java - 如何在数据删除时自动刷新ListView

Question

我希望 ListView 在删除后自动更新。我使用 adapter.notifyDataSetChanged() 但它对我不起作用

这是我的代码

数据库助手

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final String TAG = "DatabaseHelper";

    private static final String TABLE_NAME = "people_table";
    private static final String COL1 = "ID";
    private static final String COL2 = "name";


    public DatabaseHelper(Context context) {
        super(context, TABLE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTable = "CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COL2 +" TEXT)";
        db.execSQL(createTable);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i1) {
        db.execSQL("DROP IF TABLE EXISTS " + TABLE_NAME);
        onCreate(db);
    }

    public boolean addData(String item) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(COL2, item);

        Log.d(TAG, "addData: Adding " + item + " to " + TABLE_NAME);

        long result = db.insert(TABLE_NAME, null, contentValues);

        //if date as inserted incorrectly it will return -1
        if (result == -1) {
            return false;
        } else {
            return true;
        }
    }

    /**
     * Returns all the data from database
     * @return
     */
    public Cursor getData(){
        SQLiteDatabase db = this.getWritableDatabase();
        String query = "SELECT * FROM " + TABLE_NAME;
        Cursor data = db.rawQuery(query, null);
        return data;
    }

    public Cursor getItemID(String name){
        SQLiteDatabase db = this.getWritableDatabase();
        String query = "SELECT " + COL1 + " FROM " + TABLE_NAME +
                " WHERE " + COL2 + " = '" + name + "'";
        Cursor data = db.rawQuery(query, null);
        return data;
    }


    /**
     * Delete from database
     */
    public void deleteName(int id, String name){
        SQLiteDatabase db = this.getWritableDatabase();
        String query = "DELETE FROM " + TABLE_NAME + " WHERE "
                + COL1 + " = '" + id + "'" +
                " AND " + COL2 + " = '" + name + "'";
        Log.d(TAG, "deleteName: query: " + query);
        Log.d(TAG, "deleteName: Deleting " + name + " from database.");
        db.execSQL(query);
    }

}

编辑数据

public class EditDataActivity extends AppCompatActivity {

    private static final String TAG = "EditDataActivity";

    private Button btnDelete;

    DatabaseHelper mDatabaseHelper;

    private String selectedName;
    private int selectedID;

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

        ActionBar actionBar=getSupportActionBar();
        actionBar.hide();
        DisplayMetrics dm = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(dm);
        int width = dm.widthPixels;
        int height = dm.heightPixels;
        getWindow().setLayout((int)(width*.4),(int)(height*.2));
        btnDelete = (Button) findViewById(R.id.btnDelete);
        mDatabaseHelper = new DatabaseHelper(this);

        //get the intent extra from the ListDataActivity
        Intent receivedIntent = getIntent();

        //now get the itemID we passed as an extra
        selectedID = receivedIntent.getIntExtra("id",-1); //NOTE: -1 is just the default value

        //now get the name we passed as an extra
        selectedName = receivedIntent.getStringExtra("name");

        btnDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mDatabaseHelper.deleteName(selectedID,selectedName);
                toastMessage("removed from database");
                adapter.notifyDataSetChanged();
            }
        });

    }

    /**
     * customizable toast
     */
    private void toastMessage(String message){
        Toast.makeText(this,message, Toast.LENGTH_SHORT).show();
    }
}

列表数据

    public class ListDataActivity extends AppCompatActivity {

    private static final String TAG = "ListDataActivity";
    static ArrayAdapter adapter;
    DatabaseHelper mDatabaseHelper;

    private ListView mListView;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.list_layout);
        mListView = (ListView) findViewById(R.id.listView);
        mDatabaseHelper = new DatabaseHelper(this);

        populateListView();
    }

    public void populateListView() {
        Log.d(TAG, "populateListView: Displaying data in the ListView.");

        //get the data and append to a list
        Cursor data = mDatabaseHelper.getData();
        ArrayList<String> listData = new ArrayList<>();
        while(data.moveToNext()){
            //get the value from the database in column 1
            //then add it to the ArrayList
            listData.add(data.getString(1));

        }
        //create the list adapter and set the adapter
        adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, listData);
        mListView.setAdapter(adapter);


        //set an onItemClickListener to the ListView
        mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                String name = adapterView.getItemAtPosition(i).toString();
                Log.d(TAG, "onItemClick: You Clicked on " + name);

                Cursor data = mDatabaseHelper.getItemID(name); //get the id associated with that name
                int itemID = -1;
                while(data.moveToNext()){
                    itemID = data.getInt(0);
                }
                if(itemID > -1){
                    Log.d(TAG, "onItemClick: The ID is: " + itemID);
                    Intent editScreenIntent = new Intent(ListDataActivity.this, EditDataActivity.class);
                    editScreenIntent.putExtra("id",itemID);
                    editScreenIntent.putExtra("name",name);
                    startActivity(editScreenIntent);
                }
                else{
                    toastMessage("No ID associated with that name");
                }
            }
        });
    }


    private void toastMessage(String message){
        Toast.makeText(this,message, Toast.LENGTH_SHORT).show();
    }
}

主要 Activity

    public class MainActivity extends AppCompatActivity {

    DatabaseHelper mDatabaseHelper;
    private Button btnAdd, btnViewData;
    EditText editField;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btnAdd = (Button) findViewById(R.id.btnAdd);
        btnViewData = (Button) findViewById(R.id.btnView);
        mDatabaseHelper = new DatabaseHelper(this);
        editField = (EditText) findViewById(R.id.editText);
        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (editField.getText().toString().length() == 0) {
                    Toast.makeText(MainActivity.this, "Please Enter!", Toast.LENGTH_SHORT).show();
                    return;
                }
                String editText = editField.getText().toString();
                AddData(editText);

            }
        });

        btnViewData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, ListDataActivity.class);
                startActivity(intent);
            }
        });

    }

    public void AddData(String newEntry) {
        boolean insertData = mDatabaseHelper.addData(newEntry);

        if (insertData) {
            toastMessage("Data Successfully Inserted!");
        } else {
            toastMessage("Something went wrong");
        }
    }


    private void toastMessage(String message) {
        Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
    }
}

布局是

activity_main

    <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:orientation="vertical"
    tools:context="com.tabian.saveanddisplaysql.MainActivity">
    <EditText
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:hint="Enter any Thing"
        android:layout_marginBottom="47dp"
        android:layout_above="@+id/linearLayout"
        android:layout_alignParentStart="true" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentStart="true"
        android:layout_marginBottom="197dp"
        android:orientation="horizontal"
        android:id="@+id/linearLayout">
        <Button
            android:id="@+id/btnAdd"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="70dp"
            android:text="Add" />

        <Button
            android:id="@+id/btnView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="20dp"
            android:layout_toRightOf="@+id/btnAdd"
            android:text="View Data" />

    </LinearLayout>

</RelativeLayout>

编辑数据布局

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_alignParentTop="true"
    android:orientation="vertical">


    <Button
        android:id="@+id/btnDelete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="DELETE" />

</RelativeLayout>

列表布局

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/listView"/>
</LinearLayout>

Answer 1

删除后代替adapter.notifyDataSetChanged();您可以使用以下代码。它对我来说效果很好:

适配器.remove(selectedName);