DSP

读写SD卡上的文件

2019-07-13 12:54发布

站内文章 / DSP
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布局界面为【输入框】、【显示框】、【数据写入按钮】和【数据输出按钮】 为了读写SD卡上的数据，必须在应用程序的清单文件中添加读写SD卡的权限 在SD卡中创建与删除文件权限：
向SD卡写入数据的权限：

程序代码如下： package com.twac.sdcardtest; import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.IOException; 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 MainActivity extends Activity { private Button btn_write; private Button btn_read; private EditText edt_write; private EditText edt_read; private final String FILE_NAME = "/crazyit.bin"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn_write = (Button) findViewById(R.id.btn_write); btn_read = (Button) findViewById(R.id.btn_read); edt_write = (EditText) findViewById(R.id.edt_write); edt_read = (EditText) findViewById(R.id.edt_read); btn_write.setOnClickListener(new OnClickListener() { @Override public void onClick(View arg0) { // 将edt_write的内容写入文件中 write(edt_write.getText().toString()); edt_write.setText(""); } }); btn_read.setOnClickListener(new OnClickListener() { @Override public void onClick(View arg0) { edt_read.setText(read()); } }); } private void write(String content) { if (Environment.getExternalStorageState().equals( Environment.MEDIA_MOUNTED)) { // 获得SD卡的目录 File sdCardDir = Environment.getExternalStorageDirectory(); try { 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()); // 关闭RandomAccessFile raf.close(); } catch (IOException e) { e.printStackTrace(); } } } 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; // 循环读取文件内容 while ((line = br.readLine()) != null) { sb.append(line); } // 关闭资源 br.close(); return sb.toString(); } } catch (Exception e) { e.printStackTrace(); } return null; } }

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