Android UI control series: LinearLayout (linear layout)

LinearLayout is a ViewGroup that displays View elements in a linear direction, which can be horizontal or vertical.

You can reuse LinearLayout. If you want to use a nested multi-layer LinearLayout, you You can consider using RelativeLayout instead.

1. Start creating a project named HelloLinearLayout

2. Open the res/layout/main.xml file and insert the following content

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
        <LinearLayout
                android:orientation="horizontal"
                android:layout_width="fill_parent"
                android:layout_height="fill_parent"
                android:layout_weight="1">
                <TextView
                        android:text="red"
                        android:gravity="center_horizontal"
                        android:background="#aa0000"
                        android:layout_width="wrap_content"
                        android:layout_height="fill_parent"
                        android:layout_weight="1"
                />
                <TextView
                        android:text="green"
                        android:gravity="center_horizontal"
                        android:background="#00aa00"
                        android:layout_width="wrap_content"
                        android:layout_height="fill_parent"
                        android:layout_weight="1"
                />
                <TextView
                        android:text="blue"
                        android:gravity="center_horizontal"
                        android:background="#0000aa"
                        android:layout_width="wrap_content"
                        android:layout_height="fill_parent"
                        android:layout_weight="1"
                />
                <TextView
                        android:text="yellow"
                        android:gravity="center_horizontal"
                        android:background="#aaaa00"
                        android:layout_width="wrap_content"
                        android:layout_height="fill_parent"
                        android:layout_weight="1"
                />
        </LinearLayout>
        <LinearLayout
                android:orientation="vertical"
                android:layout_width="fill_parent"
                android:layout_height="fill_parent"
                android:layout_weight="1">
                <TextView
                        android:text="row one"
                        android:textSize="15pt"
                        android:layout_width="fill_parent"
                        android:layout_height="wrap_content"
                        android:layout_weight="1"
                />
                <TextView
                        android:text="row two"
                        android:textSize="15pt"
                        android:layout_width="fill_parent"
                        android:layout_height="wrap_content"
                        android:layout_weight="1"
                />
                <TextView
                        android:text="row three"
                        android:textSize="15pt"
                        android:layout_width="fill_parent"
                        android:layout_height="wrap_content"
                        android:layout_weight="1"
                />
                <TextView
                        android:text="row four"
                        android:textSize="15pt"
                        android:layout_width="fill_parent"
                        android:layout_height="wrap_content"
                        android:layout_weight="1"
                />
        </LinearLayout>
</LinearLayout>

Check this XML file carefully. There is a root element LinearLayout that defines its direction as vertical. All child Views (2 in total) are stacked vertically. The first child is another LinearLayout laid out in the horizontal direction, and the second child is stacked vertically. The second child is a LinearLayout with a vertical layout. Each of these nested LinearLayouts contains several TextView elements, and their directions are defined by the parent LinearLayout tag.

3. Now open HelloLinearLayout.java and make sure it has loaded the res/layout/main.xml layout file in the onCreate() method

public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);

setContentView(int) method has loaded it for the Activity Layout file, specified by the resource ID - R.layout.main refers to the res/layout/main.xml layout file

4. Run the program, you can see the following situation

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