ContentProvider

内容的提供者（ContentProvider）

1.作用：
    暴露本应用的私有数据，供其他应用使用。通过继承ContentProvider。

有选择地暴露插入、删除、修改和查询本应用数据的接口。

2.使用：
    继承ContentProvider抽象类，并选择性地增删改查方法

需要在清单文件中配置
authorities为包名
name为继承ContentProvider的那个类

 <!--配置内容提供者-->
        <provider
            android:authorities="com.zking.administrator.g160618_android16_sqlite.LOGIN"
            android:name=".MyProvider"
            android:exported="true"
            ></provider>

内容访问者(ContentResolver)

1. 作用
访问内容提供者，并解析返回的数据

2. 使用
通过上下文对象获取内容解析者

ContentResolver resolver = this.getContentResolver();

下面举一个实例，只在调用，操作时打印结果。

新建一个Moudle：

新建一个db连接数据库的包DBHelper

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 2017/6/27 0027. */public class DBHelper extends SQLiteOpenHelper {    /**     *     * @param context   上下文     * @param name       数据库名字(文件名)     * @param factory   数据库工厂  :null     * @param version    数据库版本     */    public DBHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);        Log.i("test","构造方法");    }    //创建表    @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");    }//    @Override//    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {//        super.onDowngrade(db, oldVersion, newVersion);//    }}

在activity_main.xml中这样写

<?xml version="1.0" encoding="utf-8"?><LinearLayout    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"    android:orientation="vertical"    tools:context="com.zking.administrator.g160618_android16_sqlite.MainActivity">    <EditText        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="用户名："        android:id="@+id/et_main_uname"        />    <EditText        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="密码："        android:id="@+id/et_main_upass"        />    <Button        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="操作"        android:onClick="operation"        /></LinearLayout>

然后在与xml相对应的java代码中MainActivity添加数据到数据库中

package com.zking.administrator.g160618_android16_sqlite;import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.EditText;import android.widget.Toast;import com.zking.db.DBHelper;public class MainActivity extends AppCompatActivity {    private EditText et_main_uname;    private EditText et_main_upass;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        et_main_uname = (EditText) findViewById(R.id.et_main_uname);        et_main_upass = (EditText) findViewById(R.id.et_main_upass);    }    public void operation(View view){        String uname=et_main_uname.getText().toString();        String upass=et_main_upass.getText().toString();        DBHelper dbHelper=new DBHelper(this,"G160618.db",null,2);        SQLiteDatabase sqLiteDatabase=dbHelper.getWritableDatabase();        //添加1        for (int i = 0; i <100 ; i++) {            sqLiteDatabase.execSQL("insert into login(uname,upass) values('"+uname+i+"','"+upass+"')");        }        //添加2//        ContentValues values=new ContentValues();//        values.put("uname",uname);//        values.put("upass",upass);//        values.putNull("uid");//        sqLiteDatabase.insert("login","uname",values);        //删除        //sqLiteDatabase.delete("login","uid=?",new String[]{102+""});        //修改//        ContentValues values=new ContentValues();//        values.put("uname",uname);//        values.put("upass",upass);//        sqLiteDatabase.update("login",values,"uid=?",new String[]{101+""});        //查询所有        int pageNo=2;    //第一页        int pageSize=5;  //每页5条        //minus//        Cursor cursor=sqLiteDatabase.rawQuery("select * from login limit ?,?",new String[]{((pageNo-1)*pageSize)+"",pageSize+""});//        while(cursor.moveToNext()){//            int uid=cursor.getInt(cursor.getColumnIndex("uid"));//            String name=cursor.getString(cursor.getColumnIndex("uname"));//            String pass=cursor.getString(cursor.getColumnIndex("upass"));//            Log.i("test",uid+" "+name+" "+pass);//        }        Toast.makeText(this, "OK", Toast.LENGTH_SHORT).show();    }}

新建java MyProvider文件把内容提供出去

package com.zking.administrator.g160618_android16_sqlite;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 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();        //sqLiteDatabase.rawQuery("select * from login",null);        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;    }}

最后在xml里面对内容提供者进行配置，加上这样一句代码

 <!--配置内容提供者-->        <provider            android:authorities="com.zking.administrator.g160618_android16_sqlite.LOGIN"            android:name=".MyProvider"            android:exported="true"            ></provider>

然后再新建一个Moudle对提供的内容进行访问

在MainActivity中对内容进行访问

package com.zking.administrator.g160618_android25_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16次课的数据        //获取内容访问者        ContentResolver cr=getContentResolver();        Uri uri=Uri.parse("content://com.zking.administrator.g160618_android16_sqlite.LOGIN");        Cursor cursor=cr.query(uri,null,null,null,null);        while(cursor.moveToNext()){           int uid=cursor.getInt(cursor.getColumnIndex("uid"));            String uname=cursor.getString(cursor.getColumnIndex("uname")) ;            String upass=cursor.getString(cursor.getColumnIndex("upass")) ;            Log.i("test",uid+" "+uname+" "+upass);        }    }}