Java & Android基础

判断字符串是不是数字（正负均可）

boolean isNumber(String str) {

    Pattern pattern = Pattern.compile("-?[0-9]+\.?[0-9]*");
    Matcher isNum = pattern.matcher(str);
    if (!isNum.matches()) {
        return false;
    }
    return true;
}

byte[]向String的转换

String string=new String(bytes, "UTF-8");

调用媒体库，返回音频文件的uri

private void chooseFile() {
    Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Audio.Media.EXTERNAL_CONTENT_URI);
    try {
        startActivityForResult(intent, 1);
    } catch (android.content.ActivityNotFoundException ex) {
        Toast.makeText(this, "You dont have a file browser.", Toast.LENGTH_SHORT).show();
    }
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (resultCode != Activity.RESULT_OK) {
        super.onActivityResult(requestCode, resultCode, data);
        return;
    }
    if (requestCode == 1) {
        fileUri = Uri.parse(pref.getString("path", ""));
    }
    super.onActivityResult(requestCode, resultCode, data);
}

uri到真实路径的转换

public static String getRealFilePath( final Context context, final Uri uri ) {
        if ( null == uri ) return null;
        final String scheme = uri.getScheme();
        String data = null;
        if ( scheme == null )
            data = uri.getPath();
        else if ( ContentResolver.SCHEME_FILE.equals( scheme ) ) {
            data = uri.getPath();
        } else if ( ContentResolver.SCHEME_CONTENT.equals( scheme ) ) {
            Cursor cursor = context.getContentResolver().query( uri, new String[] { MediaStore.Audio.AudioColumns.DATA }, null, null, null );
            if ( null != cursor ) {
                if ( cursor.moveToFirst() ) {
                    int index = cursor.getColumnIndex( MediaStore.Audio.AudioColumns.DATA );
                    if ( index > -1 ) {
                        data = cursor.getString( index );
                    }
                }
                cursor.close();
            }
        }
        return data;
    }