需要有关应用程序类的说明

Question

I'm trying to use build-in android's Application.class , but every time I want to use it, I get a NullPointerException . I'm going to share some pieces of code to show how I'm accessing my custom class, which extends Application :

This is the class I'm using:

public class SharedProperties extends Application {

    private String currentCategory;
    private String dataNews;

    public SharedProperties() {
        super();
    }

    public String getCurrentCategory() {
        return currentCategory;
    }

    public void setCurrentCategory(String currentCategory) {
        this.currentCategory = currentCategory;
    }

    public String getDataNews() {
        return dataNews;
    }

    public void setDataNews(String dataNews) {
        this.dataNews = dataNews;
    }

}

...and this how I set and get values from it:

    SharedProperties shared = ((SharedProperties)getApplication());
    shared.setCurrentCategory(categories[currentCategory]);
    shared.setDataNews(rssList.get(position).getData());

    ......

    SharedProperties shared = ((SharedProperties)getApplication());
    String category = shared.getCurrentCategory();
    String newstext = shared.getDataNews();

Is the way I'm accessing it wrong or I miss something into the SharedProperties.class ?

Here is my manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.news.reader"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="4" />

    <application android:name="SharedProperties" android:icon="@drawable/logo" android:label="@string/app_name">
        <activity android:name="Splash"
            android:label="@string/app_name"
            android:screenOrientation="portrait">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name="Home"
            android:label="@string/app_name"
            android:screenOrientation="sensor"
            android:configChanges="keyboardHidden|orientation" />
        <activity android:name="News"
            android:label="@string/app_name"
            android:screenOrientation="sensor"
            android:configChanges="keyboardHidden|orientation" />
    </application>

    <uses-permission android:name="android.permission.INTERNET"></uses-permission>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
    <uses-permission android:name="android.permission.READ_PHONE_STATE"></uses-permission>

</manifest>

Answer 1

Put the android:name attribute in the <application> entry which contains all your activities, not as a separate entity. Change it to be the fully-qualified name of the class (eg, com.this.is.your.package.SharedPreferences ).

Also, don't do this. Use a singleton . Please .

Answer 2

For starters, the name of your Application class is SharedProperties , not MyApp , so it should be cast to that.

Secondly, in order for Android to know to use your custom Application, you need to say so in your AndroidManifest.xml like so:

<application
    android:name="SharedProperties"
    android:icon="@drawable/icon"
    android:label="@string/app_name">

Answer 3

I had similar problem, don exactly remember what i did , but do try adding

public SharedProperties()
{

        super();
}