原文地址：http://wangliping.net/read-big-txt
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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。
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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：
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<Object, Object, Object> {
??????? @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：
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：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
??? android:id="@+id/text_show_linear" android:layout_width="wrap_content"
??? android:layout_height="wrap_content">
??? <ScrollView android:id="@+id/text_show_scroll"
??????? android:layout_width="fill_parent" android:layout_height="fill_parent">
??????? <net.wangliping.filemanager.SwanTextView
??????????? android:id="@+id/text_show" android:layout_width="fill_parent"
??????????? android:layout_height="wrap_content" android:scrollbars="none">
??????? </net.wangliping.filemanager.SwanTextView>
??? </ScrollView>
</LinearLayout>
代码不成熟，见笑了
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