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.
}
}
}
已经有很多答案了，这是我的。
我扩展了AppCompatSpinner，并添加了一个方法pgmSetSelection(int pos)，允许编程选择设置，而不触发选择回调。我用RxJava编写了这个代码，这样选择事件就可以通过Observable传递。
package com.controlj.view;
import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.AdapterView;
import io.reactivex.Observable;
/**
* Created by clyde on 22/11/17.
*/
public class FilteredSpinner extends android.support.v7.widget.AppCompatSpinner {
private int lastSelection = INVALID_POSITION;
public void pgmSetSelection(int i) {
lastSelection = i;
setSelection(i);
}
/**
* Observe item selections within this spinner. Events will not be delivered if they were triggered
* by a call to setSelection(). Selection of nothing will return an event equal to INVALID_POSITION
*
* @return an Observable delivering selection events
*/
public Observable<Integer> observeSelections() {
return Observable.create(emitter -> {
setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
if(i != lastSelection) {
lastSelection = i;
emitter.onNext(i);
}
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
onItemSelected(adapterView, null, INVALID_POSITION, 0);
}
});
});
}
public FilteredSpinner(Context context) {
super(context);
}
public FilteredSpinner(Context context, int mode) {
super(context, mode);
}
public FilteredSpinner(Context context, AttributeSet attrs) {
super(context, attrs);
}
public FilteredSpinner(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
public FilteredSpinner(Context context, AttributeSet attrs, int defStyleAttr, int mode) {
super(context, attrs, defStyleAttr, mode);
}
}
它的用法示例，在Fragment中调用onCreateView()，例如:
mySpinner = view.findViewById(R.id.history);
mySpinner.observeSelections()
.subscribe(this::setSelection);
其中setSelection()是封闭视图中的一个方法，看起来像这样，它既可以通过可观察对象从用户选择事件中调用，也可以在其他地方以编程方式调用，因此处理选择的逻辑对于两个选择方法来说是通用的。
private void setSelection(int position) {
if(adapter.isEmpty())
position = INVALID_POSITION;
else if(position >= adapter.getCount())
position = adapter.getCount() - 1;
MyData result = null;
mySpinner.pgmSetSelection(position);
if(position != INVALID_POSITION) {
result = adapter.getItem(position);
}
display(result); // show the selected item somewhere
}
这也不是一个优雅的解决方案。事实上，这有点像鲁布-戈德堡，但似乎很有效。通过扩展数组适配器并覆盖其getDropDownView，我确保旋转器至少被使用过一次。在新的getDropDownView方法中，我有一个布尔标志，被设置为显示下拉菜单至少被使用过一次。在设置标志之前，我会忽略对侦听器的调用。
MainActivity.onCreate ():
ActionBar ab = getActionBar();
ab.setDisplayShowTitleEnabled(false);
ab.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);
ab.setListNavigationCallbacks(null, null);
ArrayList<String> abList = new ArrayList<String>();
abList.add("line 1");
...
ArAd abAdapt = new ArAd (this
, android.R.layout.simple_list_item_1
, android.R.id.text1, abList);
ab.setListNavigationCallbacks(abAdapt, MainActivity.this);
覆盖的数组适配器:
private static boolean viewed = false;
private class ArAd extends ArrayAdapter<String> {
private ArAd(Activity a
, int layoutId, int resId, ArrayList<String> list) {
super(a, layoutId, resId, list);
viewed = false;
}
@Override
public View getDropDownView(int position, View convertView,
ViewGroup parent) {
viewed = true;
return super.getDropDownView(position, convertView, parent);
}
}
修改监听器:
@Override
public boolean onNavigationItemSelected(
int itemPosition, long itemId) {
if (viewed) {
...
}
return false;
}
这不是一个完美的解决方案，但如果你喜欢将起始字符串作为一个占位符，你可以添加占位符弹簧值("Day_of_Work_Out")
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String name = (String) parent.getItemAtPosition(position);
if (name.equals("Day_of_Work_Out")) {
}else {
workOutD = name;
Intent intent = new Intent();
workOutNam = workOutName.getText().toString();
if (workOutNam == null) {
startActivity(intent);
Log.i("NewWorkOutActivity","Name is null");
}else {
Log.i("NewWorkOutActivity","Name Not null");
Toast.makeText(NewWorkOutActivity.this, "Please Select a Day", Toast.LENGTH_LONG).show();
}
}
}
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;
}
}
我有很多问题与旋转发射时，我不想，所有的答案在这里是不可靠的。它们确实有效——但只是有时有效。您最终会遇到它们失败并将错误引入代码的情况。
对我来说，有效的方法是将最后选中的索引存储在一个变量中，并在侦听器中对其求值。如果它与新选定的索引相同，则不做任何操作并返回，否则继续使用侦听器。这样做:
//Declare a int member variable and initialize to 0 (at the top of your class)
private int mLastSpinnerPosition = 0;
//then evaluate it in your listener
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
if(mLastSpinnerPosition == i){
return; //do nothing
}
mLastSpinnerPosition = i;
//do the rest of your code now
}
相信我，这是目前为止最可靠的解决方案。一个黑客，但它工作!
