Question

我正在学习使用ListView填充ArrayList。我已使用

填充ArrayList doPostExecute()内的GetParentVitalsName()

vitalList.add(parentVitalName);

Logcat没有显示错误。但列表没有显示。我只得到一个空白页面。我发现它不会进入getView的{{1}}方法。我在这做错了什么？

MyListAdapter包含acitivity_vital_list.xml，ListView包含项目模板

vital_list_layout

vital_list_layout.xml

public class VitalListActivity extends ActionBarActivity {

    private List<String> vitalList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_vital_list);
        Intent intent = getIntent();
        String status = intent.getStringExtra(LoginActivity.EXTRA_MESSAGE);
        if(status.equals("true")){
            new GetParentVitalName().execute();
            Log.d("Tag", "Execute complete");
            populateListView();
            Log.d("Tag", "Populate complete");
        }
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_vital_list, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void populateListView() {
        ArrayAdapter<String> adapter = new MyListAdapter();
        ListView list = (ListView) findViewById(R.id.vitalsListView);
        list.setAdapter(adapter);
    }

    private class MyListAdapter extends ArrayAdapter<String>{

        public MyListAdapter(){

            super(VitalListActivity.this, R.layout.vital_list_layout, vitalList);
            Log.d("Tag", "super okay");
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            //return super.getView(position, convertView, parent);
            //Making sure we've a view to work with(may have been given null
            Log.d("TAG","Inside get view");
            View itemView = convertView;
            if (itemView == null)
                itemView = getLayoutInflater().inflate(R.layout.vital_list_layout, parent, false);

            String currentVital = vitalList.get(position);

            //Fill the view

            TextView vitalText = (TextView) itemView.findViewById((R.id.vitalTextView));
            vitalText.setText(currentVital);

            return itemView;
        }
        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return vitalList.size();
        }
    }

    private class GetParentVitalName extends AsyncTask<String, String, String> {

        protected String doInBackground(String... params){

            String responseText = null;

            HttpClient httpClient = ServiceHelper.getHttpClient();
            HttpContext localContext = new BasicHttpContext();
            HttpGet httpGet = new HttpGet("http://test.gogch.com/gch-restful/vitals/custome/added/parentvitals");
            Log.d("KMN", "Sucess");
            try {
                HttpResponse response = httpClient.execute(httpGet);
                Log.d("DFGH","Success again.");
                int statusCode = response.getStatusLine().getStatusCode();
                Log.d("Http Post Response V", Integer.toString(statusCode));
                responseText = EntityUtils.toString(response.getEntity());
                Log.d("Http Post Response V", responseText);

            }
            catch(ClientProtocolException e){
                e.printStackTrace();
            }
            catch (IOException e){
                e.printStackTrace();
            }
            return responseText;
        }

        protected void onPostExecute(String responseText){

            if (responseText != null){
                try {
                    JSONArray vitalsArray = new JSONArray(responseText);
                    for(int i =0;i<vitalsArray.length();i++){
                        JSONObject vitalsObject = vitalsArray.getJSONObject(i);
                        String parentVitalName = vitalsObject.getString("parentVitalName");
                        vitalList.add(parentVitalName);
                        Log.d("YGVJ",vitalList.get(i));
                    }
                }
                catch (JSONException e){
                    e.printStackTrace();
                }
            }
        }
    }
}

activity_vital_list.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">


    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/imageView"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Large Text"
        android:id="@+id/vitalTextView"
        android:layout_marginLeft="27dp"
        android:layout_marginStart="27dp"
        android:layout_alignParentTop="true"
        android:layout_toRightOf="@+id/imageView"
        android:layout_toEndOf="@+id/imageView" />
</RelativeLayout>

Answer 1

Logcat没有显示错误。但列表没有显示。我只是得到一个空白页

在适配器数据源中添加项目后调用notifyDataSetChanged()：

vitalList.add(parentVitalName);
adapter.notifyDataSetChanged();

注意：确保vitalList与MyListAdapter适配器类中使用的List对象相同。

修改

还覆盖getCount()类中的MyListAdapter方法：

@Override public int getCount() { // TODO Auto-generated method stub return vitalList.size(); }

Answer 2

制作您的适配器类如下所示。

private class MyListAdapter extends ArrayAdapter<String>{

Context context;
ArrayList<String> arraylist= new Arraylist<>;

    public MyListAdapter(Context context,ArrayList<String> arraylist){

        super(context, R.layout.vital_list_layout, vitalList);
        Log.d("Tag", "super okay");
        this.context=context;
        this.arraylist=arraylist;
    }

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    //return super.getView(position, convertView, parent);
    //Making sure we've a view to work with(may have been given null
    Log.d("TAG","Inside get view");
    View itemView = convertView;
    if (itemView == null)
        itemView = getLayoutInflater().inflate(R.layout.vital_list_layout, parent, false);

   // String currentVital = vitalList.get(position);

    //Fill the view

    TextView vitalText = (TextView) itemView.findViewById((R.id.vitalTextView));
    vitalText.setText(arralist.get(position));

    return itemView;
}

}

在您的Activity类中。初始化适配器并将arraylist放入其中，如下所示：

ListView list;
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_vital_list);
    list = (ListView) findViewById(R.id.vitalsListView);
    Intent intent = getIntent();
    String status = intent.getStringExtra(LoginActivity.EXTRA_MESSAGE);
    if(status.equals("true")){
        new GetParentVitalName().execute();
        Log.d("Tag", "Execute complete");
        populateListView();
        Log.d("Tag", "Populate complete");
    }
}

    private void populateListView() {
        MyListAdapter adapter = new MyListAdapter(VitalListActivity.this,vitalList); //where vitalList will be get from asynctask. 
        list.setAdapter(adapter);
        adapter.notifyDataSetChanged();
    }

Answer 3

您没有覆盖getCount（）方法。尝试这样做，它会正常工作。

@Override
public int getCount() {
    return vitalList.size();
}

然后尝试将list设置为match_parent。

Android ListView根本没有显示

3 个答案: