Question

我已尝试使用以下方法执行此任务但它无法正常工作，但根本没有显示任何错误。这是比较部分：

Cursor res = myDb.showKharcha();
final String selected= parent.getItemAtPosition(position).toString();
while(res.moveToNext()) {
    if(selected == res.getString(1)) {
        int num = Integer.parseInt(editText.getText().toString());
        num = num + Integer.parseInt(res.getString(2));
        boolean isUpdated = myDb.updateData(res.getString(0),selected,num);
        if (isUpdated == true) {
            Toast.makeText(add_trans.this,"Kharcha updated to "+ selected,Toast.LENGTH_LONG).show();
        } else {
            Toast.makeText(add_trans.this, "Kharcha not added", Toast.LENGTH_LONG).show();
        }

这是DatabaseHelper类中的showKharcha函数：

public Cursor showKharcha(){
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor tyt = db.rawQuery("select * from " + TABLE_NAME,null);
    return tyt;
}

数据库更新代码为：

public boolean updateData(String ID, String KharchaType, Integer Kharcha){
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();

    contentValues.put(COL_1,ID);
    contentValues.put(COL_2,KharchaType);
    contentValues.put(COL_3,Kharcha);
    db.update(TABLE_NAME,contentValues, "ID = ?",new String[] { ID });
    return true;

}

Answer 1

您已经讨论过比较Spinner中选定值的值。使用此using System; using System.Collections.Generic; using System.Threading.Tasks; using System.Threading; namespace ConsoleApp1 { class Program { static object lockObject = new object(); static HashSet<TaskCompletionSource<bool>> completionSources = new HashSet<TaskCompletionSource<bool>>(); static void Main(string[] args) { MainAsync().Wait(); } static async Task MainAsync() { Task t1 = T1Async(); Task t2 = T2Async(); await t1; await t2; } static async Task T1Async() { Console.WriteLine("T1 start."); if (await WaitAsync()) Console.WriteLine("Wait succeeded."); else Console.WriteLine("Wait failed."); Console.WriteLine("T1 end."); } static async Task T2Async() { Console.WriteLine("T2 start."); await Task.Delay(500); CompleteAndClear(); Console.WriteLine("T2 end."); } static async Task<bool> WaitAsync() { Console.WriteLine("Wait start."); bool res = false; TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>(); using (CancellationTokenSource cancellationTokenSource = new CancellationTokenSource(3000)) { using (CancellationTokenRegistration cancellationTokenRegistration = cancellationTokenSource.Token.Register(() => { tcs.TrySetResult(false); })) { Add(tcs); res = await tcs.Task; Remove(tcs); } } Console.WriteLine("Wait end."); return res; } static void Add(TaskCompletionSource<bool> TaskCompletionSource) { Console.WriteLine("Add start."); lock (lockObject) { completionSources.Add(TaskCompletionSource); } Console.WriteLine("Add end."); } static void Remove(TaskCompletionSource<bool> TaskCompletionSource) { Console.WriteLine("Remove start."); lock (lockObject) { if (!completionSources.Remove(TaskCompletionSource)) Console.WriteLine("TCS not found."); } Console.WriteLine("Remove end."); } static void CompleteAndClear() { Console.WriteLine("CompleteAndClear start."); lock (lockObject) { if (completionSources.Count > 0) { Console.WriteLine("Completing {0} TCSs.", completionSources.Count); foreach (TaskCompletionSource<bool> tcs in completionSources) tcs.TrySetResult(true); Console.WriteLine("Clearing TCS list."); completionSources.Clear(); } } Console.WriteLine("CompleteAndClear end."); } } }

而不是

final String text = spinner.getSelectedItem().toString();。

如果你设置OnItemSelectedListener会更好，这样当用户选择时，比较会自动发生：

final String selected= parent.getItemAtPosition(position).toString();

Answer 2

使用final String text = spinner.getSelectedItem().toString();从Spinner

和

尝试if(selected.equals(res.getString(1)))进行比较

有关==和equals

的详细信息，请参阅this

将数据库中的数据与在spinner-Android上选择的项目进行比较

2 个答案: