Android编程之文件的读写实例详解

<?xml version="1.0" encoding="utf-8"?> 
<resources> 
 <string name="app_name">数据保存</string> 
 <string name="file_name">文件名</string> 
 <string name="file_content">文件内容</string> 
 <string name="button_file_save">保存</string> 
 <string name="button_file_read">读取</string> 
 <string name="file_save_success">保存文件成功</string> 
 <string name="file_save_failed">保存文件失败</string> 
 <string name="file_read_failed">读取文件失败</string> 
</resources>

<?xml version="1.0" encoding="utf-8"?> 
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" 
  android:orientation="vertical" android:layout_width="fill_parent" 
  android:layout_height="fill_parent"> 
  <!-- 文件名 --> 
  <textview android:layout_width="fill_parent" 
    android:layout_height="wrap_content" android:text="@string/file_name" /> 
  <edittext android:layout_width="fill_parent" 
    android:layout_height="wrap_content" android:id="@+id/et_file_name" /> 
  <textview android:layout_width="fill_parent" 
    android:layout_height="wrap_content" android:text="@string/file_content" /> 
  <edittext android:layout_width="fill_parent" 
    android:layout_height="wrap_content" android:minlines="3" 
    android:id="@+id/et_file_content" /> 
  <relativelayout android:layout_width="fill_parent" 
    android:layout_height="wrap_content"> 
    <button android:layout_width="wrap_content" 
      android:layout_height="wrap_content" android:text="@string/button_file_save" 
      android:id="@+id/bt_save" /> 
    <button android:layout_width="wrap_content" 
      android:layout_height="wrap_content" android:layout_torightof="@id/bt_save" 
      android:text="@string/button_file_read" android:id="@+id/bt_read" 
      android:layout_aligntop="@id/bt_save" 
      /> 
  </relativelayout> 
</linearlayout>

package test.service; 
import java.io.bytearrayoutputstream; 
import java.io.file; 
import java.io.fileinputstream; 
import java.io.fileoutputstream; 
import android.content.context; 
import android.os.environment; 
public class fileservice { 
private context context; 
public fileservice(context context) { 
this.context = context; 
} 
public void savetosdcard(string filename, string content) throws exception{ 
if(environment.getexternalstoragestate().equals(environment.media_mounted)){ 
file file = new file(environment.getexternalstoragedirectory(), filename); 
fileoutputstream outstream = new fileoutputstream(file); 
outstream.write(content.getbytes()); 
outstream.close(); 
} 
} 
public void save(string filename, string content) throws exception{ 
fileoutputstream outstream = context.openfileoutput(filename, context.mode_private); 
outstream.write(content.getbytes()); 
outstream.close(); 
}

package test.event; 
import test.file.r; 
import test.service.fileservice; 
import android.app.activity; 
import android.util.log; 
import android.view.view; 
import android.view.view.onclicklistener; 
import android.widget.button; 
import android.widget.edittext; 
import android.widget.toast; 
public class filebuttononclickevent implements onclicklistener { 
 private activity activity; 
 // 通过fileservice读写文件 
 private fileservice fileservice; 
 // 打印信息用的标签 
 private static final string tag = "filebuttononclickevent"; 
 public filebuttononclickevent(activity activity) { 
  this.activity = activity; 
   this.fileservice = new fileservice(activity); 
 } 
public void onclick(view v) { 
button button = (button) v; 
  switch (button.getid()) { 
  case r.id.bt_save: 
    // 获取文件名 
    edittext etfilenames = (edittext) this.activity 
        .findviewbyid(r.id.et_file_name); 
    string filenames = etfilenames.gettext().tostring(); 
    // 获取文件内容 
    edittext etfilecons = (edittext) this.activity 
        .findviewbyid(r.id.et_file_content); 
    string filecontents = etfilecons.gettext().tostring(); 
    // 保存 
    try { 
      this.fileservice.save(filenames, filecontents); 
      // 在窗口中显示一个特效信息框 
      toast.maketext(this.activity, r.string.file_save_success,
         toast.length_long).show(); 
      log.i(tag, "save file success!"); 
    } catch (exception e) { 
      toast.maketext(this.activity, r.string.file_save_failed, 
         toast.length_long).show(); 
      log.e(tag, e.tostring()); 
    } 
    break; 
  case r.id.bt_read: 
    // 获取文件名 
    edittext etfilenamer = (edittext) this.activity 
        .findviewbyid(r.id.et_file_name); 
    string filenamer = etfilenamer.gettext().tostring(); 
    // 读取文件 
    try { 
      string fielcontentr = this.fileservice.readfile(filenamer); 
      edittext etfileconr = (edittext) this.activity 
         .findviewbyid(r.id.et_file_content); 
      etfileconr.settext(fielcontentr); 
      log.i(tag, "read file success!"); 
    } catch (exception e) { 
      toast.maketext(this.activity, r.string.file_read_failed, 
         toast.length_long).show(); 
      log.e(tag, e.tostring()); 
    } 
    break; 
  default: 
    break; 
  } 
} 
} 
public void saveappend(string filename, string content) throws exception{// ctrl+shift+y / x 
fileoutputstream outstream = context.openfileoutput(filename, context.mode_append); 
outstream.write(content.getbytes()); 
outstream.close(); 
} 
public void savereadable(string filename, string content) throws exception{// ctrl+shift+y / x 
fileoutputstream outstream = context.openfileoutput(filename, context.mode_world_readable); 
outstream.write(content.getbytes()); 
outstream.close(); 
} 
public void savewriteable(string filename, string content) throws exception{// ctrl+shift+y / x 
fileoutputstream outstream = context.openfileoutput(filename, context.mode_world_writeable); 
outstream.write(content.getbytes()); 
outstream.close(); 
} 
public void saverw(string filename, string content) throws exception{ 
fileoutputstream outstream = context.openfileoutput(filename, 
context.mode_world_readable+ context.mode_world_writeable); 
outstream.write(content.getbytes()); 
outstream.close(); 
} 
public void saveprw(string filename, string content) throws exception{ 
fileoutputstream outstream = context.openfileoutput(filename, 
context.mode_world_readable+ context.mode_world_writeable+context.mode_append);
outstream.write(content.getbytes()); 
outstream.close(); 
} 
public string readfile(string filename) throws exception{ 
fileinputstream instream = context.openfileinput(filename); 
byte[] data = readdata(instream); 
return new string(data); 
} 
private byte[] readdata(fileinputstream instream) throws exception{ 
bytearrayoutputstream outstream = new bytearrayoutputstream(); 
byte[] buffer = new byte[1024]; 
int len = 0; 
while( (len = instream.read(buffer))!= -1){ 
outstream.write(buffer, 0, len); 
}
outstream.close();
instream.close();
return outstream.tobytearray();
}
}

package test.file; 
import test.event.filebuttononclickevent; 
import android.app.activity; 
import android.os.bundle; 
import android.widget.button; 
public class dateactivity extends activity { 
 /** called when the activity is first created. */ 
 @override 
 public void oncreate(bundle savedinstancestate) { 
  super.oncreate(savedinstancestate); 
  setcontentview(r.layout.main); 
  // 获取所有按钮 
  button buttonread = (button) this.findviewbyid(r.id.bt_read); 
  button buttonsave = (button) this.findviewbyid(r.id.bt_save); 
  // 为按钮添加事件 
  filebuttononclickevent filebtonclickeve = new filebuttononclickevent(this); 
  buttonread.setonclicklistener(filebtonclickeve); 
  buttonsave.setonclicklistener(filebtonclickeve); 
 }
}

<!-- 在sdcard中创建与删除文件权限 -->
<uses-permission android:name="android.permission.mount_unmount_filesystems"/>
<!-- 往sdcard写入数据权限 -->
<uses-permission android:name="android.permission.write_external_storage"/>

if(environment.getexternalstoragestate().equals(environment.media_mounted)){
   file sdcarddir = environment.getexternalstoragedirectory();//获取sdcard目录
   file savefile = new file(sdcarddir, "itcast.txt");
fileoutputstream outstream = new fileoutputstream(savefile);
outstream.write("写入的内容".getbytes());
outstream.close();
}

file sdcarddir = new file("/sdcard"); //获取sdcard目录
file savefile = new file(sdcarddir, "itcast.txt"); 
//上面两句代码可以合成一句： file savefile = new file("/sdcard/itcast.txt");
//上面两句代码可以合成一句： file savefile = new file(environment.getexternalstoragedirectory(), "itcast.txt");
fileoutputstream outstream = new fileoutputstream(savefile);
outstream.write("写入的内容".getbytes());
outstream.close();