java - 如何从android数据库中删除选中的项目？

Question

您好，我想从数据库中删除所选项目。我的代码是

  **Deletion.java**

  package com.my.project;
  import java.util.ArrayList;
  import android.app.Activity;
  import android.content.Intent;
 import android.content.SharedPreferences;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
  impor t android.os.Bundle;
  import android.preference.PreferenceManager;
 import android.view.Menu;
 import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
  import android.widget.AdapterView;
 import android.widget.AdapterView.OnItemClickListener;
 import android.widget.ArrayAdapter;
 import android.widget.ListView;
 import android.widget.Spinner;
 import android.widget.Toast;
 import android.widget.AdapterView.OnItemSelectedListener;

 public class Deletion extends Activity
{
SharedPreferences my_Shared_Data;
SQLiteDatabase myDelete=null;
String DataBase_Name="deletedata";
String Table_Name="deletedetails";
Cursor c1,c2;
ListView lv1;
ArrayList<String> nameArray;
Spinner deleterecord;
ArrayAdapter<String> deleteAdapter;
private static String[] aname;

 @Override
    public void onCreate(Bundle savedInstanceState)
    {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.delete);

         lv1=(ListView)findViewById(R.id.list);
         try{
             myDelete=this.openOrCreateDatabase(DataBase_Name, MODE_PRIVATE, null);
                System.out.println("databse has been creates.....");
                myDelete.execSQL("create table if not exists " +Table_Name+ "(name varchar(50))");
                System.out.println("table has been created.....");
                c1=myDelete.rawQuery("select * from "+Table_Name , null);
                c1.moveToFirst();
                int count1=c1.getCount();
                System.out.println("columns --->"+count1);
                if(count1==1)
                {
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('asha')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('karthick')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('arunthathi')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('vasanth')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('nithyakavini')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('abhimanyu')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('charles')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('samyuktha')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('vijayalayan')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('samantha')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('shasvathi')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('yazhini')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('kannan')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('mirunalini')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('adhavan')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('subhathra')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('muhammad')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('mayadevi')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('bhazeer')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('aadhityaa')");
                    myDelete.execSQL("insert into "+Table_Name+ "(name)" +"values('vijaynarayanan')");

                    System.out.println("data has been inserted.....");
                }

                c2=myDelete.rawQuery("select * from "+Table_Name , null);
                c2.moveToFirst();
                int count2=c2.getCount();
                aname=new String[count2];
                System.out.println("columns --->"+count2);
                //final int column1=c2.getColumnIndex("name");
                nameArray= new ArrayList<String>();
                for(int i=0;i<count2;i++)
                {
                    aname[i]=c2.getString(c2.getColumnIndex("name"));
                    c2.moveToNext();
                    nameArray.add(aname[i]);
                    //System.out.println(aname[i]);

                }
                 for( int j = 0 ; j < nameArray.size();j++)
                    {

                        System.out.println(nameArray.get(j));
                    }


                 lv1.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,nameArray));
                 lv1.setTextFilterEnabled(true);
                 lv1.setOnItemClickListener(new OnItemClickListener()
                 {

                 public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3)
                 {

                 }
                 });
                 }
         catch (Exception e) 
            {
                e.printStackTrace();
            }}
                 @Override
                    public boolean onCreateOptionsMenu(Menu menu)
                    {
                        MenuInflater inflater = getMenuInflater();
                        inflater.inflate(R.menu.menu, menu);
                        return true;
                    }

                    @Override
                    public boolean onOptionsItemSelected(MenuItem item) 
                    {
                        switch (item.getItemId()) 
                        {
                            case R.id.delete:     Toast.makeText(this, "You pressed the delete menu!", Toast.LENGTH_SHORT).show();
                            Intent myIntent = new Intent(Deletion.this,DeleteData.class);
                            setResult(Activity.RESULT_OK);
                            myIntent.putExtra("my_name", nameArray);
                            finish();
                            startActivity(myIntent);
                                                break;
                            case R.id.cancel: Toast.makeText(this, "You pressed the icon and text!", Toast.LENGTH_SHORT).show();
                                                break;
                        }
                        return true;

    }    

  }

上面的java类在 ListView 中显示数据库项目。现在要选择要删除的项目。

   **DeleteData.java**

   package com.my.project;
   import java.util.ArrayList;
   public class DeleteData extends Activity 
   {

private static String[] select_data;
private static String[] data_base_data;
ArrayList<String> data_base_Array;
 ArrayList<String> my_name1;
 ListView lv2;
 Button delete;
 @Override
    public void onCreate(Bundle savedInstanceState)
    {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.deletedata);

         delete = (Button)findViewById(R.id.getchoice);

         Intent sender=getIntent();
         my_name1= new ArrayList<String>();
         my_name1=this.getIntent().getStringArrayListExtra("my_name");
         for( int k = 0 ; k < my_name1.size();k++)
            {

                System.out.println(my_name1.get(k));
            }
         lv2=(ListView)findViewById(R.id.deletelist);
         final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_multiple_choice,my_name1);

        // lv2.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_multiple_choice,my_name1));
         lv2.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
         lv2.setAdapter(adapter);

         lv2.setTextFilterEnabled(true);

         lv2.setOnItemClickListener(new OnItemClickListener()
         {

         public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3)
         {

         }
         });


          delete.setOnClickListener(new View.OnClickListener()
          {               
             @Override
             public void onClick(View v) 
             {  
                  String selected = "";
                   int cntChoice = lv2.getCount();
                   System.out.println(cntChoice);
                   my_name1= new ArrayList<String>();
                   SparseBooleanArray sparseBooleanArray = lv2.getCheckedItemPositions();
                   for(int i = 0; i < cntChoice; i++)
                   {
                        if(sparseBooleanArray.get(i)) 
                        {      
                          selected += lv2.getItemAtPosition(i).toString() + "\n";
                        //  adapter.remove(selected);
                        /*  select_data[i]=lv2.getItemAtPosition(i).toString();
                          my_name1.add(select_data[i]);*/
                         }
                  }
                  /* for( int j = 0 ; j < my_name1.size();j++)
                    {

                        System.out.println("checked data-->"+my_name1.get(j));
                    }*/

                 System.out.println("seleted items for deletion"+selected);
                 Toast.makeText(DeleteData.this,selected,Toast.LENGTH_LONG).show();
                 for(int i=0;i<cntChoice;i++)
                 {
                     System.out.println(i);                      
                 }

              }});
    }

        }
     }

显示 toast 中选中的项目。现在我想删除选定的项目。我无法将此选定的项目存储到数组列表中。我该怎么做？有人帮助我吗？提前致谢。

Answer 1

您使用这些“选定”项目的方法是不正确的。您应该在 ListView 中找到复选框，单击完成或返回后，这些项目应该在 ListView 中找到。

意味着所有被选择的项目(理想情况下你会在运行时通过列表跟踪它)，然后单击“完成”，然后你提交并从 ListView 的适配器中删除所有这些项目，然后通知 ListView 数据已完成改变了。

您当前迭代它们的方法不是一个好方法，您应该使用每个项目映射到指向数据库中特定行的特定 ID 的事实。

使用此列表并根据需要删除行。