手动创建活动

1.创建layout

2.新建layout文件

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

    <!-- 添加按钮 -->
    <Button
        android:id="@+id/button_1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Button 1"
        />

</LinearLayout>

3.设置布局

package activitytest.example.com.activitytest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class FirstActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.first_layout); // 设置默认布局
    }
}

4.注册活动，设置主活动

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="activitytest.example.com.activitytest">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <!-- 注册活动 -->
        <activity android:name=".FirstActivity" android:label="This is FirstActivity">
            <!-- 设为主活动 -->
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

5.运行

6.增加按钮事件和toast提醒

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.first_layout); // 设置默认布局

        Button button1 = (Button) findViewById(R.id.button_1);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(FirstActivity.this,"You clicked Button 1",Toast.LENGTH_SHORT).show();
            }

        });

    }