在Android中以其他布局设置图像

Question

I run on MainActivity and I have firstshow.xml with image imageView ( imshow ) and I use Inflater to show it on dialog with this code

ImageView fistTimeImv =(ImageView)findViewById(R.id.imshow);
        fistTimeImv.setImageResource(R.drawable.first1);
        AlertDialog.Builder dialog = new AlertDialog.Builder(
                MainActivity.this);
        LayoutInflater factory = LayoutInflater.from(MainActivity.this);
        final View view = factory.inflate(R.layout.firstshow, null);
        dialog.setView(view);
        dialog.show();

The above code throws NullPointerException in the following line

 fistTimeImv.setImageResource(R.drawable.first1);

Answer 1

So if I understand you correctly you want to inflate a View from xml and set that View on a Dialog but you are getting a NullPointerException when attempting to do so. To fix that you have to reorder your code as the following:

    LayoutInflater factory = LayoutInflater.from(MainActivity.this);
    final View view = factory.inflate(R.layout.firstshow, null);
    ImageView fistTimeImv =(ImageView) view.findViewById(R.id.imshow); //Make sure to call findViewById on the view you just inflated
    fistTimeImv.setImageResource(R.drawable.first1);
    AlertDialog.Builder dialog = new AlertDialog.Builder(
            MainActivity.this);
    dialog.setView(view);
    dialog.show();

There are two changes here: The first change is inflating your view before finding the ImageView . If your ImageView is a child element of your firstshow layout then that layout needs to be inflated (built) first. The second change is making sure that you try to find your ImageView from the newly inflated view . If you don't have view.findViewById(R.id.imshow); you will try to find the ImageView on whatever class you are currently working in which probably isn't what you want.