Using kotlin to develop Android Applications (4) – common basic controls

Some Base Widget in Android App

Some common controls in Android Applications

Several basic properties of control

• ID control ID
• layout_ Width: Wrap_ Content or match_ parent
• layout_ Height: Wrap_ Content or match_ parent
• Background: color / picture

1. Display control

Textview text

<TextView
    android:id="@+id/tv_user_label"
    android:layout_width="wrap_content"
    android:layout_height="50dp"
    android:text= "User name"
    android:gravity="center"
    android:textSize="24sp"
    android:textColor="#0000FF"
    android:textStyle="normal"
    android:singleLine="true"
    android:ellipsize="start"/>

Main attributes:

• Text text (recommended, refer to string.xml The elements inside)
• Textsize font size
• Textcolor font color
• TextStyle font formats are normal, bold and italics
• Position of gravity text display: top, bottom, left, right, center
• Does singleline display all content in one line
• Ellipsis: start, middle, end, marquee

ImageView image

Main attributes:

• scaleType:

  • Fitxy: display the original image in the view according to the specified size, stretch the image, do not maintain the original scale, and fill the imagebutton
  • Center: displays the image in the center of the view without zooming the image
  • Centrrop: scale the image so that the length (width) of the image is greater than or equal to the corresponding dimension of the view
  • Centerside: scale the image to make the length (width) of the image less than or equal to the corresponding dimension of the view
  • Fitcenter: scale the image to the smallest edge of the view and center it
  • Fit: scale the image to the smallest edge of the view and display it in the lower part of the view
  • Fitstart: scale the image to the smallest edge of the view and display it in the upper part of the view
  • Matrix: drawing with a matrix
• SRC image source: @ drawable / beautiful, put the image in RES / drawable folder

Using glide to load network pictures

Glide.with(getContext())
     .load("http://*.jpg")
     .into(imageDetail);

2. Form control

EditText

Main attributes:

• Text text content: text or reference values below string.xml The elements in it
• Hint text prompt content
• Password: the input content is set to password type, true
• Phonenumber: the input content is set to phonenumber type, true
• Cursorvisible sets the cursor to show / hide: the default is true

Common callbacks:

val etName = findViewById<EditText>(R.id.et_username)
        etName.addTextChangedListener(object : TextWatcher {
            override fun afterTextChanged(s: Editable?) {
                //Monitor after input
            }
            override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
                //Monitor after input
            }
            override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
                //Input text change monitoring}
            }
        })

• Addtextchangedlistener monitors changes in the input box
• Setonfocuschangelistener listens for input focus changes

CheckBox

Main attributes:

• Is ischecked selected

Common callbacks:

• Setoncheckedchangelistener listens for state changes

Radio

Main attributes:

• Is ischecked selected

Common callbacks:

• Setoncheckedchangelistener listens for state changes

Seekbar slider

Main attributes

• Max the maximum value of the slider
• The current value of the progress slider
• Thumb slide background
• Progressdrawable reference background

Common callbacks:

• Setonseekbarchangelistener listens for changes in values

Switch

Main attributes:

• Is ischecked selected

Common callbacks:

• Setoncheckedchangelistener listens for state changes

CalendarView

Main attributes:

• Maximum date supported by maxdate: “07 / 27 / 2019 is set in mm / DD / yyyy format
• Minimum date supported by mindate: “07 / 27 / 2019 is set in mm / DD / yyyy format
• The first day of week is set as the first day of each week (the number 3 corresponds to Tuesday, 4 corresponds to Wednesday, and 1 corresponds to Sunday)

Common callbacks:

• Setondatechangelistener listens for changes in values

Button

Common callbacks:

• Setonclicklistener listens for state changes