Android Arraylist迭代設置或添加基於它是否存在

我希望能夠檢查一個對象是否存在，根據其_sensor_id內ArrayList它顯示在ListView。Android Arraylist迭代設置或添加基於它是否存在

如果存在，我想設置它，如果不存在，我想添加它。每次此方法運行時，HashMap數據都會不同，我希望它根據_sensor_id來檢查它是否存在於ListView（ArrayList）中或不存在。

if (mEquipmentList.isEmpty()) { 
// Populate the Equipment List 
HashMap < String, String > equip = new HashMap < String, String >(); 
equip.put(FIRST_COLUMN, _sensor_id); 
equip.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
equip.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
equip.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
equip.put(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 
mEquipmentList.add(equip); 

for (HashMap < String, String > entry: mEquipmentList) { 
    for (String key: entry.keySet()) { 
    String value = entry.get(key); 
    //Debugging 
    Log.d("equipment contains= ", "sensorid: " + mEquipmentList.get(0)); 
    Log.d("equipment key = ", "key: " + key); 
    Log.d("equipment value = ", "value: " + value); 
    Log.d("equipment index", "value:" + (mEquipmentList.indexOf(equip))); 
    } 
} 
} else { 

// Populate the Equipment List 
HashMap < String, String > equip = new HashMap < String, String >(); 
equip.put(FIRST_COLUMN, _sensor_id); 
equip.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
equip.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
equip.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
equip.put(SECOND_COLUMN, Double.toString(mEquipmentList.size())); 
mEquipmentList.set(0, equip); 

for (HashMap < String, String > entry: mEquipmentList) { 
    for (String key: entry.keySet()) { 
    String value = entry.get(key); 
    //Debugging 
    Log.d("equipment contains= ", "sensorid: " + mEquipmentList); 
    Log.d("equipment contains= ", "sensorid: " + mEquipmentList.contains(key)); 
    Log.d("equipment key = ", "key: " + key); 
    Log.d("equipment value = ", "value: " + value); 
    Log.d("equipment index", "value:" + mEquipmentList.indexOf(equip)); 
    } 
} 
} 

// Set the adapter 
ListViewAdapter adapter = new ListViewAdapter(this, mEquipmentList); 
listView.setAdapter(adapter); 
adapter.notifyDataSetChanged(); 

}

編輯*********

public void updateEquipList(String message) { 

    if (!pathHistory.isEmpty()) { 
     double currentLat = pathHistory.getFirst().lat; 
     double currentLng = pathHistory.getFirst().lng; 
     int currentOrientation = getResources().getConfiguration().orientation; 

     ListView listView = (ListView) findViewById(R.id.equip_list); 

     HashMap<String, Equipment> equipmentMap = new HashMap<String, Equipment>(); 

     try { 
      List<String> data_list = Arrays.asList(message.split(",")); 

      // point added (checks in correct format) 
      String _sensor_id = data_list.get(0); 
      if (_sensor_id.substring(0, Math.min(_sensor_id.length(), 2)).equals("DT")) { 

       double _lat = Double.parseDouble(data_list.get(3)); 
       double _lng = Double.parseDouble(data_list.get(4)); 
       double _heading = Double.parseDouble(data_list.get(5)); 
       double _speed = Double.parseDouble(data_list.get(6)); 
       int distance = (int) Trajectory.ChordLength(currentLat, currentLng, _lat, _lng); 
       boolean doesSensorExist = false; 

       // for input _sensor_id, check if there exists an Equipment object in map. 
       Equipment equip = equipmentMap.get(_sensor_id); 
       if(equip == null) // no object for this sensor_id 
       { 
        equip = new Equipment(); 
        // populate equipment attributes in the object 
        equip.addParameter(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
        equip.addParameter(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
        equip.addParameter(FIFTH_COLUMN, Double.toString(distance) + "m"); 
        equip.addParameter(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 

        // add this Equipment Object in the map. 
        equipmentMap.put(_sensor_id, equip); 
        /// since its a new object, add same to the mEquipmentList which is a unique array of Equipment Object 
        mEquipmentList.add(equip); 
       } 
       else // Equipment object exits for input _sensor_id string 
       { 
        //Update the values for eq object if they are changed 
        equip.addParameter(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
        equip.addParameter(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
        equip.addParameter(FIFTH_COLUMN, Double.toString(distance) + "m"); 
        equip.addParameter(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 
        // here no need to add the Equipment Object in the ArrayList again. 
       } 

       // Set the adapter 
       ListViewAdapter adapter = new ListViewAdapter(this, mEquipmentList); 
       listView.setAdapter(adapter); 

       } 
      } catch(Exception e){ 
       // Marker construction failed 
       Log.d(TAG, "Updating list failed: " + e.toString()); 
      } 
     } 

    } 

class Equipment extends HashMap<String, String> { 
    HashMap<String, String> parameters; 

    void addParameter(String key, String value) 
    { 
     parameters.put(key, value); 
    } 
}

列表視圖ADAPTER

公共類ListViewAdapter延伸BaseAdapter {

public ArrayList<com.bhp.prox_aware.MapsActivity.Equipment> list; 
Activity MapsActivity; 
TextView txtFirst; 
TextView txtSecond; 
TextView txtThird; 
TextView txtFourth; 
TextView txtFifth; 

public ListViewAdapter(Activity activity, ArrayList<com.bhp.prox_aware.MapsActivity.Equipment> list){ 
    super(); 
    this.MapsActivity=activity; 
    this.list=list; 
} 

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

@Override 
public Object getItem(int position) { 
    // TODO Auto-generated method stub 
    return list.get(position); 
} 

@Override 
public long getItemId(int position) { 
    // TODO Auto-generated method stub 
    return 0; 
} 



@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    // TODO Auto-generated method stub 

    LayoutInflater inflater=MapsActivity.getLayoutInflater(); 

    if(convertView == null){ 

     convertView=inflater.inflate(R.layout.equip_row, null); 


     /* TODO add an ImageView here for an icon to display next to the list */ 
     txtFirst=(TextView) convertView.findViewById(R.id.name); 
     txtSecond=(TextView) convertView.findViewById(R.id.id); 
     txtThird=(TextView) convertView.findViewById(R.id.speed); 
     txtFourth=(TextView) convertView.findViewById(R.id.direction); 
     txtFifth=(TextView) convertView.findViewById(R.id.distance); 
    } 

    int color = Color.argb(200, 34, 34, 34); 


    HashMap<String, String> map=list.get(position); 
    txtFirst.setText(map.get(FIRST_COLUMN)); 
    txtSecond.setText(map.get(SECOND_COLUMN)); 
    txtThird.setText(map.get(THIRD_COLUMN)); 
    txtFourth.setText(map.get(FOURTH_COLUMN)); 
    txtFifth.setText(map.get(FIFTH_COLUMN)); 

    //Check if within 100m if yes change colour of background to red 
    double distanceCheck = Double.parseDouble(map.get(FIFTH_COLUMN).replace("m", "")); 
    if(distanceCheck <= 100){ 

     color = Color.argb(200, 163, 0, 0); 
    }else { 
     color = Color.argb(200, 34, 34, 34); 
    } 

    txtFirst.setTextColor(Color.WHITE); 
    txtFirst.setBackgroundColor(color); 

    txtSecond.setTextColor(Color.WHITE); 
    txtSecond.setBackgroundColor(color); 

    txtThird.setTextColor(Color.WHITE); 
    txtThird.setBackgroundColor(color); 

    txtFourth.setTextColor(Color.WHITE); 
    txtFourth.setBackgroundColor(color); 

    txtFifth.setTextColor(Color.WHITE); 
    txtFifth.setBackgroundColor(color); 

    return convertView; 
}

}

來源

2017-08-24 allen simpson

你應該能夠模擬你的代碼結構略有不同如果可能創建一個類說用的設備屬性存儲列參數，如速度，溫度等作爲地圖字符串，Stringthat類

class Equipment 
{ 
    HashMap<String, String> parameters; 

    void addParameter(String key, String value) 
    { 
    parameters.put(key, value); 
    } 
}

在你的邏輯，sensor_id的關鍵是保持的唯一性設備對象。因此，創建地圖字符串的裝備

HashMap<String, Equipment> equipmentMap = new HashMap<String, Equipment>(); 
// for input _sensor_id, check if there exists an Equipment object in map. 
Equipment equip = sensorMap.get(_sensor_id); 
if(equip == null) // no object for this sensor_id 
{ 
    equip = new Equipment(); 
    // populate equipment attributes in the object 
    equip.addParameter(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
    equip.addParameter(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
    equip.addParameter(FIFTH_COLUMN, Double.toString(distance) + "m"); 
    equip.addParameter(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 

    // add this Equipment Object in the map. 
    sensorMap.put(_sensor_id, equip); 
/// since its a new object, add same to the mEquipmentList which is a unique array of Equipment Object 
    mEquipmentList.add(eq); 
} 
else // Equipment object exits for input _sensor_id string 
{ 
    //Update the values for eq object if they are changed 
    equip.addParameter(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
    equip.addParameter(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
    equip.addParameter(FIFTH_COLUMN, Double.toString(distance) + "m"); 
    equip.addParameter(SECOND_COLUMN, Double.toString(mEquipmentList.indexOf(equip))); 

    // here no need to add the Equipment Object in the ArrayList again. 
} 
// notify adapter for data change 
adapter.notifyDataSetChanged();

HashMap中有助於保持基於_sensor_id數據的唯一性。

希望這有助於..

來源

2017-08-24 05:06:40 milindmb

這似乎是它可能是最好的方式來做到這一點，但我不完全知道如何構造它，請你給一個更詳細的例子嗎？ –

編輯我的答案更多細節。如果你想了解更多的細節，請分享一些更多的代碼，以便我更好地理解邏輯。 – milindmb

感謝您的幫助milindmb，我添加了你所做的，但我的listview不再顯示。我添加了該列表視圖的其他特定代碼。 –

我設法得到它的工作執行以下操作，雖然我相當肯定有這樣做的更好的方法。

if (currentOrientation == 2 && mSettings.get(0)) { 
        if (mEquipmentList.isEmpty()) { 
         // Populate the Equipment List 
         HashMap<String, String> map = new HashMap<String, String>(); 
         map.put(FIRST_COLUMN, _sensor_id); 
         map.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
         map.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
         map.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
         mEquipmentList.add(map); 
        } else { 

         for (HashMap<String, String> test : mEquipmentList) { 
          if (test.get(FIRST_COLUMN).equals(_sensor_id)) { 
           HashMap<String, String> map = new HashMap<String, String>(); 
           map.put(FIRST_COLUMN, _sensor_id); 
           map.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
           map.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
           map.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
           mEquipmentList.set(mEquipmentList.indexOf(test), map); 
           doesSensorExist = true; 
          } 
         } 
         if (!doesSensorExist && mEquipmentList.size() < 5) { 
          HashMap<String, String> map = new HashMap<String, String>(); 
          map.put(FIRST_COLUMN, _sensor_id); 
          map.put(THIRD_COLUMN, Double.toString(_speed) + "km/h"); 
          map.put(FOURTH_COLUMN, Double.toString(_heading) + "°"); 
          map.put(FIFTH_COLUMN, Double.toString(distance) + "m"); 
          mEquipmentList.add(map); 
         } 
        } 
          // Set the adapter 
          ListViewAdapter adapter = new ListViewAdapter(this, mEquipmentList); 
          listView.setAdapter(adapter); 
          adapter.notifyDataSetChanged(); 
        } 
       }

來源

2017-08-28 03:15:51

Android Arraylist迭代設置或添加基於它是否存在

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