我正在做一个应用程序，让你编写活动来做。在主要活动上，有一个 ListView，它根据 DialogFragment 内的 DatePicker 中指定的日期显示活动。我正在使用 SQLite 来保存活动，到目前为止保存它们没有问题。如果您长按 ListView 的某个项目，则会出现一个带有单个选项“删除活动”的上下文菜单，调用方法 removeActivity，该方法从静态 ArrayList System.activities 中删除活动，该活动存储创建的每个活动，并且应该删除来自数据库的活动，使用活动的属性 cod，该属性对于活动的每个实例都是唯一的。
public class Main extends FragmentActivity {
int mDay = Calendar.getInstance().get(Calendar.DAY_OF_MONTH);
int mMonth = Calendar.getInstance().get(Calendar.MONTH); // August, month
// starts from 0
int mYear = Calendar.getInstance().get(Calendar.YEAR);
ArrayList<String> listNames = new ArrayList<String>();
List<ActivityToDo> acts = System.activities;
boolean listHasItems = false;
int position;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Remove title bar
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
removeActivitesBeforeCurrentDate();
ToDoSQLiteHelper actdb = new ToDoSQLiteHelper(this, "db", null, 1);
SQLiteDatabase db = actdb.getReadableDatabase();
Cursor c = db.rawQuery("SELECT * FROM Activities", null);
System.activities.clear();
if (c.moveToFirst()) {
do {
ActivityToDo act = new ActivityToDo(c.getString(1),
c.getString(2), c.getString(3));
act.setDate(Integer.parseInt(c.getString(4)),
Integer.parseInt(c.getString(5)),
Integer.parseInt(c.getString(6)));
System.activities.add(act);
} while (c.moveToNext());
}
db.close();
setContentView(R.layout.main);
final Button btnNewAct = (Button) findViewById(R.id.btnNewAct);
final TextView txtV = (TextView) findViewById(R.id.txtPickDate);
final ListView listview = (ListView) findViewById(R.id.listview);
listNames.add("Pick date to search activity.");
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, listNames);
listview.setAdapter(adapter);
registerForContextMenu(listview);
listview.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
if (listHasItems) {
ActivityToDo a = acts.get(position);
String[] datosAct = new String[6];
datosAct[0] = a.getName();
datosAct[1] = a.getDescr();
datosAct[2] = a.getPriority();
datosAct[3] = Integer.toString(a.getDay());
datosAct[4] = Integer.toString(a.getMonth());
datosAct[5] = Integer.toString(a.getYear());
Intent i = new Intent();
i.setClass(getApplicationContext(), ShowActivity.class);
i.putExtra("datos", datosAct);
startActivity(i);
}
}
});
final Handler mHandler = new Handler() {
// This handles the message send from DatePickerDialogFragment on
// setting date
@Override
public void handleMessage(Message m) {
Bundle b = m.getData();
mDay = b.getInt("set_day");
mMonth = b.getInt("set_month");
mYear = b.getInt("set_year");
String date = "";
if (mDay < 10) {
date += "0" + mDay + "/";
} else {
date += mDay + "/";
}
int mes = mMonth + 1;
if (mes < 10) {
date += "0" + mes + "/";
} else {
date += mes + "/";
}
date += mYear;
txtV.setText(date);
buildList(mDay, mMonth + 1, mYear);
}
};
OnClickListener listener = new OnClickListener() {
public void onClick(View v) {
Bundle b = new Bundle();
b.putInt("set_day", mDay);
b.putInt("set_month", mMonth);
b.putInt("set_year", mYear);
DatePickerDialogFragment datePicker = new DatePickerDialogFragment(
mHandler);
datePicker.setArguments(b);
android.support.v4.app.FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.add(datePicker, "date_picker");
// Opening the DatePicker fragment
ft.commit();
}
};
txtV.setOnClickListener(listener);
btnNewAct.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent();
i.setClass(getApplicationContext(), NewActivity.class);
startActivity(i);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
protected void buildList(int d, int m, int y) {
acts = System.searchByDate(d, m, y);
listNames.clear();
if (acts != null && acts.size() != 0) {
for (int i = 0; i < acts.size(); i++) {
listNames.add(acts.get(i).getName());
}
listHasItems = true;
} else {
listHasItems = false;
listNames.add("No activities for that date.");
}
ListView listview = (ListView) findViewById(R.id.listview);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, listNames);
listview.setAdapter(adapter);
}
public void mostrarToast(String txt) {
Toast toast = Toast.makeText(getApplicationContext(), txt,
Toast.LENGTH_SHORT);
toast.show();
}
private void removeActivitesBeforeCurrentDate() {
ToDoSQLiteHelper actdb = new ToDoSQLiteHelper(getApplicationContext(),
"db", null, 1);
SQLiteDatabase db = actdb.getWritableDatabase();
ActivityToDo aux;
Cursor c = db.rawQuery("SELECT * FROM Activities", null);
if (System.activities.size() != 0 && c.moveToFirst()) {
for (int i = 0; i < System.activities.size(); i++) {
aux = System.activities.get(i);
if (aux.getYear() < Calendar.getInstance().get(Calendar.YEAR)
&& aux.getMonth() - 1 < Calendar.getInstance().get(
Calendar.MONTH)
&& aux.getDay() < Calendar.getInstance().get(
Calendar.DAY_OF_MONTH)) {
System.activities.remove(i);
int cod = aux.getCod();
db.execSQL("DELETE FROM Activities WHERE cod=" + cod);
}
}
}
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v,
ContextMenuInfo menuInfo) {
super.onCreateContextMenu(menu, v, menuInfo);
if (listHasItems) {
MenuInflater inflater = getMenuInflater();
AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) menuInfo;
position = info.position;
inflater.inflate(R.menu.menulistitem, menu);
}
}
@Override
public boolean onContextItemSelected(MenuItem item) {
removeActivity(position);
buildList(mDay, mMonth + 1, mYear);
return true;
}
private void removeActivity(int pos) {
ToDoSQLiteHelper actdb = new ToDoSQLiteHelper(getApplicationContext(),
"db", null, 1);
SQLiteDatabase db = actdb.getWritableDatabase();
ActivityToDo aux;
Cursor c = db.rawQuery("SELECT * FROM Activities", null);
if (System.activities.size() != 0 && c.moveToFirst()) {
aux = System.activities.get(pos);
System.activities.remove(pos);
int cod = aux.getCod();
db.execSQL("DELETE FROM Activities WHERE cod=" + cod);
}
c.close();
}
@Override
protected void onPause() {
super.onPause();
this.finish();
}
}
但是这db.execSQL("DELETE FROM Activities WHERE cod=" + cod);似乎不适用于数据库中保留的最后一个活动。示例：我选择了一个日期，当天有两个活动，我将它们都删除了，ListView 显示文本“该日期没有活动”，这是应该发生的，但是当我再次启动应用程序时，活动据说最后被删除了，出现在那里。如果该日期只有一个活动也是如此，这就是为什么我说如果它是数据库中的最后一件事，它似乎不会删除活动。知道为什么吗？提前致谢。
我的 SQLite 类：
public class ToDoSQLiteHelper extends SQLiteOpenHelper {
// crear tabla de usuario
// agregar DATE
String sqlCreate = "CREATE TABLE Activities (cod INTEGER, name TEXT, descr TEXT, priority TEXT, day TEXT, month TEXT, year TEXT)";
public ToDoSQLiteHelper(Context contexto, String nombre,
CursorFactory factory, int version) {
super(contexto, nombre, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(sqlCreate);
}
@Override
public void onUpgrade(SQLiteDatabase db, int versionAnterior,
int versionNueva) {
db.execSQL("DROP TABLE IF EXISTS Activities");
db.execSQL(sqlCreate);
}
}