Android Studio ListView更改项

有人可以帮助我更改列表视图中项目的名称吗?我不知道该怎么做。我正在使用SQLite数据库,这是我的更新名称:

public void doneName(String finishedName,int id,String oldName)
    {

        SQLiteDatabase db = this.getwritabledatabase();
        String query = "UPDATE " + TABLE_NAME + " SET " + COL2 + " = '" + finishedName + "' WHERE " + COL1 +
                " = '" + id + "'" + " AND " + COL2 + " = '" + oldName + "'";
        db.execSQL(query );
    }

在我的活动之后,我将onItemClicklistener设置为应更改名称的位置,但没有更改,它仅显示吐司:

            @Override
            public void onItemClick(AdapterView<?> parent,View view,int position,long id) {
                String name = parent.getItemAtPosition(position).toString();
                Cursor cursor =th.getItemID(name);
                int itemID = -1;
                while(cursor.moveToNext())
                {
                    itemID = cursor.getInt(0);
                }
                if(itemID>-1) {
                    String item = "Done";
                    th.doneName(item,selectedID,selectedName);
                    Toast.makeText(HomePageactivity.this,"You have accomplished this task!",Toast.LENGTH_SHORT).show();
                }}
        });

gary1968 回答:Android Studio ListView更改项

恐怕您不会更新相关适配器项的实例。 如果您具有与此ListView适配器一起附加的字符串列表,则应使用想要显示的名称在相关位置初始化String项。然后调用Adapter.notifyDataSetChanged刷新具有更新列表的ListView中的所有UI元素。

看来,您永远不会更新适配器列表中的String实例

,

您的问题有两个方面。

  1. 首先,您不是从数据库中提取更新的数据(您可以假设基础数据已被更新,这是有风险的)。
  2. 您没有使用更改刷新Listview,因此它显示了它知道的数据。

我建议利用 CursorAdapter 来简化事务,因为Cursor Adapters是为与Cursor一起使用而设计的,并且由于Cursor通常位于适当的位置,因此它们尤其使所有数据都可以通过adpater轻松获得。行(例如,使用onItemClick和onItemLongClick时)

下面是一个基于您的代码的示例,该代码利用 SimpleCursorAdapter 来更改单击列表中的项目时的数据库和列表视图(以演示单击同一行而不是将测试更改为完成后,文本会反转,因此每次点击都会翻转。

但是,要使用Cursor Adapoter,您必须必须有一个名为 _id 的列,并且该列应该是唯一的整数(应为长整数,而不是int),并且通常,它是rowid的别名(即使用_id INTEGER PRIMARY KEY定义(带或不带AUTOINCREMENT,最好不带)。因此,存在一个常量BaseColumns._ID,其中包含值 _id

在这种情况下,首先 DatabaseHelper (SQLiteOpenHelper的子类) DatabaseHelper.java :-

public class DatabaseHelper extends SQLiteOpenHelper {

    public static final String DBNAME = "mydb";
    public static final  int DBVERSION = 1;

    public static final String TABLE_NAME = "mytable";
    /*<<<<<<<<<< id column must be _id (BaseColumns._ID) for Cursor Adapters >>>>>>>>>*/
    public static final String COLID = BaseColumns._ID;
    public static final String COL1 = "mycol1";
    public static final String COL2 = "mycol2";

    public DatabaseHelper(@Nullable Context context) {
        super(context,DBNAME,null,DBVERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "(" +
                COLID + " INTEGER PRIMARY KEY," +
                COL1 + " TEXT," +
                COL2 + " TEXT " +
                ")"
        );
    }

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

    }

    public long insert(String col1,String col2) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues cv = new ContentValues();
        cv.put(COL1,col1);
        cv.put(COL2,col2);
        return db.insert(TABLE_NAME,cv);
    }

    public int doneName(String finishedName,int id,String oldName) {

        /*
            Alternative using the update convenience method
            Based upon :-
            String query = "UPDATE " + TABLE_NAME + " SET " + COL2 + " = '" + finishedName + "' WHERE " + COL1 +
                " = '" + id + "'" + " AND " + COL2 + " = '" + oldName + "'";

                writes the SQL for you.
                protects against SQL Injection
                returns the number of rows updated
         */
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues cv = new ContentValues();
        cv.put(COL2,finishedName);
        return db.update(TABLE_NAME,cv,COLID + "=? AND " + COL2 + "=?",new String[]{String.valueOf(id),oldName});
    }

    public Cursor getAll() {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.query(TABLE_NAME,null);
    }
}
  • 三个自定义方法插入(插入一行), getAll (返回所有行的游标)和您的 doneName 方法(重写以利用更新便利性方法)。

  • 您可能会注意到没有将提取的数据转换为对象的List / ArrayList / Array的任何方法。这是因为使用游标适配器时没有必要。

活动 MainActivity.java

public class MainActivity extends AppCompatActivity {

    ListView mListView;
    DatabaseHelper th;
    Cursor csr;
    SimpleCursorAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mListView = this.findViewById(R.id.listview);
        th = new DatabaseHelper(this);
        addSomeTestData();
        manageAdapter();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        csr.close(); //<<<<<<<<<< Should always close Cursors when done with them
    }

    private void manageAdapter() {
        /* This handles but the initialisation and the refreshing of the Listview */
        /* First time it is called it initialises the Adapter and Listview */
        /* On subsequent calls it refreshes the ListView */
        csr = th.getAll();
        if (adapter == null) {
            adapter = new SimpleCursorAdapter(
                    this,android.R.layout.simple_expandable_list_item_2,csr,new String[]{
                            DatabaseHelper.COL1,DatabaseHelper.COL2
                    },new int[]{
                            android.R.id.text1,android.R.id.text2},0
            );
            mListView.setAdapter(adapter);
            mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent,View view,int position,long id) {
                    if (th.doneName(
                            /* reverses string to test multiple updates of the same row */
                            new StringBuilder(csr.getString(csr.getColumnIndex(DatabaseHelper.COL2))).reverse().toString()
                            /* "Done" */,(int )id /* NOTE ID IS PASSED to onItemClick FOR CURSOR ADAPTER */,csr.getString(csr.getColumnIndex(DatabaseHelper.COL2)) /* NOTE Oldname isn't required as ID will identify the row */
                    ) > 0) {
                        manageAdapter(); //<<<<<<<<< after updating refresh the Cursor and the ListView
                        Toast.makeText(view.getContext(),"Updated OK.",Toast.LENGTH_SHORT).show();
                    } else {
                        Toast.makeText(view.getContext(),"Not Updated!!!",Toast.LENGTH_SHORT).show();
                    }
                }
            });
        } else {
            adapter.swapCursor(csr);
        }
    }

    private void addSomeTestData() {
        //Add some data but only if none exists
        if (DatabaseUtils.queryNumEntries(th.getWritableDatabase(),DatabaseHelper.TABLE_NAME) > 0) return;
        th.insert("TEST1 COL1","TEST1 COL2");
        th.insert("TEST2 COL1","TEST2 COL2");
        th.insert("TEST3 COL1","TEST3 COL2");
        th.insert("TEST4 COL1","TEST4 COL2");
        th.insert("TEST5 COL1","TEST5 COL2");
    }
}
  • 请注意,您可以将自己的布局与SimpleCursorAdapter一起使用(第4个(String [])和第5个(int [])用于指定数据来自的列以及ID的ID)数据进入的各个视图)

结果:-

最初运行时,您会得到:-

enter image description here

单击一行,您会得到:-

enter image description here

如果您随后单击所有行,则会得到:-

enter image description here

以此类推。

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