不能把双SharedPreferences
得到错误，方法把双重是未定义的这种类型的sharedPreferences编辑器.Eclipse是给予一个快速修复添加到编辑器投，但是当我这样做，它仍然给错误，为什么不能我把双。
代码：
@Override protected void onPause() { // TODO Auto-generated method stub super.onPause(); if (TextUtils.isEmpty(editBl.getText().toString())) { numberOfBl = 0; } else { numberOfBl = Integer.parseInt(editBl.getText().toString(); } if (TextUtils.isEmpty(editSt.getText().toString())) { tonOfSt = 0; } else { tonOfSt = Double.parseDouble(editSt.getText().toString()); } SharedPreferences prefs = getSharedPreferences( "SavedTotals", Context.MODE_PRIVATE); SharedPreferences.Editor editor = prefs.edit(); editor.putInt("savedBl", numberOfBl); editor.putDouble("savedSt", tonOfSt); editor.commit(); } 那些建议使用putFloat和getFloat的人不幸的是非常错误。 将一个double转换为float可能会导致
- 失去精确度
- 溢出
- 潜流
- 死小猫
那些建议toString和parseString没有错，但这是一个低效率的解决方案。
处理这个问题的正确方法是将双精度转换为相等的“原始长度”，并存储这个长度。 当你读取的值，转换回双。
由于两种数据类型具有相同的大小，所以不会失去精度，并且不会导致{over，under}流。
Editor putDouble(final Editor edit, final String key, final double value) { return edit.putLong(key, Double.doubleToRawLongBits(value)); } double getDouble(final SharedPreferences prefs, final String key, final double defaultValue) { return Double.longBitsToDouble(prefs.getLong(key, Double.doubleToLongBits(defaultValue))); }
或者，您可以将getter写为：
double getDouble(final SharedPreferences prefs, final String key, final double defaultValue) { if ( !prefs.contains(key)) return defaultValue; return Double.longBitsToDouble(prefs.getLong(key, 0)); }
你总是可以实现SharedPreferences并包装android实现。
package com.company.sharedpreferences; import android.content.Context; import android.content.SharedPreferences; import java.util.Map; import java.util.Set; public class EnhancedSharedPreferences implements SharedPreferences { public static class NameSpaces { public static String MY_FUN_NAMESPACE = "MyFunNameSpacePrefs"; } public static EnhancedSharedPreferences getPreferences(String prefsName) { return new EnhancedSharedPreferences(SomeSingleton.getInstance().getApplicationContext().getSharedPreferences(prefsName, Context.MODE_PRIVATE)); } private SharedPreferences _sharedPreferences; public EnhancedSharedPreferences(SharedPreferences sharedPreferences) { _sharedPreferences = sharedPreferences; } //region Overrides @Override public Map<String, ?> getAll() { return _sharedPreferences.getAll(); } @Override public String getString(String key, String defValue) { return _sharedPreferences.getString(key, defValue); } @Override public Set<String> getStringSet(String key, Set<String> defValues) { return _sharedPreferences.getStringSet(key, defValues); } @Override public int getInt(String key, int defValue) { return _sharedPreferences.getInt(key, defValue); } @Override public long getLong(String key, long defValue) { return _sharedPreferences.getLong(key, defValue); } @Override public float getFloat(String key, float defValue) { return _sharedPreferences.getFloat(key, defValue); } @Override public boolean getBoolean(String key, boolean defValue) { return _sharedPreferences.getBoolean(key, defValue); } @Override public boolean contains(String key) { return _sharedPreferences.contains(key); } @Override public Editor edit() { return new Editor(_sharedPreferences.edit()); } @Override public void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) { _sharedPreferences.registerOnSharedPreferenceChangeListener(listener); } @Override public void unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) { _sharedPreferences.unregisterOnSharedPreferenceChangeListener(listener); } //endregion //region Extension public Double getDouble(String key, Double defValue) { return Double.longBitsToDouble(_sharedPreferences.getLong(key, Double.doubleToRawLongBits(defValue))); } //endregion public static class Editor implements SharedPreferences.Editor { private SharedPreferences.Editor _editor; public Editor(SharedPreferences.Editor editor) { _editor = editor; } private Editor ReturnEditor(SharedPreferences.Editor editor) { if(editor instanceof Editor) return (Editor)editor; return new Editor(editor); } //region Overrides @Override public Editor putString(String key, String value) { return ReturnEditor(_editor.putString(key, value)); } @Override public Editor putStringSet(String key, Set<String> values) { return ReturnEditor(_editor.putStringSet(key, values)); } @Override public Editor putInt(String key, int value) { return ReturnEditor(_editor.putInt(key, value)); } @Override public Editor putLong(String key, long value) { return ReturnEditor(_editor.putLong(key, value)); } @Override public Editor putFloat(String key, float value) { return ReturnEditor(_editor.putFloat(key, value)); } @Override public Editor putBoolean(String key, boolean value) { return ReturnEditor(_editor.putBoolean(key, value)); } @Override public Editor remove(String key) { return ReturnEditor(_editor.remove(key)); } @Override public Editor clear() { return ReturnEditor(_editor.clear()); } @Override public boolean commit() { return _editor.commit(); } @Override public void apply() { _editor.apply(); } //endregion //region Extensions public Editor putDouble(String key, double value) { return new Editor(_editor.putLong(key, Double.doubleToRawLongBits(value))); } //endregion } }
我所做的是将首选项保存为字符串：
getSharedPreferences("PREFERENCE", MODE_PRIVATE).edit().putString("double", "0.01").commit();
然后检索double，只需使用Double.parseDouble：
Double.parseDouble(getSharedPreferences("PREFERENCE", MODE_PRIVATE).getString("double", "0.01"));
Kotlin扩展方式（比使用怪异的utils类或其他更漂亮）
fun SharedPreferences.Editor.putDouble(key: String, double: Double) = putLong(key, java.lang.Double.doubleToRawLongBits(double)) fun SharedPreferences.getDouble(key: String, default: Double) = java.lang.Double.longBitsToDouble(getLong(key, java.lang.Double.doubleToRawLongBits(default)))
检查这个要点https://gist.github.com/john1jan/b8cb536ca51a0b2aa1da4e81566869c4
我创建了一个Preference Utils类来处理所有的情况。
易于使用
优先存储
PrefUtils.saveToPrefs(getActivity(), PrefKeys.USER_INCOME, income);
从偏好获取
Double income = (Double) PrefUtils.getFromPrefs(getActivity(), PrefKeys.USER_INCOME, new Double(10));