android-spinner - 如何阻止 onItemSelected() 在选择项目后多次触发？

Question

我见过另一个类似的帖子，但我无法使用给定的答案解决我的问题。

我的目标说明:

我有 4 个微调器，每个微调器都有自己的字符串 ArrayList，通过适配器分配给它。所有这些数组在开头都包含相同的值。

我想在选择时从所有其他微调器中删除选定的值(例如 spinner1 中的“item”)(从 spinner2、3 和 4 中删除“item”)。

问题:

当我从不同的旋转器中前两到三次选择一个项目时(重现问题所需的选择次数各不相同)，onItemSelected() 方法会被调用多次(调用次数大于实际用户选择的次数)。

问题:

如何防止在不必要的时候调用onItemSelected();。我希望仅当实际用户在其中一个旋转器中进行选择时才调用它，并且仅在发生这种情况时调用它一次。

如果您想尝试帮助我，并且需要设备本身问题的更多代码/图像，请说出来。

这是我的整个 onItemSelected() 方法:

@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    if (inCorrection == false)
    {
        s1 = spinner1.getSelectedItemPosition();
        s2 = spinner2.getSelectedItemPosition();
        s3 = spinner3.getSelectedItemPosition();
        s4 = spinner4.getSelectedItemPosition();
        testcount++;
        switch(parent.getId())
        {
            case R.id.v1_q1_s1:
                    if((position != AdapterView.INVALID_POSITION) && (spinner1.getSelectedItem().toString() != "Default---"))
                    {
                        findLists(myList2, myList3, myList4, spinner1.getSelectedItem().toString());
                        if(returnChecks(0) != "Default---")
                        {
                            myList2.add(returnChecks(0)); 
                            myList3.add(returnChecks(0)); 
                            myList4.add(returnChecks(0)); 
                        }
                        addChecks(0, (spinner1.getSelectedItem().toString())); 
                    }
                    else
                    {
                        if(position != AdapterView.INVALID_POSITION)
                        {
                            myList2.add(returnChecks(0)); 
                            myList3.add(returnChecks(0)); 
                            myList4.add(returnChecks(0)); 
                            addChecks(0, (spinner1.getSelectedItem().toString())); 
                        }
                    }
                    adapter1.notifyDataSetChanged();
                    adapter2.notifyDataSetChanged();
                    adapter3.notifyDataSetChanged();
                    adapter4.notifyDataSetChanged();
                    Toast.makeText(Vprasalnik1.this, myList1.toString()+"\n"+myList2.toString()+"\n"+myList3.toString()+"\n"+myList4.toString()+"\n"+checks.toString(), Toast.LENGTH_LONG).show();
                break;
            case R.id.v1_q1_s2:
                if((position != AdapterView.INVALID_POSITION) && (spinner2.getSelectedItem().toString() != "Default---"))
                {
                    findLists(myList1, myList3, myList4, spinner2.getSelectedItem().toString());
                    if(returnChecks(1) != "Default---")
                    {
                        myList1.add(returnChecks(1)); 
                        myList3.add(returnChecks(1)); 
                        myList4.add(returnChecks(1)); 
                    }
                    addChecks(1, (spinner2.getSelectedItem().toString())); 
                }
                else
                {
                    if(position != AdapterView.INVALID_POSITION)
                    {
                        myList1.add(returnChecks(1)); 
                        myList3.add(returnChecks(1)); 
                        myList4.add(returnChecks(1)); 
                        addChecks(1, (spinner2.getSelectedItem().toString())); 
                    }
                }
                adapter1.notifyDataSetChanged();
                adapter2.notifyDataSetChanged();
                adapter3.notifyDataSetChanged();
                adapter4.notifyDataSetChanged();
                Toast.makeText(Vprasalnik1.this, myList1.toString()+"\n"+myList2.toString()+"\n"+myList3.toString()+"\n"+myList4.toString()+"\n"+checks.toString(), Toast.LENGTH_LONG).show();
                break;
            case R.id.v1_q1_s3:
                if((position != AdapterView.INVALID_POSITION) && (spinner3.getSelectedItem().toString() != "Default---"))
                {
                    findLists(myList2, myList1, myList4, spinner3.getSelectedItem().toString());
                    if(returnChecks(2) != "Default---")
                    {
                        myList2.add(returnChecks(2)); 
                        myList1.add(returnChecks(2)); 
                        myList4.add(returnChecks(2)); 
                        Toast.makeText(Vprasalnik1.this, "before: "+returnChecks(2), Toast.LENGTH_LONG).show();
                    }
                    addChecks(2, (spinner3.getSelectedItem().toString())); 
                    Toast.makeText(Vprasalnik1.this, "after: "+returnChecks(2), Toast.LENGTH_LONG).show();
                }
                else
                {
                    if(position != AdapterView.INVALID_POSITION)
                    {
                        myList2.add(returnChecks(2)); 
                        myList1.add(returnChecks(2)); 
                        myList4.add(returnChecks(2)); 
                        addChecks(2, (spinner3.getSelectedItem().toString())); 
                    }
                }
                adapter1.notifyDataSetChanged();
                adapter2.notifyDataSetChanged();
                adapter3.notifyDataSetChanged();
                adapter4.notifyDataSetChanged();
                Toast.makeText(Vprasalnik1.this, myList1.toString()+"\n"+myList2.toString()+"\n"+myList3.toString()+"\n"+myList4.toString()+"\n"+checks.toString(), Toast.LENGTH_LONG).show();
                break;
            case R.id.v1_q1_s4:
                if((position != AdapterView.INVALID_POSITION) && (spinner4.getSelectedItem().toString() != "Default---"))
                {
                    findLists(myList2, myList3, myList1, spinner4.getSelectedItem().toString());
                    if(returnChecks(3) != "Default---")
                    {
                        myList2.add(returnChecks(3)); 
                        myList3.add(returnChecks(3)); 
                        myList1.add(returnChecks(3)); 
                    }
                    addChecks(3, (spinner4.getSelectedItem().toString())); 
                }
                else
                {
                    if(position != AdapterView.INVALID_POSITION)
                    {
                        myList2.add(returnChecks(3)); 
                        myList3.add(returnChecks(3)); 
                        myList1.add(returnChecks(3)); 
                        addChecks(3, (spinner4.getSelectedItem().toString())); 
                    }
                }
                adapter1.notifyDataSetChanged();
                adapter2.notifyDataSetChanged();
                adapter3.notifyDataSetChanged();
                adapter4.notifyDataSetChanged();
                Toast.makeText(Vprasalnik1.this, myList1.toString()+"\n"+myList2.toString()+"\n"+myList3.toString()+"\n"+myList4.toString()+"\n"+checks.toString(), Toast.LENGTH_LONG).show();
                break;
        }
        correctSelection();
    }
}

在上述代码的末尾，有一个名为 CorrectSelection(); 的函数，它可以纠正所有微调器的选择，因为否则它无法正常工作 - 它看起来像这样:

void correctSelection()
{
    inCorrection = true;
    spinner1.setSelection(myList1.lastIndexOf(returnChecks(0)));
    spinner2.setSelection(myList2.lastIndexOf(returnChecks(1)));
    spinner3.setSelection(myList3.lastIndexOf(returnChecks(2)));
    spinner4.setSelection(myList4.lastIndexOf(returnChecks(3)));
    inCorrection = false;
}
/*it sets the position of all spinners to the last "saved"
(current) item selected, so it corrects the possible index offset that occurs otherwise
(returnChecks(); returns the last item selected from an array in a string format)

PS: To avoid the calling of onItemSelected() in case of programmatically setting the selection
of spinners, I've input a boolean flag (variable "inCorrection"), which is set to false before the
selections are made by "the application" and then set back to false when the code gets run.

*/

Answer 1

要防止在设置微调器时调用 onItemSelected()，可以这样做:

spinner.setOnItemSelectedListener(null);
adapter.notifyDatasetChanged();
spinner.setSelection(0, false);
spinner.setOnItemSelectedListener(onItemSelectedListener);

说明:
当选择发生更改时，框架会触发 onItemSelected 事件。它通过注册当前选定位置和先前选定位置(mSelectedPostion 和 mOldSelectedPosition)来检测更改。

当您调用notifyDatasetChanged时，框架会执行各种检查以查看是否可以找到先前的选择，因此在布局微调器时可能会也可能不会调用onItemSelected。

通过调用 setSelection(0, false)，这些位置被设置为 0，可能会检测到更改，但由于 onItemSelectedListener 为 null，因此 onItemSelected 不会被触发。选择位置 0 是因为我猜测“默认---”值是列表中的第一个位置。如果您愿意，可以选择其他位置。

稍后布置微调器时，没有任何变化，因此 onItemSelected 也不会在此处触发。

请注意，这是通过在 API 级别 19 (Android 4.4 KitKat) 上调试而确定的。我不知道它是否适用于其他版本，而且我在文档中找不到任何支持它的内容。