findViewById在自定義視圖中返回null後膨脹

Question

我有一個自定義RelativeLayout，我膨脹一個XML文件中的res文件。 這工作得很好，如果我在一個XML文件中使用自定義佈局，並將其設置爲內容查看，但如果我嘗試將其與new LocationItem(this)和addChild()添加在代碼中findViewById方法總是在自定義RelativeLayout的構造函數返回null。

下面是代碼：

public class LocationItem extends RelativeLayout { 

private String parcelType; 
private int countIntoBox, countFromBox; 

private RelativeLayout deliveryContainer, pickupContainer; 

private TextView countPickup, countDelivery; 

public LocationItem(Context context) { 
    this(context, null); 
} 

public LocationItem(Context context, AttributeSet attrs) { 
    this(context, attrs, 0); 
} 

public LocationItem(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 
    inflate(getContext(), R.layout.list_item_location, this); 
    deliveryContainer = (RelativeLayout) findViewById(R.id.rl_location_delivery_container); 
    pickupContainer = (RelativeLayout) findViewById(R.id.rl_location_pickup_container); 
    countPickup = (TextView) findViewById(R.id.tv_location_pickup_count); 
    countDelivery = (TextView) findViewById(R.id.tv_location_delivery_count); 

    countPickup.setOnClickListener(getShowNumberPickerListener()); 
    countDelivery.setOnClickListener(getShowNumberPickerListener()); 
} 

private OnClickListener getShowNumberPickerListener() { 
    return new OnClickListener() { 
     @Override 
     public void onClick(View view) { 
      showNumberPickerDialog(view); 
     } 
    }; 
} ... 
} 

添加自定義視圖在活動

mRootLayoutLocations.addView(new LocationItem(this)); 

的觀點是正確的膨脹，因爲我能看到它，但是當我試圖訪問內部的一個視圖使用NullPointerException自定義查看應用程序崩潰。

Answer 1

您需要使用適當的構造函數，而不是將它們重載。

public class LocationItem extends RelativeLayout { 

    private String parcelType; 
    private int countIntoBox, countFromBox; 

    private RelativeLayout deliveryContainer, pickupContainer; 

    private TextView countPickup, countDelivery; 

    public LocationItem(Context context) { 
     super(context); 
     init(context, null, 0); 
    } 

    public LocationItem(Context context, AttributeSet attrs) { 
     super(context, attrs); 
     init(context, attrs, 0); 
    } 

    public LocationItem(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attrs, defStyle); 
     init(context, attrs, defStyle); 
    } 

    private void init(Context context, AttributeSet attrs, int defStyle) { 
     inflate(getContext(), R.layout.list_item_location, this); 
     deliveryContainer = (RelativeLayout) findViewById(R.id.rl_location_delivery_container); 
     pickupContainer = (RelativeLayout) findViewById(R.id.rl_location_pickup_container); 
     countPickup = (TextView) findViewById(R.id.tv_location_pickup_count); 
     countDelivery = (TextView) findViewById(R.id.tv_location_delivery_count); 

     countPickup.setOnClickListener(getShowNumberPickerListener()); 
     countDelivery.setOnClickListener(getShowNumberPickerListener()); 
    } 

    private OnClickListener getShowNumberPickerListener() { 
     return new OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       showNumberPickerDialog(view); 
      } 
     }; 
    } 

    ... 
} 

Answer 2

我擔心你必須誇大視圖，而不是從無處找到它。該方法

findindViewById(int Id) 

必須Actvity的onCreate內或與其中的子視圖/小部件，你正在努力尋找是駐留在一個視圖中調用。

如果所有的子視圖駐留在一個單一的xml文件（單親根內）

View rootView=(View) LayoutInflater.from(context).inflate(R.layout.list_item_location); 
pickupContainer = (RelativeLayout) rootview.findViewById(R.id.rl_location_pickup_container); 

Answer 3

這應該工作

public LocationItem(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 
    this = inflate(getContext(), R.layout.list_item_location,null); 
    ... 

Answer 4

確定我充氣視圖到視圖（保持器）

View v = inflate(getContext(), R.layout.list_item_location, this); 

，然後經由v.findViewById訪問視圖。現在它正在工作。

代碼：

View v = inflate(getContext(), R.layout.list_item_location, this); 
deliveryContainer = (RelativeLayout) v.findViewById(R.id.rl_location_delivery_container); 
pickupContainer = (RelativeLayout) v.findViewById(R.id.rl_location_pickup_container); 
countPickup = (TextView) v.findViewById(R.id.tv_location_pickup_count); 
countDelivery = (TextView) v.findViewById(R.id.tv_location_delivery_count); 

countPickup.setOnClickListener(getShowNumberPickerListener()); 
countDelivery.setOnClickListener(getShowNumberPickerListener());