ContentProvider内容提供者和ContentResolver内容访问者

提供者的demo代码：

MyProvider.java

package com.zking.provider;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.Log;
import com.zking.db.DBHelper;
import android.database.sqlite.SQLiteDatabase;
/**
 * Created by Administrator on 2017/7/18 0018.
 */

public class MyProvider 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");
        //把数据查询出来
        DBHelper dbHelper=new DBHelper(getContext(),"G160618.db",null,2);
        SQLiteDatabase sqLiteDatabase=dbHelper.getReadableDatabase();
        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;
    }
}

DBHelper.java

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

/**
 * Created by Administrator on 2017/7/18 0018.
 */

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","创建表");
        db.execSQL("create table login(uid integer primary key autoincrement,uname,upass)");
    }

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

配置

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.g160628_16_widget">

    <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.example.g160628_16_widget.zhongzi"
            android:name="com.zking.provider.MyProvider"
            android:exported="true"
            ></provider>
    </application>

</manifest>

访问者的demo代码：

在这里我就直接在后台测试了，所以我们需要改动的只有一个类

MainActivity类：

package com.example.g160628_25_contentresolver;

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);

        //获取第16次课的数据
        //获取内容访问者
        ContentResolver cr=getContentResolver();
        //必须加content协议
        Uri uri=Uri.parse("content://com.example.g160628_16_widget.zhongzi");
        Cursor cursor=cr.query(uri,null,null,null,null);
        while (cursor.moveToNext()){
            String uname=cursor.getString(cursor.getColumnIndex("uname"));
            Log.i("test",uname);
        }

    }
}