安卓文件操作 将文件读取出来存放到byte类型数组

先看效果：

第一步先把工程建立起来然后布置成如下状态：

xml布局方式采用线性布局。

  

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1. xmlns:android="http://schemas.android.com/apk/res/android"
   
2.     xmlns:tools="http://schemas.android.com/tools"
   
3.     android:layout_width="match_parent"
   
4.     android:layout_height="match_parent"
   
5.     android:orientation="vertical"
   
6.     >
   
7.     
   
8.         android:id="@+id/editText"
   
9.         android:layout_width="fill_parent"
   
10.         android:layout_height="wrap_content"
    
11.         android:hint="这里输入要保存的数据"
    
12.         />
    
13.     
    
14.         android:id="@+id/writebnt"
    
15.         android:layout_width="fill_parent"
    
16.         android:layout_height="wrap_content"
    
17.         android:text="写入数据" />
    
18.       
    
19.         android:id="@+id/readbnt"
    
20.         android:layout_width="fill_parent"
    
21.         android:layout_height="wrap_content"
    
22.         android:text="读取数据" />
    
23.       
    
24.           android:id="@+id/show"
    
25.           android:layout_width="fill_parent"
    
26.           android:layout_height="wrap_content"
    
27.           android:text="这里显示读出的数据"
    
28.           />

 

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第二步：

完成文件创建和写入和读取这两三个功能代码如下：

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1. package com.nguhyw.sdcard;
   
2. 
   
3. import java.io.File;
   
4. import java.io.FileInputStream;
   
5. import java.io.FileNotFoundException;
   
6. import java.io.FileOutputStream;
   
7. import java.io.IOException;
   
8. import java.io.InputStreamReader;
   
9. import java.io.OutputStreamWriter;
   
10. import java.io.UnsupportedEncodingException;
    
11. 
    
12. import android.os.Bundle;
    
13. import android.os.Environment;
    
14. import android.app.Activity;
    
15. import android.view.Menu;
    
16. import android.view.View;
    
17. import android.widget.Button;
    
18. import android.widget.EditText;
    
19. import android.widget.TextView;
    
20. import android.widget.Toast;
    
21. 
    
22. public class MainActivity extends Activity {
    
23. 
    
24.     private EditText edit;
    
25.     private TextView show;
    
26.     private Button writebnt;
    
27.     private Button readbnt;
    
28.     byte[] buff1 = new byte[10];
    
29.     char[] buff2 = new char[10];
    
30.     File sdcard = Environment.getExternalStorageDirectory();
    
31. 
    
32. 
    
33.     protected void onCreate(Bundle savedInstanceState) {
    
34.         super.onCreate(savedInstanceState);
    
35.         setContentView(R.layout.activity_main);
    
36. 
    
37.         edit = (EditText) findViewById(R.id.editText);
    
38.         show = (TextView) findViewById(R.id.show);
    
39.         writebnt = (Button) findViewById(R.id.writebnt);
    
40.         readbnt = (Button) findViewById(R.id.readbnt);
    
41. 
    
42.         writebnt.setOnClickListener(new View.OnClickListener() {
    
43. 
    
44.             public void onClick(View arg0) {
    
45. 
    
46.                 File myfile = new File(sdcard,"Temple.fptH");
    
47. 
    
48.                 if(!sdcard.exists()){
    
49.                     Toast.makeText(getApplicationContext(), "当前系统不具备SD卡", Toast.LENGTH_SHORT).show();
    
50.                     return ;
    
51.                 }
    
52.                 for(int i=0;i<10;i++){buff1[i]=0x38;buff2[i]=(char) buff1[i];}
    
53.                 try {
    
54.                     myfile.createNewFile();
    
55.                     Toast.makeText(getApplicationContext(), "文件创建完成", Toast.LENGTH_SHORT).show();
    
56.                     FileOutputStream fos = new FileOutputStream(myfile);
    
57.                     OutputStreamWriter osw = new OutputStreamWriter(fos);
    
58.                     osw.write(buff2);
    
59.                     osw.flush();
    
60.                     osw.close();
    
61.                     fos.close();
    
62.                     Toast.makeText(getApplicationContext(), "数据写入完成", Toast.LENGTH_SHORT).show();
    
63. 
    
64.                 } catch (IOException e) {
    
65.                     e.printStackTrace();
    
66.                 }
    
67. 
    
68.             }
    
69.         });
    
70. 
    
71.         readbnt.setOnClickListener(new View.OnClickListener() {
    
72. 
    
73.             public void onClick(View arg0) {
    
74.                 File myfile = new File(sdcard,"Temple.fptH");
    
75.                 if(myfile.exists()){
    
76.                     try {
    
77.                         FileInputStream fis =new FileInputStream(myfile);
    
78.                         InputStreamReader isr =new InputStreamReader(fis);
    
79.                         char[] input = new char[fis.available()];
    
80.                         isr.read(input);
    
81.                         isr.close();
    
82.                         fis.close();
    
83.                         String str = new String(input);
    
84.                         show.setText(str);
    
85.                     } catch (FileNotFoundException e) {
    
86.                         // TODO Auto-generated catch block
    
87.                         e.printStackTrace();
    
88.                     } catch (UnsupportedEncodingException e) {
    
89.                         // TODO Auto-generated catch block
    
90.                         e.printStackTrace();
    
91.                     } catch (IOException e) {
    
92.                         // TODO Auto-generated catch block
    
93.                         e.printStackTrace();
    
94.                     }
    
95.                 }
    
96.             }
    
97.         });
    
98. 
    
99. 
    
100.     }
     
101. 
     
102. 
     
103. 
     
104. }

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第四步设置应用的权限：

即读写Sd卡的权限

点击ADD添加权限：选择用户权限

然后在name哪里找的相对于的权限

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需要两个权限，那就是Sd卡的读取和写入。

全部代码如下：
SD卡文件读写.zip

另一种方法：

用于字节行的数据。