LitePal+RecyclerView简单实现记事本

学了一段时间的Android，准备写一个简单的记事本练练手，本程序使用了litepal+recyclerview+一点Material Design中的界面设计，但由于本人审美水平原因，可能设计得不是很好看。

先上效果图：

添加依赖：

    implementation 'com.android.support:design:29.1.1'
    implementation 'androidx.recyclerview:recyclerview:1.1.0'
    implementation 'androidx.cardview:cardview:1.0.0'
    implementation 'org.litepal.android:java:3.0.0'

建立数据库

用litepal建立数据库，具体步骤我就不多说了，可以参考我上一条博客，这里就直接上代码

litepal.xml

Tickler.java这里在com.example.tickler目录下新建一个db文件夹

package com.example.tickler.db;

import org.litepal.crud.LitePalSupport;

public class Tickler extends LitePalSupport {

    private int id;
    private String content;
    private String time;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }
}

主页面代码及布局

先看主页面得布局activity_main.xml
这里用了加强版的帧布局：CoordinatorLayout，它可以解决在底部弹出消息时覆盖住了悬浮按钮的问题，然后就是Toolbar代替系统自带标题栏,还有下面的recyclerview和悬浮按钮的设置，由于是加强的帧布局，所有的控件都会在左上角，会造成recyclerview遮住toolbar的问题，这里用AppBarLayout让recyclerview下移一个toolbar的高度。

MainActivity.java

package com.example.tickler;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.Intent;

import android.os.Bundle;

import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;

import com.example.tickler.db.Tickler;
import com.google.android.material.floatingactionbutton.FloatingActionButton;

import org.litepal.LitePal;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainActivity extends AppCompatActivity {

    private List> contentList=new ArrayList>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar=(Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        FloatingActionButton addContent=(FloatingActionButton) findViewById(R.id.add_tickler);
        addContent.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(MainActivity.this,AddContentActivity.class);
                startActivity(intent);
            }
        });
    }

    public boolean onCreateOptionsMenu(Menu menu){
        getMenuInflater().inflate(R.menu.main_toolbar,menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        Toast.makeText(MainActivity.this,"敬请期待!",Toast.LENGTH_SHORT).show();
        return true;
    }

    @Override
    protected void onStart() {//每次活动有不可见变可见时调用
        super.onStart();
        contentList.clear();//清空list子项数据，实现刷新list
        initContent();//初始化
        RecyclerView recyclerView=(RecyclerView) findViewById(R.id.recycler_view);
        LinearLayoutManager layoutManager=new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        ContentAdapter adapter=new ContentAdapter(contentList);
        recyclerView.setAdapter(adapter);
        adapter.notifyDataSetChanged();
    }

    public void initContent(){
        List ticklers= LitePal.order("id desc").find(Tickler.class);
        for(Tickler tickler:ticklers){
            String content=tickler.getContent();
            String time=tickler.getTime();
            Map map=new HashMap();
            map.put("content",content);
            map.put("time",time);
            contentList.add(map);
        }
    }
}

main_toolbar.xml在res目录下新建一个文件夹menu

recyclerview的子项布局content_item.xml

recyclerview的适配器ContentAdapter.java

package com.example.tickler;

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

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

import java.util.List;
import java.util.Map;

public class ContentAdapter extends RecyclerView.Adapter {

    private List> mContentList;

    static class ViewHolder extends RecyclerView.ViewHolder{
        View ticklerView;
        TextView contentText;
        TextView showTime;

        public ViewHolder(View view){
            super(view);
            ticklerView=view;
            contentText=(TextView) view.findViewById(R.id.show_content);
            showTime=(TextView) view.findViewById(R.id.show_time);
        }
    }

    public ContentAdapter(List> contentList){
        mContentList=contentList;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull final ViewGroup parent, int viewType) {

        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.content_item,parent,false);
        //设置子项点击事件，并传递数据到添加页
        final ViewHolder holder=new ViewHolder(view);
        holder.ticklerView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int position=holder.getAdapterPosition();
                String content=mContentList.get(position).get("content");
                String time=mContentList.get(position).get("time");
                Intent intent=new Intent(parent.getContext(),AddContentActivity.class);
                intent.putExtra(AddContentActivity.CONTENT,content);
                intent.putExtra(AddContentActivity.TIME,time);
                parent.getContext().startActivity(intent);
            }
        });
        return holder;
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        holder.contentText.setText(mContentList.get(position).get("content"));
        holder.showTime.setText(mContentList.get(position).get("time"));
    }

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

添加数据页面代码及布局

activity_add_content.xml

AddContentActivity.java

package com.example.tickler;

import androidx.annotation.NonNull;
import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.example.tickler.db.Tickler;

import org.litepal.LitePal;

import java.text.SimpleDateFormat;
import java.util.Date;

public class AddContentActivity extends AppCompatActivity{

    public static final String CONTENT="content";
    public static final String TIME="time";
    private String time;
    private EditText content;
    private TextView showTime;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_content);
        content=(EditText) findViewById(R.id.add_content);
        showTime=(TextView) findViewById(R.id.time_show);
        Toolbar toolbar=(Toolbar) findViewById(R.id.toolbar_1);
        setSupportActionBar(toolbar);
        ActionBar actionBar=getSupportActionBar();
        if(actionBar!=null){//显示系统返回按钮
            actionBar.setDisplayHomeAsUpEnabled(true);
        }

        //取得内容和时间
        Intent intent=getIntent();
        time=intent.getStringExtra(TIME);
        String showContent=intent.getStringExtra(CONTENT);
        showTime.setText(time);
        content.setText(showContent);
        if(showContent!=null) {
            content.setSelection(showContent.length());//将光标移动到文本最后
        }
    }

    //配置菜单项设置点击事件
    public boolean onCreateOptionsMenu(Menu menu){
        getMenuInflater().inflate(R.menu.toolbar,menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()){
            case R.id.save_content:
                //判断当前操作是新增还是修改
                if(time!=null){
                    String inputText=content.getText().toString();
                    Tickler tickler=new Tickler();
                    tickler.setContent(inputText);
                    tickler.updateAll("time=?",time);
                    finish();
                    break;
                }else {
                    //取得新增记录时的系统时间
                SimpleDateFormat simpleDateFormat=new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
                Date date=new Date(System.currentTimeMillis());
                String inputText=content.getText().toString();
                Tickler tickler=new Tickler();
                tickler.setContent(inputText);
                tickler.setTime(simpleDateFormat.format(date));
                tickler.save();
                Toast.makeText(this,"保存成功",Toast.LENGTH_SHORT).show();
                finish();//操作完成结束当前活动
                break;}

            case R.id.delete:

                //删除操作
                String deleteContent=content.getText().toString();
                LitePal.deleteAll(Tickler.class,"content=?",deleteContent);
                finish();
                break;

            case android.R.id.home://一定添加android还有下面这行代码，我当时为这搞了半天
                onBackPressed();
                return true;
                default:
        }
        return true;
    }
}

菜单布局toolbar.xml

主要的代码就是这些，附上源码：
链接：https://pan.baidu.com/s/1XszlojQGSLsn2pPM_XaoJA
提取码：g3zw