java如何将文本从对象的ArrayList设置为TextView？

Question

我试图使用setText方法来显示从Objects的ArrayList到TextView的所有元素

我在6个不同的工具架（A、B、C、D、E、F）中有6个按钮，每个按钮都有一个弹出菜单，用户在其中选择一个基点（N、S、E、W），然后在文本视图中显示工具架字母和单击的项目。这是地图：

以下是我使用的代码：

Button buttonA, buttonB, buttonC, buttonD, buttonE, buttonF;
private TextView coordenada_view;
ArrayList<PickUpPoint> pickuppoint_array = new ArrayList<PickUpPoint>();

    @Override
    protected void onCreate{......

buttonA.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
    final PopupMenu popupMenu = new PopupMenu(Mapa.this, buttonA);
        popupMenu.getMenuInflater().inflate(R.menu.popup_menu, popupMenu.getMenu());
        popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
          @Override
          public boolean onMenuItemClick(MenuItem item) {
          String mShelving = buttonA.getText().toString();
           String mCardinalPoint = item.getTitle().toString();

                 pickuppoint_array.add(new PickUpPoint(mShelving,mCardinalPoint));
                 PickUpPoint pickUpPoint = new PickUpPoint(mShelving,mCardinalPoint);

//Here I´m trying to show all the elements of the ArrayList into the TextView
                    for (int i = 0; i < pickuppoint_array.size(); i++){
                      coordenada_view.setText( pickuppoint_array.get(i).toString());
                       }
                        return true;
                    }
                });
                popupMenu.show();

buttonB.setOnClickListener....
buttonC.setOnClickListener....
}

这是类PickUpPoint：

class PickUpPoint {
    public String shelving;
    public String cardinalPoint;

    public String getShelving() {
        return shelving;
    }

    public String getCardinalPoint() {
        return cardinalPoint;
    }

    PickUpPoint(String shelving, String cardinalPoint) {
        this.shelving = shelving;
        this.cardinalPoint = cardinalPoint;
    }
}

但我是从数组列表中得到的：

所以，我的问题是。。。如何像这样从数组列表中获取所有元素

Answer 1

使用此方法设置来自Arraylist的文本

还要检查Arraylist是否不是null且为空

public void setTextViewFromList(ArrayList<PickUpPoint> arraylist, TextView textview) {
    //Variable to hold all the values
    String output = "";

    for (int i = 0; i < arraylist.size(); i++) {
        //Append all the values to a string
        output += arraylist.get(i).getShelving();//whatever you want to show here like shelving or cordinalpoint use getCordinalPoint()
        output += "\n";
    }

    //Set the textview to the output string
   textview.setText(output);
}

用法

这样称呼这个方法

setTextViewFromList(pickuppoint_array,coordenada_view)

Answer 2

我假设coordenada_view#setText只能被调用一次

因此，首先需要将pickuppoint_数组中的元素转换为字符串 然后将其提供给setText方法

StringBuilder content = new StringBuilder();
for (int i = 0; i < pickuppoint_array.size(); i++) {
  content.append(pickuppoint_array.get(i).toString());
  content.append('\n');
}

coordenada_view.setText(content.toString());

您还希望在PickUpPoint类中实现toString（）方法，以返回每个对象所需的表示形式，例如：

public String toString() {
    StringBuilder builder = new StringBuilder();
    builder.append("SHELVING ");
    builder.append(shelving);
    builder.append(" - ");
    builder.append(cardinalPoint);
    return builder.toString();
}

附言： 如果您知道这些字符串的预期长度，那么应该将其作为参数提供给StringBuilder构造函数，这样jvm就不需要浪费时间来调整其大小

新的StringBuilder（18）可能适用于toString方法， 新的StringBuilder（19*pickuppoint_array.size（））可能适用于另一个