Question

我试图将锚约束放到subView中包含的textField上。对于前锚和后锚，它们不起作用。我不确定这是什么，我想在键盘和子视图中的项之间留一些空间，以及在UITextField和屏幕的尾随锚之间留一些空间。下面是有问题的代码

布局代码：

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Storage } from '@ionic/storage';
import { Platform } from 'ionic-angular';
import { SQLite, SQLiteObject} from '@ionic-native/sqlite'; 
import { SQLitePorter } from '@ionic-native/sqlite-porter'
import { BehaviorSubject } from 'rxjs/Rx';
import 'rxjs/add/operator/map';

/*
  Generated class for the DatabaseProvider provider.

      See https://angular.io/guide/dependency-injection for more info on                     
providers
  and Angular DI.
*/
@Injectable()
export class DatabaseProvider {
    database: SQLiteObject;
    private dbReady: BehaviorSubject<boolean>;

  constructor(public http: HttpClient, private sqlitePorter: SQLitePorter,             private storage: Storage, private sqlite: SQLite, private platform: Platform)     
{
    this.dbReady = new BehaviorSubject(false);
    this.platform.ready().then(() => {
        this.sqlite.create({
            name: 'assessment.db',
            location: 'default'
        })
        .then((db:SQLiteObject) => {
            this.database = db;
            this.storage.get('database_filled').then(val => {
                if(val){
                    this.dbReady.next(true);
                }
                else{
                    this.fillDatabase();
                }
            })
        });
    });  
}

fillDatabase(){
    this.http.get('assets/test.sql')
    .map (res => res.text())
    .subscribe(sql => { 
        this.sqlitePorter.importSqlToDb(this.database, sql)
        .then(data => {
            this.dbReady.next(true);
            this.storage.set('database_filled', true);
        })
    });
}

  getDatabaseState(){
    return this.dbReady.asObservable();
  }

}

完整的代码

func setUpLayout(){

    //myView
    self.myView.translatesAutoresizingMaskIntoConstraints = false
    self.myView.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor, constant: 0).isActive = true
  self.myView.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor, constant: 0).isActive = true
    self.myView.heightAnchor.constraint(equalToConstant: 98).isActive = true
    self.myView.bottomAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.bottomAnchor, constant: 4).isActive = true


    //CollectionView
    self.collectionView.translatesAutoresizingMaskIntoConstraints = false
    self.collectionView.leadingAnchor.constraint(equalTo: self.myView.leadingAnchor, constant: 0).isActive = true
    self.collectionView.trailingAnchor.constraint(equalTo: self.myView.trailingAnchor, constant: 0).isActive = true
    self.collectionView.bottomAnchor.constraint(equalTo: self.myView.bottomAnchor, constant: 4).isActive = true
    self.collectionView.topAnchor.constraint(equalTo: self.searchBar.bottomAnchor, constant: 4).isActive = true

    //searchbar
    self.searchBar.translatesAutoresizingMaskIntoConstraints = false
    self.searchBar.topAnchor.constraint(equalTo: self.myView.topAnchor, constant: 0).isActive = true
    self.searchBar.leadingAnchor.constraint(equalTo: self.myView.leadingAnchor, constant: 4).isActive = true
    self.searchBar.trailingAnchor.constraint(equalTo: self.myView.trailingAnchor, constant: 4).isActive = true
    self.searchBar.heightAnchor.constraint(equalToConstant: 45).isActive = true
    searchBar.backgroundColor = .white
    searchBar.layer.borderWidth = 2
    searchBar.layer.borderColor = UIColor.black.cgColor
    //PictureView
    self.PictureView.translatesAutoresizingMaskIntoConstraints = false
    self.PictureView.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor, constant: 0).isActive = true
    self.PictureView.bottomAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.bottomAnchor, constant: 0).isActive = true
    self.PictureView.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor, constant: 0).isActive = true
    self.PictureView.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor, constant: 0).isActive = true
    self.PictureView.backgroundColor = .green
}

Answer 1

对于尾部和底部锚点约束，通常必须对常量使用负数才能实现所需的效果。

例如：

searchBar.bottomAnchor.constraint(equalTo: myView.bottomAnchor, constant: 4).isActive = true

成为：

searchBar.bottomAnchor.constraint(equalTo: myView.bottomAnchor, constant: -4).isActive = true

为什么我的某些锚约束不起作用，而其他锚约束却对同一个项目起作用？

1 个答案: