如何从android中的文本文件中提取子字符串？

Question

I want to know how can I do to extract a substring from a text file in android:

the text file is as shown below :

[start_delimeter]

0|1|text1

0|1|text2

0|1|text3

0|1|text4

[end_delimiter]

I want to extract strings between start_delimeter and end_delimiter.

How can I do that in java language/ android ??

Answer 1

Sequence:

• First you need to put your text file in the assets directory (ex filename.txt )
• Read the file (using a BufferedReader ) till you read the start delimiter
• Read each line from the file and process it using Pattern and Matcher till the end delimiter is found (or with String.split("|") )

And this is the code:

    // first get the file from the assets
    InputStream is = context.getAssets().open("filename.txt");

    try {
        // start reading (line by line)
        BufferedReader r = new BufferedReader(new InputStreamReader(is));

        // wait for the start delimiter
        String line;
        while ((line = r.readLine()) != null) 
            if (line.equals("[start_delimiter]"))
                break;

        // this is the pattern for the data "int|int|String":
        Pattern p = Pattern.compile("\\|(\\d+)\\|(\\d+)\\|(.+)");

        // read it line by line...
        while ((line = r.readLine()) != null) {
            // ... till the end comes (end delimiter)
            if (line.equals("[end_delimiter]"))
                break; //done

            // if the data matches the pattern...
            Matcher m = p.matcher(line);
            if (m.matches()) {
                // ... handle it!
                int first   = Integer.parseInt(m.group(1));
                int second  = Integer.parseInt(m.group(2));
                String text = m.group(3);

                //...
            }
        }

    } finally {
        is.close();
    }

Answer 2

I want to extract strings between start_delimeter and end_delimiter.

How can I do that in java language/ android ??

Read file line by line into String. then

str.subString(startIndex,endIndex);

Answer 3

Simply put, I would read the file line-by-line with a BufferedReader. Once the starting delimiter is found evaluate each subsequent line to see if it's the ending delimiter. If it isn't the delimiter, write the string to a collection. Once the ending delimiter is reached, stop reading and close the reader.

BufferedReader example

Answer 4

Use a BufferedReader and read the file line by line.

BufferedReader r = ...;
//drop until we hit the delimiter
while (!r.readLine().equals("[start_delimeter]"));
String line;
while (!(line=r.readLine()).equals("[end_delimiter]")) {
    //do something with "line" here
}