我想过一些不那么优雅的方法来解决这个问题,但我知道我一定遗漏了什么。
我的onItemSelected立即启动,没有与用户进行任何交互,这是不希望的行为。我希望UI能够等到用户选择某样东西后再执行任何操作。
我甚至尝试在onResume()中设置监听器,希望能有所帮助,但它没有。
我怎样才能阻止它在用户可以触摸控件之前发射?
public class CMSHome extends Activity {
private Spinner spinner;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Heres my spinner ///////////////////////////////////////////
spinner = (Spinner) findViewById(R.id.spinner);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.pm_list, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
};
public void onResume() {
super.onResume();
spinner.setOnItemSelectedListener(new MyOnItemSelectedListener());
}
public class MyOnItemSelectedListener implements OnItemSelectedListener {
public void onItemSelected(AdapterView<?> parent,
View view, int pos, long id) {
Intent i = new Intent(CMSHome.this, ListProjects.class);
i.putExtra("bEmpID", parent.getItemAtPosition(pos).toString());
startActivity(i);
Toast.makeText(parent.getContext(), "The pm is " +
parent.getItemAtPosition(pos).toString(), Toast.LENGTH_LONG).show();
}
public void onNothingSelected(AdapterView parent) {
// Do nothing.
}
}
}
在抽出我的头发很长一段时间后,现在我已经创建了自己的Spinner类。我已经添加了一个方法,它可以适当地断开和连接侦听器。
public class SaneSpinner extends Spinner {
public SaneSpinner(Context context) {
super(context);
}
public SaneSpinner(Context context, AttributeSet attrs) {
super(context, attrs);
}
public SaneSpinner(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
// set the ceaseFireOnItemClickEvent argument to true to avoid firing an event
public void setSelection(int position, boolean animate, boolean ceaseFireOnItemClickEvent) {
OnItemSelectedListener l = getOnItemSelectedListener();
if (ceaseFireOnItemClickEvent) {
setOnItemSelectedListener(null);
}
super.setSelection(position, animate);
if (ceaseFireOnItemClickEvent) {
setOnItemSelectedListener(l);
}
}
}
在XML中像这样使用它:
<my.package.name.SaneSpinner
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/mySaneSpinner"
android:entries="@array/supportedCurrenciesFullName"
android:layout_weight="2" />
你所要做的就是在膨胀和调用集选择之后检索SaneSpinner实例:
mMySaneSpinner.setSelection(1, true, true);
这样,就不会触发任何事件,用户交互也不会中断。这大大降低了我的代码复杂性。这应该包括在Android的股票,因为它确实是一个PITA。
我可能在帖子上回答得太迟了,但是我设法实现了这一点,使用Android数据绑定库Android Databinding。我创建了一个自定义绑定,以确保监听器不被调用,直到选定的项目被改变,所以即使用户选择相同的位置,一遍又一遍地事件不会被触发。
布局xml文件
<layout>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="@dimen/activity_vertical_margin"
xmlns:app="http://schemas.android.com/apk/res-auto">
<Spinner
android:id="@+id/spinner"
android:layout_width="150dp"
android:layout_height="wrap_content"
android:spinnerMode="dropdown"
android:layout_below="@id/member_img"
android:layout_marginTop="@dimen/activity_vertical_margin"
android:background="@drawable/member_btn"
android:padding="@dimen/activity_horizontal_margin"
android:layout_marginStart="@dimen/activity_horizontal_margin"
android:textColor="@color/colorAccent"
app:position="@{0}"
/>
</RelativeLayout>
</layout>
App:position是你传递要选择的位置。
定制绑定
@BindingAdapter(value={ "position"}, requireAll=false)
public static void setSpinnerAdapter(Spinner spinner, int selected)
{
final int [] selectedposition= new int[1];
selectedposition[0]=selected;
// custom adapter or you can set default adapter
CustomSpinnerAdapter customSpinnerAdapter = new CustomSpinnerAdapter(spinner.getContext(), <arraylist you want to add to spinner>);
spinner.setAdapter(customSpinnerAdapter);
spinner.setSelection(selected,false);
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String item = parent.getItemAtPosition(position).toString();
if( position!=selectedposition[0]) {
selectedposition[0]=position;
// do your stuff here
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
}
你可以阅读更多关于自定义数据绑定在这里Android自定义Setter
NOTE
不要忘记在Gradle文件中启用数据绑定
android {
....
数据绑定{
Enabled = true
}
}
包括你的布局文件在<layout>标签
布尔标志或计数器的解决方案没有帮助我,因为在方向变化onItemSelected()调用“飞越”标志或计数器。
我子类化了android.widget.Spinner,并做了一些小的补充。相关部分如下。这个解决方案对我很有效。
private void setHandleOnItemSelected()
{
final StackTraceElement [] elements = Thread.currentThread().getStackTrace();
for (int index = 1; index < elements.length; index++)
{
handleOnItemSelected = elements[index].toString().indexOf("PerformClick") != -1; //$NON-NLS-1$
if (handleOnItemSelected)
{
break;
}
}
}
@Override
public void setSelection(int position, boolean animate)
{
super.setSelection(position, animate);
setHandleOnItemSelected();
}
@Override
public void setSelection(int position)
{
super.setSelection(position);
setHandleOnItemSelected();
}
public boolean shouldHandleOnItemSelected()
{
return handleOnItemSelected;
}
我的解决方案使用onTouchListener,但不限制它的使用。如果需要,它会在设置onItemSelectedListener时为onTouchListener创建一个包装器。
public class Spinner extends android.widget.Spinner {
/* ...constructors... */
private OnTouchListener onTouchListener;
private OnItemSelectedListener onItemSelectedListener;
@Override
public void setOnItemSelectedListener(OnItemSelectedListener listener) {
onItemSelectedListener = listener;
super.setOnTouchListener(wrapTouchListener(onTouchListener, onItemSelectedListener));
}
@Override
public void setOnTouchListener(OnTouchListener listener) {
onTouchListener = listener;
super.setOnTouchListener(wrapTouchListener(onTouchListener, onItemSelectedListener));
}
private OnTouchListener wrapTouchListener(final OnTouchListener onTouchListener, final OnItemSelectedListener onItemSelectedListener) {
return onItemSelectedListener != null ? new OnTouchListener() {
@Override
public boolean onTouch(View view, MotionEvent motionEvent) {
Spinner.super.setOnItemSelectedListener(onItemSelectedListener);
return onTouchListener != null && onTouchListener.onTouch(view, motionEvent);
}
} : onTouchListener;
}
}
不幸的是,解决这个问题的两个最常见的建议解决方案,即统计回调发生次数和发布Runnable以在稍后设置回调,在启用可访问性选项时都可能失败。下面是一个帮助类,它可以解决这些问题。进一步的解释在评论区。
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.Spinner;
import android.widget.SpinnerAdapter;
/**
* Spinner Helper class that works around some common issues
* with the stock Android Spinner
*
* A Spinner will normally call it's OnItemSelectedListener
* when you use setSelection(...) in your initialization code.
* This is usually unwanted behavior, and a common work-around
* is to use spinner.post(...) with a Runnable to assign the
* OnItemSelectedListener after layout.
*
* If you do not call setSelection(...) manually, the callback
* may be called with the first item in the adapter you have
* set. The common work-around for that is to count callbacks.
*
* While these workarounds usually *seem* to work, the callback
* may still be called repeatedly for other reasons while the
* selection hasn't actually changed. This will happen for
* example, if the user has accessibility options enabled -
* which is more common than you might think as several apps
* use this for different purposes, like detecting which
* notifications are active.
*
* Ideally, your OnItemSelectedListener callback should be
* coded defensively so that no problem would occur even
* if the callback was called repeatedly with the same values
* without any user interaction, so no workarounds are needed.
*
* This class does that for you. It keeps track of the values
* you have set with the setSelection(...) methods, and
* proxies the OnItemSelectedListener callback so your callback
* only gets called if the selected item's position differs
* from the one you have set by code, or the first item if you
* did not set it.
*
* This also means that if the user actually clicks the item
* that was previously selected by code (or the first item
* if you didn't set a selection by code), the callback will
* not fire.
*
* To implement, replace current occurrences of:
*
* Spinner spinner =
* (Spinner)findViewById(R.id.xxx);
*
* with:
*
* SpinnerHelper spinner =
* new SpinnerHelper(findViewById(R.id.xxx))
*
* SpinnerHelper proxies the (my) most used calls to Spinner
* but not all of them. Should a method not be available, use:
*
* spinner.getSpinner().someMethod(...)
*
* Or just add the proxy method yourself :)
*
* (Quickly) Tested on devices from 2.3.6 through 4.2.2
*
* @author Jorrit "Chainfire" Jongma
* @license WTFPL (do whatever you want with this, nobody cares)
*/
public class SpinnerHelper implements OnItemSelectedListener {
private final Spinner spinner;
private int lastPosition = -1;
private OnItemSelectedListener proxiedItemSelectedListener = null;
public SpinnerHelper(Object spinner) {
this.spinner = (spinner != null) ? (Spinner)spinner : null;
}
public Spinner getSpinner() {
return spinner;
}
public void setSelection(int position) {
lastPosition = Math.max(-1, position);
spinner.setSelection(position);
}
public void setSelection(int position, boolean animate) {
lastPosition = Math.max(-1, position);
spinner.setSelection(position, animate);
}
public void setOnItemSelectedListener(OnItemSelectedListener listener) {
proxiedItemSelectedListener = listener;
spinner.setOnItemSelectedListener(listener == null ? null : this);
}
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
if (position != lastPosition) {
lastPosition = position;
if (proxiedItemSelectedListener != null) {
proxiedItemSelectedListener.onItemSelected(
parent, view, position, id
);
}
}
}
public void onNothingSelected(AdapterView<?> parent) {
if (-1 != lastPosition) {
lastPosition = -1;
if (proxiedItemSelectedListener != null) {
proxiedItemSelectedListener.onNothingSelected(
parent
);
}
}
}
public void setAdapter(SpinnerAdapter adapter) {
if (adapter.getCount() > 0) {
lastPosition = 0;
}
spinner.setAdapter(adapter);
}
public SpinnerAdapter getAdapter() { return spinner.getAdapter(); }
public int getCount() { return spinner.getCount(); }
public Object getItemAtPosition(int position) { return spinner.getItemAtPosition(position); }
public long getItemIdAtPosition(int position) { return spinner.getItemIdAtPosition(position); }
public Object getSelectedItem() { return spinner.getSelectedItem(); }
public long getSelectedItemId() { return spinner.getSelectedItemId(); }
public int getSelectedItemPosition() { return spinner.getSelectedItemPosition(); }
public void setEnabled(boolean enabled) { spinner.setEnabled(enabled); }
public boolean isEnabled() { return spinner.isEnabled(); }
}
只是为了补充使用onTouchListener来区分对setOnItemSelectedListener的自动调用(这是Activity初始化的一部分,等等)与实际用户交互触发的对它的调用之间的提示,在尝试了其他一些建议后,我做了以下工作,并发现它用最少的代码行就能很好地工作。
只需要为你的Activity/Fragment设置一个布尔字段:
private Boolean spinnerTouched = false;
然后在你设置你的旋转器的setOnItemSelectedListener之前,设置一个onTouchListener:
spinner.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
System.out.println("Real touch felt.");
spinnerTouched = true;
return false;
}
});
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
...
if (spinnerTouched){
//Do the stuff you only want triggered by real user interaction.
}
spinnerTouched = false;