最简单的android TXT阅读器 源码 注释很详细

package com.ostrichmyself.txtReader; import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.InputStreamReader; import android.app.Activity; import android.app.AlertDialog; import android.app.Dialog; import android.content.DialogInterface; import android.os.Bundle; import android.view.Menu; import android.view.MenuInflater; import android.view.MenuItem; import android.widget.TextView; /* * 文本浏览视图 × 菜单 可切换文字编码 */ public class ViewFile extends Activity { private String fileNameString; private static final String gb2312 = "GB2312"; private static final String utf8 = "UTF-8"; private static final String defaultCode = utf8; //这个Activity 利用 intent 携带 bundle的方法 //接受到了listAllFileActivity传过来的用户要求打开的文件名称和地址 @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.filebrowser); try { Bundle bunde = this.getIntent().getExtras(); fileNameString = bunde.getString("fileName"); reCodeAndShow(defaultCode); } catch (Exception e) {} } //创建并填充MENU菜单 @Override public boolean onCreateOptionsMenu(Menu menu) { MenuInflater inflater = this.getMenuInflater(); inflater.inflate(R.menu.menu, menu); return true; } //MENU菜单动作 switch case语句 //调用 reCodeAndShow(...)重新编码并显示 @Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case R.id.gb2312: reCodeAndShow(gb2312); break; case R.id.utf8: reCodeAndShow(utf8); break; case R.id.about: doAbout(); break; default: break; } return super.onOptionsItemSelected(item); } //重新编码并且显示 private void reCodeAndShow(String code) { TextView tv = (TextView) findViewById(R.id.view_contents); String fileString = getStringFromFile(code); tv.setText(fileString); } //从文件得到字符串 public String getStringFromFile(String code) { try { StringBuffer sBuffer = new StringBuffer(); FileInputStream fInputStream = new FileInputStream(fileNameString); //java.io.InputStreamReader 直接将编码作为参数引入内部函数处理 InputStreamReader inputStreamReader = new InputStreamReader(fInputStream, code); BufferedReader in = new BufferedReader(inputStreamReader); if(!new File(fileNameString).exists()) { return null; } while (in.ready()) { sBuffer.append(in.readLine() + "\n"); } in.close(); return sBuffer.toString(); } catch (Exception e) { e.printStackTrace(); } return null; } //帮助框的标题，内容的设置 private void doAbout() { Dialog dialog = new AlertDialog.Builder(ViewFile.this) .setTitle(R.string.aboutTitle) .setMessage(R.string.aboutInfo) .setPositiveButton(R.string.aboutOK,new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialoginterface, int i) {} } ) .create(); dialog.show(); } }