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

1 package com.zzw.writeFile;
2
3 import java.io.File;
4 import java.io.FileOutputStream;
5
6 import android.app.Activity;
7 import android.os.Bundle;
8 import android.os.Environment;
9 import android.util.Log;
10
11 public class MainActivity extends Activity {
12
13     private static final String TAG = "MainActivity";
14
15     @Override
16     protected void onCreate(Bundle savedInstanceState) {
17         super.onCreate(savedInstanceState);
18         setContentView(R.layout.activity_main);
19
20         try {
21             writeFileToSDCard("Test", "Test.txt", "hello");
22         } catch (Exception e) {
23             // TODO Auto-generated catch block
24             e.printStackTrace();
25         }
26     }
27
28     private boolean writeFileToSDCard(String file_pathName, String fileName, String writeData) throws Exception {
29         // SDCard是否被挂载
30         if (Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED)) {
31             // 获取根目录
32             File parent_path = Environment.getExternalStorageDirectory();
33             Log.d(TAG, "parent_path=" + parent_path.getAbsolutePath() + "");
34
35             // 建立一个子目录专门存放自己的专属文件
36             File file_path = new File(parent_path.getAbsoluteFile(), file_pathName);
37             if (!file_path.exists()) {
38                 file_path.mkdir();
39             }
40             Log.d(TAG, "file_path=" + file_path.getAbsolutePath() + "");
41
42             // 自己的要存放的文件目录
43             File file = new File(file_path.getAbsoluteFile(), fileName);
44             if (!file.exists()) {
45                 file.createNewFile();
46                 Log.d(TAG, "创建文件" + fileName + "成功");
47             }
48             Log.d(TAG, "文件" + fileName + "存在,原文件将被置换");
49             Log.d(TAG, "file=" + file.getAbsolutePath() + "");
50
51             // 写文件
52             FileOutputStream fos = new FileOutputStream(file);
53
54             byte[] buffer = writeData.getBytes();
55
56             fos.write(buffer, 0, buffer.length);
57             fos.flush();
58             if (fos != null) {
59                 fos.close();
60             }
61
62             Log.d(TAG, "文件写入成功");
63             return true;
64
65         }
66         return false;
67     }
68 }

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

（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

1 package com.zzw.testsharedpreferences;
2
3 import android.app.Activity;
4 import android.content.SharedPreferences;
5 import android.content.SharedPreferences.Editor;
6 import android.os.Bundle;
7 import android.util.Log;
8
9 public class MainActivity extends Activity {
10
11     private static final String TAG = "MainActivity";
12
13     private final String SharedPreferences_Name = "SharedPreferences_Name";
14     private final String USER_NAME = "user_name";
15     private final String USER_PASSWORD = "user_password";
16
17     @Override
18     protected void onCreate(Bundle savedInstanceState) {
19         super.onCreate(savedInstanceState);
20         setContentView(R.layout.activity_main);
21         writeSharedPreferences();
22         readSharedPreferences();
23     }
24
25     private void writeSharedPreferences() {
26         SharedPreferences shared = this.getSharedPreferences(SharedPreferences_Name, MODE_PRIVATE);
27
28         Editor edit = shared.edit();
29         edit.putString(USER_NAME, "张三");
30         edit.putString(USER_PASSWORD, "123456");
31         edit.commit();
32     }
33
34     private void readSharedPreferences() {
35         SharedPreferences shared = this.getSharedPreferences(SharedPreferences_Name, MODE_PRIVATE);
36
37         String name = shared.getString(USER_NAME, "no_name");
38         String pass_word = shared.getString(USER_PASSWORD, "");
39         Log.d(TAG, "USER_NAME" + name + ",USER_PASSWORD:" + pass_word);
40     }
41 }