Question

所以我想通过RecyclerView适配器类中的SharedPreferences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();
                    }
                }
            });

不要介意油漆旗帜。

我正在检查我的活动中的数据（在onCreate中）：

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

获得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？

Answer 1

/**
 * 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);
            }
        });

Answer 2

在适配器类的onBindViewHolder()中，您可以输入以下内容：

boolean checked = PreferenceManager.getDefaultSharedPreferences(context).getBoolean("checkBox", false);
holder.checkBox.setChecked(checked);

然后你的ViewHolder应该是这样的：

public class ViewHolder extends RecyclerView.ViewHolder{
    public CheckBox checkBox;

    public ViewHolder(View itemView){
        super(itemView);
        checkBox = (CheckBox) itemView.findViewById(R.id.checkBoxDoneOrNotNaListi);
    }
}

onClickListener()看起来像这样：

checkBox.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch (position){
                    case 0:
                        PreferenceManager.getDefaultSharedPreferences(c).edit().putBoolean("checkBox0", checkBox.isChecked()).commit();
                        break;
                    case 1:
                        PreferenceManager.getDefaultSharedPreferences(c).edit().putBoolean("checkBox1", checkBox.isChecked()).commit();
                        break;
                    ...
                }
            }
        });

从RecyclerView Adapter类保存CheckBox状态

2 个答案: