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);        }    }}