inflate 后 findViewById 在自定义 View 中返回 null

我有一个习惯RelativeLayout我在其中填充了一个 xml res 文件。 如果我在 xml 文件中使用自定义布局并将其设置为 contentview，则效果很好，但是如果我尝试将其添加到代码中new LocationItem(this) and addChild() the findViewById方法总是返回null在自定义的构造函数中RelativeLayout.

这是代码：

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);
        }
    };
} ...
}

在 Activity 中添加自定义视图

mRootLayoutLocations.addView(new LocationItem(this));

该视图正确膨胀，因为我可以看到它，但是当我尝试访问自定义视图内的视图时，应用程序崩溃并出现 NullPointerException。

好的，我将视图充气到视图（持有者）中

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

然后通过 v.findViewById 访问视图。现在它正在发挥作用。

Code:

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());