Question

我正在构建一个使用SQLite数据库来保存列表项的列表应用程序。列表项由UUID，名称和布尔值组成，以确定其是否已解决（数据库将其存储为int）。我注意到的是，当用户关闭任务并添加新任务时，将重新加载列表，以便现在取消选中已检查的任务。此外，重新启动应用程序时，将重新加载列表，以便检查所有已检查的任务。

现在我一直在思考这些想法，到目前为止我所做的是onBindViewHolder（）方法中的TaskAdapter类，我调用setOnCheckedChangedListener（），以便当用户检查任务时吐司推出。我觉得我应该在这里做些什么来更新数据库中的特定任务，但我不知道如何。

附加说明：我使用单例类，我拥有所有数据库方法，例如添加任务，更新任务以及从数据库中检索所有任务。

ListFragment.java

public class ListFragment extends Fragment implements AddTaskDialog.addTask{

private static final String ADD_TASK_TAG = "ADD_TASK_DIALOG";
private RecyclerView mRecyclerView;
private TaskAdapter mAdapter;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setHasOptionsMenu(true);
}

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

    mRecyclerView = view.findViewById(R.id.recycler_view);
    LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
    mRecyclerView.setLayoutManager(layoutManager);
    updateUI();

    return view;
}

private void updateUI(){
    List<Task> tasks = TaskLab.getTaskLab(getContext()).getTaskList();

    if(mAdapter == null) {
        mAdapter = new TaskAdapter(tasks);
        mRecyclerView.setAdapter(mAdapter);
    }else{
        mAdapter.setTaskList(tasks);
        mAdapter.notifyDataSetChanged();
    }
}

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    super.onCreateOptionsMenu(menu, inflater);
    inflater.inflate(R.menu.toolbar_layout,menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    switch (item.getItemId()){
        case R.id.add_task_button:
            // Launch a dialog.
            AddTaskDialog dialog = new AddTaskDialog();
            FragmentManager manager = getFragmentManager();
            dialog.setTargetFragment(ListFragment.this,1);
            dialog.show(manager,ADD_TASK_TAG);
            return true;
        default:
            return super.onOptionsItemSelected(item);

    }
}

// Part of the addTask interface created in AddTaskDialog
@Override
public void addTask(String taskName) {
    Task task = new Task();
    task.setName(taskName);
    TaskLab.getTaskLab(getContext()).addTask(task);
    updateUI();
}
}

TaskAdapter.java

public class TaskAdapter extends RecyclerView.Adapter<TaskAdapter.TaskHolder> {

private List<Task> mTaskList;

public TaskAdapter(List<Task> tasks){
    mTaskList = tasks;
}
@Override
public TaskAdapter.TaskHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_layout,parent,false);
    return new TaskHolder(view);
}

@Override
public void onBindViewHolder(TaskAdapter.TaskHolder holder, int position) {
    Task task = mTaskList.get(position);
    holder.bindData(task);

    holder.mTaskCheckBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean isChecked) {
            if(isChecked){
                Toast.makeText(compoundButton.getContext(),"Task Solved!",Toast.LENGTH_SHORT).show();
            }
        }
    });
}

@Override
public int getItemCount() {
    return mTaskList.size();
}

public void setTaskList(List<Task> tasks) {
    mTaskList = tasks;
}

public class TaskHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

    private TextView mTaskName;
    private CheckBox mTaskCheckBox;

    public TaskHolder(View itemView) {
        super(itemView);
        mTaskName = itemView.findViewById(R.id.task_name);
        mTaskCheckBox = itemView.findViewById(R.id.task_checkbox);
    }

    private void bindData(Task task) {
        mTaskName.setText(task.getName());
        mTaskCheckBox.setChecked(task.isSolved());
    }

    @Override
    public void onClick(View view) {
    }
}


}

TaskLab.java （Singleton类）

public class TaskLab {

private static TaskLab sTaskLab;
private Context mContext;

private SQLiteDatabase mDatabase;

private TaskLab(Context context) {
    mContext = context.getApplicationContext();
    mDatabase = new TaskBaseHelper(mContext).getWritableDatabase();
}

public static TaskLab getTaskLab(Context context){
    if(sTaskLab == null) {
        sTaskLab = new TaskLab(context);
    }

    return sTaskLab;
}

// Add DataBase operation method here.

private ContentValues getContentValues(Task task) {
    ContentValues values = new ContentValues();
    values.put(TaskTable.Cols.UUID, task.getId().toString());
    values.put(TaskTable.Cols.NAME, task.getName());
    values.put(TaskTable.Cols.SOLVED, task.isSolved() ? 1 : 0);

    return values;
}

public void addTask(Task task) {
    ContentValues values = getContentValues(task);
    mDatabase.insert(TaskTable.TABLE_NAME,null,values);
}

// Don't really understand this method
public void updateTask(Task task) {
    String uuidString = task.getId().toString();
    ContentValues values = getContentValues(task);

    mDatabase.update(TaskTable.TABLE_NAME,values, TaskTable.Cols.UUID + " = ?",
            new String[] {uuidString});
}

public TaskCursorWrapper queryTasks(String whereClause, String[] whereArgs) {
    Cursor cursor = mDatabase.query(TaskTable.TABLE_NAME,null,whereClause,whereArgs,null,null,null);
    return new TaskCursorWrapper(cursor);
}

public List<Task> getTaskList(){

    List<Task> taskList = new ArrayList<>();
    TaskCursorWrapper cursor = queryTasks(null,null);

    try{
        cursor.moveToFirst();
        while(!cursor.isAfterLast()){
            Task task = cursor.getTask();
            taskList.add(task);
            cursor.moveToNext();
        }
    }finally {
        cursor.close();
    }

    return taskList;
}

Answer 1

在适配器中，当您使用onclick时，当前项目将更新，但滚动时单击复选框的位置将不匹配。因为适配器只考虑你从你的代码写的位置。所以请使用任何getter / setter来避免这个问题。

使用SQLite数据库保存CheckBox状态

1 个答案: