Android XML LayoutParams LayoutParams

A list,

• Android common layout unit (DP, SP, PX, PT, in, mm)

• Layout parameters are used to set the position and size of the view in the layout.

Second,xml 与 codewriting

• Layout_xxx Layout properties:

  <TextView
      android:layout_width="100dp"
      android:layout_height="200dp"
      android:layout_marginLeft="50dp"
      android:layout_marginTop="10dp"
      android:text="Hello world!"
      android:textSize="10sp" />
  Copy the code

• The ViewGroup class implements a nested class that extends ViewGroup.layoutParams and contains properties that set the size and position of the view.

  

  TextView TV = new TextView(this); LinearLayout = new LinearLayout(this); LinearLayout = new LinearLayout(this); / / get in the view layout parameter object LinearLayout. LayoutParams params = (LinearLayout. LayoutParams) TV. GetLayoutParams (); // Configure the layout property params.leftMargin = 30; // left margin params.topMargin = 30; // top margin params.width = 100; // width params.height = 200; // high // Set the configured layout parameters to the view tv.setLayoutParams(params); // Add the view module to the layout module layout.addView(TV);Copy the code

Three, attributes,

• In general, it is recommended not to use absolute units (e.g., pixel px) to specify layout width and height. It is better to use relative units of measurement (e.g., density-independent pixel units dp, WRAP_content, match_parent) to ensure that applications display correctly on screens of all sizes.

• Wrap_content: The view resizes it to the size the content needs.

• Match_parent: The view is as large as possible as its parent view group allows.

Four cases,

• XML layout code

  
          
  <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      tools:context=".MainActivity">
  
      <! The outermost layer is not Layout, so this is root Layout.
      <LinearLayout
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:background="#ffc">
          <! Add an internal view layout -->
          <LinearLayout
              android:layout_marginTop="200dp"
              android:layout_marginLeft="70dp"
              android:layout_width="300dp"
              android:layout_height="300dp"
              android:background="#fcf">
              <! Add view component -->
              <TextView
                  android:id="@+id/dzm"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:layout_marginLeft="100dp"
                  android:layout_marginTop="200dp"
                  android:text="DZM TEST"
                  android:textSize="20sp" />
          </LinearLayout>
      </LinearLayout>
  
  </androidx.constraintlayout.widget.ConstraintLayout>
  Copy the code

• The effect