Android 厘米转dip、px转dip 地图比例尺长度计算
主要解决问题：
1.Android各个长度单位转换为px（px、dip、mm等）
2.px和dip的转换
使用的工具类：
1.Android-API-工具类：TypedValue.applyDimension(int unit, float value,DisplayMetrics metrics);（大家最好读下附件中的TypedValue类源码）
参数说明：
(1)unit:输入值的类型（px、dip、mm、sp等）
(2)value:对应的值
(3)metrics:DisplayMetrics,
DisplayMetrics官方解释：A structure describing general information about a display, such as its size, density, and font scaling.
获取方法1：
DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics)
获取方法2：
context.getResources().getDisplayMetrics();
详细介绍参见：
http://www.eoeandroid.com/thread-246188-1-1.html
2.DensityUtil类
提供了px和dip的互转方法
转自：http://blog.csdn.net/arui319/article/details/6777133
备注：
有兴趣的朋友可以再封装下发布
附件：
Android.util.TypedValue类源码如下：
1 /* 2 * Copyright (C) 2007 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.util; 18 19 /** 20 * Container for a dynamically typed data value. Primarily used with 21 * {@link android.content.res.Resources} for holding resource values. 22 */ 23 public class TypedValue { 24 /** The value contains no data. */ 25 public static final int TYPE_NULL = 0x00; 26 27 /** The <var>data</var> field holds a resource identifier. */ 28 public static final int TYPE_REFERENCE = 0x01; 29 /** The <var>data</var> field holds an attribute resource 30 * identifier (referencing an attribute in the current theme 31 * style, not a resource entry). */ 32 public static final int TYPE_ATTRIBUTE = 0x02; 33 /** The <var>string</var> field holds string data. In addition, if 34 * <var>data</var> is non-zero then it is the string block 35 * index of the string and <var>assetCookie</var> is the set of 36 * assets the string came from. */ 37 public static final int TYPE_STRING = 0x03; 38 /** The <var>data</var> field holds an IEEE 754 floating point number. */ 39 public static final int TYPE_FLOAT = 0x04; 40 /** The <var>data</var> field holds a complex number encoding a 41 * dimension value. */ 42 public static final int TYPE_DIMENSION = 0x05; 43 /** The <var>data</var> field holds a complex number encoding a fraction 44 * of a container. */ 45 public static final int TYPE_FRACTION = 0x06; 46 47 /** Identifies the start of plain integer values. Any type value 48 * from this to {@link #TYPE_LAST_INT} means the 49 * <var>data</var> field holds a generic integer value. */ 50 public static final int TYPE_FIRST_INT = 0x10; 51 52 /** The <var>data</var> field holds a number that was 53 * originally specified in decimal. */ 54 public static final int TYPE_INT_DEC = 0x10; 55 /** The <var>data</var> field holds a number that was 56 * originally specified in hexadecimal (0xn). */ 57 public static final int TYPE_INT_HEX = 0x11; 58 /** The <var>data</var> field holds 0 or 1 that was originally 59 * specified as "false" or "true". */ 60 public static final int TYPE_INT_BOOLEAN = 0x12; 61 62 /** Identifies the start of integer values that were specified as 63 * color constants (starting with '#'). */ 64 public static final int TYPE_FIRST_COLOR_INT = 0x1c; 65 66 /** The <var>data</var> field holds a color that was originally 67 * specified as #aarrggbb. */ 68 public static final int TYPE_INT_COLOR_ARGB8 = 0x1c; 69 /** The <var>data</var> field holds a color that was originally 70 * specified as #rrggbb. */ 71 public static final int TYPE_INT_COLOR_RGB8 = 0x1d; 72 /** The <var>data</var> field holds a color that was originally 73 * specified as #argb. */ 74 public static final int TYPE_INT_COLOR_ARGB4 = 0x1e; 75 /** The <var>data</var> field holds a color that was originally 76 * specified as #rgb. */ 77 public static final int TYPE_INT_COLOR_RGB4 = 0x1f; 78 79 /** Identifies the end of integer values that were specified as color 80 * constants. */ 81 public static final int TYPE_LAST_COLOR_INT = 0x1f; 82 83 /** Identifies the end of plain integer values. */ 84 public static final int TYPE_LAST_INT = 0x1f; 85 86 /* ------------------------------------------------------------ */ 87 88 /** Complex data: bit location of unit information. */ 89 public static final int COMPLEX_UNIT_SHIFT = 0; 90 /** Complex data: mask to extract unit information (after shifting by 91 * {@link #COMPLEX_UNIT_SHIFT}). This gives us 16 possible types, as 92 * defined below. */ 93 public static final int COMPLEX_UNIT_MASK = 0xf; 94 95 /** {@link #TYPE_DIMENSION} complex unit: Value is raw pixels. */ 96 public static final int COMPLEX_UNIT_PX = 0; 97 /** {@link #TYPE_DIMENSION} complex unit: Value is Device Independent 98 * Pixels. */ 99 public static final int COMPLEX_UNIT_DIP = 1; 100 /** {@link #TYPE_DIMENSION} complex unit: Value is a scaled pixel. */ 101 public static final int COMPLEX_UNIT_SP = 2; 102 /** {@link #TYPE_DIMENSION} complex unit: Value is in points. */ 103 public static final int COMPLEX_UNIT_PT = 3; 104 /** {@link #TYPE_DIMENSION} complex unit: Value is in inches. */ 105 public static final int COMPLEX_UNIT_IN = 4; 106 /** {@link #TYPE_DIMENSION} complex unit: Value is in millimeters. */ 107 public static final int COMPLEX_UNIT_MM = 5; 108 109 /** {@link #TYPE_FRACTION} complex unit: A basic fraction of the overall 110 * size. */ 111 public static final int COMPLEX_UNIT_FRACTION = 0; 112 /** {@link #TYPE_FRACTION} complex unit: A fraction of the parent size. */ 113 public static final int COMPLEX_UNIT_FRACTION_PARENT = 1; 114 115 /** Complex data: where the radix information is, telling where the decimal 116 * place appears in the mantissa. */ 117 public static final int COMPLEX_RADIX_SHIFT = 4; 118 /** Complex data: mask to extract radix information (after shifting by 119 * {@link #COMPLEX_RADIX_SHIFT}). This give us 4 possible fixed point 120 * representations as defined below. */ 121 public static final int COMPLEX_RADIX_MASK = 0x3; 122 123 /** Complex data: the mantissa is an integral number -- i.e., 0xnnnnnn.0 */ 124 public static final int COMPLEX_RADIX_23p0 = 0; 125 /** Complex data: the mantissa magnitude is 16 bits -- i.e, 0xnnnn.nn */ 126 public static final int COMPLEX_RADIX_16p7 = 1; 127 /** Complex data: the mantissa magnitude is 8 bits -- i.e, 0xnn.nnnn */ 128 public static final int COMPLEX_RADIX_8p15 = 2; 129 /** Complex data: the mantissa magnitude is 0 bits -- i.e, 0x0.nnnnnn */ 130 public static final int COMPLEX_RADIX_0p23 = 3; 131 132 /** Complex data: bit location of mantissa information. */ 133 public static final int COMPLEX_MANTISSA_SHIFT = 8; 134 /** Complex data: mask to extract mantissa information (after shifting by 135 * {@link #COMPLEX_MANTISSA_SHIFT}). This gives us 23 bits of precision; 136 * the top bit is the sign. */ 137 public static final int COMPLEX_MANTISSA_MASK = 0xffffff; 138 139 /* ------------------------------------------------------------ */ 140 141 /** 142 * If {@link #density} is equal to this value, then the density should be 143 * treated as the system's default density value: {@link DisplayMetrics#DENSITY_DEFAULT}. 144 */ 145 public static final int DENSITY_DEFAULT = 0; 146 147 /** 148 * If {@link #density} is equal to this value, then there is no density 149 * associated with the resource and it should not be scaled. 150 */ 151 public static final int DENSITY_NONE = 0xffff; 152 153 /* ------------------------------------------------------------ */ 154 155 /** The type held by this value, as defined by the constants here. 156 * This tells you how to interpret the other fields in the object. */ 157 public int type; 158 159 /** If the value holds a string, this is it. */ 160 public CharSequence string; 161 162 /** Basic data in the value, interpreted according to {@link #type} */ 163 public int data; 164 165 /** Additional information about where the value came from; only 166 * set for strings. */ 167 public int assetCookie; 168 169 /** If Value came from a resource, this holds the corresponding resource id. */ 170 public int resourceId; 171 172 /** If Value came from a resource, these are the configurations for which 173 * its contents can change. */ 174 public int changingConfigurations = -1; 175 176 /** 177 * If the Value came from a resource, this holds the corresponding pixel density. 178 * */ 179 public int density; 180 181 /* ------------------------------------------------------------ */ 182 183 /** Return the data for this value as a float. Only use for values 184 * whose type is {@link #TYPE_FLOAT}. */ 185 public final float getFloat() { 186 return Float.intBitsToFloat(data); 187 } 188 189 private static final float MANTISSA_MULT = 190 1.0f / (1<<TypedValue.COMPLEX_MANTISSA_SHIFT); 191 private static final float[] RADIX_MULTS = new float[] { 192 1.0f*MANTISSA_MULT, 1.0f/(1<<7)*MANTISSA_MULT, 193 1.0f/(1<<15)*MANTISSA_MULT, 1.0f/(1<<23)*MANTISSA_MULT 194 }; 195 196 /** 197 * Retrieve the base value from a complex data integer. This uses the 198 * {@link #COMPLEX_MANTISSA_MASK} and {@link #COMPLEX_RADIX_MASK} fields of 199 * the data to compute a floating point representation of the number they 200 * describe. The units are ignored. 201 * 202 * @param complex A complex data value. 203 * 204 * @return A floating point value corresponding to the complex data. 205 */ 206 public static float complexToFloat(int complex) 207 { 208 return (complex&(TypedValue.COMPLEX_MANTISSA_MASK 209 <<TypedValue.COMPLEX_MANTISSA_SHIFT)) 210 * RADIX_MULTS[(complex>>TypedValue.COMPLEX_RADIX_SHIFT) 211 & TypedValue.COMPLEX_RADIX_MASK]; 212 } 213 214 /** 215 * Converts a complex data value holding a dimension to its final floating 216 * point value. The given <var>data</var> must be structured as a 217 * {@link #TYPE_DIMENSION}. 218 * 219 * @param data A complex data value holding a unit, magnitude, and 220 * mantissa. 221 * @param metrics Current display metrics to use in the conversion -- 222 * supplies display density and scaling information. 223 * 224 * @return The complex floating point value multiplied by the appropriate 225 * metrics depending on its unit. 226 */ 227 public static float complexToDimension(int data, DisplayMetrics metrics) 228 { 229 return applyDimension( 230 (data>>COMPLEX_UNIT_SHIFT)&COMPLEX_UNIT_MASK, 231 complexToFloat(data), 232 metrics); 233 } 234 235 /** 236 * Converts a complex data value holding a dimension to its final value 237 * as an integer pixel offset. This is the same as 238 * {@link #complexToDimension}, except the raw floating point value is 239 * truncated to an integer (pixel) value. 240 * The given <var>data</var> must be structured as a 241 * {@link #TYPE_DIMENSION}. 242 * 243 * @param data A complex data value holding a unit, magnitude, and 244 * mantissa. 245 * @param metrics Current display metrics to use in the conversion -- 246 * supplies display density and scaling information. 247 * 248 * @return The number of pixels specified by the data and its desired 249 * multiplier and units. 250 */ 251 public static int complexToDimensionPixelOffset(int data, 252 DisplayMetrics metrics) 253 { 254 return (int)applyDimension( 255 (data>>COMPLEX_UNIT_SHIFT)&COMPLEX_UNIT_MASK, 256 complexToFloat(data), 257 metrics); 258 } 259 260 /** 261 * Converts a complex data value holding a dimension to its final value 262 * as an integer pixel size. This is the same as 263 * {@link #complexToDimension}, except the raw floating point value is 264 * converted to an integer (pixel) value for use as a size. A size 265 * conversion involves rounding the base value, and ensuring that a 266 * non-zero base value is at least one pixel in size. 267 * The given <var>data</var> must be structured as a 268 * {@link #TYPE_DIMENSION}. 269 * 270 * @param data A complex data value holding a unit, magnitude, and 271 * mantissa. 272 * @param metrics Current display metrics to use in the conversion -- 273 * supplies display density and scaling information. 274 * 275 * @return The number of pixels specified by the data and its desired 276 * multiplier and units. 277 */ 278 public static int complexToDimensionPixelSize(int data, 279 DisplayMetrics metrics) 280 { 281 final float value = complexToFloat(data); 282 final float f = applyDimension( 283 (data>>COMPLEX_UNIT_SHIFT)&COMPLEX_UNIT_MASK, 284 value, 285 metrics); 286 final int res = (int)(f+0.5f); 287 if (res != 0) return res; 288 if (value == 0) return 0; 289 if (value > 0) return 1; 290 return -1; 291 } 292 293 public static float complexToDimensionNoisy(int data, DisplayMetrics metrics) 294 { 295 float res = complexToDimension(data, metrics); 296 System.out.println( 297 "Dimension (0x" + ((data>>TypedValue.COMPLEX_MANTISSA_SHIFT) 298 & TypedValue.COMPLEX_MANTISSA_MASK) 299 + "*" + (RADIX_MULTS[(data>>TypedValue.COMPLEX_RADIX_SHIFT) 300 & TypedValue.COMPLEX_RADIX_MASK] / MANTISSA_MULT) 301 + ")" + DIMENSION_UNIT_STRS[(data>>COMPLEX_UNIT_SHIFT) 302 & COMPLEX_UNIT_MASK] 303 + " = " + res); 304 return res; 305 } 306 307 /** 308 * Converts an unpacked complex data value holding a dimension to its final floating 309 * point value. The two parameters <var>unit</var> and <var>value</var> 310 * are as in {@link #TYPE_DIMENSION}. 311 * 312 * @param unit The unit to convert from. 313 * @param value The value to apply the unit to. 314 * @param metrics Current display metrics to use in the conversion -- 315 * supplies display density and scaling information. 316 * 317 * @return The complex floating point value multiplied by the appropriate 318 * metrics depending on its unit. 319 */ 320 public static float applyDimension(int unit, float value, 321 DisplayMetrics metrics) 322 { 323 switch (unit) { 324 case COMPLEX_UNIT_PX: 325 return value; 326 case COMPLEX_UNIT_DIP: 327 return value * metrics.density; 328 case COMPLEX_UNIT_SP: 329 return value * metrics.scaledDensity; 330 case COMPLEX_UNIT_PT: 331 return value * metrics.xdpi * (1.0f/72); 332 case COMPLEX_UNIT_IN: 333 return value * metrics.xdpi; 334 case COMPLEX_UNIT_MM: 335 return value * metrics.xdpi * (1.0f/25.4f); 336 } 337 return 0; 338 } 339 340 /** 341 * Return the data for this value as a dimension. Only use for values 342 * whose type is {@link #TYPE_DIMENSION}. 343 * 344 * @param metrics Current display metrics to use in the conversion -- 345 * supplies display density and scaling information. 346 * 347 * @return The complex floating point value multiplied by the appropriate 348 * metrics depending on its unit. 349 */ 350 public float getDimension(DisplayMetrics metrics) 351 { 352 return complexToDimension(data, metrics); 353 } 354 355 /** 356 * Converts a complex data value holding a fraction to its final floating 357 * point value. The given <var>data</var> must be structured as a 358 * {@link #TYPE_FRACTION}. 359 * 360 * @param data A complex data value holding a unit, magnitude, and 361 * mantissa. 362 * @param base The base value of this fraction. In other words, a 363 * standard fraction is multiplied by this value. 364 * @param pbase The parent base value of this fraction. In other 365 * words, a parent fraction (nn%p) is multiplied by this 366 * value. 367 * 368 * @return The complex floating point value multiplied by the appropriate 369 * base value depending on its unit. 370 */ 371 public static float complexToFraction(int data, float base, float pbase) 372 { 373 switch ((data>>COMPLEX_UNIT_SHIFT)&COMPLEX_UNIT_MASK) { 374 case COMPLEX_UNIT_FRACTION: 375 return complexToFloat(data) * base; 376 case COMPLEX_UNIT_FRACTION_PARENT: 377 return complexToFloat(data) * pbase; 378 } 379 return 0; 380 } 381 382 /** 383 * Return the data for this value as a fraction. Only use for values whose 384 * type is {@link #TYPE_FRACTION}. 385 * 386 * @param base The base value of this fraction. In other words, a 387 * standard fraction is multiplied by this value. 388 * @param pbase The parent base value of this fraction. In other 389 * words, a parent fraction (nn%p) is multiplied by this 390 * value. 391 * 392 * @return The complex floating point value multiplied by the appropriate 393 * base value depending on its unit. 394 */ 395 public float getFraction(float base, float pbase) 396 { 397 return complexToFraction(data, base, pbase); 398 } 399 400 /** 401 * Regardless of the actual type of the value, try to convert it to a 402 * string value. For example, a color type will be converted to a 403 * string of the form #aarrggbb. 404 * 405 * @return CharSequence The coerced string value. If the value is 406 * null or the type is not known, null is returned. 407 */ 408 public final CharSequence coerceToString() 409 { 410 int t = type; 411 if (t == TYPE_STRING) { 412 return string; 413 } 414 return coerceToString(t, data); 415 } 416 417 private static final String[] DIMENSION_UNIT_STRS = new String[] { 418 "px", "dip", "sp", "pt", "in", "mm" 419 }; 420 private static final String[] FRACTION_UNIT_STRS = new String[] { 421 "%", "%p" 422 }; 423 424 /** 425 * Perform type conversion as per {@link #coerceToString()} on an 426 * explicitly supplied type and data. 427 * 428 * @param type The data type identifier. 429 * @param data The data value. 430 * 431 * @return String The coerced string value. If the value is 432 * null or the type is not known, null is returned. 433 */ 434 public static final String coerceToString(int type, int data) 435 { 436 switch (type) { 437 case TYPE_NULL: 438 return null; 439 case TYPE_REFERENCE: 440 return "@" + data; 441 case TYPE_ATTRIBUTE: 442 return "?" + data; 443 case TYPE_FLOAT: 444 return Float.toString(Float.intBitsToFloat(data)); 445 case TYPE_DIMENSION: 446 return Float.toString(complexToFloat(data)) + DIMENSION_UNIT_STRS[ 447 (data>>COMPLEX_UNIT_SHIFT)&COMPLEX_UNIT_MASK]; 448 case TYPE_FRACTION: 449 return Float.toString(complexToFloat(data)*100) + FRACTION_UNIT_STRS[ 450 (data>>COMPLEX_UNIT_SHIFT)&COMPLEX_UNIT_MASK]; 451 case TYPE_INT_HEX: 452 return "0x" + Integer.toHexString(data); 453 case TYPE_INT_BOOLEAN: 454 return data != 0 ? "true" : "false"; 455 } 456 457 if (type >= TYPE_FIRST_COLOR_INT && type <= TYPE_LAST_COLOR_INT) { 458 return "#" + Integer.toHexString(data); 459 } else if (type >= TYPE_FIRST_INT && type <= TYPE_LAST_INT) { 460 return Integer.toString(data); 461 } 462 463 return null; 464 } 465 466 public void setTo(TypedValue other) 467 { 468 type = other.type; 469 string = other.string; 470 data = other.data; 471 assetCookie = other.assetCookie; 472 resourceId = other.resourceId; 473 density = other.density; 474 } 475 476 public String toString() 477 { 478 StringBuilder sb = new StringBuilder(); 479 sb.append("TypedValue{t=0x").append(Integer.toHexString(type)); 480 sb.append("/d=0x").append(Integer.toHexString(data)); 481 if (type == TYPE_STRING) { 482 sb.append(" \"").append(string != null ? string : "<null>").append("\""); 483 } 484 if (assetCookie != 0) { 485 sb.append(" a=").append(assetCookie); 486 } 487 if (resourceId != 0) { 488 sb.append(" r=0x").append(Integer.toHexString(resourceId)); 489 } 490 sb.append("}"); 491 return sb.toString(); 492 } 493 };
自定义DensityUtil类
说明：+0.5f的原因：根据网上的说法是为了保证结果不小于0.
1 /** 2 * 根据手机的分辨率从 dp 的单位 转成为 px(像素) 3 */ 4 public static int dip2px(Context context, float dpValue) { 5 final float scale = context.getResources().getDisplayMetrics().density; 6 return (int) (dpValue * scale + 0.5f); 7 } 8 9 /** 10 * 根据手机的分辨率从 px(像素) 的单位 转成为 dp 11 */ 12 public static int px2dip(Context context, float pxValue) { 13 final float scale = context.getResources().getDisplayMetrics().density; 14 return (int) (pxValue / scale + 0.5f); 15 }