我不知道为什么我的代码没有保存checkbox检查值;如果我检查checkbox并在点击其他标签并返回上一个标签后，checkbox未被选中...我希望您在我的代码中找到错误！
IDE对我说：FATAL EXCEPTION: main java.lang.NullPointerException at line ".onCreateView(holder.chkBox.setChecked(true);"
为什么？
ADAPTER CLASS：
public abstract class PlanetAdapter extends ArrayAdapter<Planet> implements CompoundButton.OnCheckedChangeListener{
private List<Planet> planetList;
private Context context;
ArrayList<Birra> objects;
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;
}
@Override
public View getView(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);
row.setTag(holder);
} else {
holder = (PlanetHolder) row.getTag();
}
final Planet p = planetList.get(position);
final PlanetHolder finalHolder = holder;
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 preferences = getContext().getSharedPreferences("MaterialTabs", android.content.Context.MODE_PRIVATE);
SharedPreferences.Editor mEditor = preferences.edit();
mEditor.putBoolean("CheckBox_Value", finalHolder.chkBox.isChecked());
mEditor.commit();
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 preferences = getContext().getSharedPreferences("PROJECT_NAME", android.content.Context.MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("KEY", finalHolder.edit.getText().toString().trim());
editor.commit();
}
});
} else {
finalHolder.edit.setVisibility(View.GONE);
finalHolder.edit.setEnabled(false);
finalHolder.edit.setText(null);
}
}
});
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);
return row;
}
ArrayList<Planet> getBox() {
ArrayList<Planet> box = new ArrayList<Planet>();
for (Planet p : planetList) {
if (p.selected)
box.add(p);
}
return box;
}
}
FRAGMENT：
ListView lv;
ArrayList<Planet> planetList;
PlanetAdapter plAdapter;
BirraAdapter biAdapter;
PlanetAdapter.PlanetHolder holder;
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 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, "€"));
planetList.add(new Planet("Diavola", 7,"€"));
planetList.add(new Planet("Bufalina", 5,"€"));
planetList.add(new Planet("Marinara", 5,"€"));
planetList.add(new Planet("Viennese", 4, "€"));
plAdapter = new PlanetAdapter(planetList, getContext()) {
@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);
}
}
};
lv.setAdapter(plAdapter);
}
@Override
public void onPause() {
//get the instance variables
SharedPreferences preferences = getContext().getSharedPreferences("MaterialTabs", android.content.Context.MODE_PRIVATE);
boolean mCheckBoxValue = preferences.getBoolean("CheckBox_Value", false);
if (mCheckBoxValue) {
holder.chkBox.setChecked(true);
} else {
holder.chkBox.setChecked(false);
}
super.onPause();
}
public void showResult(View v) {
String result2 = "Selected Product are :";
int totalAmount2=0;
String a="";
for (Birra b : biAdapter.getBox()){
if (b.selected){
result2 += "\n" + b.name+" "+b.distance+"€"+"q.tà :"+b.getQuantità();
int quantitaInt= Integer.parseInt(b.getQuantità());
totalAmount2+=b.distance * quantitaInt;
}
}
Toast.makeText(getActivity(), result2 + "\n" + "Total Amount:=" + totalAmount2 + "€", Toast.LENGTH_LONG).show();
}
}
答案 0 :(得分：2)
您可以在共享首选项上存储布尔值。这是一个例子。
SharedPreferences myPrefs;
SharedPreferences.Editor myPrefsPrefsEditor;
static final String MY_SHARED_PREF = "name_of_your_shared_pref";
初始化您的共享偏好
myPrefs = this.getSharedPreferences(MY_SHARED_PREF, Context.MODE_PRIVATE);
使用以下内容存储您的值。
myPrefsPrefsEditor = myPrefs.edit();
myPrefsPrefsEditor.putBoolean(key, value);
myPrefsPrefsEditor.commit();
key =用于从共享pref
中查找值value =您要存储的值
这是您阅读价值的方式
myPrefs.getBoolean(key, defaultValue);
key =您想要获得的值的关键
defaultValue =给定密钥没有值时的默认值。
希望这有帮助。
答案 1 :(得分：0)
@Override
public void afterTextChanged(Editable s) {
p.setQuantità(finalHolder.edit.getText().toString().trim());
SharedPreferences preferences = getContext().getSharedPreferences("PROJECT_NAME", android.content.Context.MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("KEY", finalHolder.edit.getText().toString().trim());
editor.putBoolean("CheckBox_Value", finalHolder.chkBox.isChecked());
editor.commit();
}
然后使用getBoolean检索它，就像你已经完成的那样
答案 2 :(得分：0)
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
checkBox = (CheckBox) findViewById(R.id.checkBox1);
SavedPreferences();
}
private void savePreferences(boolean value) {
SharedPreferences sharedPreferences = PreferenceManager
.getDefaultSharedPreferences(this);
Editor editor = sharedPreferences.edit();
editor.putBoolean(value);
editor.commit();
}
public class activity2 extends fragment{
public onCreateView extends Fragment {
SharedPreferences sharedPreferences = PreferenceManager
.getDefaultSharedPreferences(this);
boolean checkBoxValue = sharedPreferences.getBoolean("CheckBox_Value", false);
if (checkBoxValue) {
checkBox.setChecked(true);
} else {
checkBox.setChecked(false);
}
}
}