入手第一个小案例，拔打电话

直接新建一个工程，

先画图形－－－－再写点击事件－－－－＞然后给权限－－－＞测试

方法一：

activity_main.xml 配置如下

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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="com.example.admin.onclick.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/bt_call"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
       android:layout_alignParentBottom="true"
         android:layout_centerHorizontal="true"
        tools:layout_editor_absoluteX="16dp"
        tools:layout_editor_absoluteY="322dp" />

    <EditText
        android:hint="请输入电话号码"
           android:layout_width="wrap_content"
        android:layout_height="wrap_content"
          android:layout_marginBottom="53dp"
        android:id="@+id/et_phone"
         android:layout_above="@+id/bt_call"
        android:layout_centerHorizontal="true" />

</android.support.constraint.ConstraintLayout>

MainActivity.java

package com.example.admin.onclick;

import android.content.Intent;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;


public class MainActivity extends AppCompatActivity {
    private EditText et_phone;

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

        et_phone = (EditText) findViewById(R.id.et_phone);
        Button bt_call = (Button) findViewById(R.id.bt_call);
        //设点事件
        bt_call.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //获取输入的电话号码
                String phone = et_phone.getText().toString().trim();
                //创建打电话的意图
                Intent intent = new Intent();
                //设拔打电话的动作
                intent.setAction(Intent.ACTION_CALL);
                //设打电话号码
                intent.setData(Uri.parse("tel:" + phone));
                //开启打电话的意图
                startActivity(intent);
            }
        });
    }
}

 AndroidManifest.xml

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

    <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">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
    <!--给打电话权限-->
    <uses-permission android:name="android.permission.CALL_PHONE"/>
</manifest>

可参考：https://www.cnblogs.com/ahu-lichang/p/6567945.html

以上示例本人均测试过可以正常运行。