 holder.edit.setVisibility（View.GONE）; 
 holder.edit.setEnabled（false）; 
 
 
} 
 
 
 final PlanetHolder finalHolder = holder; 
 
 
 holder.chkBox.setOnCheckedChangeListener（new CompoundButton.OnCheckedChangeListener（）{
 @Override 
 public void onCheckedChanged（CompoundButton buttonView，boolean isChecked）{
 if（finalHolder.chkBox.isChecked（））{
 finalHolder.edit.setVisibility（View.VISIBLE）; 
 finalHolder.edit.setEnabled（true）; 
 SharedPreferences states = getContext（）。 getSharedPreferences（states，Context.MODE_PRIVATE）; 
 SharedPreferences.Editor editor = states.edit（）; 
 editor.putBoolean（holder.chkBox+ finalHolder.planetName.getText（）。toString ），true）; 
 editor.commit（）; 
 //Utility.putPizzaItem（p）; 
 //Utility.getPizzaItem（p）; 
 
 b $ b} else {
 SharedPreferences states = getContext（）。getSharedPreferences（states，Context.MODE_PRIVATE）; 
 SharedPreferences.Editor editor3 = states.edit（）; 
 finalHolder.edit.setVisibility（View.GONE）; 
 finalHolder.edit.setEnabled（false）; 
 finalHolder.edit.setText（）; 
 editor3.putBoolean（holder.chkBox+ finalHolder.planetName.getText（）。toString（），false）; 
 editor3.commit（）; 
 
 
} 
 / * SharedPreferences states = getContext（）。getSharedPreferences（states，Context.MODE_PRIVATE）; 
 SharedPreferences.Editor editor = states.edit（）; 
 editor.apply（）; * / 
 
} 
}）; 
 /*holder.chkBox.setOnClickListener（new View.OnClickListener（）{
 @Override 
 public void onClick（View v）{
 if（finalHolder.chkBox.isChecked（） ）{
 finalHolder.edit.setVisibility（View.VISIBLE）; 
 finalHolder.edit.setEnabled（true）; 
 SharedPreferences states = getContext（）。getSharedPreferences（states，Context.MODE_PRIVATE ）; 
 SharedPreferences.Editor editor = states.edit（）; 
 editor.putBoolean（holder.chkBox，true）; 
 //pizzaSelected.put（p.getId p）; 
 System.out.println（p.getId（））; 
} else {
 
 finalHolder.edit.setVisibility（View.GONE）; 
 finalHolder.edit.setEnabled（false）; 
 finalHolder.edit.setText（null）; 
 pizzaSelected.remove（p.getId（））; 
 
} 
 
} 
}）; 
 * / 
 
 
 finalHolder.edit.addTextChangedListener（new TextWatcher（）{
 @Override 
 public void beforeTextChanged（CharSequence s，int start，int count，int after）{
} 
 
 @Override 
 public void onTextChanged（CharSequence s，int start，int before，int count）{
} 
 
 @Override 
 public void afterTextChanged（可编辑）{
p.setQuantità（finalHolder.edit.getText（）。toString（）。trim（））; 
 SharedPreferences = getContext（）。getSharedPreferences（states，Context.MODE_PRIVATE）; 
 SharedPreferences.Editor editor = states.edit（）; 
 editor.putString（finalHolder.edit+ finalHolder.planetName.getText （）.toString（），finalHolder.edit.getText（）。toString（）。trim（））; 
 editor.commit（）; 
 
 
} $ b b}）; 
 
 
 //holder.planetName.setText（p.getName（））; 
 //holder.distView.setText（+ p.getDistance（））; 
 //holder.valuta.setText（+ p.getValuta（））; 
 // holder.chkBox.setChecked（p.isSelected（））; 
 // holder.chkBox.setTag（p）; 
 // holder.edit.setEnabled（false）; 
 // holder.id.setId（p.getId（））; 
 
 
 return row; 
} 
 
 ArrayList< Planet> getBox（）{
 ArrayList< Planet> box = new ArrayList< planet>（）; 
 for（Planet p：planetList）{
 if（p.isSelected（））
 box.add（p）; 
} 
 return box; 
} 
 
 
 
} 
  

FRAGMENT OF PLANET ADAPTER：

  public class MyListFragment extends Fragment implements 
 android.widget.CompoundButton.OnCheckedChangeListener {
 
 ListView lv; 
 ArrayList< Planet> planetList; 
 PlanetAdapter plAdapter; 
 BirraAdapter biAdapter; 
 PlanetAdapter.PlanetHolder holder; 
 
 
 
 
 @Override 
 public查看onCreateView（LayoutInflater inflater，ViewGroup容器，
 Bundle savedInstanceState）{
 //膨胀这个片段的布局
 
 ViewGroup rootView =（ViewGroup）inflater.inflate（R.layout.fragment_list2，container，false）; 
 
 / * Button mButton =（Button）rootView.findViewById（R.id.button）; 
 mButton.setOnClickListener（new View.OnClickListener（）{
 public void onClick（View v）{
 showResult（v）; 
 
 
} b $ b}）; * / 
 // return inflater.inflate（R.layout.fragment_list2，container，false）; 
 return rootView; 
} 
 
 @Override 
 public void onViewCreated（View view，@Nullable Bundle savedInstanceState）{
 super.onViewCreated（view，savedInstanceState）; 
 
 
 lv =（ListView）getView（）。findViewById（R.id.listview）; 
 displayPlanetList（）; 
 
 
} 
 
 
 private void displayPlanetList（）{
 
 planetList = new ArrayList& 
 planetList.add（new Planet（Margherita，6，€，1））; 
 planetList.add（new Planet（Diavola，7，€，2））; 
 planetList.add（new Planet（Bufalina，5，€，3））; 
 planetList.add（new Planet（Marinara，5，€，4））; 
 planetList.add（new Planet（Viennese，4，€，5））; 
 
 plAdapter = new PlanetAdapter（planetList，getActivity（））{
 @Override 
 public void onCheckedChanged（CompoundButton buttonView，boolean isChecked）{
 
 int pos = lv.getPositionForView（buttonView）; 
 if（pos！= ListView.INVALID_POSITION）{
 Planet p = planetList.get（pos）; 
 p.setSelected（isChecked）; 
 
 
 /*Toast.makeText（
 getActivity（），
点击Pizza：+ p.getName（）+。State：is
 + isChecked，Toast.LENGTH_SHORT）.show（）; * / 
} 
 
 
} 
}; 
 
 lv.setAdapter（plAdapter）; 
} 
 
} 
  

三个碎片：

  public class ThreeFragment extends Fragment implements 
 android.widget.CompoundButton.OnCheckedChangeListener {
 
 ListView lv2; 
 ArrayList< Birra> birraList; 
 BirraAdapter biAdapter; 
 PlanetAdapter plAdapter; 
 Planet p; 
 
 
 BirraAdapter.BirraHolder birraHolder; 
 PlanetAdapter.PlanetHolder holder; 
 
 
 public ThreeFragment（）{
 //必需的空公共构造函数
} 
 
 
 @Override 
 public View onCreateView（LayoutInflater inflater，ViewGroup container，
 Bundle savedInstanceState）{
 //为此片段扩充布局
 ViewGroup rootView =（ViewGroup）inflater.inflate（R.layout.fragment_three，容器，假）; 
 
 Button mButton =（Button）rootView.findViewById（R.id.button2）; 
 mButton.setOnClickListener（new View.OnClickListener（）{
 public void onClick（View v）{
 showResult（v）; 
 
 
} b $ b}）; 
 // return inflater.inflate（R.layout.fragment_list2，container，false）; 
 return rootView; 
} 
 
 
 @Override 
 public void onViewCreated（View view，@Nullable Bundle savedInstanceState）{
 super.onViewCreated（view，savedInstanceState）; 
 
 lv2 =（ListView）getView（）。findViewById（R.id.listview2）; 
 displayBirraList（）; 
} 
 
 
 private void displayBirraList（）{
 
 birraList = new ArrayList< Birra>（）; 
 birraList.add（new Birra（Paulaner，6，€））; 
 birraList.add（new Birra（Forst，7，€））; 
 birraList.add（new Birra（Peroni，5，€））; 
 birraList.add（new Birra（Corona，5，€））; 
 birraList.add（new Birra（Nastro Azzurro，4，€））; 
 biAdapter = new BirraAdapter（birraList，getContext（））{
 @Override 
 public void onCheckedChanged（CompoundButton buttonView，boolean isChecked）{
 int pos = lv2.getPositionForView（buttonView） ; 
 if（pos！= ListView.INVALID_POSITION）{
 Birra b = birraList.get（pos）; 
 b.setSelected（isChecked）; 
 
 
 /*Toast.makeText（
 getActivity（），
点击Pizza：+ p.getName（）+。State：is
 + isChecked，Toast.LENGTH_SHORT）.show（）; * / 
} 
 
 
} 
 
 
}; 
 lv2.setAdapter（biAdapter）; 
} 
 
 
 public void onCheckedChanged（CompoundButton buttonView，boolean isChecked）{
 
 
 / * int pos = lv.getPositionForView ）; 
 if（pos！= ListView.INVALID_POSITION）{
 Planet p = planetList.get（pos）; 
 p.setSelected（isChecked）; 
 
 
 * // ** // ** // ** // * Toast.makeText（
 getActivity（），
点击Planet： + p.getName（）+。State：is
 + isChecked，Toast.LENGTH_SHORT）.show（）; * // ** // ** // ** // * 
} 
 * / 
} 
 
 
 public void showResult（View v）{
 String result =Selected Product are：; 
 int totalAmount = 0; 
 String c =; 
 
 for（Birra b：biAdapter.getBox（））{
 
 if（b.selected）{
 
 result + =\\\
 + b.name ++ b.distance +€+q.tà：+b.getQuantità（）; 
 int quantitaInt = Integer.parseInt（b.getQuantità（））; 
 totalAmount + = b.distance * quantitaInt; 
 //a=String.valueOf(totalAmount）; 
 
 
} 
} 
 for（Planet p：plAdapter.getBox（））{
 if（p.isSelected（））{
 
 
 result + =\\\
+ p.getName（）++ p.getDistance（）+€+q.tà：+p.getQuantità 
 int quantitaInt = Integer.parseInt（p.getQuantità（））; 
 //totalAmount2+=p.distance * quantitaInt; 
 //z=String.valueOf(totalAmount2）; 
 
 
} 
 
 
 for（Birra b：biAdapter.getBox（））{
 if（b.selected）{
 
 result + =\\\
+ b.name ++ b.distance +€+q.tà：+b.getQuantità 
int quantitaInt = Integer.parseInt（b.getQuantità（））; 
 totalAmount + = b.distance * quantitaInt; 
 c = String.valueOf（totalAmount）; 
 
 
} 
} 
 Toast.makeText（getActivity（），result +\\\
+总金额：=+ totalAmount +€ ，Toast.LENGTH_LONG）.show（）; 
 Bundle bun2 = new Bundle（）; 
 bun2.putString（scelta2，result）; 
 TwoFragment fgsearch2 = new TwoFragment（）; 
 fgsearch2.setArguments（bun2）; 
 android.support.v4.app.FragmentTransaction transaction2 = getActivity（）。getSupportFragmentManager（）。beginTransaction（）; 
 transaction2.replace（R.id.content_main，fgsearch2）; 
 transaction2.commit（）; 
 
 
 Bundle bun = new Bundle（）; 
 bun.putString（totale2，c）; 
 TwoFragment fgsearch = new TwoFragment（）; 
 fgsearch.setArguments（bun） 
 android.support.v4.app.FragmentTransaction transaction = getActivity（）。getSupportFragmentManager（）。beginTransaction（）; 
 transaction.replace（R.id.content_main2，fgsearch）; 
 transaction.commit（）; 
 
} 
 
 
} 
} 
  

b $ b

这是我的应用程式：

enter image description here

解决方案

PlAdapter尚未初始化。你必须在这行之前初始化它： for（Planet p：plAdapter.getBox（））{因此空指针异常
最好在OnCreateView

i have tabs;if i a select a checkbox from tab "PIZZA", after,when i go on third tab "BIRRE" if i click on button "get_answer" i want that checkbox selected in first tab are in second tab "TWO"...but with my code when i click on button "get_answer" IDE say me "null pointer exception" on line "for (Planet p : plAdapter.getBox()) " in THREE FRAGMENT...i used also shared preferences to store checkbox when i click on another tab, infact checkbox are stored....but it doesn't work...i don't know why....

now i post my code...

THANKS EVERYBODY IN ADVANCE!

ADAPTER:

public abstract class PlanetAdapter extends ArrayAdapter<Planet> implements CompoundButton.OnCheckedChangeListener

{

    private List<Planet> planetList = null;
    private Context context = null;
    ArrayList<Birra> objects;
    private HashMap<Integer, Planet> pizzaSelected = new HashMap<>();
    public boolean Checked;

    public PlanetAdapter(List<Planet> planetList, Context context) {

        super(context, R.layout.single_listview_item, planetList);
        this.planetList = planetList;
        this.context = context;
    }


    public class PlanetHolder {
        public TextView planetName;
        public TextView distView;
        public TextView valuta;
        public CheckBox chkBox;
        public EditText edit;
        //public String quantità;
        public boolean checked;
        public TextView id;
    }

    @Override
    public int getCount() {
        return planetList.size();
    }

    @Override
    public Planet getItem(int position) {
        return planetList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return planetList.get(position).getId();
    }


    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {

        View row = convertView;
        PlanetHolder holder = null;

        if (row == null) {
            LayoutInflater inflater = ((Activity) context).getLayoutInflater();
            row = inflater.inflate(R.layout.single_listview_item, parent, false);
            holder = new PlanetHolder();
            holder.planetName = (TextView) row.findViewById(R.id.name);
            holder.distView = (TextView) row.findViewById(R.id.dist);
            holder.valuta = (TextView) row.findViewById(R.id.valuta);
            holder.chkBox = (CheckBox) row.findViewById(R.id.chk_box);
            holder.edit = (EditText) row.findViewById(R.id.editText);
            holder.edit.setVisibility(View.GONE);
            holder.edit.setEnabled(false);
            // holder.id = (TextView) row.findViewById(R.id.id);


            row.setTag(holder);

        } else {
            holder = (PlanetHolder) row.getTag();
        }
        final Planet p = planetList.get(position);
        holder.planetName.setText(p.getName());
        holder.distView.setText("" + p.getDistance());
        holder.valuta.setText("" + p.getValuta());
        holder.chkBox.setChecked(p.isSelected());
        holder.chkBox.setTag(p);
        holder.edit.setEnabled(false);
        SharedPreferences states = getContext().getSharedPreferences("states", Context.MODE_PRIVATE);
        boolean isChecked = states.getBoolean("holder.chkBox" + holder.planetName.getText().toString(), false);
        System.out.println(isChecked);
        if (isChecked) {
            holder.chkBox.setChecked(true);
            holder.edit.setVisibility(View.VISIBLE);
            holder.edit.setEnabled(true);
            SharedPreferences statess = getContext().getSharedPreferences("states", Context.MODE_PRIVATE);
            String string = statess.getString("finalHolder.edit" + holder.planetName.getText().toString(), holder.edit.getText().toString().trim());
            holder.edit.setText(string);


        } else {
            holder.chkBox.setChecked(false);
            holder.edit.setVisibility(View.GONE);
            holder.edit.setEnabled(false);


        }


        final PlanetHolder finalHolder = holder;


        holder.chkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if (finalHolder.chkBox.isChecked()) {
                    finalHolder.edit.setVisibility(View.VISIBLE);
                    finalHolder.edit.setEnabled(true);
                    SharedPreferences states = getContext().getSharedPreferences("states", Context.MODE_PRIVATE);
                    SharedPreferences.Editor editor = states.edit();
                    editor.putBoolean("holder.chkBox" + finalHolder.planetName.getText().toString(), true);
                    editor.commit();
                    //Utility.putPizzaItem(p);
                    //Utility.getPizzaItem(p);


                } else {
                    SharedPreferences states = getContext().getSharedPreferences("states", Context.MODE_PRIVATE);
                    SharedPreferences.Editor editor3 = states.edit();
                    finalHolder.edit.setVisibility(View.GONE);
                    finalHolder.edit.setEnabled(false);
                    finalHolder.edit.setText("");
                    editor3.putBoolean("holder.chkBox" + finalHolder.planetName.getText().toString(), false);
                    editor3.commit();


                }
               /* SharedPreferences states = getContext().getSharedPreferences("states", Context.MODE_PRIVATE);
                SharedPreferences.Editor editor = states.edit();
                editor.apply();*/

            }
        });
        /*holder.chkBox.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (finalHolder.chkBox.isChecked()) {
                    finalHolder.edit.setVisibility(View.VISIBLE);
                    finalHolder.edit.setEnabled(true);
                    SharedPreferences states = getContext().getSharedPreferences("states", Context.MODE_PRIVATE);
                    SharedPreferences.Editor editor = states.edit();
                    editor.putBoolean("holder.chkBox", true);
                    //pizzaSelected.put(p.getId(), p);
                    System.out.println(p.getId());
                } else {

                    finalHolder.edit.setVisibility(View.GONE);
                    finalHolder.edit.setEnabled(false);
                    finalHolder.edit.setText(null);
                    pizzaSelected.remove(p.getId());

                }

            }
        });
*/


        finalHolder.edit.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
            }

            @Override
            public void afterTextChanged(Editable s) {
                p.setQuantità(finalHolder.edit.getText().toString().trim());
                SharedPreferences states = getContext().getSharedPreferences("states", Context.MODE_PRIVATE);
                SharedPreferences.Editor editor = states.edit();
                editor.putString("finalHolder.edit" + finalHolder.planetName.getText().toString(), finalHolder.edit.getText().toString().trim());
                editor.commit();


            }
        });


        //holder.planetName.setText(p.getName());
        //holder.distView.setText("" + p.getDistance());
        //holder.valuta.setText("" + p.getValuta());
        // holder.chkBox.setChecked(p.isSelected());
        // holder.chkBox.setTag(p);
        // holder.edit.setEnabled(false);
        //  holder.id.setId(p.getId());


        return row;
    }

    ArrayList<Planet> getBox() {
        ArrayList<Planet> box = new ArrayList<Planet>();
        for (Planet p : planetList) {
            if (p.isSelected())
                box.add(p);
        }
        return box;
    }



    }

FRAGMENT OF PLANET ADAPTER:

public class MyListFragment extends Fragment implements
        android.widget.CompoundButton.OnCheckedChangeListener {

    ListView lv;
    ArrayList<Planet> planetList;
    PlanetAdapter plAdapter;
    BirraAdapter biAdapter;
    PlanetAdapter.PlanetHolder holder;




    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_list2, container, false);

        /*Button mButton = (Button) rootView.findViewById(R.id.button);
        mButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                showResult(v);


            }
        });*/
        //return inflater.inflate(R.layout.fragment_list2, container, false);
        return rootView;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);


        lv = (ListView)getView().findViewById(R.id.listview);
        displayPlanetList();


    }


    private void displayPlanetList() {

        planetList = new ArrayList<Planet>();
        planetList.add(new Planet("Margherita", 6, "€",1));
        planetList.add(new Planet("Diavola", 7,"€",2));
        planetList.add(new Planet("Bufalina", 5,"€",3));
        planetList.add(new Planet("Marinara", 5, "€",4));
        planetList.add(new Planet("Viennese", 4, "€", 5));

        plAdapter = new PlanetAdapter(planetList, getActivity()) {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

                int pos = lv.getPositionForView(buttonView);
                if (pos != ListView.INVALID_POSITION) {
                    Planet p = planetList.get(pos);
                    p.setSelected(isChecked);


            /*Toast.makeText(
                getActivity(),
                "Clicked on Pizza: " + p.getName() + ". State: is "
                        + isChecked, Toast.LENGTH_SHORT).show();*/
                }


            }
        };

        lv.setAdapter(plAdapter);
    }

}

THREE FRAGMENT:

public class ThreeFragment extends Fragment implements
        android.widget.CompoundButton.OnCheckedChangeListener {

    ListView lv2;
    ArrayList<Birra> birraList;
    BirraAdapter biAdapter;
    PlanetAdapter plAdapter;
    Planet p;


    BirraAdapter.BirraHolder birraHolder;
    PlanetAdapter.PlanetHolder holder;


    public ThreeFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_three, container, false);

        Button mButton = (Button) rootView.findViewById(R.id.button2);
        mButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                showResult(v);


            }
        });
        //return inflater.inflate(R.layout.fragment_list2, container, false);
        return rootView;
    }


    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        lv2 = (ListView) getView().findViewById(R.id.listview2);
        displayBirraList();
    }


    private void displayBirraList() {

        birraList = new ArrayList<Birra>();
        birraList.add(new Birra("Paulaner", 6, "€"));
        birraList.add(new Birra("Forst", 7, "€"));
        birraList.add(new Birra("Peroni", 5, "€"));
        birraList.add(new Birra("Corona", 5, "€"));
        birraList.add(new Birra("Nastro Azzurro", 4, "€"));
        biAdapter = new BirraAdapter(birraList, getContext()) {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                int pos = lv2.getPositionForView(buttonView);
                if (pos != ListView.INVALID_POSITION) {
                    Birra b = birraList.get(pos);
                    b.setSelected(isChecked);


            /*Toast.makeText(
                getActivity(),
                "Clicked on Pizza: " + p.getName() + ". State: is "
                        + isChecked, Toast.LENGTH_SHORT).show();*/
                }


            }


        };
        lv2.setAdapter(biAdapter);
    }


    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {


        /*int pos = lv.getPositionForView(buttonView);
        if (pos != ListView.INVALID_POSITION) {
            Planet p = planetList.get(pos);
            p.setSelected(isChecked);


            *//**//**//**//*Toast.makeText(
                getActivity(),
                "Clicked on Planet: " + p.getName() + ". State: is "
                        + isChecked, Toast.LENGTH_SHORT).show();*//**//**//**//*
        }
*/
    }


    public void showResult(View v) {
        String result = "Selected Product are :";
        int totalAmount = 0;
        String c = "";

        for (Birra b : biAdapter.getBox()) {

            if (b.selected) {

                result += "\n" + b.name + " " + b.distance + "€" + "q.tà :" + b.getQuantità();
                int quantitaInt = Integer.parseInt(b.getQuantità());
                totalAmount += b.distance * quantitaInt;
                //a=String.valueOf(totalAmount);


            }
        }
        for (Planet p : plAdapter.getBox()) {
            if (p.isSelected()) {


                result += "\n" + p.getName() + " " + p.getDistance() + "€" + "q.tà :" + p.getQuantità();
                int quantitaInt = Integer.parseInt(p.getQuantità());
                //totalAmount2+=p.distance * quantitaInt;
                //z=String.valueOf(totalAmount2);


            }


            for (Birra b : biAdapter.getBox()) {
                if (b.selected) {

                    result += "\n" + b.name + " " + b.distance + "€" + "q.tà :" + b.getQuantità();
                    int quantitaInt = Integer.parseInt(b.getQuantità());
                    totalAmount += b.distance * quantitaInt;
                    c = String.valueOf(totalAmount);


                }
            }
            Toast.makeText(getActivity(), result + "\n" + "Total Amount:=" + totalAmount + "€", Toast.LENGTH_LONG).show();
            Bundle bun2 = new Bundle();
            bun2.putString("scelta2", result);
            TwoFragment fgsearch2 = new TwoFragment();
            fgsearch2.setArguments(bun2);
            android.support.v4.app.FragmentTransaction transaction2 = getActivity().getSupportFragmentManager().beginTransaction();
            transaction2.replace(R.id.content_main, fgsearch2);
            transaction2.commit();


            Bundle bun = new Bundle();
            bun.putString("totale2", c);
            TwoFragment fgsearch = new TwoFragment();
            fgsearch.setArguments(bun);
            android.support.v4.app.FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
            transaction.replace(R.id.content_main2, fgsearch);
            transaction.commit();

        }


    }
}

THIS IS MY APP:

enter image description here

enter image description here

解决方案

PlAdapter has not been initialized. You have to initialize it before this line:for (Planet p : plAdapter.getBox()) { hence the null pointer exception Preferably, initialize in OnCreateView()

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