缩放Android可绘制资源

Question

I'm making a simple board game that uses a table view and a button array as the board squares. My movePlayer takes a destination row and column, places a token in that row and column and replaces its previous position with a button.

My movePlayer method is:

private void movePlayer(int moveToRow, int moveToCol, Button buttons[][])
{
    int oldRow = player.getPlayerRow();
    int oldCol = player.getPlayerCol();
    Button oldPosition = buttons[oldRow][oldCol];
    int oldWidth = oldPosition.getWidth();
    int oldHeight = oldPosition.getHeight();
    Bitmap originalBitmap = BitmapFactory.decodeResource(getResources(),
            android.R.drawable.btn_default);
    Bitmap scaledBitmap = Bitmap.createScaledBitmap(originalBitmap, oldWidth, oldHeight, true);
    Resources resource = getResources();
    oldPosition.setBackground(new BitmapDrawable(resource, scaledBitmap));
    player.setPlayerRow(moveToRow);
    player.setPlayerCol(moveToCol);
    addPlayerToken(moveToRow, moveToCol, buttons);
}

I get the error java.lang.NullPointerException: Attempt to invoke virtual method 'int android.graphics.Bitmap.getWidth()' on a null object reference at android.graphics.Bitmap.createScaledBitmap(Bitmap.java:596) at foo.bar.minions.GameBoard.movePlayer(GameBoard.java:219) .

This code works if I replace android.R.drawable.btn_default with a drawable such as R.drawable.foo .

The code will also work if I replace everything below int oldWidth with oldPosition.setBackgroundResource(android.R.drawable.btn_default); but the button isn't scaled properly or doesn't look like the other buttons. For reference I use tableRow.addView(button); to create my buttons.

What can I do to make my buttons look the same?

Answer 1

Fixed it, the problem was because the button that was drawn using tableRow.addView(button); is not the same image as android.R.drawable.btn_default so the fix was just adding button.setBackgroundResource(android.R.drawable.btn_default); to before tableRow.addView(button);