layout: post title: Android字符串格式化开源库phrase介绍 category: Android tags: Android keywords: Android,Phrase description: ndroid字符串格式化开源库phrase介绍
引言
Phrase是一个字符串格式化的开源项目，整个项目只有一个类Phrase.java，相比于String.format，通过phrase格式化字符串代码更具可读性。
phrase项目介绍
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源码：phrase项目的源代码很简单，里面总共只有一个类：Phrase.java，代码如下：
package com.eebbk.learnspell.util; import java.util.HashMap; import java.util.HashSet; import java.util.Map; import java.util.Set; import android.app.Fragment; import android.content.Context; import android.content.res.Resources; import android.text.SpannableStringBuilder; import android.view.View; public final class Phrase { private final CharSequence pattern; private final Set<String> keys = new HashSet<String>(); private final Map<String, CharSequence> keysToValues = new HashMap<String, CharSequence>(); private CharSequence formatted; private Token head; private char curChar; private int curCharIndex; private static final int EOF = 0; public static Phrase from(Fragment f, int patternResourceId) { return from(f.getResources(), patternResourceId); } public static Phrase from(View v, int patternResourceId) { return from(v.getResources(), patternResourceId); } public static Phrase from(Context c, int patternResourceId) { return from(c.getResources(), patternResourceId); } public static Phrase from(Resources r, int patternResourceId) { return from(r.getText(patternResourceId)); } public static Phrase from(CharSequence pattern) { return new Phrase(pattern); } public Phrase put(String key, CharSequence value) { if (!keys.contains(key)) { throw new IllegalArgumentException("Invalid key: " + key); } if (value == null) { throw new IllegalArgumentException("Null value for '" + key + "'"); } keysToValues.put(key, value); formatted = null; return this; } public Phrase put(String key, int value) { if (!keys.contains(key)) { throw new IllegalArgumentException("Invalid key: " + key); } keysToValues.put(key, Integer.toString(value)); formatted = null; return this; } public Phrase putOptional(String key, CharSequence value) { return keys.contains(key) ? put(key, value) : this; } public Phrase putOptional(String key, int value) { return keys.contains(key) ? put(key, value) : this; } public CharSequence format() { if (formatted == null) { if (!keysToValues.keySet().containsAll(keys)) { Set<String> missingKeys = new HashSet<String>(keys); missingKeys.removeAll(keysToValues.keySet()); throw new IllegalArgumentException("Missing keys: " + missingKeys); } SpannableStringBuilder sb = new SpannableStringBuilder(pattern); for (Token t = head; t != null; t = t.next) { t.expand(sb, keysToValues); } formatted = sb; } return formatted; } @Override public String toString() { return pattern.toString(); } private Phrase(CharSequence pattern) { curChar = (pattern.length() > 0) ? pattern.charAt(0) : EOF; this.pattern = pattern; Token prev = null; Token next; while ((next = token(prev)) != null) { if (head == null) head = next; prev = next; } } private Token token(Token prev) { if (curChar == EOF) { return null; } if (curChar == '{') { char nextChar = lookahead(); if (nextChar == '{') { return leftCurlyBracket(prev); } else if (nextChar >= 'a' && nextChar <= 'z') { return key(prev); } else { throw new IllegalArgumentException( "Unexpected character '" + nextChar + "'; expected key."); } } return text(prev); } private KeyToken key(Token prev) { StringBuilder sb = new StringBuilder(); consume(); while ((curChar >= 'a' && curChar <= 'z') || curChar == '_') { sb.append(curChar); consume(); } if (curChar != '}') { throw new IllegalArgumentException("Missing closing brace: }"); } consume(); if (sb.length() == 0) { throw new IllegalArgumentException("Empty key: {}"); } String key = sb.toString(); keys.add(key); return new KeyToken(prev, key); } private TextToken text(Token prev) { int startIndex = curCharIndex; while (curChar != '{' && curChar != EOF) { consume(); } return new TextToken(prev, curCharIndex - startIndex); } private LeftCurlyBracketToken leftCurlyBracket(Token prev) { consume(); consume(); return new LeftCurlyBracketToken(prev); } private char lookahead() { return curCharIndex < pattern.length() - 1 ? pattern.charAt(curCharIndex + 1) : EOF; } private void consume() { curCharIndex++; curChar = (curCharIndex == pattern.length()) ? EOF : pattern.charAt(curCharIndex); } private abstract static class Token { private final Token prev; private Token next; protected Token(Token prev) { this.prev = prev; if (prev != null) prev.next = this; } abstract void expand(SpannableStringBuilder target, Map<String, CharSequence> data); abstract int getFormattedLength(); final int getFormattedStart() { if (prev == null) { return 0; } else { return prev.getFormattedStart() + prev.getFormattedLength(); } } } private static class TextToken extends Token { private final int textLength; TextToken(Token prev, int textLength) { super(prev); this.textLength = textLength; } @Override void expand(SpannableStringBuilder target, Map<String, CharSequence> data) { } @Override int getFormattedLength() { return textLength; } } private static class LeftCurlyBracketToken extends Token { LeftCurlyBracketToken(Token prev) { super(prev); } @Override void expand(SpannableStringBuilder target, Map<String, CharSequence> data) { int start = getFormattedStart(); target.replace(start, start + 2, "{"); } @Override int getFormattedLength() { return 1; } } private static class KeyToken extends Token { private final String key; private CharSequence value; KeyToken(Token prev, String key) { super(prev); this.key = key; } @Override void expand(SpannableStringBuilder target, Map<String, CharSequence> data) { value = data.get(key); int replaceFrom = getFormattedStart(); int replaceTo = replaceFrom + key.length() + 2; target.replace(replaceFrom, replaceTo, value); } @Override int getFormattedLength() { return value.length(); } } } -
字符串格式化原理
通过阅读Phrase.java的代码可知，它用"{"和"}"将需要格式化的内容包起来，然后用键值对给需要改变的内容传值，包起来的内容为键，值为动态设置的内容，比如："Hi {first_name}, you are {age} years old."
我们要最终的显示内容为：“Hi UperOne, you are 26 years old.”这里的first_name和age是键，值为UperOne和26。
使用方法
使用起来很简单，通过键值对的方式插值：
CharSequence parseStr = Phrase.from("Hi {first_name}, you are {age} years old.")
.put("first_name", "UperOne")
.put("age", "26")
.format();
mParseTxt.setText( parseStr );