<?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">
  <Button
    android:text="自定义登陆"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/button5"
    android:onClick="login"/>
</LinearLayout>

<?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">
  <EditText
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="text"
    android:hint="请输入用户名"
    android:id="@+id/et_username"/>
  <EditText
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="textPassword"
    android:hint="请输入密码"
    android:id="@+id/et_password"/>
</LinearLayout>

public class AlertDialogDemo extends AppCompatActivity {
  private EditText et_username,et_password;
  @Override
  protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.alertdialog);
  }
  public void login(View v){
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("登录"); 
    //通过布局填充器获login_layout
    View view = getLayoutInflater().inflate(R.layout.login_layout,null); 
    //获取两个文本编辑框（密码这里不做登陆实现，仅演示）
    final EditText et_username = (EditText) view.findViewById(R.id.et_username);
    final EditText et_password = (EditText) view.findViewById(R.id.et_password);
    builder.setView(view);//设置login_layout为对话提示框
    builder.setCancelable(false);//设置为不可取消
    //设置正面按钮，并做事件处理
    builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialogInterface, int i) {
        String name = et_username.getText().toString().trim();
        String pass = et_password.getText().toString().trim();
        Toast.makeText(AlertDialogDemo.this,name + "正在登录....",Toast.LENGTH_SHORT).show();
      }
    });
    //设置反面按钮，并做事件处理
    builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialogInterface, int i) {
        Toast.makeText(AlertDialogDemo.this,"取消登录",Toast.LENGTH_SHORT).show();
      }
    });
    builder.show();//显示Dialog对话框
  }
}