在简单的 class 中，无法打开 Assets 文件夹中的文件以加载到 Android 应用程序中的数组

Question

I want to read from my simple java class "MyContent", and there is a static method with no arguments, as once you call the variable inside, it will do the codes inside the static method. I am trying to add code into it by reading the files in Assets folder and put into list so that the data adaptor will read it.

MyContent class:

public class MyContent extends Application {

public static final List<Element> ITEMS = new ArrayList<Element>();

private static Random random = new Random(System.currentTimeMillis());

public static final Map<String, Element> ITEM_MAP = new HashMap<String, Element>();
AssetManager assetManager = getAssets();
static {

    try {
        InputStream inputStream = getAssets().open("data.csv");
        InputStreamReader inputStreamReader=new InputStreamReader((inputStream));
        BufferedReader bufferedReader=new BufferedReader((inputStreamReader));
        String tt="";
        while ((tt=bufferedReader.readLine())!=null){
            MyContent.addItemElement(MyContent.createElement(tt));
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

}

The problem is that the AssetManager assetManager = getAssets(); can't be static, but the InputStream inputStream = getAssets().open("data.csv"); I need to put them into the static method, can anyone tell me how to deal with this issue?

Answer 1

getAssets() need application context initialised upfront before you can] call it. Below code flow should be able to achieve your objective:

public class MyContent extends Application {

    public static final Map<String, Element> ITEM_MAP;

    @Override
    public void onCreate() {
        super.onCreate();

        ITEM_MAP = new HashMap<String, Element>();
        AssetManager assetManager = getAssets();
        try {
            InputStream inputStream = getAssets().open("data.csv");
            InputStreamReader inputStreamReader=new InputStreamReader((inputStream));
            BufferedReader bufferedReader=new BufferedReader((inputStreamReader));
            String tt="";
            while ((tt=bufferedReader.readLine())!=null){
                MyContent.addItemElement(MyContent.createElement(tt));
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Edit 1

Inside your AndroidManifest.xml , remember to add your app class under tag application , eg

<application
        android:name=". MyContent"
   ...
</application>