java - "this"关键字不返回上下文

Question

我定义了自己的自定义 ArrayAdapter，命名为 WordAdapter，如下所示:

public class WordAdapter extends ArrayAdapter<Word> {
Context context;

public WordAdapter(Context context, ArrayList<Word> words) {
    super(context, 0, words);
    this.context = context;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    // Check if the existing view is being reused, otherwise inflate the view
    View listItemView = convertView;
    if (listItemView == null) {
        listItemView = LayoutInflater.from(getContext()).inflate(R.layout.list_item, parent, false);
    }

    Word currentWord = getItem(position);

    TextView miwok = (TextView) listItemView.findViewById(R.id.miwok_text_view);
    miwok.setText(currentWord.getMiwokTranslation());

    TextView english = (TextView) listItemView.findViewById(R.id.english_text_view);
    english.setText(currentWord.getEnglishTranslation());

        return listItemView;
    }
}

我在类里面需要它，它是这样使用的:

public class NumbersActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.word_list);

    ArrayList<Word> words = new ArrayList<>();
    words.add(new Word("lutti","one"));
    words.add(new Word("otiiko","two"));
    words.add(new Word("toldokosu","three"));
    words.add(new Word("oyyisa","four"));
    words.add(new Word("massoka","five"));
    words.add(new Word("temmoka","six"));
    words.add(new Word("kenekaku","seven"));
    words.add(new Word("kawinta","eight"));
    words.add(new Word("wo'e","nine"));
    words.add(new Word("na'aacha","ten"));

    WordAdapter itemsAdapter = new WordAdapter(this, words);

    ListView listView = (ListView) findViewById(R.id.list);

    listView.setAdapter(itemsAdapter);


    }
}

但是它在行 WordAdapter itemsAdapter = new WordAdapter(this, words); 中给出错误，说

WordAdapter (android.content.Context ArrayList) cannot be applied to com.example.android.miwok.NumbersActivity ArrayList

依赖关系:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.3.0'
    compile 'com.android.support:design:23.3.0'
    compile 'com.android.support:support-v4:23.3.0'
}

Answer 1

我可以看出您的代码没有问题。 AppCompatActivity 是 Context 本身。因此，传递 "this" 无论如何都应该有效。

正如我所见，存在依赖冲突。如果你已经添加了 appcompat 依赖，你不必再添加 support V4 依赖，因为 supportv4 包已经自带了 appcompat 依赖。

我的建议是删除 support v4 依赖项并再次与 gradle 同步。到时候应该没问题即使它不起作用，也只需再执行一步即可。单击 文件 -> 无效/缓存重新启动 -> 单击使缓存无效并重新启动。

现在我很确定，那个问题不会存在。