Android: ListView con CheckBox, popolato da database SQLite non abbastanza funzionante

Question

Come con molti altri post qui, sto cercando di creare un ListView che include un CheckBox per ogni riga e utilizzare un database SQLite per memorizzare lo stato corrente del selezione.

A partire dall'esempio http://appfulcrum.com/?p=351, che non ha funzionato come è, ho creato una semplice app che crea il database, lo popola con 20 elementi e visualizza l'elenco.

Recupera lo stato e memorizza lo stato della selezione.

MA, non mostra correttamente lo stato CheckBox se lo cambio, scorri fino all'altra estremità dell'elenco e scorri indietro. per esempio. se seleziono il primo CheckBox, scorri verso il basso e torni in cima, il CheckBox non è più impostato. Questo viene eseguito su un telefono Samsung Android 2.1.

Se torno alla schermata principale, ritorna nella lista, il CheckBox è impostato correttamente, quindi il database è stato effettivamente aggiornato.

L'esempio estende SimpleCursorAdapter e getView() richiama setChecked() con true o false in base al valore della colonna di selezione nella tabella.

Di seguito sono riportate tutte le fonti.

mi piacerebbe sicuramente apprezzare di essere detto, "Duh qui è il tuo problema ..."

CustomListViewDB.java

// src/CustomListViewDB.java 
package com.appfulcrum.blog.examples.listviewcustomdb; 

import android.app.ListActivity; 
import android.database.Cursor; 
import android.database.SQLException; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.ListView; 
import android.widget.Toast; 

public class CustomListViewDB extends ListActivity { 

    private ListView mainListView = null; 
    CustomSqlCursorAdapter adapter = null; 
    private SqlHelper dbHelper = null; 
    private Cursor currentCursor = null; 

    private ListView listView = null; 

    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.simple); 

     if (this.dbHelper == null) { 
      this.dbHelper = new SqlHelper(this); 

     } 

     listView = getListView(); 
     listView.setItemsCanFocus(false); 
     listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE); 
     //listView.setClickable(true); 

     Button btnClear = (Button) findViewById(R.id.btnClear); 
     btnClear.setOnClickListener(new OnClickListener() { 

      public void onClick(View v) { 
       Toast.makeText(getApplicationContext(), 
         " You clicked Clear button", Toast.LENGTH_SHORT).show(); 
       ClearDBSelections(); 
      } 
     }); 

     new SelectDataTask().execute(); 

     this.mainListView = getListView(); 

     mainListView.setCacheColorHint(0); 

    } 

    @Override 
    protected void onRestart() { 
     super.onRestart(); 
     new SelectDataTask().execute(); 
    } 

    @Override 
    protected void onPause() { 

     super.onPause(); 
     this.dbHelper.close(); 
    } 

    protected void ClearDBSelections() { 

     this.adapter.ClearSelections(); 

    } 

    private class SelectDataTask extends AsyncTask<Void, Void, String> { 

     protected String doInBackground(Void... params) { 

      try { 

       CustomListViewDB.this.dbHelper.createDatabase(dbHelper.dbSqlite); 
       CustomListViewDB.this.dbHelper.openDataBase(); 

       CustomListViewDB.this.currentCursor = CustomListViewDB.this.dbHelper 
         .getCursor(); 

      } catch (SQLException sqle) { 

       throw sqle; 

      } 
      return null; 
     } 

     // can use UI thread here 
     protected void onPostExecute(final String result) { 

      startManagingCursor(CustomListViewDB.this.currentCursor); 
      int[] listFields = new int[] { R.id.txtTitle }; 
      String[] dbColumns = new String[] { SqlHelper.COLUMN_TITLE }; 

      CustomListViewDB.this.adapter = new CustomSqlCursorAdapter(
        CustomListViewDB.this, R.layout.single_item, 
        CustomListViewDB.this.currentCursor, dbColumns, listFields, 
        CustomListViewDB.this.dbHelper); 
      setListAdapter(CustomListViewDB.this.adapter); 

     } 
    } 

} 

CustomSqlCursorAdapter.java

// src/CustomSqlCursorAdapter.java 

package com.appfulcrum.blog.examples.listviewcustomdb; 

import android.content.ContentValues; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.SQLException; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.CheckBox; 
import android.widget.CompoundButton; 
import android.widget.CompoundButton.OnCheckedChangeListener; 
import android.widget.SimpleCursorAdapter; 
import android.widget.TextView; 

public class CustomSqlCursorAdapter extends SimpleCursorAdapter { 
    private Context mContext; 

    private SqlHelper mDbHelper; 
    private Cursor mCurrentCursor; 

    public CustomSqlCursorAdapter(Context context, int layout, Cursor c, 
      String[] from, int[] to, SqlHelper dbHelper) { 
     super(context, layout, c, from, to); 
     this.mCurrentCursor = c; 
     this.mContext = context; 
     this.mDbHelper = dbHelper; 

    } 

    public View getView(int pos, View inView, ViewGroup parent) { 
     View v = inView; 
     if (v == null) { 
      LayoutInflater inflater = (LayoutInflater) mContext 
        .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
      v = inflater.inflate(R.layout.single_item, null); 
     } 

     if (!this.mCurrentCursor.moveToPosition(pos)) { 
      throw new SQLException("CustomSqlCursorAdapter.getView: Unable to move to position: "+pos); 
     } 

     CheckBox cBox = (CheckBox) v.findViewById(R.id.bcheck); 

     // save the row's _id value in the checkbox's tag for retrieval later 
     cBox.setTag(Integer.valueOf(this.mCurrentCursor.getInt(0))); 

     if (this.mCurrentCursor.getInt(SqlHelper.COLUMN_SELECTED_idx) != 0) { 
      cBox.setChecked(true); 
      Log.w("SqlHelper", "CheckBox true for pos "+pos+", id="+this.mCurrentCursor.getInt(0)); 
     } else { 
      cBox.setChecked(false); 
      Log.w("SqlHelper", "CheckBox false for pos "+pos+", id="+this.mCurrentCursor.getInt(0)); 
     } 
     //cBox.setOnClickListener(this); 
     cBox.setOnCheckedChangeListener(new OnCheckedChangeListener() { 

      @Override 
      public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { 

       Log.w("SqlHelper", "Selected a CheckBox and in onCheckedChanged: "+isChecked); 

       Integer _id = (Integer) buttonView.getTag(); 
       ContentValues values = new ContentValues(); 
       values.put(SqlHelper.COLUMN_SELECTED, 
         isChecked ? Integer.valueOf(1) : Integer.valueOf(0)); 
       mDbHelper.dbSqlite.beginTransaction(); 
       try { 
        if (mDbHelper.dbSqlite.update(SqlHelper.TABLE_NAME, values, "_id=?", 
          new String[] { Integer.toString(_id) }) != 1) { 
         throw new SQLException("onCheckedChanged failed to update _id="+_id); 
        } 
        mDbHelper.dbSqlite.setTransactionSuccessful(); 
       } finally { 
        mDbHelper.dbSqlite.endTransaction(); 
       } 

       Log.w("SqlHelper", "-- _id="+_id+", isChecked="+isChecked); 
      } 
     }); 

     TextView txtTitle = (TextView) v.findViewById(R.id.txtTitle); 
     txtTitle.setText(this.mCurrentCursor.getString(this.mCurrentCursor 
       .getColumnIndex(SqlHelper.COLUMN_TITLE))); 

     return (v); 
    } 

    public void ClearSelections() { 
     this.mDbHelper.clearSelections(); 
     this.mCurrentCursor.requery(); 

    } 
} 

ListViewWithDBActivity.java

package com.appfulcrum.blog.examples.listviewcustomdb; 

import android.app.Activity; 
import android.os.Bundle; 

public class ListViewWithDBActivity extends Activity { 
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
    } 
} 

SqlHelper

// SqlHelper.java 

package com.appfulcrum.blog.examples.listviewcustomdb; 

import android.content.ContentValues; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.SQLException; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 
import android.database.sqlite.SQLiteQueryBuilder; 
import android.database.sqlite.SQLiteStatement; 
import android.util.Log; 

public class SqlHelper extends SQLiteOpenHelper { 
    private static final String DATABASE_PATH = "/data/data/com.appfulcrum.blog.examples.listviewcustomdb/databases/"; 

    public static final String DATABASE_NAME = "TODOList"; 

    public static final String TABLE_NAME = "ToDoItems"; 
    public static final int ToDoItems_VERSION = 1; 

    public static final String COLUMN_ID = "_id";    // 0 
    public static final String COLUMN_TITLE = "title";   // 1 
    public static final String COLUMN_NAME_DESC = "description";// 2 
    public static final String COLUMN_SELECTED = "selected"; // 3 
    public static final int COLUMN_SELECTED_idx = 3; 

    public SQLiteDatabase dbSqlite; 
    private Context mContext; 

    public SqlHelper(Context context) { 
     super(context, DATABASE_NAME, null, 1); 
     mContext = context; 
    } 

    @Override 
    public void onCreate(SQLiteDatabase db) { 
     createDB(db); 
    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     Log.w("SqlHelper", "Upgrading database from version " + oldVersion 
       + " to " + newVersion + ", which will destroy all old data"); 

     db.execSQL("DROP TABLE IF EXISTS ToDoItems;"); 

     createDB(db); 
    } 

    public void createDatabase(SQLiteDatabase db) { 
     createDB(db); 
    } 

    private void createDB(SQLiteDatabase db) { 
     if (db == null) { 
      db = mContext.openOrCreateDatabase(DATABASE_NAME, 0, null); 
     } 

     db.execSQL("CREATE TABLE IF NOT EXISTS ToDoItems (_id INTEGER PRIMARY KEY, title TEXT, " 
       +" description TEXT, selected INTEGER);"); 
     db.setVersion(ToDoItems_VERSION); 

     // 
     // Generate a few rows for an example 
     // 
     // find out how many rows already exist, and make sure there's some minimum 
     SQLiteStatement s = db.compileStatement("select count(*) from ToDoItems;"); 

     long count = s.simpleQueryForLong(); 
     for (int i = 0; i < 20-count; i++) { 
      db.execSQL("INSERT INTO ToDoItems VALUES(NULL,'Task #"+i+"','Description #"+i+"',0);"); 
     } 
    } 

    public void openDataBase() throws SQLException { 
     String myPath = DATABASE_PATH + DATABASE_NAME; 

     dbSqlite = SQLiteDatabase.openDatabase(myPath, null, 
       SQLiteDatabase.OPEN_READWRITE); 
    } 

    @Override 
    public synchronized void close() { 
     if (dbSqlite != null) 
      dbSqlite.close(); 

     super.close(); 
    } 

    public Cursor getCursor() { 
     SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder(); 

     queryBuilder.setTables(TABLE_NAME); 

     String[] asColumnsToReturn = new String[] { COLUMN_ID, COLUMN_TITLE, 
       COLUMN_NAME_DESC, COLUMN_SELECTED }; 

     Cursor mCursor = queryBuilder.query(dbSqlite, asColumnsToReturn, null, 
       null, null, null, COLUMN_ID+" ASC"); 

     return mCursor; 
    } 

    public void clearSelections() { 
     ContentValues values = new ContentValues(); 
     values.put(COLUMN_SELECTED, 0); 
     this.dbSqlite.update(SqlHelper.TABLE_NAME, values, null, null); 
    } 
} 

Start.java

//src/Start.java 
package com.appfulcrum.blog.examples.listviewcustomdb; 

import android.app.Activity; 
import android.content.Intent; 
import android.os.Bundle; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.Toast; 

public class Start extends Activity { 
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

     Button btnSimple = (Button) findViewById(R.id.btnSimple); 
     btnSimple.setOnClickListener(new OnClickListener() { 

      public void onClick(View v) { 

       Toast.makeText(getApplicationContext(), 
         " You clicked ListView From DB button", Toast.LENGTH_SHORT).show(); 

       Intent intent = new Intent(v.getContext(), CustomListViewDB.class); 
       startActivityForResult(intent, 0); 
      } 
     }); 

    } 
} 

layout/main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/buttonlayout" android:orientation="vertical" 
    android:layout_width="fill_parent" android:layout_height="fill_parent" 
    android:gravity="left|top" android:paddingTop="2dp" 
    android:paddingBottom="2dp"> 

    <TextView android:id="@+id/txtTest" android:layout_width="fill_parent" 
     android:layout_height="wrap_content" android:textStyle="bold" 
     android:text="@string/app_name" android:textSize="15sp" 
     android:textColor="#FF0000" android:gravity="center_vertical" 
     android:paddingLeft="5dp"> 
    </TextView> 

    <Button android:id="@+id/btnSimple" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:textSize="15sp" 
     android:text="Listview from DB" 
     android:textColor="#000000" 
     > 
    </Button> 

</LinearLayout> 

layout/simple.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" android:layout_width="fill_parent" 
    android:layout_height="fill_parent"> 

    <LinearLayout android:id="@+id/buttonlayout" 
     android:orientation="horizontal" android:layout_width="fill_parent" 
     android:layout_height="wrap_content" android:height="32dp" 
     android:gravity="left|top" android:paddingTop="2dp" 
     android:paddingBottom="2dp"> 

     <LinearLayout android:id="@+id/buttonlayout2" 
      android:orientation="horizontal" android:layout_height="wrap_content" 
      android:gravity="left|center_vertical" android:layout_width="wrap_content" 
      android:layout_gravity="left|center_vertical"> 

      <TextView android:id="@+id/txtTest" 
       android:layout_width="fill_parent" 
       android:layout_height="fill_parent" android:textStyle="bold" 
       android:text="@string/list_header" android:textSize="15sp" 
       android:gravity="center_vertical" android:paddingLeft="5dp"> 
      </TextView> 

      <Button android:id="@+id/btnClear" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" android:text="Clear" 
       android:textSize="15sp" android:layout_marginLeft="10px" 
       android:layout_marginRight="10px" 
       android:layout_marginBottom="2px" 
       android:layout_marginTop="2px" android:height="15dp" 
       android:width="70dp"></Button> 
     </LinearLayout> 
    </LinearLayout> 

    <TableLayout android:id="@+id/TableLayout01" 
     android:layout_width="fill_parent" android:layout_height="fill_parent" 
     android:stretchColumns="*"> 
     <TableRow> 
      <ListView android:id="@android:id/list" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content"></ListView> 
     </TableRow> 

    </TableLayout> 

</LinearLayout> 

layout/single_item.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" android:layout_height="wrap_content" 
    android:orientation="horizontal" android:gravity="center_vertical"> 

    <CheckBox android:id="@+id/bcheck" 
       android:layout_width="wrap_content" 
       android:layout_height="fill_parent" /> 

     <TextView android:id="@+id/txtTitle" 
      android:layout_width="wrap_content" android:gravity="left|center_vertical" 
      android:layout_height="?android:attr/listPreferredItemHeight" 
      android:layout_alignParentLeft="true" 
      android:textSize="20sp" android:text="Test" 
      android:textStyle="bold" android:paddingLeft="5dp" 
      android:paddingRight="2dp" android:focusable="false" 
      android:focusableInTouchMode="false"></TextView> 
     <LinearLayout android:layout_width="fill_parent" 
      android:layout_height="wrap_content" android:orientation="horizontal" 
      android:gravity="right|center_vertical"> 
     </LinearLayout> 

</LinearLayout> 

valori/le stringhe.xml

<?xml version="1.0" encoding="utf-8"?> 
<resources> 
    <string name="hello">Hello World, ListViewWithDBActivity!</string> 
    <string name="app_name">ListViewWithDB</string> 
    <string name="list_header">List Headers</string> 
</resources> 

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    android:versionCode="1" android:versionName="1.0"  
    package="com.appfulcrum.blog.examples.listviewcustomdb"> 

    <application android:icon="@drawable/icon" 
     android:label="@string/app_name" 
     android:theme="@android:style/Theme.NoTitleBar"> 
     > 
     <activity android:name=".Start" android:label="@string/app_name"> 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 
       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
     <activity android:name=".CustomListViewDB"></activity> 
    </application> 

    <uses-sdk android:minSdkVersion="7" /> <!-- android 1.6 --> 
</manifest> 

Se si vuole costruire, gettare un po 'icon.png arbitraria in drawable.

Grazie in anticipo.

Answer 1

Le viste in un ListView vengono riciclate e questo sembra un problema. Probabilmente hai bisogno di invalidare il tuo onCheckedChangedListener in modo che quando fai setChecked() non chiami inavvertitamente il listener precedente. Potrebbero esserci altre ramificazioni del riciclaggio, quindi tienilo a mente.

in modo da provare:

cBox.setOnCheckedChangeListener(null); 
... 
cBox.setChecked(); 
... 
cBox.setOnCheckedChangeListner(<real listener); 

Answer 2

ho trovato la soluzione più completa al problema di fuori del sito.

A Android ListView with CheckBox : Retain State

apprezzare la gente di aiuto.