Develop Reference

how to call Asynktask for list of String inside forloop in android

ArrayList<String> list1 = splitFileList;
for (int i = 0; i < list1.size(); i++) {
tempFileName = splitFileList.get(i);
String splitFileCheckinDirectory = splitVideofilepath + Constant.SPLIT_VIDEO + "/" + list1.get(i) + Constant.FILE_EXTENSION;
File myfile = new File(splitFileCheckinDirectory);
if (!myfile.exists()) {
new TrimmVideo(getExternalFilesDir(null) + "/" + getFileNameFromFilePath(mFilePath), mStartTImelist.get(i), mEndTimelist.get(i) - mStartTImelist.get(i)).execute();
}
}
below is my Asynktask which i am trying execute inside for loop
private class TrimmVideo extends AsyncTask<Void, Void, Void> {
private final String mediaPath;
private final double endTime;
private final int length;
private double startTime;
private ProgressDialog progressDialog;
private TrimmVideo(String mediaPath, int startTime, int length) {
this.mediaPath = mediaPath;
this.startTime = startTime;
this.length = length;
this.endTime = this.startTime + this.length;
}
#Override
protected void onPreExecute() {
progressDialog = ProgressDialog.show(VideoPlayActvity.this,
"Trimming videos", "Please wait...", true);
super.onPreExecute();
}
#Override
protected Void doInBackground(Void... params) {
trimVideo();
return null;
}
#Override
protected void onPostExecute(Void result) {
progressDialog.dismiss();
dbHandler.updateFlag(fileModel == null ? tempFileName : fileModel.getfilename());
btn_save_video.setVisibility(View.INVISIBLE);
super.onPostExecute(result);
}
private void trimVideo() {
try {
File file = new File(mediaPath);
FileInputStream fis = new FileInputStream(file);
FileChannel in = fis.getChannel();
Movie movie = MovieCreator.build(in);
List<Track> tracks = movie.getTracks();
movie.setTracks(new LinkedList<Track>());
boolean timeCorrected = false;
// Here we try to find a track that has sync samples. Since we can only start decoding
// at such a sample we SHOULD make sure that the start of the new fragment is exactly
// such a frame
for (Track track : tracks) {
if (track.getSyncSamples() != null && track.getSyncSamples().length > 0) {
if (timeCorrected) {
// This exception here could be a false positive in case we have multiple tracks
// with sync samples at exactly the same positions. E.g. a single movie containing
// multiple qualities of the same video (Microsoft Smooth Streaming file)
//throw new RuntimeException("The startTime has already been corrected by another track with SyncSample. Not Supported.");
} else {
startTime = correctTimeToNextSyncSample(track, startTime);
timeCorrected = true;
}
}
}
for (Track track : tracks) {
long currentSample = 0;
double currentTime = 0;
long startSample = -1;
long endSample = -1;
for (int i = 0; i < track.getDecodingTimeEntries().size(); i++) {
TimeToSampleBox.Entry entry = track.getDecodingTimeEntries().get(i);
for (int j = 0; j < entry.getCount(); j++) {
// entry.getDelta() is the amount of time the current sample covers.
if (currentTime <= startTime) {
// current sample is still before the new starttime
startSample = currentSample;
} else if (currentTime <= endTime) {
// current sample is after the new start time and still before the new endtime
endSample = currentSample;
} else {
// current sample is after the end of the cropped video
break;
}
currentTime += (double) entry.getDelta() / (double) track.getTrackMetaData().getTimescale();
currentSample++;
}
}
movie.addTrack(new CroppedTrack(track, startSample, endSample));
}
IsoFile out = new DefaultMp4Builder().build(movie);
File storagePath = new File(getExternalFilesDir(null) + "/" + Constant.SPLIT_VIDEO + "/");
storagePath.mkdirs();
File myMovie = new File(storagePath, fileModel == null ? "/" + tempFileName + Constant.FILE_EXTENSION : fileModel.getfilename() + Constant.FILE_EXTENSION);
FileOutputStream fos = new FileOutputStream(myMovie);
FileChannel fc = fos.getChannel();
out.getBox(fc);
dbHandler.updateFlag(fileModel == null ? tempFileName : fileModel.getfilename());
fc.close();
fos.close();
fis.close();
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}
private double correctTimeToNextSyncSample(Track track, double cutHere) {
double[] timeOfSyncSamples = new double[track.getSyncSamples().length];
long currentSample = 0;
double currentTime = 0;
for (int i = 0; i < track.getDecodingTimeEntries().size(); i++) {
TimeToSampleBox.Entry entry = track.getDecodingTimeEntries().get(i);
for (int j = 0; j < entry.getCount(); j++) {
if (Arrays.binarySearch(track.getSyncSamples(), currentSample + 1) >= 0) {
// samples always start with 1 but we start with zero therefore +1
timeOfSyncSamples[Arrays.binarySearch(track.getSyncSamples(), currentSample + 1)] = currentTime;
}
currentTime += (double) entry.getDelta() / (double) track.getTrackMetaData().getTimescale();
currentSample++;
}
}
for (double timeOfSyncSample : timeOfSyncSamples) {
if (timeOfSyncSample > cutHere) {
return timeOfSyncSample;
}
}
return timeOfSyncSamples[timeOfSyncSamples.length - 1];
}
}
splitFileList list Contain 2 Size data a,b i want to execute synchronously one by one i.e loop start from 0 then it should complete asynk task for 0 then if loop will go one then it should complete please suggest me how to execute asynk task one by one in for loop .

You can't run synchronously by AsyncTask You must use thread some thing like this:
Thread t = new Thread(
new Runnable() {
public void run() {
try {
ArrayList<String> list1 = splitFileList;
for (int i = 0; i < list1.size(); i++) {
tempFileName = splitFileList.get(i);
String splitFileCheckinDirectory = splitVideofilepath + Constant.SPLIT_VIDEO + "/" + list1.get(i) + Constant.FILE_EXTENSION;
File myfile = new File(splitFileCheckinDirectory);
if (!myfile.exists()) {
trimVideo(getExternalFilesDir(null) + "/" + getFileNameFromFilePath(mFilePath), mStartTImelist.get(i), mEndTimelist.get(i) - mStartTImelist.get(i)); //here you can run synchronously work
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
});
t.start();
try {
t.join();
.....
} catch (Exception e) {
e.printStackTrace();
}
private void trimVideo(String mediaPath, int startTime, int length) {
try {
File file = new File(mediaPath);
FileInputStream fis = new FileInputStream(file);
FileChannel in = fis.getChannel();
Movie movie = MovieCreator.build(in);
List<Track> tracks = movie.getTracks();
movie.setTracks(new LinkedList<Track>());
boolean timeCorrected = false;
// Here we try to find a track that has sync samples. Since we can only start decoding
// at such a sample we SHOULD make sure that the start of the new fragment is exactly
// such a frame
for (Track track : tracks) {
if (track.getSyncSamples() != null && track.getSyncSamples().length > 0) {
if (timeCorrected) {
// This exception here could be a false positive in case we have multiple tracks
// with sync samples at exactly the same positions. E.g. a single movie containing
// multiple qualities of the same video (Microsoft Smooth Streaming file)
//throw new RuntimeException("The startTime has already been corrected by another track with SyncSample. Not Supported.");
} else {
startTime = correctTimeToNextSyncSample(track, startTime);
timeCorrected = true;
}
}
}
for (Track track : tracks) {
long currentSample = 0;
double currentTime = 0;
long startSample = -1;
long endSample = -1;
for (int i = 0; i < track.getDecodingTimeEntries().size(); i++) {
TimeToSampleBox.Entry entry = track.getDecodingTimeEntries().get(i);
for (int j = 0; j < entry.getCount(); j++) {
// entry.getDelta() is the amount of time the current sample covers.
if (currentTime <= startTime) {
// current sample is still before the new starttime
startSample = currentSample;
} else if (currentTime <= endTime) {
// current sample is after the new start time and still before the new endtime
endSample = currentSample;
} else {
// current sample is after the end of the cropped video
break;
}
currentTime += (double) entry.getDelta() / (double) track.getTrackMetaData().getTimescale();
currentSample++;
}
}
movie.addTrack(new CroppedTrack(track, startSample, endSample));
}
IsoFile out = new DefaultMp4Builder().build(movie);
File storagePath = new File(getExternalFilesDir(null) + "/" + Constant.SPLIT_VIDEO + "/");
storagePath.mkdirs();
File myMovie = new File(storagePath, fileModel == null ? "/" + tempFileName + Constant.FILE_EXTENSION : fileModel.getfilename() + Constant.FILE_EXTENSION);
FileOutputStream fos = new FileOutputStream(myMovie);
FileChannel fc = fos.getChannel();
out.getBox(fc);
dbHandler.updateFlag(fileModel == null ? tempFileName : fileModel.getfilename());
fc.close();
fos.close();
fis.close();
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}
private double correctTimeToNextSyncSample(Track track, double cutHere) {
double[] timeOfSyncSamples = new double[track.getSyncSamples().length];
long currentSample = 0;
double currentTime = 0;
for (int i = 0; i < track.getDecodingTimeEntries().size(); i++) {
TimeToSampleBox.Entry entry = track.getDecodingTimeEntries().get(i);
for (int j = 0; j < entry.getCount(); j++) {
if (Arrays.binarySearch(track.getSyncSamples(), currentSample + 1) >= 0) {
// samples always start with 1 but we start with zero therefore +1
timeOfSyncSamples[Arrays.binarySearch(track.getSyncSamples(), currentSample + 1)] = currentTime;
}
currentTime += (double) entry.getDelta() / (double) track.getTrackMetaData().getTimescale();
currentSample++;
}
}
for (double timeOfSyncSample : timeOfSyncSamples) {
if (timeOfSyncSample > cutHere) {
return timeOfSyncSample;
}
}
return timeOfSyncSamples[timeOfSyncSamples.length - 1];
}

If you can't implement #Hazem answer you can go with another approach.
For this you need to maintain counter for each of your data and forget about for loop.
First you need to call asynctask for first position of your list.Something like this:
if(list1.size() > 0) {
fileCounter=0;
tempFileName = splitFileList.get(fileCounter);
String splitFileCheckinDirectory = splitVideofilepath + Constant.SPLIT_VIDEO + "/" + tempFileName + Constant.FILE_EXTENSION;
File myfile = new File(splitFileCheckinDirectory);
if (!myfile.exists()) {
new TrimmVideo(getExternalFilesDir(null) + "/" + getFileNameFromFilePath(mFilePath), mStartTImelist.get(i), mEndTimelist.get(i) - mStartTImelist.get(i)).execute();
}
}
Then in onPostExecute of your asyncTask
#Override
protected void onPostExecute(Void result) {
progressDialog.dismiss();
dbHandler.updateFlag(fileModel == null ? tempFileName : fileModel.getfilename());
btn_save_video.setVisibility(View.INVISIBLE);
super.onPostExecute(result);
// Update your counter here
fileCounter++;
// Check if your incremented counter doesn't exceed your list size
if(fileCounter < list1.size()) {
// Then call your asynctask again with updated counter data
empFileName = splitFileList.get(fileCounter);
String splitFileCheckinDirectory = splitVideofilepath + Constant.SPLIT_VIDEO + "/" + tempFileName + Constant.FILE_EXTENSION;
File myfile = new File(splitFileCheckinDirectory);
if (!myfile.exists()) {
new TrimmVideo(getExternalFilesDir(null) + "/" + getFileNameFromFilePath(mFilePath), mStartTImelist.get(i), mEndTimelist.get(i) - mStartTImelist.get(i)).execute();
}
}
}
Hope this will help you.

How to solve "No glyph for U+000A in font Helvetica-Bold" in pdfbox (android port)

I want to write some text into a pdf. I have the data in "icrResultTxt". I am also writing the data to text.txt file before trying to write to a pdf. When I try to write to the pdf I get "No glyph for U+000A in font Helvetica-Bold". How to solve it? I dont have any fondness for "Helvetica-Bold". I am willing to change to any font.
#Override
protected Boolean doInBackground(Void... params) {
Boolean ret = false;
PDDocument document = new PDDocument();
try {
float scale = 0.8f; // alter this value to set the image size
formPreference = getSharedPreferences(SHARD_PREFERENCES,
MODE_PRIVATE);
PDPage page = new PDPage();
document.addPage(page);
PDPageContentStream contentStream = new PDPageContentStream(
document, page, false, true);
PDFont pdfFont = PDType1Font.HELVETICA_BOLD;
float fontSize = 25;
float leading = 1.5f * fontSize;
PDRectangle mediabox = page.getMediaBox();
float margin = 72;
float width = mediabox.getWidth() - 2 * margin;
float startX = mediabox.getLowerLeftX() + margin;
float startY = mediabox.getUpperRightY() - margin;
// icrResultTxt;//
writeToFile(icrResultTxt);
String text = icrResultTxt; // "I am trying to create a PDF file with a lot of text contents in the document. I am using PDFBox";
List<String> lines = new ArrayList<String>();
int lastSpace = -1;
while (text.length() > 0) {
int spaceIndex = text.indexOf(' ', lastSpace + 1);
if (spaceIndex < 0) {
lines.add(text);
text = "";
} else {
String subString = text.substring(0, spaceIndex);
float size = fontSize
* pdfFont.getStringWidth(subString) / 1000;
if (size > width) {
if (lastSpace < 0) // So we have a word longer than
// the line... draw it anyways
lastSpace = spaceIndex;
subString = text.substring(0, lastSpace);
lines.add(subString);
text = text.substring(lastSpace).trim();
lastSpace = -1;
} else {
lastSpace = spaceIndex;
}
}
}
contentStream.beginText();
contentStream.setFont(pdfFont, fontSize);
contentStream.moveTextPositionByAmount(startX, startY);
for (String line : lines) {
contentStream.drawString(line);
contentStream.moveTextPositionByAmount(0, -leading);
}
contentStream.endText();
contentStream.close();
File fz = new File(
Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)
+ File.separator + "hello.pdf");
if (!fz.exists()) {
fz.createNewFile();
} else {
fz.delete();
fz.createNewFile();
}
document.save(fz);
} catch (Exception e) {
Log.v("mango", e.getMessage());
}
private void writeToFile(String data) {
try {
File d = GetImageFile("test.txt");
if (d.exists()) {
d.delete();
d.createNewFile();
} else {
d.createNewFile();
}
FileOutputStream stream = new FileOutputStream(d);
try {
stream.write(data.getBytes());
} finally {
stream.close();
}
} catch (IOException e) {
Log.e("Exception", "File write failed: " + e.toString());
}
}

Use the following code instead "\r\n"
contentStream.moveTextPositionByAmount(100, 700);
contentStream.drawString("hello");
contentStream.endText();
contentStream.beginText();
contentStream.moveTextPositionByAmount(100, 690);//the second parameter mast between 800.0 and 0.0

Compare contents of two files line by line

public class MainActivity extends Activity {
FileOutputStream fos;
FileInputStream fOne, fTwo;
ArrayList<String> arr1 = new ArrayList<String>();
ArrayList<String> arr2 = new ArrayList<String>();
ArrayList<String> words = new ArrayList<String>();
ArrayList<String> wordsTwo = new ArrayList<String>();
int count = 0;
int countTwo = 0;
int countThree = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button fileOne = (Button)findViewById(R.id.file1);
Button fileTwo = (Button)findViewById(R.id.file2);
Button compare = (Button)findViewById(R.id.compare);
arr1.add("1");
arr1.add("2");
arr1.add("3");
arr1.add("4");
//arr1.add("3");
arr2.add("1");
arr2.add("2");
fileOne.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
try
{
fos = openFileOutput("File1", Context.MODE_PRIVATE);
for(int temp = 0; temp< arr1.size(); temp++)
{
fos.write((arr1.get(temp).getBytes()) );
fos.write(System.getProperty("line.separator").getBytes());
}
fos.close();
fos.flush();
}
catch(Exception e)
{
}
}
});
fileTwo.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
try
{
fos = openFileOutput("File2", Context.MODE_PRIVATE);
for(int temp = 0; temp< arr2.size(); temp++)
{
fos.write((arr2.get(temp).getBytes()) );
fos.write(System.getProperty("line.separator").getBytes());
}
fos.close();
fos.flush();
}
catch(Exception e)
{
}
}
});
compare.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
try
{
fOne = openFileInput("File1");
fTwo = openFileInput("File2");
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Scanner scanFile = new Scanner(new DataInputStream(fOne));
Scanner scanFileT = new Scanner(new DataInputStream(fTwo));
words = new ArrayList<String>();
wordsTwo = new ArrayList<String>();
while (scanFile.hasNextLine())
{
if(scanFile.nextLine()!=null)
{
count++;
}
while(scanFileT.hasNextLine())
{
if(scanFileT.nextLine()!=null)
{
countTwo++;
}
}
}
try
{
fOne.close();
fTwo.close();
scanFile.close();
scanFileT.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Toast.makeText(getBaseContext(), "One : " + count, 1000).show();
Toast.makeText(getBaseContext(), "Two : " + countTwo, 1000).show();
Toast.makeText(getBaseContext(), "Three : " + countThree, 1000).show();
count = 0 ;
countTwo = 0;
countThree = 0;
}
});
}
}
Above is the code to write and read the file. What I did here, write two files and read the contents..Now I have to compare contents of files line by line. What needs to be done?

Try following code. This will give you desired output. I took files from asset directory. So you need to replace that line of code if you are taking files from other directory.
private void compareFiles() throws Exception {
String s1 = "";
String s2 = "", s3 = "", s4 = "";
String y = "", z = "";
// Reading the contents of the files
BufferedReader br = new BufferedReader(new InputStreamReader(
getAssets().open("first.txt")));
BufferedReader br1 = new BufferedReader(new InputStreamReader(
getAssets().open("second.txt")));
while ((z = br1.readLine()) != null) {
s3 += z;
s3 += System.getProperty("line.separator");
}
while ((y = br.readLine()) != null) {
s1 += y;
s1 += System.getProperty("line.separator");
}
// String tokenizing
StringTokenizer st = new StringTokenizer(s1);
String[] a = new String[10000];
for (int l = 0; l < 10000; l++) {
a[l] = "";
}
int i = 0;
while (st.hasMoreTokens()) {
s2 = st.nextToken();
a[i] = s2;
i++;
}
StringTokenizer st1 = new StringTokenizer(s3);
String[] b = new String[10000];
for (int k = 0; k < 10000; k++) {
b[k] = "";
}
int j = 0;
while (st1.hasMoreTokens()) {
s4 = st1.nextToken();
b[j] = s4;
j++;
}
// comparing the contents of the files and printing the differences, if
// any.
int x = 0;
for (int m = 0; m < a.length; m++) {
if (a[m].equals(b[m])) {
} else {
x++;
Log.d("Home", a[m] + " -- " + b[m]);
}
}
Log.d("Home", "No. of differences : " + x);
if (x > 0) {
Log.d("Home", "Files are not equal");
} else {
Log.d("Home", "Files are equal. No difference found");
}
}
Input File 1
Hi
Hello
Chintan
Rathod
Input File 2
Hi
HellO
Chintan
RathoD
Output
08-26 12:07:58.219: DEBUG/Home(2350): Hello3. -- HellO3.
08-26 12:07:58.219: DEBUG/Home(2350): Rathod -- RathoD
08-26 12:07:58.229: DEBUG/Home(2350): No. of differences : 2
08-26 12:07:58.229: DEBUG/Home(2350): Files are not equal
Edit
To get Difference between two files
Use StringUtils library which is provide by Apache and check this Documentation for more about that library.
And modify following lines of code.
int x = 0;
for (int m = 0; m < a.length; m++) {
if (a[m].equals(b[m])) {
} else {
x++;
Log.d("Home", a[m] + " -- " + b[m]);
//to print difference
if (a[m].length() < b[m].length())
Log.d("Home", "" + StringUtils.difference(a[m], b[m]));
else
Log.d("Home", "" + StringUtils.difference(b[m], a[m]));
}
}
Output
08-26 17:51:26.949: DEBUG/Home(17900): 12 -- 123
08-26 17:51:26.949: DEBUG/Home(17900): Difference String : 3
08-26 17:51:26.949: DEBUG/Home(17900): No. of differences : 1
08-26 17:51:26.949: DEBUG/Home(17900): Files are not equal

Try using java.util.Scanner
while (sc1.hasNext() && sc2.hasNext()) {
String str1 = sc1.next();
String str2 = sc2.next();
if (!str1.equals(str2))
System.out.println(str1 + " != " + str2);
}

Change your while loop to the following:
while (scanFile.hasNextLine() && scanFileT.hasNextLine())
{
if(scanFileT.nextLine().equals(scanFile.nextLine()))
{
// The lines are equal.
} else {
// The lines are not equal.
}
}
if(scanFile.hasNextLine() || scanFileT.hasNextLine())
{
// If more lines remain in one of the files, they are not equal.
} else {
// If no content remains in both files, they are equal.
}
Depending on the size of your file, I would recommend some optimisation like checking the file sizes before you go through them line by line.
The overall logic reads as follows; if both have another line, compare it to see if it is equal. If they don't have another line, check if one of them has lines remaining, if so, they are not equal.
Update
After clarifying the objective of the comparison in chat, see the comments to this question, I have come to the conclusion that another comparison would be more effective and, as a matter of fact, correct. The comparison algorithm above works great if comparing the structure of text but not if comparing a data vector which may or may not be sorted. After some discussion, we came to the conclusion that data needs to be sorted or the comparison will blow the complexity to at least O(n^2)which could be done in O(2n) if the data is sorted. Here the algorithm's skeleton:
if(! scanGroupFriends.hasNextLine())
{
//simple sanity check to see if we need to compare at all. In this case, add all friends.
} else {
String nextFriend = scanGroupFriends.nextLine();
while(scanAllFriends.hasNextLine())
{
if(scanAllFriends.nextLine().equals(nextFriend))
{
// Friend already figures, do not add him and advance the list of group friends.
if(scanGroupFriends.hasNextLine())
{
nextFriend = scanGroupFriends.nextLine();
} else {
// There are no more friends in the group, add all remaining friends to list to show.
break; // Terminate the `while` loop.
}
}
}
}
However, I personally think it is bad to make to many assumptions. What I would suggest is that the friends be saved in a Set, a TreeSet for example. Then, serialize the object rather than manually writing it to file. Sets are neat because they hold several interesting objects. For example, you could easily use the following code to remove all friends in a group from the set of all friends:
allFriends.removeAll(groupFriends);
However, be aware that this removes it from the set completely so you should make a copy beforehand.

String Equation parser issue

I'm coding a method that solve various kind of equation. Now I want that the method receives a String equation that could be in the forms:
ax^2+bx+c=0
or
*ax^2+c=0*
or
bx+c=0
etc. and the order shouldn't matter.
My problem is: How could I parse the equation according the "x" grade?
The eq could contains more values of the same grade for example 2x^2+4x^2+3x+8=2 (max grade x^3).
My method should assign the a value to double a[] if on the left or on the right of a there is x^2, double b[], if on the left or on the right there is x, and double c[] if there isn't any x variable near the value (and should change the value sign if the therms is after the =).
Convert a String number in a double is simple but I don't know how I could disassemble the input String according the x grade as described.

Tested for -2x + 3x^2 - 2 + 3x = 3 - 2x^2
public Double[] parseEquation(String equation)
{
Log.d(TAG, "equation: " + equation);
// Remove all white spaces
equation = equation.replaceAll("[ ]", "");
// Get the left and right sides of =
String[] sides = equation.split("[=]"); // should be of size 2
boolean leftNegative = false;
boolean rightNegative = false;
if (sides.length != 2)
{
// There is no = or more than one = signs.
}
else
{
// if sides i starts with + remove the +
// if - we remove and put it back later
for (int i = 0; i < 2; i++)
{
if (sides[i].charAt(0) == '+')
{
sides[i] = sides[i].substring(1);
}
}
if (sides[0].charAt(0) == '-')
{
leftNegative = true;
sides[0] = sides[0].substring(1);
}
if (sides[1].charAt(0) == '-')
{
rightNegative = true;
sides[1] = sides[1].substring(1);
}
}
Log.d(TAG, "left side:" + sides[0] + " right side: " + sides[1]);
// Terms without signs need to find out later
String[] leftTerms = sides[0].split("[+-]");
String[] rightTerms = sides[1].split("[+-]");
int length = leftTerms[0].length();
if (leftNegative)
{
leftTerms[0] = "-" + leftTerms[0];
}
// put in the minus sign for the rest of the terms
for (int i = 1; i < leftTerms.length; i++)
{
Log.d(TAG, "length = " + length + " " + sides[0].charAt(length));
if (sides[0].charAt(length) == '-')
{
leftTerms[i] = "-" + leftTerms[i];
length += leftTerms[i].length();
}
else
{
length += leftTerms[i].length() + 1;
}
}
length = rightTerms[0].length();
if (rightNegative)
{
rightTerms[0] = "-" + rightTerms[0];
}
for (int i = 1; i < rightTerms.length; i++)
{
Log.d(TAG, "length = " + length + " " + sides[1].charAt(length));
if (sides[1].charAt(length) == '-')
{
rightTerms[i] = "-" + rightTerms[i];
length += rightTerms[i].length();
}
else
{
length += rightTerms[i].length() + 1;
}
}
// Now we put all the factors and powers in a list
List<ContentValues> leftLists = new ArrayList<ContentValues>();
// left side
for (int i = 0; i < leftTerms.length; i++)
{
Log.d(TAG, "leftTerm: " + leftTerms[i]);
ContentValues contentValues = new ContentValues();
int indexOfX = leftTerms[i].indexOf('x');
if (indexOfX == -1)
{
// no x mean a constant term
contentValues.put("factor", leftTerms[i]);
contentValues.put("power", "0");
}
else
{
int indexOfHat = leftTerms[i].indexOf('^');
if (indexOfHat == -1)
{
// no hat mean power = 1
contentValues.put("power", "1");
String factor = leftTerms[i].substring(0, indexOfX).trim();
contentValues.put("factor", factor);
}
else
{
String power = leftTerms[i].substring(indexOfX + 2).trim();
String factor = leftTerms[i].substring(0, indexOfX).trim();
contentValues.put("factor", factor);
contentValues.put("power", power);
}
}
Log.d(TAG, contentValues.toString());
leftLists.add(contentValues);
}
List<ContentValues> rightLists = new ArrayList<ContentValues>();
for (int i = 0; i < rightTerms.length; i++)
{
Log.d(TAG, "rightTerm: " + rightTerms[i]);
ContentValues contentValues = new ContentValues();
int indexOfX = rightTerms[i].indexOf('x');
if (indexOfX == -1)
{
// no hat mean a constant term
contentValues.put("factor", rightTerms[i]);
contentValues.put("power", "0");
}
else
{
int indexOfHat = rightTerms[i].indexOf('^');
if (indexOfHat == -1)
{
// no hat mean power = 1
contentValues.put("power", "1");
String factor = rightTerms[i].substring(0, indexOfX).trim();
contentValues.put("factor", factor);
}
else
{
String power = rightTerms[i].substring(indexOfX + 2).trim();
String factor = rightTerms[i].substring(0, indexOfX).trim();
contentValues.put("factor", factor);
contentValues.put("power", power);
}
}
Log.d(TAG, contentValues.toString());
rightLists.add(contentValues);
}
// Now add the factors with same powers.
// Suppose we solve for cubic here the end result will be
// 4 terms constant, x, x^2 and x^3
// Declare a double array of dim 4 the first will hold constant
// the second the x factor etc...
// You can allow arbitrary power by looping through the lists and get the max power
Double[] result = new Double[]{0.0, 0.0, 0.0, 0.0};
for (ContentValues c : leftLists)
{
switch (c.getAsInteger("power"))
{
case 0:
//Log.d(TAG, "power = 0, factor = " + c.toString());
result[0] += c.getAsDouble("factor");
break;
case 1:
result[1] += c.getAsDouble("factor");
break;
case 2:
result[2] += c.getAsDouble("factor");
break;
case 3:
result[3] += c.getAsDouble("factor");
break;
}
}
for (ContentValues c : rightLists)
{
switch (c.getAsInteger("power"))
{
case 0:
//Log.d(TAG, "power = 0, factor = " + c.toString());
result[0] -= c.getAsDouble("factor");
break;
case 1:
result[1] -= c.getAsDouble("factor");
break;
case 2:
result[2] -= c.getAsDouble("factor");
break;
case 3:
result[3] -= c.getAsDouble("factor");
break;
}
}
Log.d(TAG, "constant term = " + result[0] + ", x^1 = " + result[1]
+ ", x^2 = " + result[2] + ", x^3 = " + result[3]);
return result;
}

If you weren't limited by Android, I'd suggest using a lexer and parser. These are code generators, so they can work anywhere the base language works, but they tend to produce bloated code. Android might not appreciate that.

How to read TXT file in batches?

Now I am developing a reader. If the txt file is too big, it will spend a long time to read and no response. So I want to set a method like it can read the txt file in bathes.
I write the below code. It can turn the page back. But it can not page up continuous. How should I do?
Vector string;
int begin = 0;
public void readTxtByPage(String fileName) {
string.clear();
FileReader fr = null;
BufferedReader br = null;
try {
fr = new FileReader(filePath + fileName);
br = new BufferedReader(fr);
br.skip(begin);
String content = "";
char ch;
int line = 0;
int w;
int len;
int start;
FontMetrics fm = paint.getFontMetrics();
fontHeight = (int) Math.ceil(fm.descent - fm.top) + 2;
pageLineNum = textHeight / fontHeight;
float[] widths = new float[1];
while ((content = br.readLine()) != null) {
len = content.length();
w = 0;
start = 0;
for (int i = 0; i < len; i++) {
ch = content.charAt(i);
paint.getTextWidths(String.valueOf(ch), widths);
w += Math.ceil(widths[0]);
if (w > textWidth) {
string.addElement(content.substring(start, i));
begin += (i - start);
start = i;
w = 0;
line++;
if (line >= pageLineNum) {
System.out.println("begin===>"+begin);
return;
}
}
}
string.addElement(content.substring(start));
begin += (len + 2 - start);
line++;
if (line >= pageLineNum) {
return;
}
}
} catch (Exception e) {
e.printStackTrace();
}finally{
try {
br.close();
fr.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return;
}
Thanks in advance!

Sounds like it would be best if you did this work in a background thread then, you can tell the reader to sleep, and then notify it when you want the thread to start reading again. That way it wont freeze your UI and it can read the bits in batches. Maybe have the thread be notified during an onTouchEvent.