有没有办法更改我正在调用的文件名，这样我就不需要所有这些 if/else 语句了？

Question

I am currently developing a java XML based app using Android Studio, am currently messing around with image and list views, I'd like to change the image based on the user's selection and have got the app to work as intended, however, I do not like how many if statements it uses, I have looked all over the web for a way to change the R.drawable.x where x is a different filename depending on users selection, however, haven't come across anything as of yet, please find below my complete java and XML code.

I would like to know what the best way to do this would be? Thank you in advance!

MainActivity.java

public class MainActivity extends AppCompatActivity {
    private String[] fruits = {"Apple", "Watermelon", "Grapes", "Banana"};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final ListView mListView = (ListView) findViewById(R.id.fruitslist);
        final ImageView mImageView = (ImageView) findViewById(R.id.imageView);
        ArrayAdapter<String> aAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, fruits);
        mListView.setAdapter(aAdapter);
        mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> a, View v, int position, long id) {
                String fruit = fruits[position];
                Toast.makeText(MainActivity.this, "Selected :" + " " + fruit + ", " + position, Toast.LENGTH_SHORT).show();
                if (position == 0) {
                    mImageView.setImageResource(R.drawable.apple);
                } else if (position == 1) {
                    mImageView.setImageResource(R.drawable.watermelon);
                } else if (position == 2) {
                    mImageView.setImageResource(R.drawable.grapes);
                } else {
                    mImageView.setImageResource(R.drawable.banana);
                }
                mImageView.setVisibility(View.VISIBLE);
            }
        });
    }
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ListView
        android:id="@+id/fruitslist"
        android:layout_width="match_parent"
        android:layout_height="251dp" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="390dp"
        android:visibility="invisible"
        app:srcCompat="@drawable/apple" />

</LinearLayout>

Note that I have set the image to apple as default, this was simply so I had a placeholder to see where the image view was located graphically, it's set to invisible on start and not made visible until the user's selection has been made.

Answer 1

a lot of work for you for this purpose

first of all create some custom class holding your fruit objects with names and image resource

public class Fruit{

    public String name;
    public int imageRes;
    
    public Fruit(String name, int imageRes){
        this.name = name;
        this.imageRes = imageRes;
    }

    public String toString(){
        return name;
    }
}

next declare your fruits array like this

private Fruit[] fruits = {
        new Fruit("Apple", R.drawable.apple),
        ... rest of fruits

now your adapter need to handle Fruit class (adapter is generic), so declare it like below

ArrayAdapter<Fruit> aAdapter = new ArrayAdapter<>(this,
    android.R.layout.simple_list_item_1, fruits);

Fruit isn't usual String so ArrayAdapter will use toString method to get text to print (every object have toString method, String also, returns itself)

now in your onItemClick method just get proper object by position

Fruit pickedFruit = fruits[position];
mImageView.setImageResource(picketFruit.imageRes);
mImageView.setVisibility(View.VISIBLE);