[Android] 動態改變GridView的欄位個數的方法. Change the numColumns of GridView at run time

This is how to change the number of columns of a GridView at run time.

int GRID_ITEM_WIDTH = 300;  // the rough width of the grid item.

mGridView = (GridView) findViewById(R.id.gridView);
mGridView.getViewTreeObserver().addOnGlobalLayoutListener(
    new ViewTreeObserver.OnGlobalLayoutListener() {
        boolean isFirst = true;
        @Override
        public void onGlobalLayout() {  // this callback called when the width of view is available
            if (isFirst) {  // this callback would be called several times, run the following code only at the first time it called
                isFirst = false;
                int width = mGridView.getWidth();
                int numColumns = 1;
                
                if(width > GRID_ITEM_WIDTH){
                    numColumns = width/GRID_ITEM_WIDTH;        
                }
                mGridView.setNumColumns(numColumns);
            }
        }
    }
);