分享一下我老师大神的人工智能教程!零基础,通俗易懂!http://blog.csdn.net/jiangjunshow
也欢迎大家转载本篇文章。分享知识,造福人民,实现我们中华民族伟大复兴!
读写SD卡上的文件有几个步骤
1.调用Environment的getExternalStorageState() 方法判断手机上是否插入了SD卡,并且应用程序具有读写权限
如使用如下代码
//如果手机已插入SD卡,且应用程序具有读写SD卡的能力,下面语句返回true
Environment.getExternalstorageState().equals(Environment.MEDIA_MOUNTED)
2.调用Environment的getExternalStorageDirectory()方法来获取外部存储器,也就是SD卡的目录
3.使用FileInputStream,FileOutputStream,FileReader或FileWriter读,写SD卡里的文件
此外必须向AndroidManifest.xml添加SD卡的读写权限
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
下面是一个示例,用来读写SD卡里的文件
package WangLi.IO.SDCardTest;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.InputStreamReader;import java.io.RandomAccessFile;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;public class SDCardTest extends Activity { final String FILE_NAME = "/sdcardtest.txt"; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); //获取两个按钮 Button read = (Button)findViewById(R.id.read); Button write = (Button)findViewById(R.id.write); //获取两个文本框 final EditText edit1 = (EditText)findViewById(R.id.edit1); final EditText edit2 = (EditText)findViewById(R.id.edit2); //为write按钮绑定事件监听器 write.setOnClickListener(new OnClickListener(){ public void onClick(View source) { write(edit1.getText().toString()); edit1.setText(""); } }); //为read按钮绑定事件监听器 read.setOnClickListener(new OnClickListener(){ public void onClick(View source) { //读取指定文件中的内容并显示出来 edit2.setText(read()); } }); } private String read() { try { //如果手机插入了SD卡,而且应用程序具有访问SD的权限 if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { //获取SD卡对应的存储目录 File sdCardDir = Environment.getExternalStorageDirectory(); //获取指定文件对应的输入流 FileInputStream fis = new FileInputStream(sdCardDir.getCanonicalPath() + FILE_NAME); //将指定输入流包装成BufferedReader BufferedReader br = new BufferedReader(new InputStreamReader(fis)); StringBuilder sb = new StringBuilder(""); String line = null; while((line = br.readLine()) != null) { sb.append(line); } return sb.toString(); } } catch(Exception e) { e.printStackTrace(); } return null; } private void write(String content) { try { //如果手机插入了SD卡,而且应用程序具有访问SD的权限 if(Environment.getExternalStorageState() .equals(Environment.MEDIA_MOUNTED)) { //获取SD卡根目录 File sdCardDir = Environment.getExternalStorageDirectory(); File targetFile = new File(sdCardDir.getCanonicalPath() + FILE_NAME); //以指定文件创建RandomAccessFile对象 RandomAccessFile raf = new RandomAccessFile(targetFile, "rw"); //将文件记录指针移动到最后 raf.seek(targetFile.length()); //输出文件内容 raf.write(content.getBytes()); raf.close(); } } catch(Exception e) { e.printStackTrace(); } }}
上面有两个按钮,两个文本框,和上一篇一样,一个用来读,一个用来写
写入后,可以在DMSS里面找到刚刚写入的文件