自定义View之继承LinearLayout

一.最简单的继承于LinearLayout，在里面添加一个button以及其相关的点击逻辑

1.自定义View的布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="按钮" />

</LinearLayout>

2.自定义View的类文件：

package com.example.myapplication.Activity;

import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;


import androidx.annotation.Nullable;

import com.example.myapplication.R;

public class CustomLinearLayout extends LinearLayout {

    private Button mButton;


    public CustomLinearLayout(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        LayoutInflater.from(context).inflate(R.layout.layout_cuetom_linear_layout, this);
        mButton = findViewById(R.id.button);
        mButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(context, "你点击了按钮", Toast.LENGTH_SHORT).show();
            }
        });

    }

    public CustomLinearLayout(Context context) {
        super(context);
        LayoutInflater.from(context).inflate(R.layout.layout_cuetom_linear_layout, this);
        mButton = findViewById(R.id.button);
        mButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(context, "你点击了按钮", Toast.LENGTH_SHORT).show();
            }
        });

    }
}

3.主Activity的类文件：

package com.example.myapplication.Activity;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

import com.example.myapplication.R;


public class MainActivity extends AppCompatActivity {



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

}

4.主Activity的布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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=".Activity.MainActivity">

    <com.example.myapplication.Activity.CustomLinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>


</LinearLayout>

5.实现的效果：

6.将自定义View的布局文件最外层改为别的布局也是可以的，实现的效果也是一样的，如下：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="140dp"
        android:text="按钮"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>