Android_U5_UI进阶作业实现思路

Android_U5_UI进阶作业实现思路

• 使用DAO的方式访问数据库

这次作业可以参考课本P158页的例子，实现起来也比课本习题简单，先按照SimpleAdapter实现试试，看看能否完成

老师要求效果：                                 自己实现的效果:

 

准备工作：改变这个安卓应用主题、编写xml布局

1. 打开清单文件修改主题和标题

<manifest xmlns:android="http://schemas.android.com/apk/res/android"     package="com.example.u5_homework">     <application         android:allowBackup="true"         android:icon="@mipmap/ic_launcher"         android:label="@string/app_name"         android:roundIcon="@mipmap/ic_launcher_round"         android:supportsRtl="true"         android:theme="@style/Theme.AppCompat.DayNight.DarkActionBar">         <activity android:name=".MainActivity" android:label="SaveInDatabase">             <intent-filter>                 <action android:name="android.intent.action.MAIN" />                 <category android:name="android.intent.category.LAUNCHER" />             intent-filter>         activity>     application> manifest>

 

1. 编写主布局及表项布局listview

activity_main.xml

xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:app="http://schemas.android.com/apk/res-auto"     xmlns:tools="http://schemas.android.com/tools"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical"     tools:context=".MainActivity"     android:padding="20dp">     <LinearLayout         android:layout_width="match_parent"         android:layout_height="wrap_content">         <TextView             android:layout_width="0dp"             android:layout_weight="1"             android:layout_height="match_parent"             android:textSize="16sp"             android:gravity=""             android:text="姓名:"             >TextView>         <EditText             android:id="@+id/et_name"             android:layout_width="0dp"             android:layout_weight="1"             android:layout_height="wrap_content">EditText>     LinearLayout>     <LinearLayout         android:layout_width="match_parent"         android:layout_height="wrap_content">         <TextView             android:layout_width="0dp"             android:layout_weight="1"             android:layout_height="match_parent"             android:gravity=""             android:textSize="16sp"             android:text="年龄:"             >TextView>         <EditText             android:id="@+id/et_age"             android:layout_width="0dp"             android:layout_weight="1"             android:layout_height="wrap_content">EditText>     LinearLayout>     <LinearLayout         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_gravity="center"         android:layout_marginTop="20dp"         android:padding="0dp"         android:orientation="horizontal">         <Button             android:id="@+id/bt_add"             android:layout_width="0dp"             android:layout_weight="1"             android:layout_height="wrap_content"             android:layout_marginRight="20dp"             android:text="存入"             >Button>         <Button             android:id="@+id/bt_del"             android:layout_width="0dp"             android:layout_weight="1"             android:layout_height="wrap_content"             android:text="清空数据库"             >Button>     LinearLayout>     <LinearLayout         android:orientation="horizontal" android:layout_width="match_parent"         android:layout_height="wrap_content">         <TextView             android:text="序号"             android:gravity="center"             android:id="@+id/tv_id"             android:layout_width="0dp"             android:layout_weight="1"             android:layout_height="wrap_content"             >         TextView>         <TextView             android:text="姓名"             android:gravity="center"             android:id="@+id/tvname"             android:layout_width="0dp"             android:layout_weight="2"             android:layout_height="wrap_content">TextView>         <TextView             android:text="年龄"             android:gravity="center"             android:id="@+id/tvage"             android:layout_width="0dp"             android:layout_weight="2"             android:layout_height="wrap_content">TextView>     LinearLayout>     <ListView         android:id="@+id/listView"         android:layout_width="match_parent"         android:layout_height="wrap_content">     ListView> LinearLayout>

List_item.xml

xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="horizontal" android:layout_width="match_parent"     android:layout_height="match_parent">     <TextView         android:id="@+id/tv_id"         android:layout_width="0dp"         android:layout_weight="1"         android:layout_height="wrap_content"         >     TextView>     <TextView         android:id="@+id/tvname"         android:layout_width="0dp"         android:layout_weight="2"         android:layout_height="wrap_content">TextView>     <TextView         android:id="@+id/tvage"         android:layout_width="0dp"         android:layout_weight="2"         android:layout_height="wrap_content">TextView> LinearLayout>

到此，准备工作完毕

1. 设计抽象类SQLiteOpenHelper的子类MyDbHelper,其代码如下：

public class MyDbHelper extends SQLiteOpenHelper {     public static final String TB_NAME = "users";     public MyDbHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {         super(context, name, factory, version);     }     @Override     public void onCreate(SQLiteDatabase db) {         db.execSQL("CREATE TABLE IF NOT EXISTS "+TB_NAME+"(_id integer primary key autoincrement,"+                 "name varchar,"+"age integer " + ")" );     }     @Override     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {         db.execSQL("DROP TABLE IF EXISTS "+TB_NAME);         onCreate(db);     } }

1. 封装对数据库增删改查的方法到MyDao中

本类MyDAO调用了打开数据库的助手类MyDbHelper

本类MyDAO提供对数据库test.db的表users的增删改查

查询数据库表所有记录的方法：allQuery()

插入记录的方法:insertInfo(String name,int age)

删除所有记录的方法deleteAllInfo()

public class MyDAO {     private SQLiteDatabase myDb;     private MyDbHelper dbHelper;     public MyDAO(Context context){         dbHelper = new MyDbHelper(context,"test.db",null,1);         myDb = dbHelper.getReadableDatabase();     }     public Cursor allQuery(){         return myDb.rawQuery("select * from users",null);     }     public int getRecordsNumber(){         return allQuery().getCount();     }     public void insertInfo(String name,int age){         myDb = dbHelper.getWritableDatabase();         ContentValues values = new ContentValues();         values.put("name",name);         values.put("age",age);         long rowid = myDb.insert(MyDbHelper.TB_NAME,null,values);         if (rowid==-1){             Log.i("myDbDemo","数据库插入失败！");         }else {             Log.i("myDbDemo","数据库插入成功！"+rowid);         }     }     public void deleteAllInfo(){         int i = myDb.delete(MyDbHelper.TB_NAME,null,null);         if (i>0){             Log.i("myDbDemo","数据删除成功！");         }else {             Log.i("myDbDemo","数据未删除");         }     } }

1. 编写MainActivity程序：

MainActivity中完成对数据库的插入和查询，使用了MyDAO类的相关方法

首次运行时，增加两条记录并使用ListView空间显示出来

public class MainActivity extends AppCompatActivity implements View.OnClickListener {     private MyDAO myDAO;     private ListView listView;     private List> listData;     private Map listItem;     private SimpleAdapter listAdapter;     private EditText et_name;     private EditText et_age;     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         Button bt_add = (Button)findViewById(R.id.bt_add);         bt_add.setOnClickListener(this);         Button bt_del = (Button)findViewById(R.id.bt_del);         bt_del.setOnClickListener(this);         et_name = (EditText)findViewById(R.id.et_name);         et_age = (EditText)findViewById(R.id.et_age);         myDAO = new MyDAO(this);         if (myDAO.getRecordsNumber()==0){//初始化一些表项布局             myDAO.insertInfo("xiaoming",20);             myDAO.insertInfo("wangqiang",23);         }         displayRecords();     }     private void displayRecords() {         listView = (ListView)findViewById(R.id.listView);         listData = new ArrayList>();         Cursor cursor = myDAO.allQuery();         while (cursor.moveToNext()){             int id = cursor.getInt(0);             String name = cursor.getString(1);             int age = cursor.getInt(cursor.getColumnIndex("age"));             listItem = new HashMap();//必须在循环体中新建             listItem.put("_id",id);             listItem.put("name",name);             listItem.put("age",age);             listData.add(listItem);         }         listAdapter = new SimpleAdapter(this,listData,R.layout.list_item,new String[]{"_id","name","age"},new int[]{R.id.tv_id,R.id.tvname,R.id.tvage});         listView.setAdapter(listAdapter);     }     @Override     public void onClick(View v) {         String p1 = et_name.getText().toString().trim();         String p2 = et_age.getText().toString().trim();         switch (v.getId()){             case R.id.bt_add:                 if (p1.equals("")||p2.equals("")){                     Toast.makeText(getApplicationContext(),"姓名和年龄不能为空",Toast.LENGTH_SHORT).show();                 }else {                     myDAO.insertInfo(p1,Integer.parseInt(p2));//第二个参数要转成符合数据库的类型                 }                 displayRecords();                 break;             case R.id.bt_del:                 myDAO.deleteAllInfo();                 displayRecords();                 break;         }     } }

如果想消除数据库表autoincrement的影响可以在MainActivity修改此处代码，即可实现每次都是从序号1开始递增