我希望列表视图在删除后自动更新。我使用adapter.notifyDataSetChanged()，但它对我不起作用
这是我的代码
DatabaseHelper
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);
}
}
EditData
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();
}
}
的ListData
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();
}
}
MainActivity
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
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>
edit_data_layout
<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>
list_layout
<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>
答案 0 :(得分：0)
删除后而不是adapter.notifyDataSetChanged（）;您可以使用以下代码。它适用于我：
adapter.remove（selectedName）;