android-listview - 如何使用单击侦听器更新和删除 SQLite 数据库中的列表视图数据？

问题描述

我是 SQLite 数据库的初学者。我在从 listView 更新和删除数据时遇到问题。当我单击我的 listView 数据时，我将我的数据插入到 listView 中，它将进入 UpdateActivity。现在我想在新的 UpdateActivity 中获取那些 listView 选择的值，以便我可以编辑或删除。怎么做。

ListDataActivity.Java

public  void loadData() {
                //Create an arraylist so that i can load the data to add in the  arraylist
                ArrayList<String> listData = new ArrayList<>();

                Cursor cursor = databaseHelper.showAllData();

        if (cursor.getCount() == 0) {
            Toast.makeText(getApplicationContext(), "no data is available", Toast.LENGTH_LONG).show();
        } else {
            while (cursor.moveToNext()) {
                listData.add(cursor.getString(1) + " \t " + cursor.getString(2));
            }
        }
                    
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.list_item, R.id.textViewId, listData);
                listView.setAdapter(adapter);

                listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
                String selectedValue = adapterView.getItemAtPosition(position).toString();

                Toast.makeText(getApplicationContext(), "Selected Value : " + selectedValue, 
               Toast.LENGTH_LONG).show();
                Intent intent = new Intent(ListDataActivity.this,UpdateActivity.class);
                startActivity(intent);

            }
        });

更新活动.Java

private DatabaseHelper databaseHelper;
    private String selectedName;
    private String selectedID;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_update);


        databaseHelper = new DatabaseHelper(this);
        SQLiteDatabase sqLiteDatabase = databaseHelper.getWritableDatabase();

        Intent receiveIntent = getIntent();

        selectedID = receiveIntent.getStringExtra("name");

        selectedName = receiveIntent.getStringExtra("surName");

当我插入数据时，我点击我的列表，它会进入这种类型的设计更新活动。我想要 UpdateActivity 中的 Clicked Listview 数据。我该如何解决？

标签： android-listviewandroid-sqlite

解决方案

现在我想在新的 UpdateActity 中获取那些列表视图选择的值，以便我可以编辑或删除。怎么做。

这是一个更新（转到 UpdateActivity）和删除（在项目的长按上）的工作示例。这使用了一个 CursorAdapter，即普通的 SimpleCursorAdapter。为 SQLite 数据使用游标适配器非常简单。

首先是DatabaseHelper：-

class DatabaseHelper extends SQLiteOpenHelper {
    public DatabaseHelper(@Nullable Context context) {
        super(context, "mydatabase", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL("CREATE TABLE IF NOT EXISTS mytable (_id INTEGER PRIMARY KEY, name TEXT, surname TEXT, phone TEXT)");
        /* Add some test data */
        add("Fred","Bloggs","0000000000",sqLiteDatabase);
        add("Jane","Doe","1111111111",sqLiteDatabase);
        add("Mary","Johnston","2222222222",sqLiteDatabase);
        add("Tom","cobboly","3333333333",sqLiteDatabase);
        add("Anne","Walker","4444444444",sqLiteDatabase);

    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }

    public long update(long id, String name, String surname, String phone) {
        long rv = 0;
        ContentValues cv = new ContentValues();
        if (name != null && name.length() > 0) cv.put("name",name);
        if (surname != null && surname.length() > 0) cv.put("surname",surname);
        if (phone != null && phone.length() > 0) cv.put("phone",phone);
        if (cv.size() > 0) rv = this.getWritableDatabase().update("mytable",cv,"_id=?",new String[]{String.valueOf(id)});
        return rv;
    }

    public long delete(long id) {
        return this.getWritableDatabase().delete("mytable","_id=?",new String[]{String.valueOf(id)});
    }

    public Cursor getAll() {
        return this.getWritableDatabase().query("mytable",null,null,null,null,null,null);
    }

    public Cursor getById(long id) {
        return this.getWritableDatabase().query("mytable",null,"_id=?",new String[]{String.valueOf(id)},null,null,null);
    }

    private long add(String name, String surname, String phone, SQLiteDatabase db) {
        ContentValues cv = new ContentValues();
        cv.put("name",name);
        cv.put("surname",surname);
        cv.put("phone",phone);
        return db.insert("mytable",null,cv);
    }

    public long add(String name, String surname, String phone) {
        return add(name,surname,phone,this.getWritableDatabase());
    }
}

重要说明游标适配器需要一个 id 列并且它被命名为_id。
注意这增加了一些测试数据。
包括所有访问方法
- getAll 返回一个包含表中所有行的游标。
- 根据传递的值更新更新，它仅用于更新值（例如，由于没有 editSurname EditText，因此传递了 null，因此姓氏保持原样。）
- getById 根据 id 返回具有所有值的游标
- 不带第 4 个参数的 add 是典型的 add，带第 4 个参数的那个是允许在 DatabaaeHelper 完全实例化之前在 onCreate 中使用。

列表数据活动

public class ListDataActivity extends AppCompatActivity {

    ListView listview;
    SimpleCursorAdapter sca;
    DatabaseHelper databaseHelper;
    Cursor cursor;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listview = this.findViewById(R.id.mylistview);
        databaseHelper = new DatabaseHelper(this);
        setOrRefreshListView();
    }

    /* handles the ListView */
    private void setOrRefreshListView() {
        cursor = databaseHelper.getAll(); /* Gets the data to be listed */
        /* If first time then setup the adapter listeners etc */
        if (sca == null) {
            sca = new SimpleCursorAdapter(
                    this,
                    android.R.layout.simple_expandable_list_item_2,
                    cursor,
                    new String[]{"name","phone"},
                    new int[]{android.R.id.text1, android.R.id.text2},
                    0
            );
            listview.setAdapter(sca); // attach the adapter to the listview
            // setup On Item Click to start the update activity passing the id
            listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                    Intent intent = new Intent(ListDataActivity.this,UpdateActivity.class);
                    intent.putExtra("my_id_extra",l);
                    startActivity(intent);
                }
            });
            // setup the on Item LONG Click to delete a row
            listview.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
                @Override
                public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
                    databaseHelper.delete(l);
                    setOrRefreshListView(); // after deletion refresh the data
                    return true;
                }
            });
        } else {
            sca.swapCursor(cursor); // if not the first time just tell the adapter the data has changed
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        setOrRefreshListView(); // refresh the listview when returning to the activity
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        cursor.close(); // clean up
    }
}

ListDataActivity 的布局（非常基本的只是一个 ListView）：-

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

    <ListView
        android:id="@+id/mylistview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/teal_200"
        >
    </ListView>

</LinearLayout>

背景设置，因此很容易看到 ListView。

更新活动：-

public class UpdateActivity extends AppCompatActivity {

    DatabaseHelper databaseHelper;
    EditText editName, editPhone;
    Button saveButtonId,showButtonId;
    long currentId;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_update);
        editName = this.findViewById(R.id.editName);
        editPhone = this.findViewById(R.id.editPhone);
        saveButtonId = this.findViewById(R.id.savebuttonId);
        showButtonId = this.findViewById(R.id.showbuttonId);
        databaseHelper = new DatabaseHelper(this);
        currentId =  this.getIntent().getLongExtra("my_id_extra",-1);
        if (currentId < 0 ) {
            // do something as invalid id passed
            finish();
        }
        showData();
        showButtonId.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                finish();
            }
        });
        saveButtonId.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                databaseHelper.update(currentId,editName.getText().toString(),null,editPhone.getText().toString());
            }
        });
    }

    private void showData() {
        Cursor cursor = databaseHelper.getById(currentId);
        if (cursor.moveToFirst()) {
            editName.setText(cursor.getString(cursor.getColumnIndex("name")));
            editPhone.setText(cursor.getString(cursor.getColumnIndex("phone")));
        }
        cursor.close();
    }
}

showData 按钮返回到 ListDataActivity （我相信这就是你想要的）。

结果：-

重新开始时：-

单击玛丽（并将号码编辑为 999999999 但不保存）：-
点击保存（同2）
点击显示：-

长按弗雷德：-

重新启动应用程序：-

android-listview - 如何使用单击侦听器更新和删除 SQLite 数据库中的列表视图数据？

问题描述

解决方案

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