通过从ListView（SQLite数据库）中的longclick来删除

Question

我尝试长时间从listview（SQLite）中删除一行。

到目前为止我能做些什么？

1. 在列表视图中按行显示所有数据。
2. 长按其中一行显示菜单（删除或更新）。

我到现在为止做不了什么？

1. 如果我长时间点击它，从行中取出id。

**删除和更新过程我尝试稍后完成，现在我只需要点击我点击的行的id。

我已经包含了相关的文件和行上长按后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

要获得所选择的行的索引中，添加以下代码为“onContextItemSelected（菜单项项目）'：

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

用下面的语句你所选择的行中的ListView的数据：

(DataProvider)listDataAdaptar.getItem(mySelectedRowIndex); 

没有ID（=数据库主键），所以你只能从表中删除所有行“UserCourse.NewCourseInfo .TABLE_NAME“，它与所选ListView行中的值匹配。我不知道你对SQL知道多少 - 所以要警告：如果一行的值匹配输入值，这行就会被删除！如果你想删除一行，也许你应该包括一个主键为表）。

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(); 
    } 



}