我正在尝试在我的应用程序中使用AlertDialog来选择项目的数量。问题在于，调用AlertDialog的活动在将项目添加到 SQLite 数据库并更改意向之前不会等待它更新项目。
此时，QuantitySelector（AlertDialog）出现，然后立即消失，并通过意图更改更改更改MealActivity类（这只是从数据库中读取的ListView），并对数量为0的数据库进行更新。
我需要Activity等待AlertDialog关闭，然后再更新数据库。
实现这一点的正确方法是什么？
下面是一些代码：
QuantitySelector（运行警报对话框）：
public class QuantitySelector{
protected static final int RESULT_OK = 0;
private Context _context;
private DatabaseHandler db;
private HashMap<String, Double> measures;
private Item item;
private View v;
private EditText quan;
private NumberPicker pick;
private int value;
private Quantity quantity;
/**
* Function calls the quantity selector AlertDialog
* @param _c: The application context
* @param item: The item to be added to consumption
* @return The quantity that is consumed
*/
public void select(Context _c, Item item, Quantity quantity){
this._context = _c;
this.item = item;
this.quantity = quantity;
db = new DatabaseHandler(_context);
//Get the measures to display
createData();
//Set up the custom view
LayoutInflater inflater = LayoutInflater.from(_context);
v = inflater.inflate(R.layout.quantity_selector, null);
//Set up the input fields
quan = (EditText) v.findViewById(R.id.quantityNumber);
pick = (NumberPicker) v.findViewById(R.id.numberPicker1);
//Set up the custom measures into pick
pick.setMaxValue(measures.size()-1);
pick.setDisplayedValues(measures.keySet().toArray(new String[0]));
//Start the alert dialog
runDialog();
}
public void createData(){
measures = new HashMap<String, Double>();
//Get the measurements from the database
if(item!=null){
measures.putAll(db.getMeasures(item));
}
//Add grams as the default measurement
if(!measures.keySet().contains("grams")){
//Add grams as a standard measure
measures.put("grams", 1.0);
}
}
public void runDialog(){
AlertDialog dialog = new AlertDialog.Builder(_context).setTitle("Select Quantity")
.setView(v)
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
//Change the consumption to the new quantity
if(!quan.getText().toString().matches("")){
value = Integer.parseInt(quan.getText().toString());
//Check if conversion from other units is needed
String s[] = pick.getDisplayedValues();
String a = s[pick.getValue()];
//Convert the chosen measure back to grams
if(!a.equals("grams")){
for(String m : measures.keySet()){
if(m==a){
value = (int) (value * measures.get(m));
}
}
}
}
quantity.setQuantity(value);
dialog.dismiss();
}
})
.setNegativeButton("Cancel", null).create();
dialog.show();
}
}
来自 favoritesAdapter 的方法（调用 alertdialog）：
add.setOnClickListener(new OnClickListener(){
public void onClick(View arg0) {
QuantitySelector q = new QuantitySelector();
Quantity quan = new Quantity();
q.select(_context, db.getItem(p.getID()), quan);
db.addConsumption(p.getID(), p.getFavouriteShortName(), quan.getQuantity(), "FAVOURITE");
Intent intent = new Intent(_context,MealActivity.class);
_context.startActivity(intent);
}
});
感谢所有帮助:)
使用异步任务并在doInBackGround和onPostExecute方法Show Dialog中更新数据。
你想要这样做的方法是在对方按下肯定按钮时实际开始下一个意图。 简而言之，您需要在附加到警报对话框的正面按钮的OnClickListener中启动下一个活动。
public void runDialog(){
AlertDialog dialog = new AlertDialog.Builder(_context).setTitle("Select Quantity")
.setView(v)
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
//Change the consumption to the new quantity
if(!quan.getText().toString().matches("")){
value = Integer.parseInt(quan.getText().toString());
//Check if conversion from other units is needed
String s[] = pick.getDisplayedValues();
String a = s[pick.getValue()];
//Convert the chosen measure back to grams
if(!a.equals("grams")){
for(String m : measures.keySet()){
if(m==a){
value = (int) (value * measures.get(m));
}
}
}
}
quantity.setQuantity(value);
dialog.dismiss();
//The only catch now is passing through your _context
Intent intent = new Intent(_context,MealActivity.class);
_context.startActivity(intent);
}
})
.setNegativeButton("Cancel", null).create();
dialog.show();
}
实际上，您的问题是您在销毁警报对话框之前调用了 MealACtivity 的启动活动，因此可以按如下方式更新代码：
更新通过以下代码调用警报对话框的方法：
add.setOnClickListener(new OnClickListener(){
public void onClick(View arg0) {
QuantitySelector q = new QuantitySelector();
Quantity quan = new Quantity();
q.select(_context, db.getItem(p.getID()), quan);
db.addConsumption(p.getID(), p.getFavouriteShortName(), quan.getQuantity(), "FAVOURITE");
/* Intent intent = new Intent(_context,MealActivity.class);
_context.startActivity(intent);*/
}
});
并使用以下方法更新数量选择器类：
public class QuantitySelector{
protected static final int RESULT_OK = 0;
private Context _context;
private DatabaseHandler db;
private HashMap<String, Double> measures;
private Item item;
private View v;
private EditText quan;
private NumberPicker pick;
private int value;
private Quantity quantity;
/**
* Function calls the quantity selector AlertDialog
* @param _c: The application context
* @param item: The item to be added to consumption
* @return The quantity that is consumed
*/
public void select(Context _c, Item item, Quantity quantity){
this._context = _c;
this.item = item;
this.quantity = quantity;
db = new DatabaseHandler(_context);
//Get the measures to display
createData();
//Set up the custom view
LayoutInflater inflater = LayoutInflater.from(_context);
v = inflater.inflate(R.layout.quantity_selector, null);
//Set up the input fields
quan = (EditText) v.findViewById(R.id.quantityNumber);
pick = (NumberPicker) v.findViewById(R.id.numberPicker1);
//Set up the custom measures into pick
pick.setMaxValue(measures.size()-1);
pick.setDisplayedValues(measures.keySet().toArray(new String[0]));
//Start the alert dialog
runDialog();
}
public void createData(){
measures = new HashMap<String, Double>();
//Get the measurements from the database
if(item!=null){
measures.putAll(db.getMeasures(item));
}
//Add grams as the default measurement
if(!measures.keySet().contains("grams")){
//Add grams as a standard measure
measures.put("grams", 1.0);
}
}
public void runDialog(){
AlertDialog dialog = new AlertDialog.Builder(_context).setTitle("Select Quantity")
.setView(v)
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
//Change the consumption to the new quantity
if(!quan.getText().toString().matches("")){
value = Integer.parseInt(quan.getText().toString());
//Check if conversion from other units is needed
String s[] = pick.getDisplayedValues();
String a = s[pick.getValue()];
//Convert the chosen measure back to grams
if(!a.equals("grams")){
for(String m : measures.keySet()){
if(m==a){
value = (int) (value * measures.get(m));
}
}
}
}
quantity.setQuantity(value);
Intent intent = new Intent(_context,MealActivity.class);
_context.startActivity(intent);
dialog.dismiss();
}
})
.setNegativeButton("Cancel", null).create();
dialog.show();
}