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;
    }
}

 <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

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);
    }
}