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ContentProvider内容提供者与ContentResolver内容访问者

程序员文章站 2024-02-09 18:01:58
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1.   ContentProvider的概念解析:

            android官方指出数据存储的方式:Shared Preferences,网络存储,文件存储,外储存储,SQLite

            这些存储都只是在单独的一个应用程序之中达到一个数据的共享。当我们操作其他应用程序的

            一些数据,如操作系统里的媒体库,通讯录等,这时要通过ContentProvider来满足我们的要求。

    小知识:

       ContentProvider为存储和获取数据提供了统一的接口。对数据进行封装,不用关心数据存储的细节。

       使用表的形式来组织数据。

       使用ContentProvider 可以在不同的应用程序共享数据

       android为常见的一些数据提供了默认ContentProvider(音频,视频,图片,通讯录等)

 

2. Uri介绍

     为系统的每一个资源给其一个名字,比方说通话记录

每个ContentProvider都拥有一个公共的URI,这个URI用于表示这个ContentProvider所提供的数据


3.ContentResolver是对ContentProvider所提供的数据访问

4.运用:

package com.zking.db;

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

/**
 * Created by Administrator on 2017/7/17 0017.
 */

public class DBHelper extends SQLiteOpenHelper{
    public DBHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
        Log.i("test","构造方法");

    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        Log.i("test","onCreate");
        db.execSQL("create table login(uname,upass)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.i("test","更新版本");
    }
}

package com.zking.sqlite;

import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.zking.db.DBHelper;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        DBHelper dbHelper=new DBHelper(this,"login.db",null,1);
        SQLiteDatabase sqLiteDatabase=dbHelper.getWritableDatabase();
        //添加
        for (int i = 1; i <=5 ; i++) {
            sqLiteDatabase.execSQL("insert into login(uname,upass) values('言"+i+"','12"+i+"')");
        }

    }
}

package com.zking.contentprovider;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.Log;

import com.zking.db.DBHelper;

/**
 * Created by Administrator on 2017/7/17 0017.
 */

public class SQLContentProvider extends ContentProvider{
    @Override
    public boolean onCreate() {
        Log.i("test","onCreate");
        return false;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
        Log.i("test","query");
        DBHelper dbHelper=new DBHelper(getContext(),"login.db",null,1);
        SQLiteDatabase sqLiteDatabase=dbHelper.getWritableDatabase();
        return sqLiteDatabase.rawQuery("select * from login",null);
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        Log.i("test","getType");
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
        Log.i("test","insert");
        return null;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        Log.i("test","delete");
        return 0;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
        Log.i("test","update");
        return 0;
    }
}

配置:

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

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

                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        
        <provider
            android:authorities="com.zking.sqlite.LOGIN"
            android:name="com.zking.contentprovider.SQLContentProvider"
            android:exported="true"></provider>
    </application>

</manifest>

调用数据

package com.zking.contentprovider;

import android.content.ContentResolver;
import android.database.Cursor;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

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

        //获取内容访问者
        ContentResolver contentResolver=getContentResolver();
        Uri uri=Uri.parse("content://com.zking.sqlite.LOGIN");
        Cursor cursor=contentResolver.query(uri,null,null,null,null);
        while (cursor.moveToNext()){
            String uname=cursor.getString(cursor.getColumnIndex("uname"));
            String upass=cursor.getString(cursor.getColumnIndex("upass"));
            Log.i("test",uname+"\t\t\t:"+upass);
        }


    }
}