Simple Android weather app (III) -- city management and database operation

Easy Android weather app( One )—— analysis Json data 、 Data class encapsulation
Easy Android weather app( Two )—— Adapter 、 Hourly data display
Easy Android weather app( 3、 ... and )—— city management 、 Database operation

demand ️

When we look at the weather , We all have our own mobile phones , We all know that today's smart phones can automatically query the weather information of the location according to the location , This depends on the location function of the mobile phone , The project here is purely for practicing , It does not involve positioning operations , I gave up all those steps , So we can sneak around with this function ,,, incorrect , Opportunistic from the weather api Try to get the interface .（ See the end of the page for the source code ）

The weather used in this project api Interface The weather api
See Chapter 1 for details -->🧿 Easy Android weather app（ One ）—— analysis Json data <--

When we default not to splice parameters for this interface , Direct access will get the temperature of the current location Json data , This makes up for our shortcomings in positioning , So good , When we add parameters （ this api According to the parameters of city query, you need ＋&city=( The city name )） that , When we add only parameters but no parameter values （&city=） He will still position himself according to his current position , It's wonderful .
So the next step is Android SQLite Some operations of the database , Save the current location information to the database （ City name , City temperature , Update time ）
To be achieved ：

The database successfully inserts the current location data information （ In the previous test, a test reference data from Beijing was inserted ）：
The information of location Shangqiu has been successfully inserted , After insertion , The subsequent operation is to update the database in real time

Contents involved

• SQLite Database operation , Create database , new table , Add, delete, check and change operations
• Adapter adapter Add click event
• Page value transfer jump

Project structure

Other contents are not involved for the time being , This article only covers urban management , A series of operations to add cities to the database, etc , The previous basic content moves to the top address

Interface design

Interface design of urban management city_manager.xml

city_manager.xml Interface layout source code ：

<?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="@mipmap/bg" android:orientation="vertical">

    <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginTop="5dp" android:orientation="horizontal">

        <ImageView android:id="@+id/iv_add" android:layout_width="35dp" android:layout_height="30dp" android:layout_marginLeft="20dp" android:src="@drawable/add" />

        <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:gravity="center" android:text=" city management " android:layout_gravity="center" android:layout_weight="1" android:textColor="@color/purple_200" android:textSize="20dp" />

        <ImageView android:id="@+id/iv_more" android:layout_width="35dp" android:layout_height="30dp" android:layout_marginRight="20dp" android:src="@drawable/more" />
    </LinearLayout>

    <View android:layout_width="390dp" android:layout_height="8px" android:layout_gravity="center" android:layout_marginBottom="5dp" android:alpha="0.6" android:background="@color/white" />

    <androidx.recyclerview.widget.RecyclerView android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/city_manager"/>

</LinearLayout>

added_city.xml The page represents the city data to be displayed ：

Source code ：

<?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="55dp" android:textSize="20sp" android:layout_marginLeft="40dp" android:layout_marginRight="40dp" android:layout_marginTop="5dp" android:background="@drawable/blackground" android:gravity="center_vertical" android:paddingLeft="10dp" >

    <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal">
        <TextView android:layout_width="220dp" android:layout_height="wrap_content" android:id="@+id/city_city" android:layout_marginLeft="10dp" android:textSize="22dp" android:textColor="@color/white" android:text=" Xi'an " />
        <TextView android:layout_width="wrap_content" android:layout_height="match_parent" android:text="16°C" android:textSize="24dp" android:textColor="@color/white" android:id="@+id/city_tem"/>


    </LinearLayout>

</LinearLayout>

The effect of getting information from the database ：

Adapter AddCityAdapter

After the interface layout design is completed, the next step is the adapter AddCityAdapter
public class AddCityAdapter extends RecyclerView.Adapter<AddCityAdapter.AddViewHolder>

The adapter is the one that determines this city management page RecyclerView Which page is displayed in , Same as before , The previous articles all have space to summarize , Some basic operations are ,
Add a constructor ,

	private Context mContext;
    private List<CityBean> mCityBeans;

    public AddCityAdapter(Context context, List<CityBean> cityBeans) {
    
        mContext = context;
        this.mCityBeans = cityBeans;
    }

Create a class class AddViewHolder extends RecyclerView.ViewHolder To bind the control , At this point, click a city on the city management page , The value needs to be transferred to MainActivity, And get the weather information of the designated city
So add a click event to the adapter , First, add an interface to the adapter

	public interface OnItemClickListener {
    

        /** *  When RecyclerView Call back when a certain item is clicked  * @param view  Click on item The view of  * @param position  Click to get the data , Parameter customization  */
        public void onItemClick(View view, int position);

    }

    private OnItemClickListener onItemClickListener;

    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
    
        this.onItemClickListener = onItemClickListener;
    }

Then the class in the adapter AddViewHolder Bind click event in

	class AddViewHolder extends RecyclerView.ViewHolder {
    

        TextView cityCity,cityTem;// City name , temperature 

        public AddViewHolder(@NonNull View itemView) {
    
            super(itemView);
            // Binding controls 
            cityCity=itemView.findViewById(R.id.city_city);
            cityTem = itemView.findViewById(R.id.city_tem);
            // Bind click event 
            itemView.setOnClickListener(new View.OnClickListener() {
    
                @Override
                public void onClick(View view) {
    
                    if (onItemClickListener!=null) {
    
                        onItemClickListener.onItemClick(view,getLayoutPosition());
                    }
                }
            });
        }
    }

Then, as always, rewrite the three methods

	@NonNull
    @Override
    public AddViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    
    	// Binding controls , Which page is displayed in RecyclerView in ,R.layout.added_city
        View view = LayoutInflater.from(mContext).inflate(R.layout.added_city, parent, false);
        AddViewHolder cityViewHolder = new AddViewHolder(view);
        return cityViewHolder;
    }

    @Override
    public void onBindViewHolder(@NonNull AddViewHolder holder, int position) {
    
        CityBean cityBean = mCityBeans.get(position);
        // Control 
        holder.cityCity.setText(cityBean.getName());
        holder.cityTem.setText(cityBean.getTem());
    }

    @Override
    public int getItemCount() {
    
        return (mCityBeans == null) ? 0 : mCityBeans.size();
    }

Adapter AddCityAdapter Source code ：

public class AddCityAdapter extends RecyclerView.Adapter<AddCityAdapter.AddViewHolder>{
    

    private Context mContext;
    private List<CityBean> mCityBeans;

    public AddCityAdapter(Context context, List<CityBean> cityBeans) {
    
        mContext = context;
        this.mCityBeans = cityBeans;
    }

    @NonNull
    @Override
    public AddViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    
        View view = LayoutInflater.from(mContext).inflate(R.layout.added_city, parent, false);
        AddViewHolder cityViewHolder = new AddViewHolder(view);
        return cityViewHolder;
    }

    @Override
    public void onBindViewHolder(@NonNull AddViewHolder holder, int position) {
    
        CityBean cityBean = mCityBeans.get(position);

        holder.cityCity.setText(cityBean.getName());
        holder.cityTem.setText(cityBean.getTem());
    }

    @Override
    public int getItemCount() {
    
        return (mCityBeans == null) ? 0 : mCityBeans.size();
    }

    class AddViewHolder extends RecyclerView.ViewHolder {
    

        TextView cityCity,cityTem;

        public AddViewHolder(@NonNull View itemView) {
    
            super(itemView);

            cityCity=itemView.findViewById(R.id.city_city);
            cityTem = itemView.findViewById(R.id.city_tem);

            // Bind click event 
            itemView.setOnClickListener(new View.OnClickListener() {
    
                @Override
                public void onClick(View view) {
    
                    if (onItemClickListener!=null) {
    
                        onItemClickListener.onItemClick(view,getLayoutPosition());
                    }
                }
            });
        }
    }
    /** *  Click to respond to the event  */
    public interface OnItemClickListener {
    

        /** *  When RecyclerView Call back when a certain item is clicked  * @param view  Click on item The view of  * @param position  Click to get the data  */
        public void onItemClick(View view, int position);

    }

    private OnItemClickListener onItemClickListener;

    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
    
        this.onItemClickListener = onItemClickListener;
    }
}

Operating the database

Then build the database tools , To operate the database , General methods need entity classes , Then there is the encapsulation of urban entity classes , When obtaining the current positioning weather information , Save this data class to the database
So first build the urban entity class CityBean

public class CityBean {
    

    private String name;// The city name 
    private String[] area;// county / District 
    private String tem;// temperature 
    private String updateTime;// Update time 

// Constructor customization , It mainly focuses on database operation and new Time transmission value 
    public CityBean() {
    
    }

    public CityBean(String name) {
    
        this.name = name;
    }

    public CityBean(String name, String tem, String updateTime) {
    
        this.name = name;
        this.tem = tem;
        this.updateTime = updateTime;
    }
//get and set、toString notes 
    
}

Then there is the database CityDatabaseConfig, There is a database name , Table name information , In case the operation database writes the wrong name , So it is written under this configuration ：

public class CityDatabaseConfig {
    
    // Database name 
    public static final String DATABASE_NAME = "cityDb";
    // Table name 
    public static final String TABLE_NAME = "city_weather";
}

And then there was CityDbHelper Inherited from SQLiteOpenHelper

public class CityDbHelper extends SQLiteOpenHelper {
    

    public CityDbHelper(Context context) {
    
    	// Create database CityDatabaseConfig.DATABASE_NAME
        super(context, CityDatabaseConfig.DATABASE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
    
    // Create table , Field (cityName text,tem text,updateTime text)
        String sql = "create table if not exists "+CityDatabaseConfig.TABLE_NAME+"(cityName text,tem text,updateTime text)";
        db.execSQL(sql);
        Log.i(CityDatabaseConfig.DATABASE_NAME,"created success!!");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    

        Log.i(CityDatabaseConfig.DATABASE_NAME,"updated success!!");
    }

}

Then there are some database operation tools , There are some methods that can be used , You can expand it by yourself

public class DBUtils {
    

    private Context context;
    private CityDbHelper helper;

    /** *  The singleton pattern  * @param context */
    public DBUtils(Context context) {
    
        this.context = context;
        helper = new CityDbHelper(context) {
    
        };
    }

    /** *  Insert... Into the table  * * @param * @return */
    public boolean insertData(String cityName,String tem,String updateTime) {
    
        SQLiteDatabase db = helper.getReadableDatabase();
        ContentValues values = new ContentValues();

        values.put("cityName", cityName);
        values.put("tem", tem);
        values.put("updateTime", updateTime);
        long insert = db.insert(CityDatabaseConfig.TABLE_NAME, null, values);
        if (insert > 0) {
    
            return true;
        }
        return false;
    }

// Update data according to city name 
    public boolean updateByName(String cityName,String tem,String updateTime){
    
        SQLiteDatabase db = helper.getReadableDatabase();
        ContentValues values = new ContentValues();

        values.put("cityName", cityName);
        values.put("tem", tem);
        values.put("updateTime", updateTime);
        long update = db.update(CityDatabaseConfig.TABLE_NAME,values,"cityName=?", new String[]{
    cityName});

        if (update>0){
    
            return true;
        }return false;
    }

    /** *  Query all the information  * * @return */
    public List<CityBean> getAllCity() {
    
        List<CityBean> list = new ArrayList<>();
        SQLiteDatabase db = helper.getReadableDatabase();
        Cursor cursor = db.rawQuery("select * from " + CityDatabaseConfig.TABLE_NAME, null);
        if (cursor != null && cursor.getCount() > 0) {
    
            while (cursor.moveToNext()) {
    

                String cityName = cursor.getString(0);
                String tem = cursor.getString(1);
                String updateTime = cursor.getString(2);

                CityBean cityBean = new CityBean(cityName,tem,updateTime);
                list.add(cityBean);
            }
        }
        return list;
    }

    /** *  Query a message according to the city name  */
    public CityBean getCityByName(String cityName) {
    
        CityBean cityBean = new CityBean();
        SQLiteDatabase db = helper.getReadableDatabase();
        Cursor cursor = db.rawQuery("select * from " + CityDatabaseConfig.TABLE_NAME + " where cityName=?", new String[]{
    cityName});
        if (cursor != null && cursor.getCount() > 0) {
    
            while (cursor.moveToFirst()) {
    

                String cityNameResult = cursor.getString(0);
                cityBean.setName(cityName);
                break;
            }

        }
        return cityBean;

    }

	/** *  Delete a piece of data according to the city name  * @param cityName * @return */
    public boolean delCityByName(String cityName){
    
        SQLiteDatabase db = helper.getReadableDatabase();

        long delRow = db.delete(CityDatabaseConfig.TABLE_NAME, "cityName=?", new String[]{
    cityName});
        if (delRow > 0) {
    
            return true;
        }
        return false;

    }

}

Jump to the page , Display data

After some basic methods are written MainActivity.java file , use Intent Jump to the city management interface , Pay attention to introducing the database operation tool first

DBUtils dbUtils = new DBUtils(MainActivity.this);

Set the click event of the icon in the upper right corner , This dot icon is bound to ivMore

	ivMore.setOnClickListener(new View.OnClickListener() {
    
            @Override
            public void onClick(View view) {
    
                if (null == dbUtils.getCityByName(tvCity.getText().toString()).getName()) {
    
                    // If the database does not exist, insert this city 
                    dbUtils.insertData(tvCity.getText().toString(),tvTem.getText().toString(),tvTime.getText().toString());
                }
                else {
    
                    // Update when there is 
                    dbUtils.updateByName(tvCity.getText().toString(),tvTem.getText().toString(),tvTime.getText().toString());
// dbUtils.insertData(" Beijing ","30°C","2022-06-19 21:23:35"); Test use 
// dbUtils.delCityByName(" Shangqiu "); Test use 
                    List<CityBean> list = dbUtils.getAllCity();
                    Log.d("getAllCity", "allList<CityBean>>>>》》》" + list.toString());

                    ToastUtil.showShortToast(MainActivity.this, " The current position :" + tvCity.getText());
                    Intent intent = new Intent(MainActivity.this, CityManagerActivity.class);
                    Log.d("getNowCity", "nowCity<CityBean>>>>》》》" + tvCity.getText());
//  It is required to jump to the page and pass the value back ,requestCode：200;
                    startActivityForResult(intent, 200);
                }
            }
        });

Jump to the city management page , add to activity.java file , name CityManagerActivity

public class CityManagerActivity extends AppCompatActivity {
    

    private AddCityAdapter addCityAdapter;// Adapter 
    private RecyclerView rvAddedCity;

    private List<CityBean> cityDbBeanList;
    DBUtils dbUtils= new DBUtils(CityManagerActivity.this);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.city_manager);

        initView();
    }


    public void initView() {
    

        rvAddedCity = findViewById(R.id.city_manager);

        cityDbBeanList = dbUtils.getAllCity();
        Log.d("cityList",">>>>> Data in the database 》》》》》》"+cityDbBeanList);
        addCityAdapter = new AddCityAdapter(CityManagerActivity.this,cityDbBeanList);
        rvAddedCity.setAdapter(addCityAdapter);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        rvAddedCity.setLayoutManager(layoutManager);
		// Set click event 
        addCityAdapter.setOnItemClickListener(new AddCityAdapter.OnItemClickListener() {
    
            @Override
            public void onItemClick(View view, int position) {
    
// ToastUtil.showShotToast(CityManagerActivity.this, cityDbBeanList.get(position).getName());
                Intent intent = new Intent(CityManagerActivity.this,MainActivity.class);
                intent.putExtra("selectedCity",cityDbBeanList.get(position).getName());
				// return MainActivity Page and transfer values setResult(200,intent); Set up resultCode：200;
                setResult(200,intent);
                finish();

// ToastUtil.showShotToast(CityManagerActivity.this,"finish");
            }
        });
    }

}

Then, since the page is required to return the value ,MainActivity You have to rewrite the method onActivityResult Accept the incoming value

	@Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == 200 && resultCode == 200) {
    
        //getString Get the transmitted value 
            String dt = data.getExtras().getString("selectedCity");
            tvCity.setText(dt);
            nowCity=dt;
            // From again api Get the weather according to the city name 
            getWeather(nowCity);
            ToastUtil.showLongToast(this,dt+" Weather update ~");
        }
    }

Since then, some functions have been realized , Jump to the city management page , Exhibition City , Specify the city to display weather information ,

Database operation realizes ：

1. Get all the city information in the database 、
2. Insert a piece of data 、
3. Update data according to city name 、
4. Delete a piece of data to be completed ,, Self expanding , As long as the tool class deletion method is written correctly , Nothing more than adding an event to call the delete method

More refined search of cities , Actively add cities to the database according to the searched cities , Later articles will be gradually improved , This article is mainly about some database operations and adapter adding click events , Subscribe to this column to synchronously obtain the project construction process

Source code address ：Gitee