学习的内容

在上次课我们学习recyclerview的用法建立了简单的微信聊天界面。这次我们要根据上次设计的界面进行跳转设计。

效果展示

在这里插入图片描述
点击第一栏跳转

主要的文件代码

MainActivity2.java

package com.example.mywork;

import android.os.Bundle;
import android.util.Log;
import android.view.View;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.collection.ArraySet;

import java.util.ArrayList;
import java.util.List;

public class MainActivity2 extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        Log.d("生命周期", "oncreate");
    }
    @Override
    protected void onStart() {
        super.onStart();
        Log.d("生命周期", "onstart");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d("生命周期", "onpause");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d("生命周期", "onresume");
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        Log.d("生命周期", "onrestart");
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d("生命周期", "onstop");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d("生命周期", "ondestroy");
    }

        }

myadapter.java的修改

在适配器里我们要加入点击监听事件

package com.example.mywork;


import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.TextView;

        import androidx.annotation.NonNull;
import androidx.collection.CircularArray;
import androidx.recyclerview.widget.RecyclerView;

        import java.util.List;


public class myadapter extends RecyclerView.Adapter<myadapter.Myviewholder> {

    private static OnRecyclerItemClickListener onItemClickListener;
    private List<chat> mList;
    private Context context;

    public myadapter(Context context,List<chat> list) {
        this.mList= list;
        this.context=context;
    }

    public myadapter() {

    }


    @NonNull
    @Override
    public Myviewholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType){
        View view=(View)LayoutInflater.from(parent.getContext()).inflate(R.layout.item,parent,false);
        Myviewholder myviewholder= new Myviewholder((view));
        return myviewholder;
    }

    @Override
    public void onBindViewHolder(@NonNull Myviewholder holder, int position) {
        chat chat = mList.get(position);
        holder.Image.setImageResource(chat.getImageid());
        holder.Name.setText(chat.getName());
        holder.Message.setText(chat.getMessage());

    }

    @Override
    public int getItemCount() {
        return mList.size();
    }

    public  class Myviewholder extends RecyclerView.ViewHolder{
        private ImageView Image;
        private TextView Name;
        private TextView Message;

        public Myviewholder(@NonNull View itemView) {
            super(itemView);
            Image = itemView.findViewById(R.id.item_img);
            Name = itemView.findViewById(R.id.item_name);
            Message = itemView.findViewById(R.id.item_message);
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if(onItemClickListener!=null){
                        onItemClickListener.onRecyclerItemClick(getAdapterPosition());
                    }
                }
            });

        }
    }

    public static void setRecyclerItemClickListener(OnRecyclerItemClickListener listener){
        onItemClickListener=listener;
    }
    public interface  OnRecyclerItemClickListener{
        void  onRecyclerItemClick(int position);
    }

}

weixinFagment.java的修改

我们返回的是item的位置，当点击所有item时都会显示“在线”当点击第一个事件item时会到MainActivity2，其余不会

package com.example.mywork;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;

import android.app.Fragment;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.Toast;

import androidx.recyclerview.widget.DividerItemDecoration;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;
import java.util.List;


public class weixinFragment extends Fragment {
    private Context context;
    private List<chat> mList = new ArrayList<chat>();
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;


    public weixinFragment() {
        // Required empty public constructor
    }


    // TODO: Rename and change types and number of parameters
    public static weixinFragment newInstance(String param1, String param2) {
        weixinFragment fragment = new weixinFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view= inflater.inflate(R.layout.tab01, container, false);
        context = (Activity) view.getContext();
        InitData();
        RecyclerView recyclerView = view.findViewById(R.id.recyclerview);
        myadapter adapter = new myadapter(context,mList);
        recyclerView.setAdapter(adapter);
        LinearLayoutManager manager = new LinearLayoutManager(context);
        manager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(manager);
        recyclerView.addItemDecoration(new DividerItemDecoration(context,LinearLayoutManager.VERTICAL ));
        myadapter.setRecyclerItemClickListener(new myadapter.OnRecyclerItemClickListener() {


            @Override
            public void onRecyclerItemClick(int position) {
                Toast.makeText(getActivity(),"在线",Toast.LENGTH_LONG).show();
                if (position==0){
                Intent intent=new Intent(getActivity(),MainActivity2.class);
                startActivity(intent);}

            }
        });
        return view;
    }

    private void InitData() {
            for (int i = 0; i < 10; i++) {
                chat lianxiren_1 = new chat(i, R.drawable.lianxiren_1, "ckbxb","天气挺好");
                mList.add(lianxiren_1);
                chat lianxiren_2= new chat(i, R.drawable.lianxiren_2, "dghj","吃午饭吗");
                mList.add(lianxiren_2);
                chat lianxiren_3 = new chat(i, R.drawable.lianxiren_3, "vdhje","电影怎么样");
                mList.add(lianxiren_3);
                chat lianxiren_4 = new chat(i, R.drawable.lianxiren_4, "ehjhgw","我觉得挺好玩的");
                mList.add(lianxiren_4);
                chat lianxiren_5 = new chat(i, R.drawable.lianxiren_5, "dehg","下次见");
                mList.add(lianxiren_5);
                chat lianxiren_6 = new chat(i, R.drawable.lianxiren_6, "xbsk","哈哈哈哈");
                mList.add(lianxiren_6);
                chat lianxiren_7 = new chat(i, R.drawable.lianxiren_7, "wygdq","带纸了吗");
                mList.add(lianxiren_7);
                chat lianxiren_8 = new chat(i, R.drawable.lianxiren_8, "dekw","周末出去吗");
                mList.add(lianxiren_8);
                chat lianxiren_9 = new chat(i, R.drawable.lianxiren_9, "hweyqk","可以呀");
                mList.add(lianxiren_9);
                chat lianxiren_10 = new chat(i, R.drawable.lianxiren_10, "dbjehg","没事");
                mList.add(lianxiren_10);

            }
        }


}

写main_activity2.xml文件

这部分文件可以按照喜好写新的布局，这里的布局和item的布局一样。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="#ffffff">
    <!--左侧的图片布局盒子-->
    <LinearLayout
        android:id="@+id/ll_1"
        android:layout_width="wrap_content"
        android:layout_height="125dp"
        android:gravity="center">
        <ImageView
            android:id="@+id/item_img"
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:layout_margin="10dp"
            android:src="@drawable/lianxiren_1"
            android:background="#DFDFDF"/>
    </LinearLayout>
    <!--右侧文字盒子布局-->
    <LinearLayout
        android:id="@+id/ll_2_name"
        android:layout_width="match_parent"
        android:layout_height="125dp"
        android:orientation="vertical">
        <!--名字TextView所在盒子布局-->
        <LinearLayout
            android:id="@+id/ll_2_name1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:layout_marginBottom="10dp">

            <TextView
                android:id="@+id/item_name"
                android:layout_width="190dp"
                android:layout_height="25dp"
                android:text="ckbxb"
                android:textSize="20sp"
                android:textColor="#000000" />
        </LinearLayout>

        <LinearLayout
            android:id="@+id/ll_2_message"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp">

            <TextView
                android:id="@+id/item_message"
                android:layout_width="190dp"
                android:layout_height="25dp"
                android:text="天气挺好"
                android:textSize="20sp"
                android:textColor="#000000" />
        </LinearLayout>
    </LinearLayout>
</LinearLayout>

其余的注意事项

在manifests里要加入

        <activity
            android:name=".MainActivity2" />

对Activity的周期的理解

我们将mainactivity的生命周期注释消掉

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_main);
        initView();
        initEvent();
        initFragment();
        selectfragment(0);
//        Log.d("生命周期", "oncreate1");
    }

//    @Override
//    protected void onStart() {
//        super.onStart();
//        Log.d("生命周期","onstart1");
//    }
//
//    @Override
//    protected void onPause() {
//        super.onPause();
//        Log.d("生命周期","onpause1");
//    }
//
//    @Override
//    protected void onResume() {
//        super.onResume();
//        Log.d("生命周期","onresume1");
//    }
//
//    @Override
//    protected void onRestart() {
//        super.onRestart();
//        Log.d("生命周期","onrestart1");
//    }
//
//    @Override
//    protected void onStop() {
//        super.onStop();
//        Log.d("生命周期","onstop1");
//    }
//
//    @Override
//    protected void onDestroy() {
//        super.onDestroy();
//        Log.d("生命周期","ondestroy1");
//    }
}

我们在logcat中观察activity的生命周期
（oncreate1为mainactivity的启动，oncreate为mainactivity2的启动）

Activity的七种状态总结及演示

onCreate: Activity的创建他的生命周期的开始也是唯一一个必须要传入参数的(参数一般是默认的。)
onStart：当程序执行到这里是Activity才能被用户所看见
onResume：当程序执行到这里当前Activity才可以响应用户的点击事件
onPause：程序执行到这里Activity为可见状态或者透明状态但是不可操作
onStop：Activity处于后台挂起状态
onRestart：当程序从后台重新调用就会执行到这里
onDestroy：Activity已经被销毁

1.先在安卓上找到mywork的app点击
Activity1先创建——开始——展示
在这里插入图片描述
2.点击第一个item进行跳转
Activity1此时暂停了——创建Activity2——Activity2开始——Activity2展示——Activity1停止