红橙Darren视频笔记 builder设计模式 navigationbar 导航栏第二版

1.builder设计模式简介

builder的实际应用的典型案例有AlertDialog和OKHttp

例如

    // AlertDialogAlertDialog alertDialog = new AlertDialog.Builder(MainActivity.this).setTitle("标题").setNegativeButton("取消", (dialog, which) -> {dialog.dismiss();Toast.makeText(MainActivity.this, "点击了取消", Toast.LENGTH_SHORT).show();}).setPositiveButton("确定", (dialog, which) -> Toast.makeText(MainActivity.this, "点击了确定", Toast.LENGTH_SHORT).show()).setCancelable(false).setIcon(R.drawable.ic_launcher_background).setMessage("这是消息这是消息这是消息这是消息").setView(button).create();alertDialog.show();// OKhttpprivate void doOKHttpGet() {Runnable runnable = () -> {String response = "";try {response = getRequest("https://raw.github.com/square/okhttp/master/README.md");} catch (IOException e) {Log.d(TAG, e.getMessage());e.printStackTrace();}Log.d(TAG, "doOKHttpGet: " + response);};Thread thread = new Thread(runnable);thread.start();}String getRequest(String url) throws IOException {Request request = new Request.Builder().url(url).build();try (Response response = client.newCall(request).execute()) {return response.body().string();}}

建造者模式通常用于创建较复杂对象，例如上面两种情况都是参数有很多且有参数是可有可无的情况

之前写过一些类似的文章

下面这篇是利用builder设计模式模仿Android AlertDialog写的自己自定义的Dialog

https://blog.csdn.net/u011109881/article/details/114336196

下面这篇是利用builder设计模式进一步写导航条

https://blog.csdn.net/u011109881/article/details/114548479

上面的两篇类结构比较简单还有稍微复杂的建造者demo

https://blog.csdn.net/u011109881/article/details/57182402

2.导航栏升级版

利用builder设计模式写导航栏

2.1 接口类INavigation

public interface INavigation {void createNavigationBar();void attachNavigationParams();//TextView findViewById(int viewId);void attachParent(View navigationBar, ViewGroup parent);//AbsNavigationBar.Builder getBuilder();
}

2.2 抽象类AbsNavigationBar

public abstract class AbsNavigationBar <B extends AbsNavigationBar.Builder> implements INavigation {private final B mBuilder;private View mNavigationBar;protected AbsNavigationBar(B builder) {this.mBuilder = builder;createNavigationBar();}@Overridepublic void createNavigationBar() {mNavigationBar = LayoutInflater.from(mBuilder.mContext).inflate(mBuilder.mLayoutId, mBuilder.mParent, false);// 实际上false改成true可以不用调用下面attachParent的方法// 将布局添加到父容器attachParent(mNavigationBar, mBuilder.mParent);// 绑定参数到Builder内部attachNavigationParams();}// 利用AbsNavigationBar引用绑定参数到AbsNavigationBar内部类Builder@Overridepublic void attachNavigationParams() {// 设置文本Map<Integer, CharSequence> textMaps = mBuilder.mTextMaps;for (Map.Entry<Integer, CharSequence> entry : textMaps.entrySet()) {TextView textView = findViewById(entry.getKey());if (textView == null) {throw new IllegalArgumentException("TextView should not be null");}textView.setText(entry.getValue());}// 设置点击事件Map<Integer, View.OnClickListener> clickListenerMaps = mBuilder.mClickListenerMaps;for (Map.Entry<Integer, View.OnClickListener> entry : clickListenerMaps.entrySet()) {View view = findViewById(entry.getKey());if (view == null) {throw new IllegalArgumentException("view should not be null");}view.setOnClickListener(entry.getValue());}}@Overridepublic void attachParent(View navigationBar, ViewGroup parent) {parent.addView(navigationBar, 0);}// 返回泛型类型 前面的T是泛型声明 后面的T是返回类型protected  <T extends View> T findViewById(int viewId) {return mNavigationBar.findViewById(viewId);}protected B getBuilder() {return mBuilder;}/*** 构建类 主要任务是存储参数*/public static abstract class Builder<B extends Builder> {// 类泛型 里面用到泛型B 继承自当前的内部类builderpublic Context mContext;public int mLayoutId;public ViewGroup mParent;public Map<Integer, CharSequence> mTextMaps;public Map<Integer, View.OnClickListener> mClickListenerMaps;public Builder(Context context, int layoutId, ViewGroup parent) {this.mContext = context;this.mLayoutId = layoutId;this.mParent = parent;this.mTextMaps = new HashMap<>();this.mClickListenerMaps = new HashMap<>();}// 创建NavigationBarpublic abstract AbsNavigationBar create();// 利用builder设置文本public B setText(int viewId, String text) {mTextMaps.put(viewId, text);return (B) this;}// 利用builder设置点击事件public B setOnClickListener(int viewId, View.OnClickListener clickListener) {mClickListenerMaps.put(viewId, clickListener);return (B) this;}}
}

2.3 具体实现类1 NavigationBar

public class NavigationBar extends AbsNavigationBar{protected NavigationBar(Builder builder) {super(builder);}public static class Builder extends AbsNavigationBar.Builder<NavigationBar.Builder> {// 这里的泛型覆盖父类中的泛型（父类中泛化 子类中具现） 使得setText setOnClickListener返回的B为NavigationBar.Builderpublic Builder(Context context, int layoutId, ViewGroup parent) {super(context, layoutId, parent);}@Overridepublic NavigationBar create() {return new NavigationBar(this);}}
}

2.4 具体实现类2 DefaultNavigationBar

public class DefaultNavigationBar extends AbsNavigationBar<DefaultNavigationBar.Builder>{protected DefaultNavigationBar(Builder builder) {super(builder);}@Overridepublic void attachNavigationParams() {super.attachNavigationParams();TextView leftView = findViewById(R.id.back_tv);leftView.setVisibility(getBuilder().mLeftVisible);// 这里能够访问到mLeftVisible 因为getBuilder返回的是泛型类型// DefaultNavigationBar extends AbsNavigationBar<DefaultNavigationBar.Builder> 具现化了B为DefaultNavigationBar.Builder// 因此 getBuilder()返回的是DefaultNavigationBar.Builder 能够调用mLeftVisible变量}public static class Builder extends AbsNavigationBar.Builder<DefaultNavigationBar.Builder>{public int mLeftVisible = View.VISIBLE;public Builder(Context context, ViewGroup parent) {super(context, R.layout.defualt_navigation_bar, parent);}public Builder setLeftText(String text){setText(R.id.back_tv,text);return this;}public Builder setLeftClickListener(View.OnClickListener clickListener){setOnClickListener(R.id.back_tv,clickListener);return this;}public Builder hideLeftText() {mLeftVisible = View.INVISIBLE;return this;}@Overridepublic DefaultNavigationBar create() {return new DefaultNavigationBar(this);}}
}

2.5 使用到的布局

//activity_main<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:id="@+id/view_root"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity"><TextViewandroid:layout_centerInParent="true"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Hello World!"/></RelativeLayout>//defualt_navigation_bar
<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:id="@+id/view_root"android:background="#ccc"android:layout_height="wrap_content"><TextViewandroid:id="@+id/back_tv"android:textColor="@android:color/white"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="default bar" /></androidx.appcompat.widget.Toolbar>//navigationbar
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="wrap_content"android:background="@color/design_default_color_secondary"android:paddingTop="10dp"android:paddingBottom="10dp"tools:context=".MainActivity"><TextViewandroid:id="@+id/left_text"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Hello World!"android:textColor="@color/white" /><TextViewandroid:id="@+id/title"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_centerHorizontal="true"android:text="Hello World!"android:textColor="@color/white" /><ImageViewandroid:id="@+id/right_icon"android:layout_width="20dp"android:layout_height="20dp"android:layout_alignParentEnd="true"android:src="@drawable/ic_launcher_background" />
</RelativeLayout>

另外注意需要将application的主题设置为android:theme="@style/Theme.Design.Light.NoActionBar"

课程里面说是导航栏的升级版,但个人感觉不出哪里升级了- -！要说有变化的化主要是用到了一些泛型在继承上面的一些高级用法，需要多花时间琢磨琢磨