java - 从RecyclerView Adapter类保存CheckBox状态

所以我想通过SharedPreferences在RecyclerView适配器类中保存CheckBox状态，如下所示：

checkBox.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (checkBox.isChecked()){
                        title.setPaintFlags(title.getPaintFlags() | Paint.STRIKE_THRU_TEXT_FLAG);
                        title.setAlpha(0.5f);
                        PreferenceManager.getDefaultSharedPreferences(c).edit().putBoolean("checkBox", checkBox.isChecked()).commit();
                    } else if (!checkBox.isChecked()){
                        title.setPaintFlags(0);
                        title.setAlpha(0.8f);
                        PreferenceManager.getDefaultSharedPreferences(c).edit().putBoolean("checkBox", checkBox.isChecked()).commit();
                    }
                }
            });

不要介意油漆标志。

我正在这样的活动中检索数据（在onCreate中）：

 checkBox = (CheckBox) findViewById(R.id.checkBoxDoneOrNotNaListi);
        boolean checked = PreferenceManager.getDefaultSharedPreferences(this).getBoolean("checkBox", false);
        checkBox.setChecked(checked);

并获取NullPointerException

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.CheckBox.setChecked(boolean)' on a null object reference

我做错了什么？

最佳答案

/**
 * save selected <position, checkBoxState>
 */
private SparseBooleanArray mSelectedItem = new new SparseBooleanArray(listData.size());
/**
 * true: allow checkbox change, else otherwise
 * purpose update checkbox state on bind data
 */
private boolean isAllowOnCheckChange = true;

@onBindViewHolder

isAllowOnCheckChange = false;
itemHolder.checkBox.setChecked(mSelectedItem.get(position));
isAllowOnCheckChange = true;
itemHolder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton compoundButton, boolean isChecked) {
                if (isAllowOnCheckChange)
                    mSelectedItem.put(position, isChecked);
            }
        });