java-Spinner onItemSelected()执行不当

可能重复：

Android Spinner OnItemSelected被错误调用(在打开Spinner时没有用户操作)

有谁知道如何在实例化布局时阻止onItemSelected()(OnItemSelectedListener接口)方法运行？ 我需要知道是否有一种方法可以这样做，因为我想保持实例化布局的方式与此侦听器分开。

我尝试过创建一个if语句，该语句最初在被覆盖的方法内部的所有代码周围都设置为false，但是无法知道何时将其设置为true，因为被覆盖的方法在onCreate()，onStart()和 每次都使用onResume()方法。

我还没有找到任何明确的答案。 任何明确的解决方案将不胜感激。

David asked 2020-08-01T12:05:57Z

6个解决方案

64 votes

大卫，这是我为这个问题写的教程。

问题陈述

画廊(或微调器)正在初始化时，触发了不良的onItemSelected()。这意味着代码会过早执行； 仅在用户实际进行选择时才执行的代码。

解

在onCreate()中，计算视图中有多少个Gallery(或Spinner)小部件。 (mGalleryCount)

在onItemSelected()中，计算它触发的频率。 (mGalleryInitializedCount)

当(mGalleryInitializedCount

代码示例

public class myActivity extends Activity implements OnItemSelectedListener

{

//this counts how many Gallery's are on the UI

private int mGalleryCount=0;

//this counts how many Gallery's have been initialized

private int mGalleryInitializedCount=0;

//UI reference

private Gallery mGallery;

@Override

public void onCreate(Bundle savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.myxmllayout);

//get references to UI components

mGallery = (Gallery) findViewById(R.id.mygallery);

//trap selection events from gallery

mGallery.setOnItemSelectedListener(this);

//trap only selection when no flinging is taking place

mGallery.setCallbackDuringFling(false);

//

//do other stuff like load images, setAdapter(), etc

//

//define how many Gallery's are in this view

//note: this could be counted dynamically if you are programmatically creating the view

mGalleryCount=1;

}

public void onItemSelected(AdapterView> parent, View view, int position, long id)

{

if (mGalleryInitializedCount < mGalleryCount)

{

mGalleryInitializedCount++;

}

else

{

//only detect selection events that are not done whilst initializing

Log.i(TAG, "selected item position = " + String.valueOf(position) );

}

}

}

为什么这样做

该解决方案之所以有效，是因为Gallery在用户实际能够进行选择之前就完成了初始化。

Someone Somewhere answered 2020-08-01T12:06:53Z

13 votes

这是“某处某人”代码的修改版本。 如果您有一个视图，则可以使用它。

public class myActivity extends Activity implements OnItemSelectedListener

{

// Set view initialization to false while the it is being built

private boolean initializedView = false;

//UI reference

private Gallery mGallery;

@Override

public void onCreate(Bundle savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.myxmllayout);

//get references to UI components

mGallery = (Gallery) findViewById(R.id.mygallery);

//trap selection events from gallery

mGallery.setOnItemSelectedListener(this);

//trap only selection when no flinging is taking place

mGallery.setCallbackDuringFling(false);

//

//do other stuff like load images, setAdapter(), etc

//

}

public void onItemSelected(AdapterView> parent, View view, int position, long id)

{

if (initializedView == false)

{

initializedView = true;

}

else

{

//only detect selection events that are not done whilst initializing

Log.i(TAG, "selected item position = " + String.valueOf(position) );

}

}

}

Kalimah Apps answered 2020-08-01T12:07:14Z

11 votes

相同的解决方案：

private int m_intSpinnerInitiCount = 0;

private static final int NO_OF_EVENTS = 1;

...

m_spnTemplates.setOnItemSelectedListener(new Spinner.OnItemSelectedListener() {

@Override

public void onItemSelected(AdapterView> parentView,

View selectedItemView, int position, long id) {

//trying to avoid undesired spinner selection changed event, a known problem

if (m_intSpinnerInitiCount < NO_OF_EVENTS) {

m_intSpinnerInitiCount++;

} else {

//YOUR CODE HERE

}

}

Dimitar Vukman answered 2020-08-01T12:07:33Z

1 votes

我昨天遇到了一个OnCheckedChangedListener这个问题。 我最终在访问器方法isListenerEnabled()的适配器类内部添加了一个初始化为true的布尔实例变量。 然后，在布局代码中将变量设置为false，并在布局代码的末尾再次将其设置为true。 在侦听器中，我检查变量的值，以决定是否执行侦听器代码。

James answered 2020-08-01T12:07:54Z

1 votes

您可以在每次调用onPause时将变量设置回false。至于何时将其设置为true，您可以在onResume之后的第一个运动/键/轨迹球事件中执行此操作。

Joseph Earl answered 2020-08-01T12:08:14Z

1 votes

我也在互联网上寻找了一个好的解决方案，但没有找到满足我需求的解决方案。因此，我已在Spinner类上编写了此扩展，因此您可以设置一个简单的OnItemClickListener，其行为与ListView相同。

仅当项目被“选中”时，才会调用onItemClickListener。

玩得开心！

public class MySpinner extends Spinner

{

private OnItemClickListener onItemClickListener;

public MySpinner(Context context)

{

super(context);

}

public MySpinner(Context context, AttributeSet attrs)

{

super(context, attrs);

}

public MySpinner(Context context, AttributeSet attrs, int defStyle)

{

super(context, attrs, defStyle);

}

@Override

public void setOnItemClickListener(android.widget.AdapterView.OnItemClickListener inOnItemClickListener)

{

this.onItemClickListener = inOnItemClickListener;

}

@Override

public void onClick(DialogInterface dialog, int which)

{

super.onClick(dialog, which);

if (this.onItemClickListener != null)

{

this.onItemClickListener.onItemClick(this, this.getSelectedView(), which, this.getSelectedItemId());

}

}

}

Cliffus answered 2020-08-01T12:08:43Z