Android ListView適配器不會刷新

Question

我在使用自定義適配器刷新列表視圖時遇到了很多麻煩。我一直在網上搜索過去的一小時，我似乎無法找到任何解決方案，這將使我的列表視圖刷新。

我試過notifyDataSetChanged，也listView.invalidate，但似乎沒有工作。任何幫助將不勝感激。我可以看到使用logcat更新的數據，但它並沒有在屏幕上刷新，我不知道爲什麼。

以下是代碼。

ArrayList<Student> students = new ArrayList<Student>(); 

listview = (ListView) findViewById(R.id.listView); 
adapter = new StudentAdapter(this, R.layout.listitemlayout, students); 
listview.setAdapter(adapter); 

定義適配器

public class StudentAdapter extends ArrayAdapter<Student>{ 

    Context context; 
    int layoutResourceId;  
    ArrayList<Student> data = null; 

    public StudentAdapter(Context context, int layoutResourceId, ArrayList<Student> data) { 
     super(context, layoutResourceId, data); 
     this.layoutResourceId = layoutResourceId; 
     this.context = context; 
     this.data = data; 
    } 

    public void updateStudentsList(ArrayList<Student> newlist){ 
     data.clear(); 
     data = newlist; 
     this.notifyDataSetChanged(); 
    } 

    public void updateStudentTime(){ 
     for (Student s : data) { 
      s.updateElapsedTime();   
     } 
     this.notifyDataSetChanged(); 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     View row = convertView; 
     if(row == null){ 
      LayoutInflater inflater = ((Activity)context).getLayoutInflater(); 
      row = inflater.inflate(layoutResourceId, parent, false); 

      Student student = data.get(position); 

      TextView title = (TextView)row.findViewById(R.id.txtTitle); 
      title.setText(student.getFirstname() + " " + student.getLastname()); 

      TextView subTitle = (TextView)row.findViewById(R.id.txtSubTitle); 
      subTitle.setText(student.getStudentID());  

      TextView duration = (TextView)row.findViewById(R.id.textDuration); 
      duration.setText(student.getElapsedTime()); 
     } 
     return row; 
    } 
} 

我更新使用一個線程，每隔一段時間數據。

Runnable runnable = new Runnable() { 
      public void run() { 
       runOnUiThread(new Runnable() { 
        public void run() { 
         // Updates how long the student is in the centre. 
         adapter.updateStudentTime(); 
         adapter.notifyDataSetChanged(); 
         listview.invalidate(); 
         Log.i("Debug", "Running on UI Thread"); 
        } 
       }); 
       handler.postDelayed(this, 1000); 
      } 
     }; 
     handler.postDelayed(runnable, 1000); 

Answer 1

ListView將回收視圖，因此您必須在getView中設置數據。 和i f(row == null){表示數據不會刷新，只使用舊數據。

，你應該這樣做：

Class ViewHolder { 
    TextView title; 
    TextView subTitle; 
    TextView duration; 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    View row = convertView; 
    ViewHolder holder = null; 
    if(row == null){ 
     LayoutInflater inflater = ((Activity)context).getLayoutInflater(); 
     row = inflater.inflate(layoutResourceId, parent, false); 

     Student student = data.get(position); 
     holder = new ViewHolder(); 
     holder.title = (TextView)row.findViewById(R.id.txtTitle); 
     holder.subTitle = (TextView)row.findViewById(R.id.txtSubTitle); 
     holder.duration = (TextView)row.findViewById(R.id.textDuration); 
     row.setTag(holder); 
    } else { 
     holder = row.getTag(); 
    } 
    holder.title.setText(student.getFirstname() + " " + student.getLastname()); 
    holder.subTitle.setText(student.getStudentID()); 
    holder.duration.setText(student.getElapsedTime());  
    return row; 
} 

Answer 2

想想下面的代碼，防止您刷新列表。

if(row == null){  
... 
} 

該代碼表示​​當列表刷新時。它將檢查行是否爲空（表示屏幕中的行顯示是否被創建）。刷新列表時，已經創建了該行。所以它不是NULL，新的數據不會設置！

你應該改變這樣的：在UI

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

    View row = convertView; 

    if(row == null){ 
     LayoutInflater inflater = ((Activity)context).getLayoutInflater(); 
     row = inflater.inflate(layoutResourceId, parent, false); 

    } 

    Student student = data.get(position); 
    ... 

}