原文：http://zkl-1987.iteye.com/blog/1055394

由于现在TXT文本很多，特别是好多小说也是以这个文件格式出现，毕竟这个格式所占用不必要的空间比较小。像我这样的人就非常喜欢在手机上看小说，经常下载好多的TXT格式小说存到手机上以便空闲时候看。于是乎也试图做了一下如何在Android上实现看大文本的txt文档。 虽然现在类似的应用还真不少，不过个人看到的基本不公布源码，而公布源码的基本都是不能看大文本的，所以自己去实现了一下。现在只是粗略实现了，实现方法是每次当滑动到屏幕底端时，从文件读2048字节出来显示到屏幕上。到屏幕底端再读是为了不给用户有刷屏的感觉，使用起来感觉不到只读了2048字节出来，比较流畅。现在由于只是试验流畅性，所以只写了向下浏览的，而没有写往回读，也就是说往回翻是无效的。 废话不多说，代码是王道。这个是主文件：

package net.wangliping.filemanager;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStreamReader;

import java.nio.CharBuffer;

import android.app.Activity;

import android.net.Uri;

import android.os.AsyncTask;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.text.TextUtils;

import android.util.Log;

import android.widget.ScrollView;

import net.wangliping.test.R;

public class TxtReader extends Activity implements

RealTimeTextView.OnTextChangedListener {

private static final String LOG_TAG = "TxtReader";

private static final int SHOW_TXT = 1;

private SwanTextView mTextShow;

private ScrollView mScrollView;

private String mStringShow = null;

private boolean mContinueRead = true;

private boolean mHaveNewText = false;

private int mCurBottom = -1;

private int mNum = -1;

private final Handler mHandler = new Handler() {

@Override

public void handleMessage(Message msg) {

switch (msg.what) {

case SHOW_TXT:

mTextShow.setText((CharBuffer) msg.obj);

break;

default:

super.handleMessage(msg);

}

}

};

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.txt_reader);

Uri uri = getIntent().getData();

mScrollView = (ScrollView) findViewById(R.id.text_show_scroll);

mTextShow = (RealTimeTextView) findViewById(R.id.text_show);

mTextShow.setOnTextChangedListener(this);

new TextShowTask().execute(uri);

}

private void showText(Uri uri) throws IOException, InterruptedException {

InputStreamReader is = new InputStreamReader(new FileInputStream(

uri.getPath()), "GB2312");

StringBuilder sb = new StringBuilder();

char[] buf = new char[1024 * 2];

while (true) {

if (mCurBottom == mScrollView.getScrollY()) {

Log.d(LOG_TAG, "curBtm:" + mCurBottom + " scroll:"

+ mScrollView.getScrollY());

mCurBottom = -1;

mNum++;

if (mNum % 2 == 0) {

mContinueRead = true;

Log.d(LOG_TAG, "YES");

}

}

if (mContinueRead && is.read(buf) > 0) {

mContinueRead = false;

if (sb.length() > 4096) {

sb.delete(0, 2048);

Message msg = mHandler.obtainMessage(SHOW_TXT);

msg.obj = CharBuffer.wrap(sb.toString());

mHandler.sendMessage(msg);

mStringShow = sb.append(buf).toString();

mHaveNewText = true;

} else {

while (sb.length() < 4096) {

sb.append(buf);

is.read(buf);

}

sb.append(buf);

Message msg = mHandler.obtainMessage(SHOW_TXT);

msg.obj = CharBuffer.wrap(sb.toString());

mHandler.sendMessage(msg);

}

}

}

}

private class TextShowTask extends AsyncTask {

@Override

protected void onPostExecute(Object param) {

Log.d(LOG_TAG, "Send broadcast");

}

@Override

protected Object doInBackground(Object... params) {

Uri uri = (Uri) params[0];

try {

showText(uri);

} catch (Exception e) {

Log.d(LOG_TAG, "Exception", e);

}

return null;

}

}

@Override

public void onPreOnDraw(int bottom) {

mCurBottom = bottom - mScrollView.getHeight();

if (mHaveNewText && !TextUtils.isEmpty(mStringShow)) {

mHaveNewText = false;

Message msg = mHandler.obtainMessage(SHOW_TXT);

msg.obj = CharBuffer.wrap(mStringShow);

mHandler.sendMessage(msg);

}

}

}

这个为了得到TextView底部的位置而扩展了TextView类：

package net.wangliping.filemanager;

import android.content.Context;

import android.graphics.Canvas;

import android.util.AttributeSet;

import android.widget.TextView;

public class SwanTextView extends TextView {

private int mPreBottom = -1;

private OnTextChangedListener textChangedListener = null;

public SwanTextView(Context context) {

super(context);

}

public SwanTextView(Context context, AttributeSet attrs) {

super(context, attrs);

}

public SwanTextView(Context context, AttributeSet attrs,

int defStyle) {

super(context, attrs, defStyle);

}

@Override

protected void onDraw(Canvas canvas) {

if (mPreBottom != getBottom()) {

mPreBottom = getBottom();

if (textChangedListener != null)

textChangedListener.onPreOnDraw(mPreBottom);

}

super.onDraw(canvas);

}

public static interface OnTextChangedListener {

public void onPreOnDraw(int bottom);

}

public void setOnTextChangedListener(OnTextChangedListener listener) {

textChangedListener = listener;

}

}

这个就是资源文件了：

android:id="@+id/text_show_linear" android:layout_width="wrap_content"

android:layout_height="wrap_content">

android:layout_width="fill_parent" android:layout_height="fill_parent">

android:id="@+id/text_show" android:layout_width="fill_parent"

android:layout_height="wrap_content" android:scrollbars="none">