5种数据存储方式之文件和Preferences

l文件

Context.MODE_PRIVATE：为默认操作模式，代表该文件是私有数据，只能被应用本身访问，在该模式下，写入的内容会覆盖原文件的内容，如果想把新写入的内容追加到原文件中。可以使用Context.MODE_APPEND

Context.MODE_APPEND：模式会检查文件是否存在，存在就往文件追加内容，否则就创建新文件。

Context.MODE_WORLD_READABLE和Context.MODE_WORLD_WRITEABLE用来控制其他应用是否有权限读写该文件。

MODE_WORLD_READABLE：表示当前文件可以被其他应用读取；MODE_WORLD_WRITEABLE：表示当前文件可以被其他应用写入。

如果希望文件被其他应用读和写，可以传入：

openFileOutput("itcast.txt", Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE);

/** * @author   * @文件操作类：新建文件、删除、读写 * */package com.gogler.gps.infor;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.PrintStream;import android.content.Context;import android.os.Environment;public class FileHelper{        private final Context context;        /** SD卡是否存在 **/        private boolean       hasSD = false;        /** SD卡的路径 **/        private final String  SDPATH;        /** 当前程序包的路径 **/        private final String  FILESPATH;        /**     * 从调用者传入     * @param Context like this.getApplicationContext()     *      *      * */    public FileHelper ( Context context )    {    this.context = context;hasSD = Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED);SDPATH = Environment.getExternalStorageDirectory().getPath();FILESPATH = this.context.getFilesDir().getPath();    }        /**     *      * 在SD卡上创建文件     *      *      *      * @throws IOException     */        public File createSDFile(String fileName) throws IOException    {    final File file = new File(SDPATH + "//" + fileName);if (!file.exists()){        file.createNewFile();    }return file;    }        /**     *      * 删除SD卡上的文件      *      *      * @param fileName     */        public boolean deleteSDFile(String fileName)    {    final File file = new File(SDPATH + "//" + fileName);if ((file == null) || !file.exists() || file.isDirectory()){    return false;}return file.delete();    }        public String getFILESPATH()    {    return FILESPATH;    }        public String getSDPATH()    {    return SDPATH;    }        public boolean hasSD()    {    return hasSD;    }        /**     *      * 读取SD卡中文本文件     *      *      *      * @param fileName     *      * @return String     */        public String readSDFile(String fileName)    {    final StringBuffer sb = new StringBuffer();final File file = new File(SDPATH + "//" + fileName);try{        final FileInputStream fis = new FileInputStream(file);        int c;        while ((c = fis.read()) != -1)    {sb.append((char) c);    }        fis.close();    }catch (final FileNotFoundException e){        e.printStackTrace();    }catch (final IOException e){        e.printStackTrace();    }return sb.toString();    }        /**     *      *      * 写SD卡上的文件     *      *      * @param String     *            fileName,String content     *      *      * @return boolean     *      *      * @author Administrator     */        public boolean writeFileData(String fileName, String content)    {    try{    final FileOutputStream fout = new FileOutputStream(SDPATH + "//"    + fileName, true);    final PrintStream ps = new PrintStream(fout);    ps.println(content);    ps.close();}catch (final IOException e){    // TODO Auto-generated catch block    e.printStackTrace();}return true;    }    }

lSharedPreferences

创建可跨程序使用的Preferrence

package com.gogler.SharePreferences;import android.app.Activity;import android.content.Context;import android.content.SharedPreferences;import android.content.SharedPreferences.Editor;import android.content.res.Resources;import android.os.Bundle;public class SharePreferencesTestActivity extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);//        使用可跨程序读写的Preference        SharedPreferences sp = getSharedPreferences("hello", Context.MODE_WORLD_READABLE+Context.MODE_WORLD_WRITEABLE);        Editor editor = sp.edit();        String str = "SharePreferencesTestActivity: "+getResources().getString(R.string.hello);        editor.putString("helloStr", str );        editor.commit();    }}

读取其他APP的Preference

package sharePreferences.gogler.com;import android.app.Activity;import android.content.Context;import android.content.SharedPreferences;import android.content.pm.PackageManager.NameNotFoundException;import android.os.Bundle;import android.widget.TextView;public class UseSharePreferencesTestActivity extends Activity {    final String packageName = "com.gogler.SharePreferences";    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);//        访问其他APP的Preference        try {Context otherAppContext = createPackageContext(packageName, Context.CONTEXT_IGNORE_SECURITY);SharedPreferences sp = otherAppContext.getSharedPreferences("hello", Context.MODE_WORLD_READABLE); TextView tv=(TextView)findViewById(R.id.tv); tv.setText(sp.getString("helloStr", ""));} catch (NameNotFoundException e) { e.printStackTrace();}    }}