Summary of JFrame knowledge points 1

MyEclipse Key techniques in ：

Class, right click to rename the selected change Refactor—>Rename  or alt+shift+R

If you forget how to write words by dictation, you can press and hold Alt+/ Let him remind you

Comment code Ctrl+/ or Ctrl+shift+/

Ctrl+D Delete current row

Ctrl+i Alignment code

SetText(); Set realistic text

Right click Debug As Modulation , You need to set the breakpoint first and right-click the leftmost place where the code is added Toogle Breakpoint

1. JPanel, Represents a container , Finished panel .
2. JButton, Represents a button control

Set up a container first

JPanel root= new JPanel();

frame.setContentPane(root);;

Then add controls

JButton button new JButton(“ test ”);// Button

root.add(button);

1. JLabel lable=new JLabel();// label

root.add(lable);

JLabel lable=new JLabel(" Hello ");

              root.add(lable);

       // Abbreviation

        root.add(new JLabel(" How do you do "));

1. Customize a window

Public class MyFrame extends JFrame{

}

1. Event handling , Monitor , When the button is clicked , There are 3 Ways to create ( Inner class 、 Anonymous inner class 、Lambda expression )

The first inner class

1 Add a listener class , Realization ActionListener Interface

Class MyActionListener implements ActionListener{

}

2 Set listener

MyActionListener listener =new MyActionListener();

Button.addActionListener(listener);

The second anonymous inner class — simplify

button.addActionListener(new ActionListener() {

});

The third kind of Lambda expression --- More simplified

Button.addActionListener((e)->){

}

Parentheses (e) Is the parameter , Curly braces {} Is the method body .

1. Text box control JTextField, Single line text box

JTextField textField=new JTextField(20);//20 Denotes initialization 20 The width of English characters

JTextField Of API：

Set text ：

textField.setText(str);

Get text ：

Str=textField.getText();

1. Check box control JCheckBox

JCheckBox agreeField=new JCheckBox(“ Agree to the user agreement ”);

relevant API

setSelected(true/false);// Initialization setting selected

isSelected(); Is it checked?

addActionListener();// Check or cancel the acquisition event

1. The drop-down list .JComboBox

（1） establish JComboBox

JComboBox<String> colorField=new JComboBox<>();

so ,JComboBox It's a generic , Parameter type T It represents the type of data item

（2） Data item API Method

-addItem(T) Add data items ,T The type of is specified at creation , Here is String type , That is, every item Item The data type of is String

-getItemcount（） Number of data items

-getItemAt（index） Specify index data items

for example ：

colorField.addItem(" red ");

        colorField.addItem(" green ");

        colorField.addItem(" blue ");

（3） Selected items Access by index

     getSelectedIndex(); Get the index of the selected item

     setSelectedIndex(); Set initialization selection

     remove(index); Security index deleted

 （4） Access by data item

     getSelectedItem(); Gets the value of the selected item

     setSelectedItem();

     remove(item);

  (5) Event handling

Use addActionListener() Realize the event processing selected by the user

1. JLabel  Label control

1. typeface // style // Font size

Label.setFont(new Font(“ Microsoft Tahoma ”,Font.PLAIN,14));

1. The font color Use RGB

Label.setForeground(new Color(255,255,255));

     (4)   Background color

          Label.setOpaque(true);// The background is opaque

          Label.setBackground(new Color(0,0,255));

         The default background is transparent , So we need to setOpaque() Set to opaque

          white ：255,255,255 Red ：255,0,0 black ：0,0,0

          green ：0,255,0  Blue 0,0,255 yellow ：255,255,0

   （5） Control size

        Label.setPreferredSize(new Dimension(60,30));

(6) text alignment

    Label.setHorizontalAlignment(SwingConstants.CENTER);

1. Layout device LayoutManager Be responsible for the layout of each sub control

default ,JPanel Bring one with you. FlowLayout Flow layout

LayoutManager layout=new FlowLayout();

Root.setLayout(layout);// setLayout() Set up a layout manager

among ,FlowLayout For child controls, from left to right , Arrange from top to bottom

11. Manual layout , That is, do not use the layout , When the window size changes , The position of child controls will not change adaptively

   1 Do not use the layout

root.setLayout(null);

   2 Add child control

root.add(a1);

   3 Specify the location of the control

     a1.setBounds(0,0,100,50); 0,0 Represents the upper left corner Height ：100  Width ：50

.setBounds(x,y,width,height);

among ,x,y Top left coordinates width,height Width , Height , Unit is pixel

GUI Coordinate system ： The upper left corner is the origin ,X Shaft to the right ,Y Axis down

1. Custom cloth layout

The layout should implement the following interfaces

LayoutManager,LayoutManager2 among LayoutManager2 Is the new version , Inherited from LayoutManager

1. Add a class SimpleLayout, Realization LayoutManager2

Class SimpleLayout implements LayoutManager2{

   When adding child controls to this container, call

   -void addLayoutComponent(Component comp,Object constraints)

   Call this method when the control is deleted

   -void removelLayoutComponent(Component comp);

   Call this method when the container needs layout

   -void layoutContainer(Container parent);

}

1. Use custom layout

root.setLayout(new SimpleLayout());

  JPanel The upward trace belongs to Container, And all kinds of controls belong to Component

     int width=parent.getWidth();// Gets the width of the container

         int height=parent.getHeight();// Get the height of the container

         Component[] children=parent.getComponents();// Take out all the child controls to get the control array

1. Short for custom layout

To make the code simpler , add to LayoutAdapter（ Adapter 、 adapter ）

First step Declared as an abstract class abstract, There are 3 Two methods are not implemented

When customizing the layout , Direct inheritance layoutAdapter that will do , You can hide unused methods , Just focus on the methods we want to see

1. Private layout

Private layout , Only responsible for the layout of the current window

demonstration ： Add an inner class

Private class MyCustomLayout extends LayoutAdapter{

}

14. Custom control

  Public class MyControl extends JPanel{

      // Rewrite the method , Responsible for the drawing of controls

      Protected void paintComponet(Graphics g){

        Super.paintComponent(g);

        …

}

}

among JPanel, It's a container , Is also a control .

… Write in

// Width of control 、 Height

              int width=this.getWidth();

              int height=this.getHeight();

              // Set background color

              g.setColor(new Color(225,0,0));

              // Draw a rectangle

              g.fillRect(0, 0, width, height);// In turn, the coordinates of the upper left corner , Width height

Add to the main form

MyControl c=new MyControl();

Root.add(c);

c.setPreferredSize(new Dimension(100,50))// Set size

15.

（1）RGB 0-255

  FF FF FF or （255,255,255） white

  00 00 00 or （0,0,0） black

  FF 00 00 or （255,0,0） Red

  FF FF 0 or （255,255,0） Yellow other colors can be found in Baidu

Color Class represents a color , for example ：

  new Color(255,0,0); or new Color(Color.RED);// Color.RED Is the red constant

   perhaps new Color(0XFF0000); Hexadecimal

（2）RGBA, Colors with transparency indicate . among A representative Alpha transparency , be located 0-255, for example ：

   Translucent blue ：

  new Color(0,0,255,128); perhaps

  new Color(0x800000FF,true)

（3） To add a second custom label, you need to add （ white ） Background color

Draw an ellipse Oval  The peripheral rectangle is taken as the parameter

g.setColor(Color.RED);

g.fillOval(30,30,100,50);//30 30 Is the upper left coordinate ,100 Width 50 Height

Drawing fan

g.setColor(Color.RED);

g.fillArc(30,30,100,50,0,120); startAngle 0 Is the starting angle ,arcAngle 120 Is the arc angle

（4）g.fill Rect() With fil The beginning is the filling effect

g.fillRect(); Filled rectangle

With draw The beginning is stroke

g.drawRect();// Stroke rectangle

g.drawOval();// Stroke ellipse

g.drawArc();/ Stroke sector

（5） Other drawing methods

  g.drawLine(); Draw line segments

  g.drawImage(); Drawing pictures

  g.drawPolygon(); Draw polygon

  g.drawString(); Draw text

1. The drawing of pictures

（1） Prepare a picture 1.jpg, Put it in data Under the table of contents

Loading pictures , obtain Image object

  File file=new File(“data/1.jpg”);

  BufferedImage image=ImageIO.read(file);

  c.setImage(image);

among ,Image Abstract class ,BufferImage Depending on the specific implementation class

（2）g.drawImage(image,x,y,width,height,observer);

among -image Picture object to draw

-x,y,width,height The position of the drawing   observer Set to null

  

When the window changes every time, it will call paintComponent(Graphics g) Method , The same image will be constantly loaded inside

In order to avoid repeated loading of pictures, it is necessary to put the above loaded picture content in the construction method , Just load it once .

1. encapsulation ：

Three criteria for good code ： Can be read 、 reusable 、 Scalable .

1. The frame of the picture

g.drawRect(0,0,width-1,height-1)

Rectangle relevant API

Rectangle rect=new Rectangle(0,0,width,height);

Rect.grow(h,v) To expand outward h v Pixel . When h,v Less than 0 when , To contract

1. Icon ：

Icon Icon, Usually smaller square pictures 、PNG Format , You can set it yourself , Or get it from the website, for example ： Website www.iconfont.cn

Use PictureView Show icons , Just like adding picture display

Image icon=ImageIO.read();

c.setImage(icon);

18. Resource file Resource, Put your finger on src File released under .

   Add resource files to src Catalog ,- stay src Add a package res ,- hold png Copy the picture to res Next

   Be careful ,bin\ and src\ Directories are synchronized ,Eclipse Will automatically copy a copy of

   Loading of resource files ：

   Path to resource file ：“/res/like.png”

   Read resources ：

  InputStream res=this.getClass().getResourceAsStream(“/res/like.png”);// The return is an input stream

  Load resources as pictures

  Image image=ImageIO.read(res);

19. Package optimization ：

   Add one at a time try catch More trouble , So the loaded resource file is encapsulated

   Optimize PictureView, add to 2 A way

  PictureView.setImage（File file）

  PictureView.setImage(String resourcePath)

20. Mouse events ：

  Mouse event use 3 Class listener ：

1. .addMouseListener(); Click on 、 Press down 、 lift 、 move 、 Removed from the

2.addMouseMotionListener(); Move 、 Drag the

3.addMouseWheeIListener() The mouse wheel turns

The following mouse actions are supported ：

The mouse click mousePressed The mouse is raised mouseReleased

Mouse migration mouseEntered Mouse removal mouseExited

Mouse movement mouseMoved Mouse drag mouseDragged

Mouse wheel mouseWheeIMoved

Mouse events are basic events , All controls support , Custom controls are also supported

Parameters of mouse events ：

MouseEvent Represents a mouse event

-getPoint() /getX() /getY(): The coordinates of the click , Relative to the upper left corner of the control

-getPointOnScreen()/getXOnScreen()/getYOnScreen(): Screen coordinates

-getSource(): Event source . That is, the control in the point

-getButton() : left-click 、 In the key , Right click

-getClickCount() : stand-alone 、 double-click 、 Three strikes

21.MouseAdapter, Mask mouse events , Used to simplify code

22. Mouse click event ：

-mousePressed(); The mouse click

-mouseReleased() The mouse is raised

-mouseClicked() Mouse click , This event is triggered when the mouse is pressed and raised in place

MouseListener And ActionListener：

-MouseListener Low-level events

-ActionListener Senior event

about JButton, You can also use MouseListener

23. Mouse in and out ：

 -mouseEntered();

-mouseExited();

You can use settings to highlight the state when the mouse moves in , Different displays

24. Mouse movement events MouseMotionListener

-mouseMoved() Mouse movement

-mouseDragged() Press and hold the mouse and move , Drag the

26. Sine curve ：

Math.sin（angle） Method can calculate an angle angle The sine of . It should be noted that , there angle To specify the radian value

Curve simulation ： Take multiple points on the curve , Like a curve , Use these points drawLine(p1,p2) Method to connect , It is similar to a curve

Sampling point ： The denser the sampling points , The closer the result is to a perfect curve , The parameter is called granularity