如何使用sqlite数据库保存此列表？

gopyfrb3  于 2021-07-14  发布在  Java
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所以我最近才了解sqlite数据库，我真的很想在我的应用程序中实现它。我已经试了三天了，但都是徒劳的。。。所以我这里有一个子任务列表，它由一个子任务名（textview），两个图像视图组成，向用户显示任务的优先级和时间消耗（用户之前通过单选按钮输入），最后是一个delete按钮。当用户在列表中输入元素时，我想使用sqlite数据库保存这个列表。另外，我想删除按钮的功能与数据库协调。。。我该怎么办？
这是我的列表适配器的代码：

// full subtask adapter code

package com.example.taskmasterv3;

import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.database.SQLException;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

import java.util.ArrayList;

public class SubtaskAdapter extends ArrayAdapter<subtask> {

    private final Context context;
    private ArrayList<subtask> values;

    public SubtaskAdapter(Context context, ArrayList<subtask> list) {

        //since your are using custom view,pass zero and inflate the custom view by overriding getview

        super(context, 0 , list);
        this.context = context;
        this.values = list;

    }

    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {

        //check if its null, if so inflate it, else simply reuse it
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.subtask_item, parent, false);
        }

        //use convertView to refer the childviews to populate it with data
        TextView tvSubtaskName = convertView.findViewById(R.id.tvSubtaskName);
        ImageView ivPri = convertView.findViewById(R.id.ivPri);
        ImageView ivTime = convertView.findViewById(R.id.ivTime);
        ImageView ivDelete = convertView.findViewById(R.id.ivDelete);

        String subname = tvSubtaskName.getText().toString().trim();

        ivDelete.setTag(position);

        ivDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
            int position = (Integer) v.getTag();
            remove(values.remove(position));
            notifyDataSetChanged();

            }
        });

        tvSubtaskName.setText(values.get(position).getSubtaskName());

        if (values.get(position).isPriHigh()) {
            ivPri.setImageResource(R.drawable.priority_high);
        } else if (values.get(position).isPriMed()) {
            ivPri.setImageResource(R.drawable.priority_med);
        } else if (values.get(position).isPriLow()) {
            ivPri.setImageResource(R.drawable.priority_low);
        }

        if (values.get(position).isTimeMore()) {
            ivTime.setImageResource(R.drawable.time_symbol_more);
        } else if (values.get(position).isTimeMed()) {
            ivTime.setImageResource(R.drawable.time_symbol_med);
        } else if (values.get(position).isTimeLess()) {
            ivTime.setImageResource(R.drawable.time_symbol_less);
        }

        //return the view you inflated
        return convertView;
    }

    //to keep adding the new subtasks try the following
    public void addANewSubTask(subtask newSubTask){
        ArrayList<subtask> newvalues = new ArrayList<>(this.values);
        newvalues.add(newSubTask);
        this.values = newvalues;
        notifyDataSetChanged();

    }

    @Override
    public int getCount() {
        if (this.values.size()>11)
        {
            Toast.makeText(context, "Max subtask limit reached", Toast.LENGTH_SHORT).show();
            return 10;

        }
        else
        {
            return super.getCount();
        }
    }

}

向用户显示列表的活动的代码：

package com.example.taskmasterv3;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.widget.NestedScrollView;
import androidx.recyclerview.widget.RecyclerView;

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.text.Editable;
import android.text.InputFilter;
import android.text.Spanned;
import android.text.TextUtils;
import android.text.TextWatcher;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.ScrollView;
import android.widget.Scroller;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class TaskInfo extends AppCompatActivity {

    //Declaring variables
    EditText etWorkingHours, etWorkingMinutes, etTaskName, etWorkingMins, etWorkinghrs, etSubtaskName;
    Button btnNewSubtask;
    Button btnSaveTaskName;
    Button btnProceed;
    ImageView ivLeft, ivRight;
    TextView tvBreakTime;
    TextView tvTaskName;
    int breaktime = 10;
    final int ENTER_SUBTASK = 20;
    final int EDIT_SUBTASK = 40;
    ListView lvSubtasks;
    ArrayList<subtask> subtaskList = new ArrayList<>();
    ScrollView scrollView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_task_info);

        //Connecting XML to JAVA
        etWorkingHours = findViewById(R.id.etWorkingHours);
        etWorkingMinutes = findViewById(R.id.etWorkingMinutes);
        etTaskName = findViewById(R.id.etTaskName);
        btnNewSubtask = findViewById(R.id.btnNewSubtask);
        ivLeft = findViewById(R.id.ivLeft);
        ivRight = findViewById(R.id.ivRight);
        tvBreakTime = findViewById(R.id.tvBreakTime);
        etWorkinghrs = findViewById(R.id.etWorkingHrs);
        etWorkingMins = findViewById(R.id.etWorkingMins);
        lvSubtasks = findViewById(R.id.lvSubtasks);
        scrollView = findViewById(R.id.scrollView);
        btnSaveTaskName = findViewById(R.id.btnSaveTask);
        tvTaskName = findViewById(R.id.tvTaskName);
        btnProceed = findViewById(R.id.btnProceed);

        tvTaskName.setVisibility(View.INVISIBLE);

        if (tvTaskName.getText().equals(""))
        {
            tvTaskName.setClickable(false);
        }
        else
        {
            tvTaskName.setClickable(true);
        }

// Code for the left right arrows along with break duration
        ivRight.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if (breaktime >= 10 && breaktime < 60)
                {breaktime += 5;
                    String time = breaktime + "";
                    tvBreakTime.setText(time);}

                else
                {
                    String time = breaktime + "";
                    tvBreakTime.setText(time);
                }
            }
        });

        ivLeft.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if (breaktime > 10 && breaktime <= 60)
                {
                    breaktime -= 5;
                    String time = breaktime + "";
                    tvBreakTime.setText(time);}

                else
                {
                    String time = breaktime + "";
                    tvBreakTime.setText(time);
                }
            }
        });

        btnNewSubtask.setEnabled(false);
        btnSaveTaskName.setEnabled(false);

        //save button enabler when task name is written

        etTaskName.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) {

                btnSaveTaskName.setEnabled(!TextUtils.isEmpty(s.toString().trim()));
            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });

        btnSaveTaskName.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                tvTaskName.setVisibility(View.VISIBLE);
                tvTaskName.setText(etTaskName.getText().toString().toUpperCase().trim());
                etTaskName.setVisibility(View.GONE);
                btnSaveTaskName.setVisibility(View.GONE);
                btnNewSubtask.setEnabled(true);
            }
        });

        tvTaskName.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String tasksname = tvTaskName.getText().toString().trim();
                tvTaskName.setText("");
                etTaskName.setVisibility(View.VISIBLE);
                etTaskName.setText(tasksname);
                btnSaveTaskName.setVisibility(View.VISIBLE);
            }
        });

        btnNewSubtask.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Intent i2 = new Intent(TaskInfo.this, SubtaskActivity.class);
                startActivityForResult(i2, ENTER_SUBTASK);
                overridePendingTransition(R.anim.slide_in_up, R.anim.slide_out_up);

            }
        });

        //Applying the max min thing for which the class InputFilterMinMax is defined
        etWorkingHours.setFilters(new InputFilter[]{new InputFilterMinMax("0", "24")});
        etWorkingMinutes.setFilters(new InputFilter[]{new InputFilterMinMax("0", "59")});

        etWorkinghrs.setFilters(new InputFilter[]{new InputFilterMinMax("0", "24")});
        etWorkingMins.setFilters(new InputFilter[]{new InputFilterMinMax("0", "59")});

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == ENTER_SUBTASK)
        {
            if (resultCode == RESULT_OK)
            {

                SubtaskAdapter adapter = new SubtaskAdapter(this, subtaskList);
                assert data != null;
                String subtaskName = data.getStringExtra("subtaskName");
                boolean priHigh = data.getBooleanExtra("priHigh", false);
                boolean priMed = data.getBooleanExtra("priMed", false);
                boolean priLow = data.getBooleanExtra("priLow", false);
                boolean timeMore = data.getBooleanExtra("timeMore", false);
                boolean timeMed = data.getBooleanExtra("timeMed", false);
                boolean timeLess = data.getBooleanExtra("timeLess", false);
                lvSubtasks.setAdapter(adapter);
                subtask subtask = new subtask(subtaskName, priHigh, priMed, priLow, timeMore, timeMed, timeLess);
                subtaskList.add(subtask);
                adapter.addANewSubTask(subtask);

            }

        }

    }

    // Menu (action bar) code
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return super.onCreateOptionsMenu(menu);
    }
    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {

        switch (item.getItemId())
        {
            case (R.id.settings):
                startActivity(new Intent(this, SettingsActivity.class));
                break;
        }
        return super.onOptionsItemSelected(item);
    }

    //Class to make max and min value on the edit text of hours and minutes, so that they cant enter anything more than 24 hours, and 59 minutes
    static class InputFilterMinMax implements InputFilter {

        private int min, max;

        public InputFilterMinMax(int min, int max) {
            this.min = min;
            this.max = max;
        }

        public InputFilterMinMax(String min, String max) {
            this.min = Integer.parseInt(min);
            this.max = Integer.parseInt(max);
        }

        @Override
        public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
            try {
                int input = Integer.parseInt(dest.toString() + source.toString());
                if (isInRange(min, max, input))
                    return null;
            } catch (NumberFormatException nfe) { }
            return "";
        }

        private boolean isInRange(int a, int b, int c) {
            return b > a ? c >= a && c <= b : c >= b && c <= a;
        }
    }

}

谢谢。

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