安卓SD卡读写、String和byte转换

小鱼儿 2022-08-20 07:30 240阅读 0赞

**一、SD卡读写**

package com.example.storage\_sdcard2;  
  
  
import java.io.ByteArrayOutputStream;  
import java.io.File;  
import java.io.FileInputStream;  
import java.io.FileNotFoundException;  
import java.io.FileOutputStream;  
import java.io.IOException;  
  
  
import android.app.Activity;  
import android.os.Bundle;  
import android.os.Environment;  
import android.view.Menu;  
import android.view.View;  
import android.view.View.OnClickListener;  
import android.widget.Button;  
  
  
public class MainActivity extends Activity \{  
  
  
@Override  
protected void onCreate(Bundle savedInstanceState) \{  
super.onCreate(savedInstanceState);  
setContentView(R.layout.activity\_main);  
Button but1 = (Button)findViewById(R.id.button1);  
Button but2 = (Button)findViewById(R.id.button2);  
but1.setOnClickListener(new OnClickListener() \{  
  
@Override  
public void onClick(View v) \{  
// TODO Auto-generated method stub  
File file = new File(Environment.getExternalStorageDirectory(),"MyFile.txt");  
FileOutputStream outputStream = null;  
try \{  
outputStream = new FileOutputStream(file);  
if(Environment.getExternalStorageState().equals(Environment.MEDIA\_MOUNTED))\{  
String str = "hello sdcard";  
byte\[\] data = str.getBytes();  
outputStream.write(data);  
\}  
\} catch (FileNotFoundException e) \{  
// TODO Auto-generated catch block  
e.printStackTrace();  
\} catch (IOException e) \{  
// TODO Auto-generated catch block  
e.printStackTrace();  
\}finally\{  
if(outputStream != null)\{  
try \{  
outputStream.close();  
\} catch (IOException e) \{  
// TODO Auto-generated catch block  
e.printStackTrace();  
\}  
\}  
\}  
  
\}  
\});  
but2.setOnClickListener(new OnClickListener() \{  
  
@Override  
public void onClick(View v) \{  
// TODO Auto-generated method stub  
File file = new File(Environment.getExternalStorageDirectory(),"MyFile.txt");  
FileInputStream inputStream = null;  
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();  
if(Environment.getExternalStorageState().equals(Environment.MEDIA\_MOUNTED))\{  
try \{  
inputStream = new FileInputStream(file);  
int len = 0;  
byte\[\] data = new byte\[1024\];  
while((len = inputStream.read(data)) != -1)\{  
outputStream.write(data, 0, len);  
\}  
System.out.println("--" + outputStream.toString());  
\} catch (FileNotFoundException e) \{  
// TODO Auto-generated catch block  
e.printStackTrace();  
\} catch (IOException e) \{  
// TODO Auto-generated catch block  
e.printStackTrace();  
\}finally\{  
if(inputStream != null)\{  
try \{  
inputStream.close();  
\} catch (IOException e) \{  
// TODO Auto-generated catch block  
e.printStackTrace();  
\}  
\}  
\}  
  
\}  
\}  
\});  
\}  
  
  
@Override  
public boolean onCreateOptionsMenu(Menu menu) \{  
// Inflate the menu; this adds items to the action bar if it is present.  
getMenuInflater().inflate(R.menu.main, menu);  
return true;  
\}  
  
  
\}

**二、String与byte转换**

1、string 转 byte\[\]  
String str = "Hello";  
byte\[\] data = str.getBytes();2、byte\[\] 转 string  
String res = new String(srtbyte);  
转换可设定编码方式：  
String str = "hello world你好";  
byte\[\] data = str.getBytes("UTF-8");String res = new String(data,"utf-8");