The container JRE System Library JavaSE references non existing library

FLAG_KEEP_SCREEN_ON saving energy. Protects the battery if a user closing applications using the Return button on device. The device will returned to user screen mode settings.

@Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        //..........
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
    }

Try this code:

final String ERROR = "my error message....";

 private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
// some code and method ..... see AsyncTask

       @Override
        protected String doInBackground(String... urls) {

              URL urlL = null;
                try {
                    urlL = new URL(url);//"//chmi.cz..../"
                    HttpURLConnection urlConnection = null;
                    try {
                         urlConnection = (HttpURLConnection) urlL.openConnection();
                        InputStream in = new BufferedInputStream(urlConnection.getInputStream());
                      response =  readStream(in);
                        return response;
                    } catch (IOException e) {
                        //throw new RuntimeException(e);

                    } finally {
                        if(urlConnection != null)
                            urlConnection.disconnect();
                        return ERROR;
                    }
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                    return ERROR;
                }
           }
            return response;
        }

        private String readStream(InputStream is) {
            try {
                ByteArrayOutputStream bo = new ByteArrayOutputStream();
                int i = is.read();
                while(i != -1) {
                    bo.write(i);
                    i = is.read();
                }
                return bo.toString();
            } catch (IOException e) {
                return "";
            }
        }

Very dark picture, in photo editor black remains black


Very bright picture, in photo editor white will white


Dark picture but the chart is not in black color area - dark shades can be lighten in graphics editor

UNEXPECTED TOP-LEVEL EXCEPTION:
java.lang.IllegalArgumentException: already added: Lcz/okhelp/MyMathClass;

First try this solution!!!!!
Select your project in project tree and go to the Eclipse menu Project » Clean » Clean projects selected below » select your project and click OK.

If you create *.apk package with proguard sometimes you must back up the project, delete project, and create new project if you are unable to create *.apk file.

Check your AndroidManifest.xml if all Activity is correctly inserted. If you add a library project to Main project you have to insert Activity from library to Main project AndroidManifest.xml


Problem with the library.
I deleted library project from project tree and again put the _library project into the main project. This problem was resolved.
1.)Go to Project » Properties » Java Build Path » Libraries and remove (your projects) click OK.
2.)Go to Project » Clean » Clean projects selected below » select your project and click OK.
3.)Add again your LIBRARY project to your MAIN project Project » Properties » Java Build Path » Libraries.
See image below.

Problem with a *.apk file
If you create signed *.apk, you have to delete previous *.apk from your PC folder.

FrameLayou, fragment have to unique id android:id="@+id/your_id_unique"

<FrameLayout xmlns:android="//schemas.android.com/apk/res/android"
    xmlns:tools="//schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <fragment
        android:id="@+id/your_id_unique"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        class="cz.okhelp.notepad.AddNoteFragment"
        tools:layout="@layout/add_note" />

</FrameLayout>