使用contentprovider的方法类进行数据获取

代码功能

contentprovider主要用于在不同的应用程序之间实现数据共享的功能，允许一个程序访问另一个程序中的数据，同时还能保证被访数据的安全性。

第一个APP:contentprovide中可以切换访问第二个APP:resolver，resolver可以调用contentprovider。

主要代码

provider项目

MainActivity.java

package com.example.provider;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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

        MyDAO myDAO=new MyDAO(this);
    }
}

MyContentProvider.java

package com.example.provider;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;

public class MyContentProvider extends ContentProvider {
    private MyDAO myDAO;
    public MyContentProvider() {

    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // Implement this to handle requests to delete one or more rows.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public String getType(Uri uri) {
        // TODO: Implement this to handle requests for the MIME type of the data
        // at the given URI.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // TODO: Implement this to handle requests to insert a new row.

        //getContext().getContentResolver().insert(uri, values);
        return  myDAO.DAOinsert(values);
    }

    @Override
    public boolean onCreate() {
        // TODO: Implement this to initialize your content provider on startup.
        Context context=getContext();
        myDAO=new MyDAO(context);
        return false;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        // TODO: Implement this to handle query requests from clients.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        // TODO: Implement this to handle requests to update one or more rows.
        throw new UnsupportedOperationException("Not yet implemented");
    }
}

MyDAO.java

package com.example.provider;

import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

public class MyDAO {
    private Context context;
    private SQLiteDatabase database;
    public MyDAO(Context context){
        this.context=context;

        MyDBhelper dBhelper =new MyDBhelper(context,"DB",null,1);
        database=dBhelper.getReadableDatabase();
    }

    public Uri DAOinsert(ContentValues contentValues){
        long rowid=database.insert("student",null,contentValues);

        Uri uri=Uri.parse("content://lx.provider2/student");
        Uri inserturi=ContentUris.withAppendedId(uri,rowid);
        context.getContentResolver().notifyChange(inserturi,null);
        return inserturi;
    }
}

MyDBhelper.java

package com.example.provider;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

import androidx.annotation.Nullable;

public class MyDBhelper extends SQLiteOpenHelper {
    public MyDBhelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
        Log.d("pxr","MyDBhelper...");

    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL("create table student(" +
                "id integer primary key autoincrement,name varchar,age integer)");
        Log.d("pxr","onCreate...");

    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        Log.d("pxr","onUpgrade...");

    }
}

Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.provider">

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.Provider"
        tools:targetApi="31">
        <provider
            android:name=".MyContentProvider"
            android:authorities="pxr.provider2"
            android:enabled="true"
            android:exported="true"></provider>

        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

resovler项目

MainActivity.java

spackage com.example.resovler;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentResolver;
import android.content.ContentValues;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

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

        ContentResolver resolver=getContentResolver();

        ContentValues values=new ContentValues();
        values.put("name","pxr");
        values.put("age",20);

        Uri uri=Uri.parse("content://lx.provider2/student");

        Button button = findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                resolver.insert(uri,values);
            }
        });
    }
}