How to thicken the brush in the graphical interface

 public void actionPerformed(ActionEvent e) {
    	String bstr=e.getActionCommand();// Get the text content on the component ;\
    	str =e.getActionCommand();
    	// Determine whether the brush needs to be thickened ;setStoke The method can make the brush bold ; Understand that the object to be filled is an interface. Normally 
    	// Is to create a class to implement the abstract method of the interface , But search interface Stroke You can know the class BasicStroke Rewriting has been implemented 
    	if (str.equals(" In bold "))
    	{
    		BasicStroke stroke =new BasicStroke(2.0f);// Use an instance to host , Set the information of the brush 
    		Graphics2D gr2 = (Graphics2D) gr;// I don't understand why gr2 Set the brush size , result gr Also set the size 
    		gr2.setStroke(stroke);
    	}
    	if (str.equals(" Restore brush ")) 
    	{
    		BasicStroke stroke =new BasicStroke(1.0f);// Use an instance to host , Set the information of the brush 
    		Graphics2D gr2 = (Graphics2D) gr;// I don't understand why gr2 Set the brush size , result gr Also set the size 
    		gr2.setStroke(stroke);
    	}

1. First of all, I know in Graphics There is no method to set the brush thickness in the component

2. So the introduction of Graphics2D Components , And use this class （ Components ） Another instance is created

3.gr2.setStroke(stroke)

stroke The role of ： This instance stores brush thickness information , It through setStroke（） Function passed to object gr2;

Observe setStroke（） Source code for method

  See that the type of its parameter needs to be an instance of a class （Stroke）

see Stroke Source code

1. 

  The observed Stroke It's an interface , If you want to in setStroke（） If you set parameters , According to the original method, you need to rewrite a class to inherit the interface , Rewrite the abstract methods of the interface

however Java There are already classes that inherit this interface ; We can use it directly and make the result simple ; Directly reference the inherited class ; Then create an instance with this class ; Store the brush thickness information in the instance , Add this instance to the brush

Document query image

 

  Found already BrokeStroke Class inherits the interface