AlertDialog自定义

<?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">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="用户名"/>

        <EditText
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="密码"/>

        <EditText
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>

    </LinearLayout>

</LinearLayout>

package com.pingyijinren.helloworld.activity;

import android.content.DialogInterface;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.Button;

import com.pingyijinren.helloworld.R;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private AlertDialog alertDialog;
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button=(Button)findViewById(R.id.button);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        AlertDialog.Builder builder=new AlertDialog.Builder(this);
        builder.setIcon(R.mipmap.ic_launcher);
        builder.setTitle("用户登录");
        builder.setView(R.layout.alert_dialog_layout);
        builder.setPositiveButton("退出", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                finish();
            }
        });
        builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {

            }
        });
        alertDialog=builder.create();
        alertDialog.show();
    }
}