在API级别28上找不到画布变量

Question

下面Canvas没有在android 28中找到的变量.

canvas.saveLayer(0, 0, getWidth(), getHeight(), null,
                Canvas.MATRIX_SAVE_FLAG |
                        Canvas.CLIP_SAVE_FLAG |
                        Canvas.HAS_ALPHA_LAYER_SAVE_FLAG |
                        Canvas.FULL_COLOR_LAYER_SAVE_FLAG |
                        Canvas.CLIP_TO_LAYER_SAVE_FLAG);

Answer 1

这些标志已在API 28中删除.请参见此处:

类android.graphics.Canvas

删除方法int save(int)

删除字段int CLIP_SAVE_FLAG
int CLIP_TO_LAYER_SAVE_FLAG
int FULL_COLOR_LAYER_SAVE_FLAG
int HAS_ALPHA_LAYER_SAVE_FLAG
int MATRIX_SAVE_FLAG

该方法在API 26中已弃用.请参见此处:

此方法在API级别26中已弃用.请改用saveLayer(float,float,float,float,Paint).

用什么代替

根据CanvasAPI 28 的源代码,您使用的标志组合起来等于以下值ALL_SAVE_FLAG:

public  static  final  int ALL_SAVE_FLAG =  0x1F;
public  static  final  int MATRIX_SAVE_FLAG =  0x01;
public  static  final  int CLIP_SAVE_FLAG =  0x02;
public  static  final  int HAS_ALPHA_LAYER_SAVE_FLAG =  0x04;
public  static  final  int FULL_COLOR_LAYER_SAVE_FLAG =  0x08;
public  static  final  int CLIP_TO_LAYER_SAVE_FLAG =  0x10;

从相同的源代码调用 Canvas#saveLayer(left, top, right, bottom, paint)默认为使用ALL_SAVE_FLAG:

/**  
 * Convenience for {@link #saveLayer(RectF, Paint)} that takes the four float coordinates of the  
 * bounds rectangle. */
public int saveLayer(float left, float top, float right, float bottom, @Nullable Paint paint) {  
    return saveLayer(left, top, right, bottom, paint, ALL_SAVE_FLAG);  
}

因此,看起来您的代码等同于以下代码,您可以将其用作替换:

canvas.saveLayer(0, 0, getWidth(), getHeight(), null);