Android dynamically draws a rectangular effect on the screen by touching

Requirements overview:

Draw an area with your finger on the screen and return the coordinates of the area circled.

Technical realization:

Customize the view, set the brush and corresponding parameters, and judge the touch event in the ontouchevent() callback function. Draw a rectangular shape.

Code:

Custom view:

When calling, you only need to add it directly in oncreate() function:

You can add a function that returns the delimited range in the user-defined class as needed.

PS: it should be noted that when the finger moves and the screen needs to update the rectangle, in principle, delete the original rectangle and draw a new rectangle. However, due to the thickness of the edge of the hollow rectangle,

In this case, the border thickness will be subtracted to solve the above problem.

design sketch:

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