android 笔记 --- Android大TXT文本文档读取

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<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：

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：

<?xml version="1.0" encoding="utf-8"?>
<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>

评论

2 楼 ominc 2012-04-22  

结尾会有乱码吧

1 楼 sunnygql 2011-10-08  

能不能发个Demo