iOS設置按鈕的圖片爲Aspetfit

通過以下代碼實現:

UIButton *backBtn = [UIButtonbuttonWithType:UIButtonTypeCustom];

    [backBtn setImage:[UIImageimageNamed:@"return"]forState:UIControlStateNormal];

    backBtn.frame = CGRectMake(20, 40, 15,15);

    backBtn.imageView.contentMode =UIViewContentModeScaleAspectFill;

    [backBtn addTarget:selfaction:@selector(backItemClicked)forControlEvents:UIControlEventTouchUpInside];