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.
}
}
}
我用最简单的方法做到了:
private AdapterView.OnItemSelectedListener listener;
private Spinner spinner;
onCreate ();
spinner = (Spinner) findViewById(R.id.spinner);
listener = new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int position, long l) {
Log.i("H - Spinner selected position", position);
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
};
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
spinner.setOnItemSelectedListener(listener);
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
Done
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();
}
}
}
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
}
