RecyclerView item间距

import android.graphics.Rect;
import android.view.View;

import androidx.recyclerview.widget.RecyclerView;

public class MyItemDecoration extends RecyclerView.ItemDecoration{
        //默认值
        private int space=8;
        public MyItemDecoration(int space){
            this.space=space;
        }
        @Override
        public void getItemOffsets(Rect outRect, View view,
                                   RecyclerView parent, RecyclerView.State state) {
            outRect.left = space;
            outRect.right = space;
            outRect.bottom = space;
            // Add top margin only for the first item to avoid double space between items
            if (parent.getChildPosition(view) == 0)
                outRect.top = space;
        }
    }

开启子线程

不能在UI线程中执行耗时操作此时，需要开启一个新的线程去执行耗时操作

findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        new Thread(() -> {
            if(mRemoteBookManager!=null){
                try {
                    //假设getBookList是服务端的一个耗时方法
                    List<Book> newList=mRemoteBookManager.getBookList();
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
});

从子线程切换到UI线程

获取当前进程

package com.hnucm.chapter5_2.utils;

import android.app.ActivityManager;
import android.app.Application;
import android.content.Context;
import android.os.Build;
import android.os.Process;
import android.text.TextUtils;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

import java.lang.reflect.Method;
import java.util.List;

public class ProcessUtil {
  private static String currentProcessName;

  /**
  * @return 当前进程名
  */
  @Nullable
  public static String getCurrentProcessName(@NonNull Context context) {
    if (!TextUtils.isEmpty(currentProcessName)) {
      return currentProcessName;
    }

    //1)通过Application的API获取当前进程名
    currentProcessName = getCurrentProcessNameByApplication();
    if (!TextUtils.isEmpty(currentProcessName)) {
      return currentProcessName;
    }

    //2)通过反射ActivityThread获取当前进程名
    currentProcessName = getCurrentProcessNameByActivityThread();
    if (!TextUtils.isEmpty(currentProcessName)) {
      return currentProcessName;
    }

    //3)通过ActivityManager获取当前进程名
    currentProcessName = getCurrentProcessNameByActivityManager(context);

    return currentProcessName;
  }


  /**
  * 通过Application新的API获取进程名，无需反射，无需IPC，效率最高。
  */
  public static String getCurrentProcessNameByApplication() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
      return Application.getProcessName();
    }
    return null;
  }

  /**
  * 通过反射ActivityThread获取进程名，避免了ipc
  */
  public static String getCurrentProcessNameByActivityThread() {
    String processName = null;
    try {
      final Method declaredMethod = Class.forName("android.app.ActivityThread", false, Application.class.getClassLoader())
        .getDeclaredMethod("currentProcessName", (Class<?>[]) new Class[0]);
      declaredMethod.setAccessible(true);
      final Object invoke = declaredMethod.invoke(null, new Object[0]);
      if (invoke instanceof String) {
        processName = (String) invoke;
      }
    } catch (Throwable e) {
      e.printStackTrace();
    }
    return processName;
  }

  /**
  * 通过ActivityManager 获取进程名，需要IPC通信
  */
  public static String getCurrentProcessNameByActivityManager(@NonNull Context context) {
    if (context == null) {
      return null;
    }
    int pid = Process.myPid();
    ActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
    if (am != null) {
      List<ActivityManager.RunningAppProcessInfo> runningAppList = am.getRunningAppProcesses();
      if (runningAppList != null) {
        for (ActivityManager.RunningAppProcessInfo processInfo : runningAppList) {
          if (processInfo.pid == pid) {
            return processInfo.processName;
          }
        }
      }
    }
    return null;
  }
}