在 android studio 中更新列表视图

Question

我正在 android studio 中创建一个应用程序。

我需要使用通过短信发送的新网址更新 列表视图。

如何将新的 url 添加到我的列表中？

这是我目前的主要代码。

 public class MainActivity extends AppCompatActivity {

 ListView list;
WebView webView;
ArrayList<String> sites = new ArrayList<> ("https://www.google.com", "https://www.yahoo.com", "https://www.apple.com");
String [] url = {"https://www.google.com", "https://www.yahoo.com", "https://www.apple.com"};

MyBroadcastReceiver receiver;


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



    list = (ListView)findViewById(R.id.listview);
    MyListAdapter adapter = new MyListAdapter(this, sites);
    sites.add("new site");
    adapter.notifyDataSetChanged();
    list.setAdapter(adapter);
    list.setDividerHeight(5);
    webView = (WebView)findViewById(R.id.webview);
    webView.setWebViewClient(new WebViewClient(){});

    list.setOnItemClickListener(new AdapterView.OnItemClickListener(){
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int position, long id){
            Toast.makeText(getApplicationContext(),sites[position], Toast.LENGTH_SHORT).show();
            webView.loadUrl("https://www.google.com");
            webView.loadUrl(url[position]);

        }
    });

    receiver = new MyBroadcastReceiver();
    IntentFilter filter = new IntentFilter(Intent.ACTION_AIRPLANE_MODE_CHANGED);
    registerReceiver(receiver,filter);
}


} 

我的列表适配器：

public class MyListAdapter extends ArrayAdapter<String> {
private Activity context_;
private ArrayList<String> sites;

//constructor
public MyListAdapter(Activity context, ArrayList<String> sites){
    super(context,R.layout.row,sites);
    context_ = context;
    this.sites = sites;
}

public View getView (int position, View convertView, ViewGroup parent){
    if(convertView == null){
        LayoutInflater inflater = context_.getLayoutInflater();
        convertView = inflater.inflate(R.layout.row,null);
    }

    ViewHolder holder = (ViewHolder) convertView.getTag();

    if(holder == null){
        holder = new ViewHolder(convertView);
        holder.tv_link.setText(sites.get(position));
    }
    else{
        holder.tv_link.setText(sites.get(position));
    }
    return convertView;
}

private class ViewHolder{
    TextView tv_link;
    public ViewHolder(View row){
        tv_link = (TextView) row.findViewById(R.id.tv_link);
    }
}

}

Answer 1

您将 sites 定义为 final，您也无法更新它，而不是 String[] 使用 String 的数组列表：

  ArrayList<String> sites = new ArrayList<>();

将适配器的构造函数更改为接受 ArrayList 而不是数组，并且在收到新数据时使用：

sites.add("new site !");
adapter.notifyDataSetChanged();

如果你这样做，在适配器的构造函数中：

  public class MyListAdapter extends ArrayAdapter<String> {

    private Context context;
    private ArrayList<String> array;

    public MyListAdapter(Context ctx, ArrayList<String> mArray) {
        super(ctx, 0, mArray);
        this.context = ctx;
        this.array = mArray; 
    }

    //other methods
}

adapter.notifyDataSetChanged();可以更新数据集和更新listView！

但如果你喜欢以下：

 public class MyListAdapter extends ArrayAdapter<String> {

    private Context context;
    private ArrayList<String> array;

    public MyListAdapter(Context ctx, ArrayList<String> mArray) {
        super(ctx, 0, mArray);
        this.context = ctx;
        for (int i = 0; i < mArray.size(); i++) // copy global ArrayList
            this.array.add(mArray.get(i));
    }

    //other methods
}

首先，你必须创建一个方法来更新Adapter的localDataset然后调用this.adapter.notifyDataSetChanged();

如下：

 public void newDataReceived(ArrayList<String> newArr){
            this.array.clear();
            for (int i = 0; i < newArr.size(); i++)
                this.array.add(newArr.get(i));

            this.notifyDataSetChanged();
        }

并在收到新数据时调用适配器方法！

 sites.add("new site ");
    adapter.newDataReceived(sites); 

代码是手动输入的，可能语法错误，希望对你有帮助

Answer 2

尝试使用 ArrayList，然后在需要在该 arrayList 中添加新 url 时添加。然后调用 adapter.notifyDataSetChanged()

如果您知道可能需要更新值，请不要使用 final