【发布时间】：2019-05-08 17:10:57
【问题描述】：
我正在尝试使用 retrofit2 获取数据并使用作为自定义适配器参数传递的列表显示这些数据。当我在onResponse() 方法中的列表中存储数据时，onResponse() 方法中的列表有一些价值。但在oncreate() 方法中，它给我null。不过，我将 List 声明为全局。当我运行应用程序时，有时它什么也不显示，有时应用程序崩溃。我知道这听起来很疯狂。但它正在发生。所以，我想知道，我的代码有什么问题？如何在列表视图中显示数据？
如果我的问题模式有问题，但这是我在这个网站上的第一个问题，请原谅我。
MainActivity`
public class LaboratoryValues extends AppCompatActivity {
public List<Data> productList = null;
List<Data>arrayList = null;
int size;
String st;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_laboratory_values);
//productList = new ArrayList<Data>();
getInvestigation();
for(int i =0; i < size; i++){
st = arrayList.get(i).getName();
}
System.out.println("Name : "+st);//here print Name : null
ListView lview = (ListView) findViewById(R.id.listview);
ListviewAdapter adapter = new ListviewAdapter(this, arrayList);
lview.setAdapter(adapter);
}
private void getInvestigation() {
/* final ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
progressDialog.setCancelable(false); // set cancelable to false
progressDialog.setMessage("Please Wait"); // set body
progressDialog.show(); // show progress dialog*/
ApiInterface apiService =
Api.getClient(ApiInterface.BASE_URL).create(ApiInterface.class);
Call<Investigation> investigationCall = apiService.getInvestigation();
investigationCall.enqueue(new Callback<Investigation>() {
@Override
public void onResponse(Call<Investigation> call, Response<Investigation> response) {
arrayList = response.body().getData();
//productList.addAll(arrayList);
size = response.body().getData().size();
for (int i = 0; i < size; i++) {
System.out.println("Name : " + arrayList.get(i).getName());//here printing Name is ok
}
}
@Override
public void onFailure(Call<Investigation> call, Throwable t) {
Toast.makeText(getApplicationContext(),"data list is empty",Toast.LENGTH_LONG).show();
}
});
}
}
自定义适配器 (listviewAdapter)
public class ListviewAdapter extends BaseAdapter {
public List<Data> productList;
Activity activity;
//Context mContext;
public ListviewAdapter(Activity activity, List<Data> productList) {
super();
this.activity = activity;
this.productList = productList;
}
@Override
public int getCount() {
return productList.size();
}
@Override
public Object getItem(int position) {
return productList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
private class ViewHolder {
TextView name;
TextView normal_finding;
TextView increased;
TextView decreased;
TextView others;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
LayoutInflater inflater = activity.getLayoutInflater();
if (convertView == null) {
convertView = inflater.inflate(R.layout.listview_row, null);
holder = new ViewHolder();
holder.name = convertView.findViewById(R.id.name);
holder.normal_finding =convertView.findViewById(R.id.normal_finding);
holder.increased = convertView.findViewById(R.id.increased);
holder.decreased = convertView.findViewById(R.id.decreased);
holder.others =convertView.findViewById(R.id.others);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
Data item = productList.get(position) ;
holder.name.setText(item.getName());
System.out.println("holderName : "+item.getName() );
holder.normal_finding.setText(item.getNormal_finding());
System.out.println("holderName : "+item.getNormal_finding() );
holder.increased.setText(item.getIncreased());
holder.decreased.setText(item.getDecreased());
holder.others.setText(item.getOthers());
return convertView;
}
}
【问题讨论】：
-
该改造操作是异步的，这意味着在调用
enqueue()后您的代码将立即继续执行，并且您可能在实例化并设置Adapter之前不会得到响应在ListView。这就是您在日志中获得空值的原因。需要等到onResponse()中获取数据后才能设置Adapter中的数据。
标签： android list listview retrofit2 custom-adapter