Swing, part 2Tutorial 07

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Leonid Barenboim

25/4/2010

MVC (Model View Controller)

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“Model–view–controller (MVC) is a software architectural pattern for implementing user interfaces.It divides a given software application into three interconnected parts, so as to separate internal representations of information from the ways that information is presented to or accepted from the user.”-Wikipedia

MVC (Model View Controller)

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“A controller can send commands to the model to update the model's state (e.g., editing a document). It can also send commands to its associated view to change the view's presentation of the model (e.g., by scrolling through a document).

A model stores data that is retrieved by the controller and displayed in the view. Whenever there is a change to the data it is updated by the controller.

A view requests information from the model that it uses to generate an output representation to the user.”-Wikipedia

Outline

1 Using the Default Models

2 File Browser

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Outline

1 Using the Default Models

2 File Browser

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Using the Default Models

Swing supplies default, mutable models for all

widgets: List

Tree (nodes)

Table

Spinner and Slider

. . .

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Default List Model Example

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Add and remove elements from a list using the default model:

public class SimpleList extends JFrame { pr ivate JList _ l i s t ;

pr ivate DefaultListModel _model;

. . .

}

Constructor with Default List Model

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public SimpleList() { super("List Demo");

setModel(new DefaultListModel()); setList(new JList(_model));

getList().setPreferredSize(new Dimension(100, 300)); getContentPane().add(getList(), BorderLayout.CENTER); JToolBar tBar = new JToolBar();

JButton tAdd = new JButton("+"); // calls add()tBar.add(tAdd);JButton tRem = new JBut ton("-" ) ; // calls rem()tBar.add(tRem);getContentPane().add(tBar, BorderLayout.NORTH);. . .}

Adding and Removing with the Default Model

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private void add() {Str ing tVal = JOptionPane.showInputDialog(

t h i s , "Add new value") ;i f ( tVal != nu l l )

{ getModel().add(getModel().getSize(), tVa l ) ;

}}

private void rem() {i n t [ ] i s = getList() .getSelectedIndices();

Ar rays.sor t ( is ) ;f o r ( i n t i = is. length - 1; i >= 0; i - - )

{ getModel() .remove(is[ i] ) ;}}

Outline

1 Using the Default Models

2 File Browser

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A Simple File Broswer

The file browser

shows:

Directories treeList of files in the

selected directory

Content of the selected file

Plus:

The event dispatcher thread should not hang while reading the content of a file

Only the event dispatcher thread should update the screen

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Outline

1 Using the Default Models

2 File BrowserTree ModelTree Cell Renderer List Cell Renderer The File BroswerWriting a Swing Worker

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A Model for the Tree View

Tree model

Get root

Get children count per

node Get child for index

Check if a node is a leaf

Directories tree model

Root Top directory

Children Files in

directory

Leaf An directory without sub-directories

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The Directories Tree Model

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public class DirTreeModel implements TreeModel { pr ivate F i le _d i r ;

public DirTreeModel(File d i r ) { se tD i r (d i r ) ;

}

private s ta t i c F i leF i l t e r _FILTER = new F i l e F i l t e r ( ) { public boolean accept(File f i l e ) {return f i l e . i sD i r ec t o r y ( ) ;

}} ;

pr ivate F i l e [ ] l i s t ( F i l e f i l e ) { return f i le . l is tF i les(_FILTER);

}

Tree Model Inferface Methods

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public Object getRoot() { return getDi r ( ) ;

}

public Object getChild(Object parent, i n t index) { F i l e [ ] tChildren = l i s t ( (F i l e )pa ren t ) ;

return tChildren[ index];}

public i n t getChildCount(Object parent) { return l is t ( (F i le )parent ) . length ;

}

Tree Model Interface Methods (cont’d)

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public boolean isLeaf(Object node) { return getChildCount(node) == 0;

}

public i n t getIndexOfChild(Object parent, Object ch i ld ) { List<File> tF i les = Ar rays.asLis t ( l is t ( (F i le)parent ) ) ; return tF i les. indexOf( (F i le)ch i ld) ;

}

Empty Tree Model Interface Methods

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public void valueForPathChanged(TreePath p, Object v)

public void addTreeModelListener(TreeModelListener l )

public void removeTreeModelListener(TreeModelListener l )

Tree nodes are not added or removed dynamically in this model, so the tree model listener is redundant

Outline

1 Using the Default Models

2 File BrowserTree ModelTree Cell Renderer List Cell Renderer The File BroswerWriting a Swing Worker

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Rendering a Directories Tree Cell

public class DirTreeCellRenderer extends DefaultTreeCellRenderer

{public Component getTreeCellRendererComponent(

JTree t ree , Object value,boolean se l , boolean expanded, boolean l ea f ,

i n t row, boolean hasFocus) {

super.getTreeCellRendererComponent(...);F i le tRoot = ( F i l e ) tree.getModel().getRoot();

F i le t F i l e = ( F i l e ) value; setText(tRoot.equals(value) ?

tFile.getAbsolutePath() : tFile.getName()); setIcon(expanded ? openIcon : closedIcon); return t h i s ;} } 17 /

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Files List Model

public class FilesListModel implements ListModel { pr ivate F i le _d i r ;

pr ivate List<File> _ f i l e s ;private Collection<ListDataListener> _l is teners;

private s ta t i c F i leF i l t e r _FILTER = new F i l e F i l t e r ( ) { public boolean accept(File f ) {

return f . i s F i l e ( ) ;}

} ;

public FilesListModel() {setListeners(new LinkedList<ListDataListener>());

setFiles(Collections.EMPTY_LIST);}

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Setting the Directory

public F i le getDir( ) { return _d i r ;

}

public void setDir (Fi le d i r ) {_dir = d i r ;i n t tOldSize =

getSize();F i l e [ ] tF i les = dir. l istFi les(_FILTER);

setFi les(Arrays.asList ( tF i les)) ;i n t tMax = Math.max(tOldSize, getSize()) ;

ListDataEvent tEvt =new ListDataEvent(this, LDE.CONTENTS_CHANGED, 0,tMax);

f o r (ListDataListener tListener : getListeners()) {tListener.contentsChanged(tEvt);

}} 19 /

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Files List Model Interface Methods

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public i n t getSize() { return ge tF i les ( ) . s ize( ) ;

}

public Object getElementAt(int index) { return getFi les() .get( index);

}

public void addListDataListener(ListDataListener l ) { getListeners() .add( l) ;

}

public void removeListDataListener(ListDataListener l ) { getListeners().remove(l);

}

Outline

1 Using the Default Models

2 File BrowserTree ModelTree Cell Renderer List Cell Renderer The File BroswerWriting a Swing Worker

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Rendering a Files List Cell

public class FilesListCellRenderer extends DefaultListCellRenderer

{private s ta t i c Color _ALT = new Color(220, 220, 220);

public Component getListCellRendererComponent(JList l i s t , Object value, i n t index,

boolean isSelected, boolean cellHasFocus) {

super.getListCellRendererComponent(...); F i le f = ( F i l e ) value; setText(f.getName());i f (! isSelected && index % 2 ==

0) setBackground(_ALT);return t h i s ;

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Outline

1 Using the Default Models

2 File BrowserTree ModelTree Cell Renderer List Cell Renderer The File BroswerWriting a Swing Worker

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Putting It Together

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public class FileBrowser extends JFrame

implements TreeSelectionListener, ListSelectionListener

{private JTree _tree; private

JTextArea _content; pr ivate JList _ f i l e s ;

. . .}

File Broswer Constructor

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public FileBrowser(File f i l e ) { super(f i le.getAbsolutePath());

// TreesetTree(new JTree(new DirTreeModel(f i le))) ;

getTree().setCellRenderer(new DirTreeCellRenderer()); getTree().addTreeSelectionListener(this);

// File listsetFiles(new JList(new Fi lesListModel())) ;

getFiles().setCellRenderer(new FilesListCellRenderer()); getFiles().setSelectionMode(LSM.SINGLE_SELECTION); getFiles().addListSelect ionListener(this);

// Text areasetContent(new JTextArea(10, 30)) ;. . .}

Listening to Tree Events

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public void valueChanged(TreeSelectionEvent e) {F i le tD i r = ( F i l e ) e.getPath().getLastPathComponent(); ( (Fi lesListModel)getFi les() .getModel()) .setDir( tDir) ;

}

Listening to List Events

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public void valueChanged(ListSelectionEvent e) {// Gotcha 1: Check if value is adjustingi f (e.getValueIsAdjusting()) return;// Gotcha 2: Don’t use e’s indicesFi le t F i l e = ( F i l e ) getFiles().getSelectedValue(); getContent().setText("");// Gotcha 3: Don’t re-use a workerSwingWorker tWorker =

new FileReaderWorker(tFile, getContent()); tWorker.execute();}

Outline

1 Using the Default Models

2 File BrowserTree ModelTree Cell Renderer List Cell Renderer The File BroswerWriting a Swing Worker

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Writing a Swing Worker

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public class FileReaderWorker extends SwingWorker<Void, String>

{private F i le _ f i l e ;

pr ivate JTextArea _text ;

. . .}

Do in Background

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protected Void doInBackground() throws Exception { t r y {BufferedReader t I n =

new BufferedReader(new FileReader(getFile())); Str ing tL ine;while ( ( tL ine = t In. readLine()) != nu l l )

{ publ ish( tLine) ;}t I n . c lose( ) ;} catch (IOException e)

{ publish(e.getMessage());}return n u l l ;}

Process and Done

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protected void process(List<String> chunks) { f o r (Str ing tLine : chunks) {getText().append(tLine + " \ n " ) ;

}}

protected void done() { getText().setCaretPosit ion(0);

}