如何使用资源 id (R.string.) 将 ArrayAdapter 设置为字符串数组

Question

1. 我尝试将资源中的返回值转换为字符串，但它不起作用。

2. 这是我的代码：

    import androidx.appcompat.app.AppCompatActivity;
    import android.os.Bundle;
    import android.widget.ArrayAdapter;
    import android.widget.ListView;
   
    public class MainActivity extends AppCompatActivity {
   
        String[] storiesTitles = {(String) getText(R.string.first_story_title), (String) getText(R.string.second_story_title), (String) getText(R.string.third_story_title)};
   
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
   
            ArrayAdapter adapter = new ArrayAdapter(MainActivity.this, android.R.layout.simple_expandable_list_item_1, storiesTitles);
   
            ListView list = findViewById(R.id.lv_stories);
            list.setAdapter(adapter);
   
        }
    }
   

Answer 1

你可以参考这个链接： Android documentation: string resources

这就是您正在寻找的解决方案：

Resources res = getResources();
String[] planets = res.getStringArray(R.array.planets_array);

“行星”数组将包含您在 strings.xml 中为其定义的所有字符串

Answer 2

在onCreate函数内部调用字符串数组

    public class MainActivity extends AppCompatActivity {
    
    
         @Override
         protected void onCreate(Bundle savedInstanceState) {
             super.onCreate(savedInstanceState);
             setContentView(R.layout.activity_main);
   
 String[] storiesTitles = {(String) getText(R.string.first_story_title), (String) getText(R.string.second_story_title), (String) getText(R.string.third_story_title)};

             ArrayAdapter adapter = new ArrayAdapter(MainActivity.this, android.R.layout.simple_expandable_list_item_1, storiesTitles);
    
             ListView list = findViewById(R.id.lv_stories);
             list.setAdapter(adapter);
    
         }
     }

Answer 3

你可能明白了：

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.myniprojects.testsave/com.myniprojects.testsave.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference

你必须像这样在onCreate 中初始化数组：

public class MainActivity extends AppCompatActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        String[] storiesTitles = {(String) getText(R.string.first_story_title), (String) getText(R.string.second_story_title), (String) getText(
                R.string.third_story_title)};

        ArrayAdapter adapter = new ArrayAdapter(MainActivity.this,
                                                android.R.layout.simple_expandable_list_item_1,
                                                storiesTitles
        );

        ListView list = findViewById(R.id.lv_stories);
        list.setAdapter(adapter);
    }
}

现在应该可以了。但更简单的方法是这样做：

在res/values/strings.xml 添加：

<string-array name="titles_array">
    <item>First title</item>
    <item>Second title</item>
    <item>Third title</item>
</string-array>

还有 MainActivity：

public class MainActivity extends AppCompatActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        String[] storiesTitles = getResources().getStringArray(R.array.titles_array);

        ArrayAdapter<String> adapter = new ArrayAdapter<>(MainActivity.this,
                                                          android.R.layout.simple_expandable_list_item_1,
                                                          storiesTitles
        );

        ListView list = findViewById(R.id.lv_stories);
        list.setAdapter(adapter);
    }
}