三 类微信界面

一、作业内容
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、请自建一个provider，然后在另一个app中使用resolver调用这个provider。

3、本次作业请启用新项目，理论上需要两个APP进行实验。

二、作业目标
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。

三、作业内容
1、首先先创建两个项目，provider和resovler

2、provider中的内容

MainActivity

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

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

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,"lxDB",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

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,"lyr",null,1);
        database=dBhelper.getReadableDatabase();
    }

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

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

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,"lxDB",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;
    }
}

3、resovler中的内容
MainActivity

package com.example.resolver;

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","lyr");
        values.put("age",20);

        Uri uri=Uri.parse("content://lyr.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>