Android开发笔记（八十四）使用Properties读写属性值

Properties概述

Java中的配置文件常为.properties文件，而Properties类便是读写此类文件的工具。属性文件有两种格式，一种是文本格式，其内容是“键=值”的形式，文本注释信息可以用"#"来注释。另一种是XML格式，键值对遵循XML规范，Android的SharedPreferences也是以xml存储的。


下面是Properties的常用方法：
load : 从属性文件中加载属性对象
store : 把属性对象保存到属性文件
getProperty : 获取属性值
setProperty : 设置属性值
loadFromXML : 从XML格式的属性文件中加载属性对象
storeToXML : 把属性对象保存到XML格式的属性文件

Properties实际应用

下面是Properties的工具类代码例子：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Properties;

import android.content.Context;
import android.os.Environment;
import android.util.Log;

public class PropertiesUtil {
	private final static String TAG = "PropertiesUtil";

	private Context mContext;
	private String mPath;
	private String mFile;
	private Properties mProp;
	private static PropertiesUtil mPropUtil = null;
	
	public static PropertiesUtil getInstance(Context context) {
		if (mPropUtil == null) {
			mPropUtil = new PropertiesUtil();
			mPropUtil.mContext = context;
			mPropUtil.mPath = Environment.getExternalStorageDirectory() + "/ExmKeyValue";
			mPropUtil.mFile = "properties.ini";
		}
		return mPropUtil;
	}
	
	public PropertiesUtil setPath(String path) {
		mPath = path;
		return this;
	}

	public PropertiesUtil setFile(String file) {
		mFile = file;
		return this;
	}
	
	public PropertiesUtil init() {
		Log.d(TAG, "path="+mPath+"/"+mFile);
		try {
			File dir = new File(mPath);
			if (!dir.exists()) {
				dir.mkdirs();
			}
			File file = new File(dir, mFile);
			if (!file.exists()) {
				file.createNewFile();
			}
			InputStream is = new FileInputStream(file);
			mProp = new Properties();
			mProp.load(is);
			is.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
		return this;
	}
	
	public void commit() {
		try {
			File file = new File(mPath + "/" + mFile);
			OutputStream os = new FileOutputStream(file);
			mProp.store(os, "");
			os.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
		mProp.clear();
	}

	public void clear() {
		mProp.clear();
	}
	
	public void open() {
		mProp.clear();
		try {
			File file = new File(mPath + "/" + mFile);
			InputStream is = new FileInputStream(file);
			mProp = new Properties();
			mProp.load(is);
			is.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
    public void writeString(String name, String value) {
    	mProp.setProperty(name, value);
    }

    public String readString(String name, String defaultValue) {
        return mProp.getProperty(name, defaultValue);
    }

    public void writeInt(String name, int value) {
    	mProp.setProperty(name, ""+value);
    }

    public int readInt(String name, int defaultValue) {
        return Integer.parseInt(mProp.getProperty(name, ""+defaultValue));
    }

    public void writeBoolean(String name, boolean value) {
    	mProp.setProperty(name, ""+value);
    }

    public boolean readBoolean(String name, boolean defaultValue) {
        return Boolean.parseBoolean(mProp.getProperty(name, ""+defaultValue));
    }

    public void writeDouble(String name, double value) {
    	mProp.setProperty(name, ""+value);
    }

    public double readDouble(String name, double defaultValue) {
        return Double.parseDouble(mProp.getProperty(name, ""+defaultValue));
    }

}

下面是向属性文件写入键值对的代码：

			PropertiesUtil mProp = PropertiesUtil.getInstance(this).init();
			mProp.writeString("name", "Mr Lee");
			mProp.writeInt("age", (int)(Math.random()*100%100));
			mProp.writeBoolean("married", true);
			mProp.writeDouble("weight", 100f);
			mProp.writeString("time", Utils.getNowDateTime());
			mProp.commit();

下面是从属性文件读取键值对的代码：

			PropertiesUtil mProp = PropertiesUtil.getInstance(this).init();
			mProp.open();
			String name = mProp.readString("name", "");
			int age = mProp.readInt("age", 0);
			boolean married = mProp.readBoolean("married", false);
			double weight = mProp.readDouble("weight", 0f);
			String time = mProp.readString("time", "");

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