Question

有人可以帮我解释为什么这个小部件服务代码只能运行@ api 8,9和10？这不适用于Android API 17 4.2.2，安装时也会出错。

当我在2.3.3终端上运行时，它会运行并显示提要！

我在4.2.2终端上运行时获得的logcat是这样的：

12-13 22:00:27.907: D/widget(1438): onUpdate()
12-13 22:00:27.957: D/widget(1438): Beginning update cycle...
12-13 22:00:28.017: D/AndroidRuntime(1438): Shutting down VM
12-13 22:00:28.017: W/dalvikvm(1438): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
12-13 22:00:28.059: E/AndroidRuntime(1438): FATAL EXCEPTION: main
12-13 22:00:28.059: E/AndroidRuntime(1438): java.lang.RuntimeException: Unable to start service com.example.rss.widgetservice@40ce59f8 with Intent { cmp=com.example.rss/.widgetservice }: java.lang.NullPointerException: println needs a message
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2673)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.app.ActivityThread.access$1900(ActivityThread.java:141)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1331)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.os.Looper.loop(Looper.java:137)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.app.ActivityThread.main(ActivityThread.java:5041)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at java.lang.reflect.Method.invokeNative(Native Method)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at java.lang.reflect.Method.invoke(Method.java:511)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at dalvik.system.NativeStart.main(Native Method)
12-13 22:00:28.059: E/AndroidRuntime(1438): Caused by: java.lang.NullPointerException: println needs a message
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.util.Log.println_native(Native Method)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.util.Log.d(Log.java:138)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at com.example.rss.widgetservice.onStart(widgetservice.java:44)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.app.Service.onStartCommand(Service.java:450)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2656)
12-13 22:00:28.059: E/AndroidRuntime(1438):     ... 10 more

以下是代码：

请有人帮助我理解这一点！

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

import android.app.Service;
import android.appwidget.AppWidgetManager;
import android.content.ComponentName;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
import android.widget.RemoteViews;

public class widgetservice extends Service {  
      @Override  
      public void onStart(Intent intent, int startId) {  
         RemoteViews rviews = new RemoteViews(this.getPackageName(), R.layout.widget_layout);  
         DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();  
         ComponentName meuWidget = new ComponentName(this, widget.class);  
         AppWidgetManager manager = AppWidgetManager.getInstance(this);  
         try {  
             rviews.setTextViewText(R.id.TextView01, "Updating...");  
             manager.updateAppWidget(meuWidget, rviews);  
             Log.d("widget", "Beginning update cycle...");  
             DocumentBuilder builder = factory.newDocumentBuilder();  
             Document dom = builder.parse("http://blog.masterd.pt/index.php/feed/");  
             Element root = dom.getDocumentElement();  
             NodeList items = root.getElementsByTagName("item");  
             if (items.getLength() > 0) {  
                Element entrada = (Element) items.item(0);  
                NodeList titulos = entrada.getElementsByTagName("title");  
                Element titulo = (Element) titulos.item(0);  
                String texto = titulo.getFirstChild().getNodeValue();  
                rviews.setTextViewText(R.id.TextView01, texto);  
                Log.d("widget", "Update cycle completed!");  
                manager.updateAppWidget(meuWidget, rviews);  
             }  
        }  
        catch(Exception ex) {  
            Log.d("widget", ex.getMessage());  
        }  
      }  

      @Override  
         public IBinder onBind(Intent intent) {  
           return null;  
        }  
      }

这是我的清单

 <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.rss"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="7"
        android:targetSdkVersion="18" />
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <receiver android:name="com.example.rss.widget">
            <intent-filter>
                <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
            </intent-filter>
            <meta-data android:name="android.appwidget.provider" 
                android:resource="@xml/widget_info">
                        </meta-data>
            </receiver>
        <activity
            android:name="com.example.rss.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <service android:name="com.example.rss.widgetservice" />

    </application>

</manifest>

我的小部件提供商

import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProvider;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

public class widget  extends AppWidgetProvider {


    @Override  
    public void onUpdate(Context context,   
        AppWidgetManager appWidgetManager,  
        int[] appWidgetIds) {  
      Log.d("widget", "onUpdate()");  
      context.startService(new Intent(context, widgetservice.class));  
    } 
}

Answer 1

12-13 22:00:28.059: E/AndroidRuntime(1438): Caused by: java.lang.NullPointerException: println needs a message
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.util.Log.println_native(Native Method)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at android.util.Log.d(Log.java:138)
12-13 22:00:28.059: E/AndroidRuntime(1438):     at com.example.rss.widgetservice.onStart(widgetservice.java:44)

java.lang.NullPointerException：println需要一条消息

似乎ex.getMessage()在此块返回null

catch(Exception ex) {  
    Log.d("widget", ex.getMessage());  
}

将代码更改为：

catch(Exception ex) {  
    String error = (ex.getMessage()==null)?"Some message error":ex.getMessage();
    Log.d("widget", error);  
}

Answer 2

感谢大家的帮助！ @Ramaral你让我看到了什么问题...在蜂窝到果冻豆我们必须使用异步任务...所以一个简单的方法来获得这个工作在果冻豆是删除使用sdk最小和最大版本
现在一切都很完美！非常感谢！案例已解决

Android小部件服务只能在API9之前工作吗？

2 个答案: