Question

I’m using this example of gridview http://developer.android.com/resources/tutorials/views/hello-gridview.html just with less images and a rotate button in one corner. I want to click a image, then click rotate button to rotate that image, but I can’t find how to do it.

Anyone have any idea?

Answer 1

Rotating the image can be done using setImageMatrix() within getView if you keep track of which images you want rotated. Something like this:

HashMap<Integer, Matrix> mImageTransforms = new HashMap<Integer,Matrix>();
Matrix mIdentityMatrix = new Matrix();

// create a new ImageView for each item referenced by the Adapter
public View getView(int position, View convertView, ViewGroup parent) {
    ImageView imageView;
    if (convertView == null) {  // if it's not recycled, initialize some attributes
        imageView = new ImageView(mContext);
        imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        imageView.setPadding(8, 8, 8, 8);
    } else {
        imageView = (ImageView) convertView;
    }

    Matrix m = mImageTransforms.get(position);
    if ( null == m ) {
        m = mIdentityMatrix;
    }
    imageView.setImageMatrix(m);
    imageView.setImageResource(mThumbIds[position]);
    return imageView;
}

void setImageRotation(int position, int degrees) {
    Matrix m = mImageTransforms.remove(position);        
    if ( degrees != 0 ) {
        if ( null == m ) m = new Matrix();
        m.setRotate(degrees);
        mImageTransforms.put(position, m);
    }
    notifyDataSetChanged();
}

One thing to note. In touch mode lists and grids do not have a selection per-se, however they can be checked. It’s a bit tricky to get a grid view to show the checked state, that being said the Honeypad Tutorial shows how to use checked views within a list view which may be helpful.