You cannot set the content of a TextureView manually, I'm afraid. Your best bet is to make a new ImageView on top of your TextureView and set its image when you need to.
public void onButtonClicked(View view) {
// if we don't need to keep previewing new frames, stop the preview
mCameraManager.stopPreview();
// now, show our ImageView (which should be in front of the TextureView)
Bitmap myBitmap = BitmapFactory.decodeFile(file_path_here);
myImageView.setImageBitmap(myBitmap);
myImageView.setVisibility(View.VISIBLE);
}