SD卡讀寫之FileNotFoundException: /storage/emulated/0object.txt: open failed: ENOENT

讀寫sd卡中的文件按照如下步驟：1調用Environment的getExternalStorageState（）方法判斷手機上是否插入了sd卡，並且應用程序具有讀寫SD卡的能力

//如果手機已經插入了SD卡，且具有讀寫sd卡的能力，下面的語句將會返回true

Environment.getExternalStorageState().equals(Envronment.MEDIA_MOUNTED)

2）調用environment的getExternalStorageDIrectory（）方法獲取外部存儲器，也就是SD卡的目錄

3）使用FileInputStream、FileOUtputStream FileReader或者FileWriter來讀寫sd卡中的文件

註冊權限

<--!在SD卡中創建與刪除文件權限-->

<uses-permission android:name="android.permission.MOUNT_FORMAT_FILESYSTEMS"/>
<--!向SD卡寫入數據的權限--->
<uses-permission android:name="androd.permission.WRITE_EXTERNAL_STORAGE"/>
<--!讀取數據的權限--->
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

實例代碼：

有兩個EditText 和兩個Button組件，text_Write用於寫入數據，Button（write）組件用於讀取text_Write中的數據並寫入/storage/emulated/0/object.txt 文件中；

Button（read）組件用於從SD卡的/storage/emulated/0/object.txt中讀取數據，並顯示在text_Read組件中。

<span style="font-size:18px;"><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical"     android:paddingBottom="@dimen/activity_vertical_margin"     android:paddingLeft="@dimen/activity_horizontal_margin"     android:paddingRight="@dimen/activity_horizontal_margin"     android:paddingTop="@dimen/activity_vertical_margin"     tools:context="com.example.sdcard03.MainActivity$PlaceholderFragment" >      <EditText                  android:id="@+id/text_Write"         android:layout_width="match_parent"         android:layout_height="45dp"          />     <EditText         android:id="@+id/text_Read"         android:layout_width="match_parent"         android:layout_height="45dp"          />     <Button          android:id="@+id/read"         android:layout_height="wrap_content"         android:layout_width="match_parent"         android:text="read"/>      <Button          android:id="@+id/write"         android:layout_height="wrap_content"         android:layout_width="match_parent"         android:text="write"/>       </LinearLayout> </span>

主程序：

<span style="font-size:18px;">package com.example.sdcard03;  import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStreamReader;  import android.app.Activity; import android.os.Bundle; import android.os.Environment; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.Toast;  public class MainActivity extends Activity { 	private EditText read_Text; 	private EditText write_Text; 	private Button read; 	private Button write; 	private String fileName = <span style="color:#FF6666;">"/object.txt";</span>  	@Override 	protected void onCreate(Bundle savedInstanceState) { 		super.onCreate(savedInstanceState); 		setContentView(R.layout.fragment_main); 		read = (Button) findViewById(R.id.read); 		write = (Button) findViewById(R.id.write); 		read_Text = (EditText) findViewById(R.id.text_Read); 		write_Text = (EditText) findViewById(R.id.text_Write); 		read.setOnClickListener(new OnClickListener() {  			@Override 			public void onClick(View v) { 				// TODO Auto-generated method stub 				String s = readFromSdcard(); 				read_Text.setText(s);  			} 		}); 		// ------------------------ 		write.setOnClickListener(new OnClickListener() {  			@Override 			public void onClick(View v) { 				// TODO Auto-generated method stub 				String s2 = write_Text.getText().toString(); 				writeToSdcard(s2);  			}  		});  	}  	public String readFromSdcard() {  		if (Environment.getExternalStorageState().equals( 				Environment.MEDIA_MOUNTED)) {  			try { 				File sdPath = Environment<span style="color:#FF0000;">.getExternalStorageDirectory()</span>; 				<span style="color:#6633FF;">System.out.println(sdPath.toString());</span>  				FileInputStream fis = new FileInputStream(sdPath 						.<span style="color:#FF0000;">getCanonicalFile()</span>.toString() + fileName); 				<span style="color:#3366FF;">System.out.println(sdPath.getCanonicalFile().toString());</span> 				BufferedReader br = new BufferedReader(new InputStreamReader( 						fis)); 				StringBuilder sb = new StringBuilder(""); 				String line = null; 				while ((line = br.readLine()) != null) { 					sb.append(line);  				} 				fis.close(); 				br.close(); 				return sb.toString(); 			} catch (IOException e) { 				// TODO Auto-generated catch block 				e.printStackTrace(); 			} 		}  		return null;  	}  	// ------------------------------------------------------- 	public void writeToSdcard(String s) { 		if (Environment.getExternalStorageState().equals( 				Environment.MEDIA_MOUNTED)) { 			File sdCardDir = Environment.getExternalStorageDirectory(); 			try { 				File file = new File(sdCardDir.getCanonicalPath() + fileName); 				FileOutputStream fos = new FileOutputStream(file); 				 				fos.write(s.getBytes()); 				fos.close();  			} catch (IOException e) { 				// TODO Auto-generated catch block 				e.printStackTrace(); 			}  		}  		else { 			Toast.makeText(MainActivity.this, "sd卡異常", Toast.LENGTH_LONG) 					.show(); 		}  	} } </span>

幾點注意：1 不要忘記註冊權限

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