android 41 Environment

assets通常存储音频视频文件，但不要太大。
Environment可以获取sd卡的相关信息，
sd卡的根路径：/storage/sdcard

package com.sxt.day06_07;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.widget.Toast;

public class MainActivity extends Activity {

private static final String FILE_NAME = "sxt_logo.png";
//将工程assets下的sxt_logo.png图片保存进sd卡
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(Environment.getExternalStorageState().equals(Environment.MEDIA_UNMOUNTED)){//MEDIA_UNMOUNTED没有挂载
//若没有sd卡
Toast.makeText(this, "sd卡没有准备好", 2000).show();
return ;
}
InputStream in = null;
OutputStream out=null;
try {
in=getAssets().open(FILE_NAME);//getAssets返回AssetManager对象(管理Asset的管理器)，获取了工程磁盘assets下的sxt_logo.png图片
File dir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);//获取sd卡的保存图pain的路径/storage/sdcard/Pictures
File file=new File(dir, FILE_NAME);
out=new FileOutputStream(file);
int len;
byte[] buffer=new byte[8*1024];//每次读取8K
while((len=in.read(buffer))!=-1){
out.write(buffer, 0, len);//将内存中的buffer写到输出流代表的sd卡
}
Toast.makeText(MainActivity.this, "文件保存完毕", 2000).show();
} catch (IOException e) {
e.printStackTrace();
}finally{
try {
if(out!=null){
out.close();
}
if(in!=null){
in.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}

}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.sxt.day06_07"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>   申请读sd卡的权限
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>         申请写sd卡的权限
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.sxt.day06_07.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

</manifest>