Question

我长时间尝试从列表视图中删除一行（SQLite）。

到目前为止我能做些什么？

按列表视图中的行显示所有数据。
长按其中一行显示菜单（删除或更新）。

直到现在我还做不到什么？

如果我长按它就从行中取出id。

**删除和更新过程我尝试稍后完成，我现在只需要获取我点击的行的ID。

我在长时间点击行后包含了相关文件和prtscrn

DataListActivity.java - ** 最相关的文件 **

package com.example.ido.grades;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.ListView;
import android.widget.Toast;
public class DataListActivity extends ActionBarActivity {
    ListView listView;
    SQLiteDatabase sqLiteDatabase;
    CourseDbHelper courseDbHelper;
    Cursor cursor;
    ListDataAdaptar listDataAdaptar;
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.data_list_layout);
        listView = (ListView) findViewById(R.id.list_view);
        listDataAdaptar = new ListDataAdaptar(getApplicationContext(),R.layout.row_layout);
        listView.setAdapter(listDataAdaptar);
        registerForContextMenu(listView);
        courseDbHelper = new CourseDbHelper(getApplicationContext());
        sqLiteDatabase = courseDbHelper.getReadableDatabase();
        cursor = courseDbHelper.getInformation(sqLiteDatabase);
        registerForContextMenu(listView);
        if (!cursor.moveToFirst()){
        }
        else {
            do {
                String year,semester,course,points,grade;
                year = cursor.getString(0);
                semester = cursor.getString(1);
                course = cursor.getString(2);
                points = cursor.getString(3);
                grade = cursor.getString(4);
                DataProvider dataProvider  = new DataProvider(year,semester,course,points,grade);
                listDataAdaptar.add(dataProvider);
            }
            while (cursor.moveToNext());
        }
    }
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_data_list, menu);

    }
    public boolean onContextItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.update_item:
                Toast.makeText(this,"update",Toast.LENGTH_LONG).show();
                return true;
            case R.id.delete_item:
                Toast.makeText(this,"delete",Toast.LENGTH_LONG).show();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
    }

data_list_layout.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    tools:context="com.example.ido.grades.DataListActivity">

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/list_view"
        ></ListView>


</RelativeLayout>

ListDataAdapter.java

  package com.example.ido.grades; 
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;

public class ListDataAdaptar extends ArrayAdapter{
        List list = new ArrayList();
    public ListDataAdaptar(Context context, int resource) {
        super(context, resource);
    }

    static class LayoutHandler{
        TextView YEAR,SEMESTER,COURSE,POINTS,GRADE;
    }
    @Override
    public void add(Object object) {
        super.add(object);
        list.add(object);
    }


    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;
        LayoutHandler layoutHandler;
        if (row == null){
            LayoutInflater layoutInflater = (LayoutInflater) this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row  = layoutInflater.inflate(R.layout.row_layout,parent,false);
            layoutHandler = new LayoutHandler();
            layoutHandler.YEAR = (TextView)row.findViewById(R.id.textYear);
            layoutHandler.SEMESTER = (TextView)row.findViewById(R.id.textSemester);
            layoutHandler.COURSE = (TextView)row.findViewById(R.id.textCourse);
            layoutHandler.POINTS = (TextView)row.findViewById(R.id.textPoints);
            layoutHandler.GRADE = (TextView)row.findViewById(R.id.textGrade);
            row.setTag(layoutHandler);
        }
        else{
            layoutHandler = (LayoutHandler) row.getTag();

        }
        DataProvider dataProvider = (DataProvider) this.getItem(position);
        layoutHandler.YEAR.setText(dataProvider.getYear());
        layoutHandler.SEMESTER.setText(dataProvider.getSemester());
        layoutHandler.COURSE.setText(dataProvider.getCourse());
        layoutHandler.POINTS.setText(dataProvider.getPoints());
        layoutHandler.GRADE.setText(dataProvider.getGrade());
        return row;
    }
}

CourseDbHelper.java

 package com.example.ido.grades;
    import android.content.ContentValues;
    import android.content.Context;
    import android.database.Cursor;
    import android.database.sqlite.SQLiteDatabase;
    import android.database.sqlite.SQLiteOpenHelper;
    import android.util.Log;

    public class CourseDbHelper extends SQLiteOpenHelper {

        private static final String DATABASE_NAME  = "COURSEINFO.DB";
        private static final int DATABASE_VERSION = 1;


        public String CREATE_QUERY = "CREATE TABLE " + UserCourse.NewCourseInfo.TABLE_NAME + "("+ UserCourse.NewCourseInfo.YEAR+" TEXT,"
                + UserCourse.NewCourseInfo.SEMESTER+" TEXT,"+ UserCourse.NewCourseInfo.COURSE+" TEXT,"+ UserCourse.NewCourseInfo.POINTS+" TEXT,"
                + UserCourse.NewCourseInfo.GRADE+" TEXT);";

        public  CourseDbHelper (Context context){

            super(context, DATABASE_NAME, null, DATABASE_VERSION);
            Log.e("DATABASE_OPERATIONS","Database created/opened...");
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL(CREATE_QUERY);
            Log.e("DATABASE_OPERATIONS", "Table created");

        }
        public void putInformation(String year, String semester, String course, String points,String grade,SQLiteDatabase db){
            ContentValues cv = new ContentValues();
            cv.put(UserCourse.NewCourseInfo.YEAR, year);
            cv.put(UserCourse.NewCourseInfo.SEMESTER, semester);
            cv.put(UserCourse.NewCourseInfo.COURSE, course);
            cv.put(UserCourse.NewCourseInfo.POINTS,points);
            cv.put(UserCourse.NewCourseInfo.GRADE, grade);
            db.insert(UserCourse.NewCourseInfo.TABLE_NAME, null, cv);
            Log.e("DATABASE_OPERATIONS", "One raw inserted");

        }

        public Cursor getInformation(SQLiteDatabase db){
            Cursor cursor;
            String[] projections = {UserCourse.NewCourseInfo.YEAR,UserCourse.NewCourseInfo.SEMESTER,
                    UserCourse.NewCourseInfo.COURSE, UserCourse.NewCourseInfo.POINTS,UserCourse.NewCourseInfo.GRADE};
              cursor=     db.query(UserCourse.NewCourseInfo.TABLE_NAME,projections,null,null,null,null,null );
            return cursor;
        }
        public void deleteInformation(String  id){

        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        }

    }

Answer 1

要获取所选行的索引，请将以下代码添加到'onContextItemSelected（MenuItem item）'：

   AdapterContextMenuInfo info = 
               (AdapterContextMenuInfo) item.getMenuInfo();`
   int mySelectedRowIndex = info.position;

使用以下语句，您将获得所选行中的ListView数据：

(DataProvider)listDataAdaptar.getItem(mySelectedRowIndex);

没有id（=数据库主键），因此您只能删除表'UserCourse.NewCourseInfo.TABLE_NAME'中与所选ListView行中的值匹配的每一行。

（我不知道你对SQL了解多少 - 所以请注意：如果行的值与输入值匹配，则行将被删除！如果你想只删除一行，你可能应该包含一个主键表）。

所以你必须改变'deleteInformation（）'方法：

public void deleteInformation(String  year, String semester, 
            String grade, String course, String points){
    SQLiteDatabase db = null;
    try
    {
         db = this.getWritableDatabase();

         String where = UserCourse.NewCourseInfo.YEAR + " = ? AND "
                  + UserCourse.NewCourseInfo.SEMESTER + " = ? AND "
                  + UserCourse.NewCourseInfo.COURSE + " = ? AND "
                  + UserCourse.NewCourseInfo.POINTS + " = ? AND "
                  + UserCourse.NewCourseInfo.GRADE + " = ?";

         int iNumberDeleted = db.delete(
                               UserCourse.NewCourseInfo.TABLE_NAME, 
                               where,
                      new String[]{year, semester, course, points, grade}
                               );
        // you might want to evaluate the number of affected rows
    }
    catch (Exception ex)
    {
        Log.d("DB_DELETE", "...your data..." + "\n" + ex.getMessage());

    }
    finally
    {
        if (db != null)
            db.close();
    }



}

从ListView（SQLite数据库）中通过longclick删除行

1 个答案: