I am not busy recently, so I look back on what I have learned and contacted in this year. I suddenly feel that blogging is a good way, and I hope I can stick to it.
Custom View process
- Create a custom class to inherit the View, and override the constructor. There are four constructors in total. We only need to inherit the first two for now
public CircleView(Context context) {
super(context);
}
public CircleView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
The first construction method is used when you dynamically add a custom View
The second construction method is called when used in xml
<example.com.testactivity.CircleView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"/>
- Override onDraw() method
/**
* Override the method of drawing
* @param canvas
*/
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(Color.parseColor("#018172 "); / / 1. Set the background color
float radius=100; //radius
float x=100;
float y=100;
Paint paint=new Paint(); //Instantiate a paint object brush
paint.setColor(Color.WHITE); // 2. Set brush color
paint.setStyle(Paint.Style.STROKE); //Void, default is solid
canvas.drawCircle(x,y,radius,paint); //Specifies the shape drawn circle
}
paint.setStyle(Paint.Style.STROKE) sets the style of the brush. You can specify whether the center of the circle is solid or hollow. This method is mainly used for rectangle and circle
-
Style.FILL: solid
-
Style.fill'and'strike: show both black and white
-
Style.STROKE: void
-
Override onMeasure method
/**
- Function: if you want to achieve adaptive size in xml, you need to rewrite this method to give the View a raw size value
- @param widthMeasureSpec
- @param heightMeasureSpec
*/
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int width=200;
int height=200; //Set the original size of View adaption
int HEIGHT_MODE=MeasureSpec.getMode(heightMeasureSpec); // 1. Extract the mode (one of the following three modes) according to the provided measurement value (format)
int HEIGHT_SIZE=MeasureSpec.getSize(heightMeasureSpec); //2. Extract the size value according to the provided measurement value (format) (this size is what we usually call the size)
int WIDTH_MODE=MeasureSpec.getMode(widthMeasureSpec);
int WIDTH_SIZE=MeasureSpec.getSize(widthMeasureSpec);
if (HEIGHT_MODE==MeasureSpec.EXACTLY){ //If the measurement mode is accurate, use the obtained value directly
height=HEIGHT_SIZE;
}else if (HEIGHT_MODE==MeasureSpec.AT_MOST){
height=Math.min(height,HEIGHT_SIZE); //If wrap content is set in xml, the minimum value is taken
}
if (WIDTH_MODE==MeasureSpec.EXACTLY){
width=WIDTH_SIZE;
}else if (WIDTH_MODE==MeasureSpec.AT_MOST){
width=Math.min(width,WIDTH_SIZE);
}
setMeasuredDimension(width,height); //Use this method to set the real size after measurement
}
Note: measurespec.getmode (highmeasurespec) means to get the high mode set in xml
There are three modes
- Exact mode when the set length is match [parent] or given a specific size
- At most when set to wrap content
- UNSPECIFIED this mode is rarely used
Reference link