从片段中的自定义 ArrayAdapter 单击 ListView 中的 'delete' 按钮从数据库中删除相应的项目

Question

我正在创建一个演示 Android 应用程序，它在片段中显示了一个 ListView。每个列表项目都有一个文本和一个删除按钮，项目存储在 SQLite 数据库中。单击删除按钮时，我无法理解如何从数据库中删除相应的项目。网上找了各种方法，都想不通如何获取DB中row item的_ID值（设置为autoincrement），从而删除该item。

自定义适配器class

public class CustomListAdapter extends ArrayAdapter<DataModel> implements View.OnClickListener{
private ArrayList<DataModel> dataSet;
Context mContext;
private TaskHelper_tab1 mHelper;

public CustomListAdapter(@NonNull Context context, int resource, @NonNull ArrayList<DataModel> data) {
    super(context, resource, data);
    this.dataSet = data;
    this.mContext=context;
}

private static class ViewHolder {
    TextView txtName;
    Button btn;
}

@Override
public void onClick(View v) {
    int position=(Integer) v.getTag();
    Object object= getItem(position);
    DataModel dataModel=(DataModel)object;
    switch (v.getId())
    {
        case R.id.task_delete:
            Snackbar.make(v, "Release date " +dataModel.getName(), Snackbar.LENGTH_LONG)
                    .setAction("No action", null).show();
            break;
    }
}
private int lastPosition = -1;

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

    // Get the data item for this position
    final DataModel dataModel = getItem(position);

    // Check if an existing view is being reused, otherwise inflate the view
    final ViewHolder viewHolder; // view lookup cache stored in tag
    final View result;

    if (convertView == null) {

        viewHolder = new ViewHolder();
        LayoutInflater inflater = LayoutInflater.from(getContext());
        convertView = inflater.inflate(R.layout.task_list_long_term_item, parent, false);
        viewHolder.txtName = (TextView) convertView.findViewById(R.id.task_title);
        viewHolder.btn = (Button) convertView.findViewById(R.id.task_delete);
        result=convertView;
        convertView.setTag(viewHolder);
        viewHolder.btn.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {

                int id2 = (int) getItemId(position);

                Toast.makeText(mContext,id2 + " Button clicked" + position,Toast.LENGTH_SHORT).show();
                deleteTask(id2);
                notifyDataSetChanged();
            }
        });
    } else {
        viewHolder = (ViewHolder) convertView.getTag();
        result=convertView;
    }
    lastPosition = position;
    viewHolder.txtName.setText(dataModel.getName());
    return convertView;
}

public void deleteTask(int position){
    mHelper = new TaskHelper_tab1(getContext());
    SQLiteDatabase db = mHelper.getWritableDatabase();
    db.execSQL("DELETE FROM " + Task_tab1.TaskEntry.TABLE + " WHERE " + Task_tab1.TaskEntry._ID + "= '" + position + "'");
    db.close();
}

}

片段代码

public class fragment_tab1 extends Fragment{
//for db tasks
EditText editText = null;
private TaskHelper_tab1 mHelper;
FloatingActionButton fab_tab1;
private PopDialog.PopDialogListener listener; //listener to pass the text to parent activity
private TextView textViewDescr;
private CustomListAdapter mAdapter;

private View view;
private ListView list_calllog;
private ArrayList<DataModel> callLog;

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

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    mHelper = new TaskHelper_tab1(getContext());
    list_calllog = (ListView) getActivity().findViewById(R.id.list);
    updateUI(); //this works -- keep this to initially populate the UI on opening app
}

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    if(view==null)
    {
        view=inflater.inflate(R.layout.fragment_tab1, container,false);
    }
    else
    {
        ViewGroup parent = (ViewGroup) view.getParent();
        parent.removeView(view);
    }

    callLog= new ArrayList<>();
    callLog.add(new DataModel("Apple Pie", null)); //maybe add button here
    callLog.add(new DataModel("Banana Bread",null ));

    CustomListAdapter adapter=new CustomListAdapter(getActivity(),R.layout.task_list_long_term_item,callLog);
    list_calllog=(ListView)view.findViewById(R.id.list);
    list_calllog.setAdapter(adapter);

    fab_tab1 = (FloatingActionButton) view.findViewById(R.id.fab_tab1);
    fab_tab1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View tab1) {
            AlertDialog.Builder alert = new AlertDialog.Builder(getContext());

            LayoutInflater inflater = getActivity().getLayoutInflater();
            View view = inflater.inflate(R.layout.pop_dialog_layout, null);

            alert.setTitle("info")
                    .setMessage("dialog box message")
                    .setView(view)
                    .setPositiveButton("ok", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {

                                    String edittext_descr = editText.getText().toString();
                                    applyTexts(edittext_descr);

                                    Toast toast = Toast.makeText(getContext(), "adadadaa", Toast.LENGTH_LONG);
                                    toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
                                    toast.show();
                                }
                            }
                    );
            alert.show();
            editText = view.findViewById(R.id.edit_text);
        }
    });
    return view;
}

@Override
public void applyTexts(String edittext_descr) {
    String task = String.valueOf(edittext_descr);
    SQLiteDatabase db = mHelper.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put(Task_tab1.TaskEntry.COL_TASK_TITLE, task);
    db.insertWithOnConflict(Task_tab1.TaskEntry.TABLE, null, values, SQLiteDatabase.CONFLICT_REPLACE);
    db.close();
    updateUI();
}

private void updateUI() {
    ArrayList<DataModel> taskList = new ArrayList<>();
    SQLiteDatabase db = mHelper.getReadableDatabase();
    Cursor cursor = db.query(Task_tab1.TaskEntry.TABLE,
            new String[] {Task_tab1.TaskEntry._ID, Task_tab1.TaskEntry.COL_TASK_TITLE}, null, null, null, null, null);

    while(cursor.moveToNext()){
        int index = cursor.getColumnIndex(Task_tab1.TaskEntry.COL_TASK_TITLE);
        //add new task
        String str = cursor.getString(index);
        DataModel dm = new DataModel(str,null );
        taskList.add(dm);
    }

    if(mAdapter == null){
        mAdapter = new CustomListAdapter(getActivity(), R.layout.task_list_long_term_item, taskList );
        list_calllog.setAdapter(mAdapter);
    } else {
        mAdapter.clear();
        mAdapter.addAll(taskList);
        mAdapter.notifyDataSetChanged();
    }
    cursor.close();
    db.close();
}

}

Answer 1

I searched for various ways online, and could not figure out how to get the _ID value (set to autoincrement) of the row item in the DB, so that the item could be deleted.

你从数据库中读数据的时候不是在查询对象的ID属性吗？如果不是，则执行此操作并存储在 DataModel 中。然后当你得到被点击的对象时，你有ID：

DataModel dataModel=(DataModel)object;

// TODO: Use dataModel.getId()

希望对您有所帮助！

从片段中的自定义 ArrayAdapter 单击 ListView 中的 'delete' 按钮从数据库中删除相应的项目

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