自定義視圖子失去引用

Question

我想這樣

public class CustomViewSubclass extends HorizontalScrollView{ 

private LinearLayout layout; 

public CustomViewSubclass(Context context) { 
    this(context,null,0); 
} 

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

public CustomViewSubclass(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 

    layout = new LinearLayout(context); 
} 

// This is called from the `Activity` 
public void startAsyncTask() { // code } 

// This method is called in the `onPostExecute()` of an `AsyncTask` subclass 
public void doSomething(Context context) { 
    ImageView image = ImageView(context); 

    layout.addView(image); // NullPointerException here, layout seems to be null 
} 

的東西，但它似乎layout上doSomething()爲空。這怎麼可能呢？我正在初始化它的構造函數...並且我不再重新初始化它;

我通過XML

<com.mypackage.CustomViewSubclass 
    android:layout_width="wrap_content" 
    android:layout_width="match_parent" /> 

Answer 1

好吧我固定它，這是一個愚蠢的錯誤我做的加入我的自定義視圖：

我在3種方法中使用super()，而是採用this() 。

public CustomViewSubclass(Context context) { 
    super(context,null,0); 
} 
public CustomViewSubclass(Context context, AttributeSet attrs) { 
    super(context,attr,0); 
} 
public CustomViewSubclass(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 

    layout = new LinearLayout(context); 
} 

解決方案：

public CustomViewSubclass(Context context) { 
    this(context,null,0); 
} 
public CustomViewSubclass(Context context, AttributeSet attrs) { 
    this(context,attr,0); 
} 
public CustomViewSubclass(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 

    layout = new LinearLayout(context); 
}