移动开发-使用contentprovider的方法类进行数据获取_android 如何获取三方contentprovider类

设计目标：

1、contentprovider是安卓四大组件之一，请使用其方法类进行数据获取；

2、自建一个provider，然后在另一个app中使用resolver调用这个provider；

3、理论上需要两个APP进行实验。

功能说明：

1、contentprovider主要用于在不同的应用程序之间实现数据共享的功能，它提供了一套完整的机制，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。

2、在本次实验中具体表现为以下效果，在第一个APP:contentprovide中可以切换访问第二个APP:resolver，resolver可以调用contentprovider。

代码展示：

项目provider：

MainActivity.java：

package com.example.provider;
 
import androidx.appcompat.app.AppCompatActivity;
 
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：（出现了构成它生命周期的几个方法，包括增、删、改、查、获得类型getType和创建onCreate，只需要在onCreate中传值并new一个MyDAO的方法即可。）

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：（数据处理层，需要在这里写一套真正在数据库上的增删改查。）

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,"JOJODB",null,1);
        database=dBhelper.getReadableDatabase();
    }
 
    public Uri DAOinsert(ContentValues contentValues){
        long rowid=database.insert("student",null,contentValues);
 
        Uri uri=Uri.parse("content://JOJO.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("JOJO","MyDBhelper...");
 
    }
 
    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL("create table student(" +
                "id integer primary key autoincrement,name varchar,age integer)");
        Log.d("JOJO","onCreate...");
 
    }
 
    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        Log.d("JOJO","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="JOJO.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：

package 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","JOJO");
        values.put("age",20);
 
        Uri uri=Uri.parse("content://JOJO.provider2/student");
 
        Button button = findViewById(R.id.button);
 
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                resolver.insert(uri,values);
            }
        });
    }
}

activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".MainActivity">
 
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="resovler"
        android:textSize="45dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.526"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.363" />
 
    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="insert"
        android:textSize="45dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.555"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.587" />
 
</androidx.constraintlayout.widget.ConstraintLayout>

效果展示：

运行进入resovler项目界面

点击INSETR按钮

在provider项目的数据库中增添信息

源码仓库： Lzr2002/LZR (github.com)