Question

我是Android开发的新手。

我需要从SD卡读取文本文件并显示该文本文件。有没有办法直接在Android中查看文本文件，或者如何阅读和显示文本文件的内容？

Answer 1

In your layout您需要显示文字的内容。 TextView是显而易见的选择。所以你会有这样的事情：

<TextView 
    android:id="@+id/text_view" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"/>

您的代码将如下所示：

//Find the directory for the SD Card using the API
//*Don't* hardcode "/sdcard"
File sdcard = Environment.getExternalStorageDirectory();

//Get the text file
File file = new File(sdcard,"file.txt");

//Read text from file
StringBuilder text = new StringBuilder();

try {
    BufferedReader br = new BufferedReader(new FileReader(file));
    String line;

    while ((line = br.readLine()) != null) {
        text.append(line);
        text.append('\n');
    }
    br.close();
}
catch (IOException e) {
    //You'll need to add proper error handling here
}

//Find the view by its id
TextView tv = (TextView)findViewById(R.id.text_view);

//Set the text
tv.setText(text);

这可以采用您onCreate()的{{1}}方法或其他地方，具体取决于您想要做什么。

Answer 2

回应

不要硬编码/ sdcard /

有时我们必须对其进行硬编码，因为在某些手机型号中，API方法会返回内部手机内存。

已知类型：HTC One X和Samsung S3。

Environment.getExternalStorageDirectory().getAbsolutePath() gives a different path - Android

Answer 3

您应该具有READ_EXTERNAL_STORAGE权限才能读取sdcard。在manifest.xml中添加权限

#include <cstdint>

static const int MSG_SIZE = 256;
static const int MSG_SIZE_IN_BYTES = MSG_SIZE/8;
std::bitset<MSG_SIZE> msg = ...;
uint8_t msg_in_bits[MSG_SIZE_IN_BYTES] = {0};
for (int i = 0; i < MSG_SIZE; ++i)
    if (msg[i])
        msg_in_bits[i/8] |= 1 << (i%8);
MPI_Send(msg_in_bits, MSG_SIZE_IN_BYTES, MPI_BYTE, 1, 0, MPI_COMM_WORLD);

从android 6.0或更高版本开始，您的应用必须要求用户在运行时授予危险权限。请参考此链接 Permissions overview

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

Answer 4

package com.example.readfilefromexternalresource;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.os.Bundle;
import android.os.Environment;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
import android.os.Build;

public class MainActivity extends Activity {
    private TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        textView = (TextView)findViewById(R.id.textView);
        String state = Environment.getExternalStorageState();

        if (!(state.equals(Environment.MEDIA_MOUNTED))) {
            Toast.makeText(this, "There is no any sd card", Toast.LENGTH_LONG).show();


        } else {
            BufferedReader reader = null;
            try {
                Toast.makeText(this, "Sd card available", Toast.LENGTH_LONG).show();
                File file = Environment.getExternalStorageDirectory();
                File textFile = new File(file.getAbsolutePath()+File.separator + "chapter.xml");
                reader = new BufferedReader(new FileReader(textFile));
                StringBuilder textBuilder = new StringBuilder();
                String line;
                while((line = reader.readLine()) != null) {
                    textBuilder.append(line);
                    textBuilder.append("\n");

                }
                textView.setText(textBuilder);

            } catch (FileNotFoundException e) {
                // TODO: handle exception
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            finally{
                if(reader != null){
                    try {
                        reader.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }

        }
    }
}

Answer 5

BufferedReader br = null;
try {
        String fpath = Environment.getExternalStorageDirectory() + <your file name>;
        try {
            br = new BufferedReader(new FileReader(fpath));
        } catch (FileNotFoundException e1) {
            e1.printStackTrace();
        }
        String line = "";
        while ((line = br.readLine()) != null) {
         //Do something here 
        }

Answer 6

注意：有些手机有2个sdcards，一个内置固定卡和一个可移动卡。您可以通过标准应用找到最后一个的名称：＆＃34; Mijn Bestanden＆＃34; （英文：＆＃34; MyFiles＆＃34;？）当我打开这个应用程序（项目：所有文件）时，打开文件夹的路径是＆＃34; / sdcard＆＃34; ，向下滚动有一个条目＆＃34; external-sd＆＃34; ，单击此按钮将打开文件夹＆＃34; / sdcard / external_sd /＆＃34; 。假设我要打开一个文本文件＆＃34; MyBooks.txt＆＃34;我会用一些东西：

   String Filename = "/mnt/sdcard/external_sd/MyBooks.txt" ;
   File file = new File(fname);...etc...

如何从Android中的SD卡读取文本文件？

6 个答案: