Android小部件的固定更新频率

Question

In order to have Widget , we need to maintain an XML file (AppWidgetProviderInfo) which describes the properties of the widget, eg size or fixed update frequency like this:

<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
    android:minWidth="160dp" 
    android:minHeight="72dp"
    android:initialLayout="@layout/widget_layout"
    android:updatePeriodMillis="1800000"
    android:configure="android.project.WidgetConfigure" >

</appwidget-provider>

and Maintain the App Widget configuration in the AndroidManifest.xml.

<meta-data
        android:name="android.appwidget.provider"
        android:resource="@xml/widget_info" />
 </receiver>

I know that we can not edit the updatePeriodMillis . programmatically and we need to use AlarmManager. ( Android Widget set android:updatePeriodMillis programmatically )

But how can I read that value from the xml file programmatically. Is there any way ?

Addenda:

try {
        AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(getApplicationContext());
        AppWidgetProviderInfo info = appWidgetManager.getAppWidgetInfo(R.xml.widget_info);
        System.out.println("Time: " + info.updatePeriodMillis);
    } catch(Exception err) {
        err.printStackTrace();
    }

If I use this code in an Activity, it returns NullPointerException in catch.

Answer 1

updatePeriodMillis is a value which the system uses in order to send you a proper broadcast once that period's time has come. Why will you want to read it and trigger an AlarmManager intent for the exact same time?

After your edit: You are passing the wrong "id"; you should pass the actual widget id, not its XML metadata id. As I wrote in my last comment, try this: AppWidgetManager.getInstance() , then use AppWidgetManager.getAppWidgetIds() to retrieve your widget(s) id, then continue as discussed ( AppWidgetManager.getAppWidgetInfo() ...)