写在前面
课程作业需要，于是忙活好几天抄了一个简单的记事本，使用已学内容包括Android UI布局，Activity的跳转，SQLite数据库。
开发环境：Android Studio
目录
一.界面预览
- 主界面
- 编辑界面
- 长按删除
二.基本实现
- 布局实现代码
初始界面功能，最上方标题下为用户创建的各条记录，点击进行修改，长按删除，最下方有添加笔记按钮进行笔记的增加操作。实现的布局文件有初始界面activity_main.xml（里面包含可以以列表的形式展示数据内容的ListView控件）、note_item（ListView对应的item布局，以显示每个条目信息）、note_editor（新建文本编辑界面）、activity_show（文本修改界面）
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#eaeaea"
android:orientation="vertical"
tools:context=".MainActivity" >
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Notepad"
android:textSize="20sp"
android:textStyle="bold"
android:background="#efdede"
android:paddingTop="10dp"
android:paddingBottom="5dp"
android:paddingLeft="10dp"
android:gravity="left">
</TextView>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#eaeaea"
android:layout_weight="1">
<ListView
android:id="@+id/lv_note"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="5dp">
</ListView>
</LinearLayout>
<Button
android:id="@+id/btn_add"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:layout_marginBottom="10dp"
android:textSize="20sp"
android:text="添加笔记"/>
</LinearLayout>note_item.xml
<?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="match_parent"
android:orientation="vertical">
<TextView
android:id="@+id/tv_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:lines="1"
android:text=""
android:textStyle="bold"
android:textAppearance="?android:attr/textAppearanceLarge"/>
<TextView
android:id="@+id/tv_content"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:lines="1"/>
<TextView
android:id="@+id/tv_time"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:text="" />
</LinearLayout>
note_editor.xml
<?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="match_parent"
android:background="#eaeaea"
android:orientation="vertical">
<EditText
android:id="@+id/et_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入标题">
<requestFocus />
</EditText>
<TextView
android:id="@+id/edit_time"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#d7d5d5"
android:gravity="right"
android:textSize="10sp"/>
<EditText
android:id="@+id/et_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:hint="请输入内容"
android:gravity="left"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center">
<Button
android:id="@+id/btn_save"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginBottom="10dp"
android:text="保存"
android:textSize="20sp"/>
<Button
android:id="@+id/btn_cancel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginBottom="10dp"
android:text="取消"
android:textSize="20sp"/>
</LinearLayout>
</LinearLayout>
activity_show.xml
<?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="match_parent"
android:orientation="vertical">
<EditText
android:id="@+id/show_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:hint="标题">
<requestFocus />
</EditText>
<TextView
android:id="@+id/show_time"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="right"
android:textSize="10sp"/>
<EditText
android:id="@+id/show_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:hint="内容"
android:gravity="left"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center">
<Button
android:id="@+id/show_save"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginBottom="10dp"
android:text="保存"
android:textSize="20sp"/>
<Button
android:id="@+id/show_cancel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginBottom="10dp"
android:text="取消"
android:textSize="20sp"/>
</LinearLayout>
</LinearLayout>
- 功能实现
首先SQLite数据库的创建。新建一个DBService类继承自SQLiteOpenHelper,设置静态常量属性，表名、id、标题、内容、创建时间。
DBService.java
package zut.edu.cn.notepad;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DBService extends SQLiteOpenHelper {
public static final String TABLE = "notes";
public static final String ID = "_id";
public static final String TITLE ="title";
public static final String CONTENT = "content";
public static final String TIME = "time";
public DBService(Context context) {
super(context,"notepad.db",null,1);
}
@Override
public void onCreate(SQLiteDatabase db) {
String sql = "CREATE TABLE "+TABLE+"( "+ID+
" INTEGER PRIMARY KEY AUTOINCREMENT, "+
TITLE +" VARCHAR(30) ,"+
CONTENT + " TEXT , "+
TIME + " DATETIME NOT NULL )";
db.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
MainActivity.java
package zut.edu.cn.notepad;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
DBService myDb;
private Button mBtnAdd;
private ListView lv_note;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//实例化自己创建的数据库类
myDb = new DBService(this);
//初始化函数
init();
}
public void init(){
mBtnAdd = findViewById(R.id.btn_add);
lv_note = findViewById(R.id.lv_note);
//创建Values类型的list保存数据库中的数据
List<Values> valuesList = new ArrayList<>();
//获得可读SQLiteDatabase对象
SQLiteDatabase db = myDb.getReadableDatabase();
//查询数据库中的数据
Cursor cursor = db.query(DBService.TABLE,null,null,
null,null,null,null);
if(cursor.moveToFirst()){
Values values;
while (!cursor.isAfterLast()){
//实例化values对象
values = new Values();
//把数据库中的一个表中的数据赋值给values
values.setId(Integer.valueOf(cursor.getString(cursor.getColumnIndex(DBService.ID))));
values.setTitle(cursor.getString(cursor.getColumnIndex(DBService.TITLE)));
values.setContent(cursor.getString(cursor.getColumnIndex(DBService.CONTENT)));
values.setTime(cursor.getString(cursor.getColumnIndex(DBService.TIME)));
//将values对象存入list对象数组中
valuesList.add(values);
cursor.moveToNext();
}
}
cursor.close();
db.close();
//设置list组件adapter
final MyBaseAdapter myBaseAdapter = new MyBaseAdapter(valuesList,this,R.layout.note_item);
lv_note.setAdapter(myBaseAdapter);
//按钮点击事件
mBtnAdd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, zut.edu.cn.notepad.EditActivity.class);
startActivity(intent);
}
});
//单击查询
lv_note.setOnItemClickListener(new AdapterView.OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(MainActivity.this,ShowActivity.class);
Values values = (Values) lv_note.getItemAtPosition(position);
intent.putExtra(DBService.TITLE,values.getTitle().trim());
intent.putExtra(DBService.CONTENT,values.getContent().trim());
intent.putExtra(DBService.TIME,values.getTime().trim());
intent.putExtra(DBService.ID,values.getId().toString().trim());
startActivity(intent);
}
});
//长按删除
lv_note.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
final Values values = (Values) lv_note.getItemAtPosition(position);
new AlertDialog.Builder(MainActivity.this)
.setTitle("提示框")
.setMessage("是否删除?")
.setPositiveButton("yes",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
SQLiteDatabase db = myDb.getWritableDatabase();
db.delete(DBService.TABLE,DBService.ID+"=?",new String[]{String.valueOf(values.getId())});
db.close();
myBaseAdapter.removeItem(position);
lv_note.post(new Runnable() {
@Override
public void run() {
myBaseAdapter.notifyDataSetChanged();
}
});
//MainActivity.this.onResume();
}
})
.setNegativeButton("no",null).show();
return true;
}
});
}
//创建继承自BaseAdapter的实现类进行ListView的展示
class MyBaseAdapter extends BaseAdapter{
private List<Values> valuesList;
private Context context;
private int layoutId;
public MyBaseAdapter(List<Values> valuesList, Context context, int layoutId) {
this.valuesList = valuesList;
this.context = context;
this.layoutId = layoutId;
}
@Override
public int getCount() {
if (valuesList != null && valuesList.size() > 0)
return valuesList.size();
else
return 0;
}
@Override
public Object getItem(int position) {
if (valuesList != null && valuesList.size() > 0)
return valuesList.get(position);
else
return null;
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder;
if (convertView == null) {
convertView = LayoutInflater.from(
getApplicationContext()).inflate(R.layout.note_item, parent,
false);
viewHolder = new ViewHolder();
viewHolder.title = (TextView) convertView.findViewById(R.id.tv_title);
viewHolder.content = convertView.findViewById(R.id.tv_content);
viewHolder.time = (TextView) convertView.findViewById(R.id.tv_time);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
String title = valuesList.get(position).getTitle();
String content = valuesList.get(position).getContent();
viewHolder.title.setText(title);
viewHolder.content.setText(content);
viewHolder.time.setText(valuesList.get(position).getTime());
return convertView;
}
public void removeItem(int position){
this.valuesList.remove(position);
}
}
class ViewHolder{
TextView title;
TextView content;
TextView time;
}
}
Values.java
Values类实现对数据的保存
package zut.edu.cn.notepad;
public class Values {
private Integer id;
private String title;
private String content;
private String time;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
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;
}
@Override
public String toString() {
return "Values{" +
"id=" + id +
", title='" + title + '\'' +
", content='" + content + '\'' +
", time='" + time + '\'' +
'}';
}
}
Edit_Activity.java
package zut.edu.cn.notepad;
import android.content.ContentValues;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import java.text.SimpleDateFormat;
import java.util.Date;
public class EditActivity extends AppCompatActivity {
DBService myDb;
private Button btnCancel;
private Button btnSave;
private EditText titleEditText;
private EditText contentEditText;
private TextView timeTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.note_editor);
init();
if(timeTextView.getText().length()==0)
timeTextView.setText(getTime());
}
private void init() {
myDb = new DBService(this);
SQLiteDatabase db = myDb.getReadableDatabase();
titleEditText = findViewById(R.id.et_title);
contentEditText = findViewById(R.id.et_content);
timeTextView = findViewById(R.id.edit_time);
btnCancel = findViewById(R.id.btn_cancel);
btnSave = findViewById(R.id.btn_save);
//按钮点击事件
btnCancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(EditActivity.this,MainActivity.class);
startActivity(intent);
}
});
btnSave.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = myDb.getWritableDatabase();
ContentValues values = new ContentValues();
String title= titleEditText.getText().toString();
String content=contentEditText.getText().toString();
String time= timeTextView.getText().toString();
if("".equals(titleEditText.getText().toString())){
Toast.makeText(EditActivity.this,"标题不能为空",Toast.LENGTH_LONG).show();
return;
}
if("".equals(contentEditText.getText().toString())) {
Toast.makeText(EditActivity.this,"内容不能为空",Toast.LENGTH_LONG).show();
return;
}
values.put(DBService.TITLE,title);
values.put(DBService.CONTENT,content);
values.put(DBService.TIME,time);
db.insert(DBService.TABLE,null,values);
Toast.makeText(EditActivity.this,"保存成功",Toast.LENGTH_LONG).show();
Intent intent = new Intent(EditActivity.this,MainActivity.class);
startActivity(intent);
db.close();
}
});
}
//获取当前时间
private String getTime() {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date = new Date(System.currentTimeMillis());
String str = sdf.format(date);
return str;
}
}
ShowActivity
package zut.edu.cn.notepad;
import android.annotation.SuppressLint;
import android.content.ContentValues;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import java.text.SimpleDateFormat;
import java.util.Date;
public class ShowActivity extends AppCompatActivity {
private Button btnSave;
private Button btnCancel;
private TextView showTime;
private EditText showContent;
private EditText showTitle;
private Values value;
DBService myDb;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show);
init();
}
public void init() {
myDb = new DBService(this);
btnCancel = findViewById(R.id.show_cancel);
btnSave = findViewById(R.id.show_save);
showTime = findViewById(R.id.show_time);
showTitle = findViewById(R.id.show_title);
showContent = findViewById(R.id.show_content);
Intent intent = this.getIntent();
if (intent != null) {
value = new Values();
value.setTime(intent.getStringExtra(DBService.TIME));
value.setTitle(intent.getStringExtra(DBService.TITLE));
value.setContent(intent.getStringExtra(DBService.CONTENT));
value.setId(Integer.valueOf(intent.getStringExtra(DBService.ID)));
showTime.setText(value.getTime());
showTitle.setText(value.getTitle());
showContent.setText(value.getContent());
}
//按钮点击事件
btnSave.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = myDb.getWritableDatabase();
ContentValues values = new ContentValues();
String content = showContent.getText().toString();
String title = showTitle.getText().toString();
values.put(DBService.TIME, getTime());
values.put(DBService.TITLE,title);
values.put(DBService.CONTENT,content);
db.update(DBService.TABLE,values,DBService.ID+"=?",new String[]{value.getId().toString()});
Toast.makeText(ShowActivity.this,"修改成功",Toast.LENGTH_LONG).show();
db.close();
Intent intent = new Intent(ShowActivity.this,MainActivity.class);
startActivity(intent);
}
});
btnCancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final String content = showContent.getText().toString();
final String title = showTitle.getText().toString();
new AlertDialog.Builder(ShowActivity.this)
.setTitle("提示框")
.setMessage("是否保存当前内容?")
.setPositiveButton("yes",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
SQLiteDatabase db = myDb.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(DBService.TIME, getTime());
values.put(DBService.TITLE,title);
values.put(DBService.CONTENT,content);
db.update(DBService.TABLE,values,DBService.ID+"=?",new String[]{value.getId().toString()});
Toast.makeText(ShowActivity.this,"修改成功",Toast.LENGTH_LONG).show();
db.close();
Intent intent = new Intent(ShowActivity.this,MainActivity.class);
startActivity(intent);
}
})
.setNegativeButton("no",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Intent intent = new Intent(ShowActivity.this,MainActivity.class);
startActivity(intent);
}
}).show();
}
});
}
String getTime() {
@SuppressLint("SimpleDateFormat")
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy年MM月dd日 HH:mm");
//获取当前时间
Date date = new Date(System.currentTimeMillis());
return simpleDateFormat.format(date);
}
}
偷偷地写在最后
基本实现就是以上了，还有很多地方不太完善，希望能够从一次一次的实践当中学习到更多的东西。
曾经沧海难为水，除却巫山不是云。
源码已上传：github.Notepad
参考博客：https://blog.csdn.net/zouguo1211/article/details/83474845