往Android SDCard中读写入数据

一、用Environment

（写）

1、API获取sdcard的路径

　　File path=Environment.getExternalStorageDirectory();

　　path=new File(path,"test.txt");

2、用流写入内容

3、获取WRITE_EXTERNAL_STORAGE权限

写入后的文件夹是：/mnt/sdcard/文件名及后缀

 package com.zzw.writeFile;

 import java.io.File;
 import java.io.FileOutputStream;

 import android.app.Activity;
 import android.os.Bundle;
 import android.os.Environment;
 import android.util.Log;

 public class MainActivity extends Activity {

     private static final String TAG = "MainActivity";

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         try {
             writeFileToSDCard("Test", "Test.txt", "hello");
         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
     }

     private boolean writeFileToSDCard(String file_pathName, String fileName, String writeData) throws Exception {
         // SDCard是否被挂载
         if (Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED)) {
             // 获取根目录
             File parent_path = Environment.getExternalStorageDirectory();
             Log.d(TAG, "parent_path=" + parent_path.getAbsolutePath() + "");

             // 建立一个子目录专门存放自己的专属文件
             File file_path = new File(parent_path.getAbsoluteFile(), file_pathName);
             if (!file_path.exists()) {
                 file_path.mkdir();
             }
             Log.d(TAG, "file_path=" + file_path.getAbsolutePath() + "");

             // 自己的要存放的文件目录
             File file = new File(file_path.getAbsoluteFile(), fileName);
             if (!file.exists()) {
                 file.createNewFile();
                 Log.d(TAG, "创建文件" + fileName + "成功");
             }
             Log.d(TAG, "文件" + fileName + "存在,原文件将被置换");
             Log.d(TAG, "file=" + file.getAbsolutePath() + "");

             // 写文件
             FileOutputStream fos = new FileOutputStream(file);

             byte[] buffer = writeData.getBytes();

             fos.write(buffer, 0, buffer.length);
             fos.flush();
             if (fos != null) {
                 fos.close();
             }

             Log.d(TAG, "文件写入成功");
             return true;

         }
         return false;
     }
 }

Environment

  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

权限操作

（读）

同样的通过IO操作，注意权限

二、获取shared_prefs目录,读写xml。使用SharedPreferences

写入目录：data/data/包名/shared_prefs/文件名.xml

1、获取SharedPreferences

　　SharedPreferences shared

　　=context.getSharedPreferences("xml名字",context.MODE_WORLD_READABLE+context.MODE_WORLD_WRITEABLE);//后者为权限

2、得到Editor(编辑器)

　　Editor edit=shared.edit();

3、放入数据

　　　　　　　　 　(K,V)

　　edit.putString("hello","world");

　　//获取我们保存的信息：shared.getString(key, defValue);

4、提交编辑内容

　　edit.commit();

5、获得权限

 package com.zzw.testsharedpreferences;

 import android.app.Activity;
 import android.content.SharedPreferences;
 import android.content.SharedPreferences.Editor;
 import android.os.Bundle;
 import android.util.Log;

 public class MainActivity extends Activity {

     private static final String TAG = "MainActivity";

     private final String SharedPreferences_Name = "SharedPreferences_Name";
     private final String USER_NAME = "user_name";
     private final String USER_PASSWORD = "user_password";

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         writeSharedPreferences();
         readSharedPreferences();
     }

     private void writeSharedPreferences() {
         SharedPreferences shared = this.getSharedPreferences(SharedPreferences_Name, MODE_PRIVATE);

         Editor edit = shared.edit();
         edit.putString(USER_NAME, "张三");
         edit.putString(USER_PASSWORD, "123456");
         edit.commit();
     }

     private void readSharedPreferences() {
         SharedPreferences shared = this.getSharedPreferences(SharedPreferences_Name, MODE_PRIVATE);

         String name = shared.getString(USER_NAME, "no_name");
         String pass_word = shared.getString(USER_PASSWORD, "");
         Log.d(TAG, "USER_NAME" + name + ",USER_PASSWORD:" + pass_word);
     }
 }

SharedPreferences