TypedValue.applyDimension 中dp和sp之间转化的真相

 1 //转换dip为px 
 2 public static int convertDipOrPx(Context context, int dip) { 
 3     float scale = context.getResources().getDisplayMetrics().density; 
 4     return (int)(dip*scale + 0.5f*(dip>=0?1:-1)); 
 5 } 
 6  
 7 //转换px为dip 
 8 public static int convertPxOrDip(Context context, int px) { 
 9     float scale = context.getResources().getDisplayMetrics().density; 
10     return (int)(px/scale + 0.5f*(px>=0?1:-1)); 
11 } 

1 public static int dp2sp(float dpVal){
2     return (int)(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dpVal,
3             MyAppliction.getInstance().getApplicationContext().getResources().getDisplayMetrics()));
4 }
5  //?????
6 public static int sp2dp(float spVal){
7     return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, spVal,
8             MyAppliction.getInstance().getApplicationContext().getResources().getDisplayMetrics()));
9 }

getDimension(DisplayMetrics metrics)

 1  public static float applyDimension(int unit, float value,
 2                                        DisplayMetrics metrics)
 3     {
 4         switch (unit) {
 5         case COMPLEX_UNIT_PX:
 6             return value;
 7         case COMPLEX_UNIT_DIP:
 8             return value * metrics.density;
 9         case COMPLEX_UNIT_SP:
10             return value * metrics.scaledDensity;
11         case COMPLEX_UNIT_PT:
12             return value * metrics.xdpi * (1.0f/72);
13         case COMPLEX_UNIT_IN:
14             return value * metrics.xdpi;
15         case COMPLEX_UNIT_MM:
16             return value * metrics.xdpi * (1.0f/25.4f);
17         }
18         return 0;
19     }

 1 //转换dip为px 
 2   public static int convertDipOrPx(Context context, int dip) { 
 3       float scale = context.getResources().getDisplayMetrics().density; 
 4       return (int)(dip*scale + 0.5f*(dip>=0?1:-1)); 
 5   } 
 6    
 7   //转换px为dip 
 8   public static int convertPxOrDip(Context context, int px) { 
 9       float scale = context.getResources().getDisplayMetrics().density; 
10      return (int)(px/scale + 0.5f*(px>=0?1:-1)); 
11  } 
12  
13   public static int sp2px(Context context, float spValue) {
14         float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
15         return (int) (spValue * fontScale + 0.5f);
16     }
17 
18     public static int px2sp(Context context, float pxValue) {
19         float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
20         return (int) (pxValue / fontScale + 0.5f);
21     }