开源Kotlin小项目，非常适合练手

一个非常小型的Kotlin项目，但是该有的都有。如果您觉得有意思就帮我star下，人多了我就会放更多的福利哦。github

先上福利。Release1.0

特点

1. 列表显示图片，点击查看更多。

2. 快速跳转至顶部，底部，指定位置。

3. 收藏，查看历史记录。

4. 设置壁纸。

5. 离线缓存。

组成

1. 语言：Kotlin，Java

2. 网络请求：HttpUrlConnection

3. 数据库：Sqlite

4. 数据源：Jsoup

5. 第三方库：Glide

概述

1) 网络请求

网络框架并没有使用RxRetrofit等，为了保证精简高效直接使用的HttpUrlConnection

• get

val request = AsyncNetwork()
request.request(Constants.HOST_MOBILE_URL, null)
request.setRequestCallback(object : IRequestCallback {
    override fun onSuccess(httpURLConnection: HttpURLConnection?, response: String) {
        //todo
    }
})

• post

val request = AsyncNetwork()
request.request(Constants.HOST_MOBILE_URL, mutableMapOf())
request.setRequestCallback(object : IRequestCallback {
    override fun onSuccess(httpURLConnection: HttpURLConnection?, response: String) {
        //todo
    }
})

2) 数据库

数据库没有使用第三方框架，直接使用的sql语句。

CREATE TABLE tb_class_page_list ( 
                    _id           INTEGER PRIMARY KEY ASC AUTOINCREMENT,
                    href          STRING  UNIQUE,
                    description   STRING,
                    image_url     STRING,
                    id_class_page INTEGER REFERENCES tb_class_page (_id) ON DELETE CASCADE ON UPDATE CASCADE,
                    [index]       INTEGER);

3) 读写缓存

Serializable的效率远低于Parcelable，所以采用Parcelable实现的缓存机制，速度快了大概7，8倍。

• 读取缓存

val helper = PageListCacheHelper(container?.context?.filesDir?.absolutePath)
val pageModel: Any? = helper.get(key)

• 写入缓存

val helper = PageListCacheHelper(context.filesDir.absolutePath)
helper.put(key, object)

• 删除缓存

val helper = PageListCacheHelper(context.filesDir.absolutePath)
helper.remove(key)

4) jsoup获取数据

由于数据是用从html页面中提取的，所以速度偏慢，为了不影响体验做了一套缓存机制，来做到流畅体验。

Document doc = Jsoup.parse(html);
Elements elements = body.getElementsByTag("a");
String text = elements.get(0).text();
String imageUrl = elements.get(0).attr("src");
...

5) 组件

• Activity fragment替代activity来显示新界面

  因为activity需要在Manifiest中注册，所以当有多个activity的时候，就需要编写很长的Manifiest文件，严重影响了Manifiest的可读性，界面的风格也比较笨重。所以一个新页面就注册一个activity不太合适，我们通过用activity做为容器添加不同的Fragment来达到注册一个activity启动多个不同页面的效果。生命周期由activity管理，更方便简洁。

  open class BaseFragmentActivity : BaseActionActivity() {
  
      companion object {
  
          private const val EXTRA_FRAGMENT_NAME = "extra_fragment_name"
          private const val EXTRA_FRAGMENT_ARG = "extra_fragment_arguments"
  
          @JvmOverloads
          @JvmStatic
          fun newInstance(context: Context, fragment: Class<*>, bundle: Bundle? = null,
                                        clazz: Class<out Activity> = getActivityClazz()): Intent {
              val intent = Intent(context, clazz)
              intent.putExtra(EXTRA_FRAGMENT_NAME, fragment.name)
              intent.putExtra(EXTRA_FRAGMENT_ARG, bundle)
              return intent
          }
  
          protected open fun getActivityClazz(): Class<out Activity> {
              return BaseFragmentActivity::class.java
          }
      }
  
      override fun onCreate(savedInstanceState: Bundle?) {
          super.onCreate(savedInstanceState)
          setContentView(R.layout.cc_activity_base_fragment)
          val fragmentName = intent.getStringExtra(EXTRA_FRAGMENT_NAME)
          var fragment: Fragment? = null
          if (TextUtils.isEmpty(fragmentName)) {
              //set default fragment
              //fragment = makeFragment(MainFragment::class.java!!.getName())
          } else {
              val args = intent.getBundleExtra(EXTRA_FRAGMENT_ARG)
              try {
                  fragment = makeFragment(fragmentName)
                  if (args != null)
                      fragment?.arguments = args
              } catch (e: Exception) {
                  e.printStackTrace()
              }
  
          }
  
          if (fragment == null) return
  
          supportFragmentManager
                  .beginTransaction()
                  .replace(R.id.fragment_container, fragment)
                  .commit()
      }
  
      fun makeFragment(name: String): Fragment? {
          try {
              val fragmentClazz = Class.forName(name)
              return fragmentClazz.newInstance() as Fragment
          } catch (e: Exception) {
              e.printStackTrace()
          }
  
          return null
      }
  
  }

6) 序列化性能

性能测试，Serializable VS Externalizable，为了避免干扰，我们使用AndroidTest进行测试。

模型

class Model1 implements Serializable {
    String text;
    int code;
    boolean bool;
    Model1 child;
}

class Model2 extends Model1 implements Externalizable {

    public Model2() {
    }

    @Override
    public void readExternal(ObjectInput input) throws IOException, ClassNotFoundException {
        text = input.readUTF();
        code = input.readInt();
        bool = input.readBoolean();

        child = new Model2();
        child.text = input.readUTF();
        child.code = input.readInt();
        child.bool = input.readBoolean();
    }

    @Override
    public void writeExternal(ObjectOutput output) throws IOException {
        output.writeUTF(text);
        output.writeInt(code);
        output.writeBoolean(bool);
        if (child != null) {
            output.writeUTF(child.text);
            output.writeInt(child.code);
            output.writeBoolean(child.bool);
        }
    }
}

测试

@Test
public void serializableVSExternalizable() throws Exception {
    List<Model1> testModel1 = new ArrayList<>();
    for (int i = 0; i < 50000; i++) {
        Model1 model1 = new Model1();
        model1.text = "Hello World " + i;
        model1.code = i;
        model1.bool = false;

        Model1 child = new Model1();
        child.text = "Hello World Child" + i;
        child.code = i;
        child.bool = false;

        model1.child = child;
        testModel1.add(model1);
    }
    long startTime = System.currentTimeMillis();
    File file = new File("/sdcard/serializable");
    ObjectOutputStream oStream = new ObjectOutputStream(new FileOutputStream(file));
    oStream.writeObject(testModel1);
    oStream.close();
    Log.e("serializable", "write time " + (System.currentTimeMillis() - startTime));
    startTime = System.currentTimeMillis();
    ObjectInputStream iStream = new ObjectInputStream(new FileInputStream(file));
    testModel1 = (List<Model1>) iStream.readObject();
    iStream.close();
    Log.e("serializable", "read time " + (System.currentTimeMillis() - startTime));
    testModel1 = null;

    List<Model2> testModel2 = new ArrayList<>();
    for (int i = 0; i < 50000; i++) {
        Model2 model2 = new Model2();
        model2.text = "Hello World " + i;
        model2.code = i;
        model2.bool = false;

        Model2 child = new Model2();
        child.text = "Hello World Child" + i;
        child.code = i;
        child.bool = false;

        model2.child = child;
        testModel2.add(model2);
    }
    startTime = System.currentTimeMillis();
    file = new File("/sdcard/externalizable");
    oStream = new ObjectOutputStream(new FileOutputStream(file));
    oStream.writeObject(testModel2);
    oStream.close();
    Log.e("externalizable", "write time " + (System.currentTimeMillis() - startTime));
    startTime = System.currentTimeMillis();
    iStream = new ObjectInputStream(new FileInputStream(file));
    testModel2 = (List<Model2>) iStream.readObject();
    iStream.close();
    Log.e("externalizable", "read time " + (System.currentTimeMillis() - startTime));
}

结果

序列化5000个对象
Serializable：写入耗时4026 ms，读取耗时177 ms
Externalizable：写入耗时2680 ms，读取耗时79 ms

序列化50000个对象
Serializable：写入耗时46872 ms，读取耗时1807 ms
Externalizable：写入耗时41334 ms，读取耗时792 ms

从结果上可以看到Externalizalbe相比于Serializable是稍微快一些点不管是写入还是读取速度。对象存储还可以使用一些对象关系映射（ORM）型的数据库。如GreenDao等等。

7) Java中的深拷贝

由于System.arrayCopy()该方法拷贝数组的时候，如果是基本数据类型则是深拷贝，如果是对象类型则会是浅拷贝，无法做到深拷贝，所以想深拷贝一个数组就得循环创建对象并赋值，这显得很麻烦。所以项目中使用序列化的方法进行深拷贝。PS：Serializable序列化方式读取的时候并不会调用对象构造方法，而Externalizable序列化方式读取时会调用对象的无参构造方法。

@SuppressWarnings("unchecked")
public static <T> T deepCopyOrThrow(T src) throws IOException, ClassNotFoundException {
    ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
    ObjectOutputStream out = new ObjectOutputStream(byteOut);
    out.writeObject(src);

    ByteArrayInputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());
    ObjectInputStream in = new ObjectInputStream(byteIn);
    return (T) in.readObject();
}

public static <T> T deepCopy(T src) {
    try {
        return deepCopyOrThrow(src);
    } catch (Exception ignore) {
        ignore.printStackTrace();
        return null;
    }
}