[Android Software Development] ExploreMN:
I'm developing an application that utilizes zooming in and out (for readability) and allows for swiping left and right to change pages.

Basically the flipping back and forth part works and zoom works. However, if I do any kind of zooming and then try to change a page the program crashes.

I've only tested this on the Epic 4G and on the G2 with the same problem.

Any help that can tell me what is going on or what I need to change would be greatly appreciated. (I tried to code out on the net to fix the HTC incredible having this kind of issue but the problem is still there)

package my.package;

import java.io.IOException;
import java.io.InputStreamReader;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.util.Log;
import android.view.GestureDetector;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.SubMenu;
import android.view.View;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.View.OnTouchListener;
import android.webkit.WebView;

public class LessonShower extends Activity {
private char[] buffer = new char[128];
private WebView webView;
private int lessonNumber, lessonPage;
private AssetManager assetManager;
private int lessonsCount;

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
int lessonNumber = getIntent().getIntExtra("lessonNumber", 1);
int lessonPage = getIntent().getIntExtra("lessonPage", 1);
webView = new MyWebView(this);
assetManager = getAssets();
try {
lessonsCount = assetManager.list("").length - 3;
loadPage(lessonNumber, lessonPage);
} catch (IOException e) {
}

SimpleOnGestureListener gestureListener = new SimpleOnGestureListener(){
private static final int SWIPE_MIN_DISTANCE = 120;
private static final int SWIPE_THRESHOLD_VELOCITY = 200;

@Override
public boolean onDown(MotionEvent e) {
return true;
}

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2,
float velocityX, float velocityY) {
Log.d("debugging", "onFling");
if(Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY && e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE){
loadNextPage();
return true;
}
else if(e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE){
loadPrevPage();
return true;
}
if(e1.getY() - e2.getY() > SWIPE_MIN_DISTANCE){
webView.pageDown(false);
}
else if(e2.getY() - e1.getY() > SWIPE_MIN_DISTANCE){
webView.pageUp(false);
}
return super.onFling(e1, e2, velocityX, velocityY);
}
};
final GestureDetector gDetector = new GestureDetector(webView.getContext(), gestureListener);
webView.setOnTouchListener(new OnTouchListener() {

@Override
public boolean onTouch(View arg0, MotionEvent arg1) {
return gDetector.onTouchEvent(arg1);
}
});

webView.getSettings().setBuiltInZoomControls(true);
setContentView(webView);
}

public void loadNextPage(){
int nextPage = lessonPage + 1;
try{
InputStreamReader is = new InputStreamReader(assetManager.open("lesson" + lessonNumber + "/" + nextPage + ".html"));
readPage(is);
lessonPage++;
}
catch(IOException ex){
final CharSequence[] items = {"Home", "Next lesson"};

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Choose an action");

builder.setItems(items, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int item) {
if(item == 0){
finish();
}
else{
if(lessonNumber < lessonsCount){
lessonNumber++;
lessonPage = 1;
loadPage(lessonNumber, lessonPage);
}
}
}
});
AlertDialog alert = builder.create();
alert.show();
}
}

public void loadPrevPage(){
if(lessonPage > 1){
try{
InputStreamReader is = new InputStreamReader(assetManager.open("lesson" + lessonNumber + "/" + --lessonPage + ".html"));
readPage(is);
}
catch(IOException ex){}
}
}

private void readPage(InputStreamReader is){
StringBuilder webPage = new StringBuilder();
int len = 0;
try {
while((len = is.read(buffer)) > 0){
webPage.append(buffer, 0, len);
}
} catch (IOException e) {
e.printStackTrace();
}
webView.loadData(webPage.toString(), "", "");
}

public void loadPage(int lessonNumber, int lessonPage){
if(lessonNumber > lessonsCount){
return;
}
this.lessonNumber = lessonNumber;
this.lessonPage = lessonPage;
setTitle("Lesson" + lessonNumber);

InputStreamReader is = null;
try {
is = new InputStreamReader(assetManager.open("lesson" + lessonNumber + "/" + lessonPage + ".html"));
} catch (IOException e) {
}
readPage(is);
}

private static final int homeMenuItem = 1;
private static final int exitMenuItem = 2;
@Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
menu.add(Menu.NONE, homeMenuItem, Menu.NONE, "Home");
SubMenu pagesMenu = menu.addSubMenu("Pages");
try {
int lessonPages = assetManager.list("lesson" + lessonNumber).length;
for(int i = 1; i <= lessonPages; i++)
//"+ 1000" is used to escape collision with other menu items
pagesMenu.add(Menu.NONE, i + 1000, Menu.NONE, "Page" + i);

} catch (IOException e) {}
finally{
menu.add(Menu.NONE, exitMenuItem, Menu.NONE, "Hide");
}
return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);

switch(item.getItemId()){
case homeMenuItem:
finish();
break;
case exitMenuItem:
moveTaskToBack(true);
break;
default:
//Page was selected
if(item.getItemId() > 1000){
lessonPage = item.getItemId() - 1000;
loadPage(lessonNumber, lessonPage);
}
}
return true;
}

}

class MyWebView extends WebView{
private LessonShower lp = null;
public MyWebView(Context context) {
super(context);
lp = (LessonShower) context;
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event){
if(keyCode == KeyEvent.KEYCODE_DPAD_LEFT){
lp.loadPrevPage();
}
else if(keyCode == KeyEvent.KEYCODE_DPAD_RIGHT){
lp.loadNextPage();
}
return false;
}
}