如何在按下设备后退按钮或工具栏后退箭头时显示警告对话框或对话框

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

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

        // 监听后退按钮或工具栏后退箭头的点击事件
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

    @Override
    public boolean onSupportNavigateUp() {
        // 弹出警告对话框
        showConfirmationDialog();
        return true;
    }

    private void showConfirmationDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("确认后退");
        builder.setMessage("确定要后退吗？");
        builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                // 用户点击确定，执行后退操作
                onBackPressed();
            }
        });
        builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                // 用户点击取消，不执行后退操作
            }
        });
        builder.show();
    }
}