如何在Android中创建类似“通知”类的类？

Question

最近我一直在学习如何在Android中构建通知，我遇到过这个问题：

NotificationCompat.Builder nBuilder = new NotificationCompat.Builder(this)
                .setSmallIcon(R.mipmap.test_image)
                .setLargeIcon(largeIcon)
                .setContentTitle("Notification Compat")
                .setContentText("Notification area --> 
                Modifiable!").setNumber(num);

无论我如何编写代码，结果都是一样的。 即例如，如果我改变顺序，则在setContentTitle（）之前调用setContentText（）。它返回相同的Notification Builder对象。 代码：

NotificationCompat.Builder nBuilder = new NotificationCompat.Builder(this)
                .setSmallIcon(R.mipmap.test_image)
                .setLargeIcon(largeIcon)
                .setContentText("Notification area --> Modifiable!") // Modification
                .setContentTitle("Notification Compat").setNumber(num);

谁能告诉我这怎么可能？ 谢谢。

Answer 1

Here是如何创建Builder pattern的示例。

示例

public class FooBar {
   private int mA, mB;

   private FooBar(int a, int b) {
      this.mA = a;
      this.mB = b;
   }

   public int getA() {
      return mA;
   }

   public void setA(int a) {
      this.mA = a;
   }

   public int getB() {
      return mB;
   }

   public void setB(int b) {
      this.mB = b;
   }

   public static class FooBarBuilder {
      private int mNestedA, mNestedB;

      public FooBarBuilder() {
          this.mNestedA = 0;
          this.mNestedB = 0;
      }

      public FooBarBuilder(int nestedA, int nestedB) {
          this.mNestedA = nestedA;
          this.mNestedB = nestedB;
      }

      public int getNestedA() {
          return mNestedA;
      }

      public FooBarBuilder setNestedA(int nestedA) {
          this.mNestedA = nestedA;
          return this;
      }

      public int getNestedB() {
          return mNestedB;
      }

      public FooBarBuilder setNestedB(int nestedB) {
          this.mNestedB = nestedB;
          return this;
      }

      public FooBar create() {
          return new FooBar(mNestedA, mNestedB);
      }
   }
}

Answer 2

这是一个Builder模式。每次调用Builder的方法时，它都会设置一些作为参数传递的值，并返回相同的Builder对象。所以顺序无关紧要。如果在不返回对象的情况下调用setters方法，则相同。 Builder的示例代码：

public class Builder {

    String mTitle;
    int mCount;

    public Builder setTitle(String title) {
        mTitle = title;
        return this;
    }

    public Builder setCount(int count) {
        mCount = count;
        return this;
    }
}

用法：

Builder builder = new Builder()
    .setTitle("Some title")
    .setCount(count);