原文：http://zkl-/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 .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">
