android - 使 ImageView 从方法中不可见

Question

我创建了如下所示的 HideImages() 函数。问题是，运行此代码会导致 NullPointerExcpection。当我注释掉 setVisibility 行时，它工作正常。我做错了什么？

public class MainActivity extends Activity implements SurfaceHolder.Callback {
  ImageView img_w0, img_w1, img_w2;
  public void onCreate(Bundle savedInstanceState) {
    ImageView img_w0 = (ImageView)findViewById(R.id.img0);
    ImageView img_w1 = (ImageView)findViewById(R.id.img1);
    ImageView img_w2 = (ImageView)findViewById(R.id.img2);

    HideImages();

  }
  public void HideImages() {
    img_w0.setVisibility(View.INVISIBLE);
    img_w1.setVisibility(View.INVISIBLE);
    img_w2.setVisibility(View.INVISIBLE);
}
}

Answer 1

将ImageView的所有引用设为Global as

public class MainActivity extends Activity implements SurfaceHolder.Callback {
  ImageView img_w0, img_w1, img_w2;
  public void onCreate(Bundle savedInstanceState) {
    img_w0 = (ImageView)findViewById(R.id.img0);
     img_w1 = (ImageView)findViewById(R.id.img1);
     img_w2 = (ImageView)findViewById(R.id.img2);

    HideImages();

  }
  public void HideImages() {
    img_w0.setVisibility(View.INVISIBLE);
    img_w1.setVisibility(View.INVISIBLE);
    img_w2.setVisibility(View.INVISIBLE);
}
}