空ImageView的参考

问题描述

我试图让一个ImageView的对象，不管出于什么原因，它让回来为空的参考。

I'm trying to get a reference to an ImageView object and for whatever reason, it keeps coming back as null.

XML：

<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:padding="6dip">
  <ImageView android:id="@+id/application_icon" android:layout_width="wrap_content" android:layout_height="wrap_content" />
  <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/label" android:text="Application Name" />
  <CheckBox android:id="@+id/check" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="right" />
</LinearLayout>

Java的：

ImageView img = (ImageView) v.findViewById(R.id.application_icon);

我不觉得我做错什么但我的IMG变种总是回来空。什么是不对的图片？

I don't feel like I'm doing anything wrong yet my img var always comes back as null. What's wrong with this picture?

推荐答案

周六的答案是正确的，也就是说，你需要一个适当的布局，但的setContentView（） 是不是引用的视图的唯一途径。您可以使用膨胀的查看（即使没有示出）的母体布局和使用新充气布局引用视图。

Sat's answer is correct, i.e., you need a proper layout, but setContentView() is not the only way to reference a View. You can use a LayoutInflater to inflate a parent layout of the View (even if it is not shown) and use that newly inflated layout to reference the View.

public class MyActivity extends Activity {
  Context context;
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    context = this;
// the rest of yout code

private void someCallback() {
  LayoutInflater inflater = (LayoutInflater) context.getSystemService
     (Context.LAYOUT_INFLATER_SERVICE);
  LinearLayout ll = (LinearLayout) inflater.inflate(R.layout.iconLayout, null);
  ImageView img = (ImageView) ll.findViewById(R.id.application_icon);
// you can do whatever you need with the img (get the Bitmap, maybe?)

您需要将您的XML文件中唯一的变化是一个ID添加到父布局，所以你可以使用它 LayoutInflater ：

The only change you need to your xml file is to add an ID to the parent layout, so you can use it with the LayoutInflater:

<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="iconLayout"
<!-- all the rest of your layout -->
  <ImageView android:id="@+id/application_icon" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<!-- all the rest of your layout -->
</LinearLayout>

这篇关于空ImageView的参考的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！