先上两张应用截图
编辑界面
删除一条记录时
此应用共包括2个activity 主界面列表显示所有便笺的MainActivity和添加一条便笺的编辑界面SecondActivity
MainActivity
主要使用一个listView显示数据库中所有便笺 并添加点击条目编辑 长按条目删除
代码如下
public class MainActivity extends AppCompatActivity {
private Button button;
private ListView listView;
private MyDataBase myDataBase;
private LayoutInflater layoutInflater;
private ArrayList<Note> arrayList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.listView1);
layoutInflater = getLayoutInflater();
myDataBase = new MyDataBase(this);
button = (Button) findViewById(R.id.button1);
arrayList = myDataBase.getArray();
MyAdapter myAdapter = new MyAdapter(layoutInflater,arrayList);
listView.setAdapter(myAdapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView,View view,int i,long l) {
Intent intent = new Intent(MainActivity.this,SecondActivity.class);
intent.putExtra("id",arrayList.get(i).getId());
startActivity(intent);
MainActivity.this.finish();
}
});
/** * 参数 parent 发生点击事件的 AbsListView。 view AbsListView 中被点击的视图。 position 视图在一览中的位置（索引）。 id 被点击条目的行 ID。 返回值 如果回调函数处理了长按事件，返回真；否则返回假。 */
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> adapterView,final int position,long l) {
new AlertDialog.Builder(MainActivity.this).setTitle("删除").setMessage("数据无价，谨慎操作!")
.setNegativeButton("关闭",new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface,int i) {
}
}).setPositiveButton("删除",new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface,int i) {
myDataBase.deleteNote(arrayList.get(position).getId());
arrayList = myDataBase.getArray();
MyAdapter myAdapter = new MyAdapter(layoutInflater,arrayList);
listView.setAdapter(myAdapter);
}
}).create().show();
return true;
}
});
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this,SecondActivity.class);
startActivity(intent);
MainActivity.this.finish();
}
});
}
###SecondActivity 实现新建和编辑一条便笺的功能
和主界面通过Intent进行交互 并保存到数据库中
代码如下
public class SecondActivity extends Activity{
Button save;
TextView textView1; //标题
TextView textView2; //内容
EditText title;
EditText content;
MyDataBase myDataBase;
Note note2; //第二个activity里面的note
int id;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
save=(Button)findViewById(R.id.save);
textView1=(TextView)findViewById(R.id.t1);
textView2=(TextView)findViewById(R.id.t2);
title=(EditText)findViewById(R.id.title2);
content=(EditText)findViewById(R.id.content2);
myDataBase=new MyDataBase(this);
id=getIntent().getIntExtra("id",0);
if(id!=0){
note2=myDataBase.getTitleandContent(id);
title.setText(note2.getTitle());
content.setText(note2.getContent());
}
save.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
isSave();
}
}
);
}
@RequiresApi(api = Build.VERSION_CODES.N)
@Override
public void onBackPressed() {
/* SimpleDateFormat simpleDateFormat= new SimpleDateFormat("yyyy.MM.dd HH:mm:ss");
*/Date currentDate=new Date(System.currentTimeMillis());//获取当前时间
String time=currentDate.toLocaleString();
//simpleDateFormat.format(currentDate);
String titles=title.getText().toString();
String contents=content.getText().toString();
//修改数据
if (id != 0) {
note2 = new Note( id,titles,contents,time);
myDataBase.toUpdate(note2);
Intent intent = new Intent(SecondActivity.this,MainActivity.class);
startActivity(intent);
SecondActivity.this.finish();
}
//新建文本
else {
note2 = new Note(titles,time);
myDataBase.toInsert(note2);
Intent intent = new Intent(SecondActivity.this,MainActivity.class);
startActivity(intent);
SecondActivity.this.finish();
}
}
private void isSave(){
java.text.SimpleDateFormat formatter = new java.text.SimpleDateFormat("yyyy.MM.dd HH:mm:ss");
Date curDate = new Date(System.currentTimeMillis());//获取当前系统时间
String times = formatter.format(curDate);
String titles=title.getText().toString();
String contents=content.getText().toString();
//修改数据
if (id!=0) {
note2 = new Note(id,times);
myDataBase.toUpdate(note2);
Intent intent = new Intent(SecondActivity.this,MainActivity.class);
startActivity(intent);
SecondActivity.this.finish();
}
//新建一条便笺
else {
if(titles!=null||contents!=null){
note2 = new Note(titles,times);
myDataBase.toInsert(note2);
}
Intent intent = new Intent(SecondActivity.this,MainActivity.class);
startActivity(intent);
SecondActivity.this.finish();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main,menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// TODO Auto-generated method stub
switch (item.getItemId()) {
case R.id.action_settings:
Intent intent = new Intent(Intent.ACTION_SEND);
intent.setType("text/plain");
intent.putExtra(Intent.EXTRA_TEXT,"标题" + title.getText().toString() + "内容" + content.getText().toString());
startActivity(intent);
break;
default:
break;
}
return false;
}
}
###数据库部分
MyDataBase 主要实现数据库的添加删除 修改 通过android提供的sqliteOpenHelper的自定义的子类MyDatabaseHelper实现对数据库的操作
MyDataBase代码
public class MyDataBase {
Context context;
sqliteDatabase sqliteDatabase;
MyDatabaseHelper myDatabaseHelper;
public MyDataBase(Context context){
this.context=context;
myDatabaseHelper=new MyDatabaseHelper(context);
}
public ArrayList getArray(){
ArrayList arrayList=new ArrayList();
ArrayList arrayList1=new ArrayList();
sqliteDatabase=myDatabaseHelper.getWritableDatabase();
//rawQuery()方法的第一个参数为select语句；
// 第二个参数为select语句中占位符参数的值，
// 如果select语句没有使用占位符，该参数可以设置为null。
Cursor cursor=sqliteDatabase.rawQuery(“select id,title,date from note”,null);
cursor.moveToFirst();
while (!cursor.isAfterLast()){
int id=cursor.getInt(cursor.getColumnIndex("id"));
String title=cursor.getString(cursor.getColumnIndex("title"));
String date=cursor.getString(cursor.getColumnIndex("date"));
Note note=new Note(id,date);
arrayList.add(note);
cursor.moveToNext();
}cursor.close();
sqliteDatabase.close();
for(int i=arrayList.size();i>0;i--){
arrayList1.add(arrayList.get(i-1));
}
return arrayList1;
//return arrayList;
}
//第二个activity用到的 标题+内容
public Note getTitleandContent( int id){
sqliteDatabase=myDatabaseHelper.getWritableDatabase();
Cursor cursor=sqliteDatabase.rawQuery("select title,content from note where id='"+id+"'",null);
cursor.moveToFirst();
String title=cursor.getString(cursor.getColumnIndex("title"));
String content =cursor.getString(cursor.getColumnIndex("content"));
Note note=new Note(title,content);
cursor.close();
return note;
}
//execsql(String sql,Object[] bindArgs)方法的第一个参数为sql语句，
// 第二个参数为sql语句中占位符参数的值，参数值在数组中的顺序要和占位符的位置对应。
// 修改数据
public void toUpdate(Note note){
sqliteDatabase =myDatabaseHelper.getWritableDatabase();
sqliteDatabase.execsql("update note set title='"+ note.getTitle()+"',date='"+note.getDate()+"',content='"+note.getContent() +"' where id='"+ note.getId()+"'");
sqliteDatabase.close();
}
//插入数据,新建一条便笺
public void toInsert(Note note){
sqliteDatabase=myDatabaseHelper.getWritableDatabase();
sqliteDatabase.execsql("insert into note(title,content,date) values('"+ note.getTitle()+"','"+note.getContent()+"','"+note.getDate()+"')");
sqliteDatabase.close();
}
//删除一条数据
public void deleteNote(int id){
sqliteDatabase=myDatabaseHelper.getWritableDatabase();
sqliteDatabase.execsql("delete from note where id=" + id+ "" );
sqliteDatabase.close();
}
}
MyDatabaseHelper代码如下:
public class MyDatabaseHelper extends sqliteOpenHelper {
private Context context;
public static final String CREATE_NOTE=”create table if not exists note (id integer primary key autoincrement,title text,content text,date text)”;
public MyDatabaseHelper(Context context) {
super(context,“note”,null,1);
this.context=context;
}
@Override public void onCreate(sqliteDatabase sqliteDatabase) { sqliteDatabase.execsql(CREATE_NOTE); } @Override public void onUpgrade(sqliteDatabase sqliteDatabase,int i,int j) { }
}
###下面是一些实体和工具类
Note`public class Note {
private String title;
private String content;
private int id;
private String date;
public Note(int id,String title,String content,String date){
this.content=content;
this.title=title;
this.date=date;
this.id=id;
}
public Note(int id,String date){
this.date=date;
this.title=title;
this.id=id;
}
public Note(String title,String content){
this.title=title;
this.content=content;
}
public Note(String title,String date) {
this.title=title;
this.date=date;
this.content=content;
}
public String getTitle(){
return title;
}
public String getContent(){
return content;
}
public int getId(){
return id;
}
public String getDate(){
return date;
}
}
adapter以及优化listView的viewHolder
public class MyAdapter extends BaseAdapter {
LayoutInflater layoutInflater;
ArrayList arrayList;
public MyAdapter(LayoutInflater layoutInflater,ArrayList arrayList){
this.arrayList=arrayList;
this.layoutInflater=layoutInflater;
}
@Override
public int getCount() {
return arrayList.size();
}
@Override
public Object getItem(int i) {
return arrayList.get(i);
}
@Override
public long getItemId(int i) {
return i;
}
@Override
public View getView(int i,ViewGroup viewGroup) {
ViewHolder viewHolder=new ViewHolder();
if(view==null){
view=layoutInflater.inflate(R.layout.adapter_listview,null);
viewHolder.textView1=(TextView)view.findViewById(R.id.textview1);
viewHolder.textView2=(TextView)view.findViewById(R.id.textview2);
view.setTag(viewHolder);
}
viewHolder=(ViewHolder)view.getTag();
viewHolder.textView1.setText(arrayList.get(i).getTitle());
viewHolder.textView2.setText(arrayList.get(i).getDate());
return view;
}
}
public class ViewHolder {
TextView textView1;
TextView textView2;
}
“`
