Android - 开发实例(12)：安卓开发中最佳单例模式实现

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做开发的朋友肯定对单例模式不陌生，大概有下面两种实现方式。

public class Singleton{private static Singleton instance = null;private Singleton(){}public static synchronized Singleton getInstance(){if(instance == null){instance = new Singleton();}return instance;}}

public class Singleton{private static Singleton instance=new Singleton();private Singleton(){}public static Singletonget Instance(){return instance;}}

但是在我们Android中，经常会使用到Context的引用，于是你写下下面这种单例

public class Singleton{private static Singleton instance = null;private Singleton(Context ctx){}// Context 参数public static synchronized Singleton getInstance(Context ctx){if(instance == null){instance = new Singleton(ctx);}return instance;}}

每次获取单例的时候都要传入一个Context对象，如果我们要在纯Java类下使用，岂不是就歇菜了？

所以正确的单例模式应该是这样的，以PreferenceUtils为例

我们只需要在Application里面调用createInstance(Context ctx)，在其他地方使用的时候只需要getInstance()即可

package cn.gavinliu.formater.util;import java.util.Map.Entry;import android.content.ContentValues;import android.content.Context;import android.content.SharedPreferences;public class PreferenceUtils {private static PreferenceUtils util;private SharedPreferences mPreference;public static void createInstance(Context ctx) {util = new PreferenceUtils(ctx);}public static PreferenceUtils getInstance() {return util;}private PreferenceUtils(Context ctx) {mPreference = ctx.getApplicationContext().getSharedPreferences(ctx.getPackageName() + "_preferences", Context.MODE_PRIVATE);}public boolean putString(String key, String value) {return mPreference.edit().putString(key, value).commit();}public boolean putInt(String key, int value) {return mPreference.edit().putInt(key, value).commit();}public boolean putBoolean(String key, boolean value) {return mPreference.edit().putBoolean(key, value).commit();}public boolean putValues(ContentValues values) {SharedPreferences.Editor editor = mPreference.edit();for (Entry<String, Object> value : values.valueSet()) {editor.putString(value.getKey(), value.getValue().toString());}return editor.commit();}public String getString(String key) {return getString(key, "");}public String getString(String key, String defValue) {return mPreference.getString(key, defValue);}public int getInt(String key) {return getInt(key, -1);}public int getInt(String key, int defValue) {return mPreference.getInt(key, defValue);}public boolean getBoolean(String key) {return getBoolean(key, false);}public boolean getBoolean(String key, boolean defValue) {return mPreference.getBoolean(key, defValue);}}

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