无法解析构造函数ArrayAdapter（Context，int，java.util.List）[复制]

Question

这个问题在这里已有答案：

• Cannot resolve constructor ArrayAdapter(android.Content.Context, int, java.util.ArrayList<MyObject>) 3回答

所以我试着读一个CSV文件并在ListView中显示它。我在原始目录中有csv文件，我已成功读取每一行并将其输出到日志中。下一步是获取该数据并在ListView中显示。我的数据存储在ArrayList中，所以我试图使用ArrayAdapater，但我看到了问题标题中看到的错误。

main act vi同意.Java:

    private final List<Sample> coordArray = new ArrayList<>();

private void readGPSData() {
    // Read the raw csv file
    InputStream is = getResources().openRawResource(R.raw.rawgps);
    // Reads text from character-input stream, buffering characters for efficient reading
    BufferedReader reader = new BufferedReader(
            new InputStreamReader(is, Charset.forName("UTF-8"))
    );
    // Initialization
    String line = "";
    // Initialization
    try {
        // Step over headers
        reader.readLine();
        // If buffer is not empty
        while ((line = reader.readLine()) != null) {
            Log.d("MyActivity","Line: " + line);
            // use comma as separator columns of CSV
            String[] tokens = line.split(",");
            // Read the data
            Sample sample = new Sample();
            // Setters
            sample.setLat(tokens[0]);
            sample.setLon(tokens[1]);

            // Adding object to a class
            coordArray.add(sample);
            final ArrayAdapter<String> adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, coordArray);
            listView.setAdapter(adapter);
            // Log the object
            Log.d("My Activity", "Just created: " + sample);
        }

    } catch (IOException e) {
        // Logs error with priority level
        Log.wtf("MyActivity", "Error reading data file on line" + line, e);

        // Prints throwable details
        e.printStackTrace();
    }
}

我已经使用了很多次ArrayAdapter并且从未遇到过这个问题。任何帮助表示赞赏！

Answer 1

你的代码有问题：

private final List<Sample> coordArray = new ArrayList<>();

是类型Sample和ArrayAdapter是类型“字符串”。

ArrayAdapter期望与List相同的类型，然后你把它放在构造函数中，解决方案对你有相同的类型，例如：

List<Sample> coordArray = new ArrayList<Sample>();
ArrayAdapter<Sample> adapter = new ArrayAdapter<Sample>(getApplicationContext(), android.R.layout.simple_list_item_1, coordArray);

Answer 2

/**
 * Constructor
 *
 * @param context The current context.
 * @param resource The resource ID for a layout file containing a TextView to use when
 *                 instantiating views.
 * @param objects The objects to represent in the ListView.
 */
public ArrayAdapter(@NonNull Context context, @LayoutRes int resource,
        @NonNull List<T> objects) {
    this(context, resource, 0, objects);
}

如您所见，ArrayAdapter的构造函数接收一个T的列表（T是泛型类型）。因为您指定泛型类型是String，但列表中每个项的类型是Sample，为什么编译器显示错误。

首先更改您的代码

final ArrayAdapter<Sample> adapter = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_list_item_1, coordArray);

然后在toString类中覆盖Sample方法，因为当列表视图显示Sample列表时，默认情况下它将在每个toString对象上调用Sample方法。

class Sample{

    // Your code goes here

    @Override
    public String toString() {
        // TODO: Return a string will be displayed on list view for this object, it can be a properties for example.
        return "";
    }
}

Answer 3

尝试使用getActivity()而不是getApplicationContext(）。