android 学习随笔二十一（内容提供者 ）

Posted 2020-08-14

一、内容提供者
* 应用的数据库是不允许其他应用访问的
* 内容提供者的作用就是让别的应用访问到你的私有数据
* 自定义内容提供者，继承ContentProvider类，重写增删改查方法，在方法中写增删改查数据库的代码，举例增方法

@Override
public Uri insert(Uri uri, ContentValues values) {
db.insert("person", null, values);
return uri;
}
* 在清单文件中定义内容提供者的标签，注意必须要有authorities属性，这是内容提供者的主机名，功能类似地址

<provider android:name="com.itheima.contentprovider.PersonProvider"
android:authorities="com.itheima.person"
android:exported="true"
></provider>

package com.itheima.mycontentprovider.db;

import java.io.Serializable;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Parcelable;

public class MyOpenHelper extends SQLiteOpenHelper {

    public MyOpenHelper(Context context) {
        super(context, "people.db", null, 2);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table person(_id integer primary key autoincrement, name char(10), phone char(20), money integer(10))");
        
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("create table handsome(_id integer primary key autoincrement, name char(10), phone char(20))");
    }

}

定义数据库

package com.itheima.mycontentprovider;

import com.itheima.mycontentprovider.db.MyOpenHelper;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

public class PersonProvider extends ContentProvider {

    private SQLiteDatabase db;
    //创建uri匹配器
    UriMatcher um = new UriMatcher(UriMatcher.NO_MATCH);
    {
        //添加匹配规则
        //arg0:主机名
        //arg1:路径
        //arg2:匹配码
        um.addURI("com.itheima.people", "person", 1);//content://com.itheima.people/person
        um.addURI("com.itheima.people", "handsome", 2);//content://com.itheima.people/handsome
        um.addURI("com.itheima.people", "person/#", 3);//content://com.itheima.people/person/10
    }
    
    //内容提供者创建时调用
    @Override
    public boolean onCreate() {
        MyOpenHelper oh = new MyOpenHelper(getContext());
        db = oh.getWritableDatabase();
        return false;
    }

    //values:其他应用要插的数据
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        if(um.match(uri) == 1){
            db.insert("person", null, values);
            
            //数据库改变了,内容提供者发出通知
            //arg0:通知发到哪个uri上，注册在这个uri上的内容观察者都可以收到通知
            getContext().getContentResolver().notifyChange(uri, null);
        }
        else if(um.match(uri) == 2){
            db.insert("handsome", null, values);
            
            getContext().getContentResolver().notifyChange(uri, null);
        }
        else{
            throw new IllegalArgumentException("uri传错啦傻逼");
        }
        return uri;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int i = 0;
        if(um.match(uri) == 1){
            i = db.delete("person", selection, selectionArgs);
        }
        else if(um.match(uri) == 2){
            i = db.delete("handsome", selection, selectionArgs);
        }
        else{
            throw new IllegalArgumentException("uri又传错啦傻逼");
        }
        
        return i;
    }
    
    @Override
    public int update(Uri uri, ContentValues values, String selection,
            String[] selectionArgs) {
        int i = db.update("person", values, selection, selectionArgs);
        return i;
    }
    
    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
            String[] selectionArgs, String sortOrder) {
        Cursor cursor = null;
        if(um.match(uri) == 1){
            cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder, null);
        }
        else if(um.match(uri) == 2){
            cursor = db.query("handsome", projection, selection, selectionArgs, null, null, sortOrder, null);
        }
        else if(um.match(uri) == 3){
            //取出uri末尾携带的数字
            long id = ContentUris.parseId(uri);
            cursor = db.query("person", projection, "_id = ?", new String[]{"" + id}, null, null, sortOrder, null);
        }
        return cursor;
    }
    
    //返回通过指定uri获取的数据的mimetype
    @Override
    public String getType(Uri uri) {
        if(um.match(uri) == 1){
            return "vnd.android.cursor.dir/person";
        }
        else if(um.match(uri) == 2){
            return "vnd.android.cursor.dir/handsome";
        }
        else if(um.match(uri) == 3){
            return "vnd.android.cursor.item/person";
        }
        return null;
    }

    

}

内容提供者

package com.itheima.mycontentprovider;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

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


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    
}

MainActivity

package com.itheima.mycontentprovider;

import com.itheima.mycontentprovider.db.MyOpenHelper;

import android.test.AndroidTestCase;

public class Test extends AndroidTestCase {

    public void test(){
        MyOpenHelper oh = new MyOpenHelper(getContext());
        oh.getWritableDatabase();
    }
}

test

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.itheima.mycontentprovider"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />
<instrumentation android:name="android.test.InstrumentationTestRunner"
    android:targetPackage="com.itheima.mycontentprovider"></instrumentation>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        
        <uses-library android:name="android.test.runner"/>
        <activity
            android:name="com.itheima.mycontentprovider.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
        <provider 
            android:name="com.itheima.mycontentprovider.PersonProvider"        
            android:authorities="com.itheima.people"
            
            android:exported="true"
>
        </provider>
    </application>

</manifest>

AndroidManifest

 

* 创建一个其他应用，访问自定义的内容提供者，实现对数据库的插入操作

public void click(View v){
//得到内容分解器对象
ContentResolver cr = getContentResolver();
ContentValues cv = new ContentValues();
cv.put("name", "小方");
cv.put("phone", 138856);
cv.put("money", 3000);
//url:内容提供者的主机名
cr.insert(Uri.parse("content://com.itheima.person"), cv);
}

package com.itheima.other;

import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.view.Menu;
import android.view.View;

public class MainActivity extends Activity {

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

    public void insert(View v){
        //通过内容提供者把数据插入01数据库
        //1.获取contentResolver
        ContentResolver resolver = getContentResolver();
        //2.访问内容提供者，插入数据
        ContentValues values = new ContentValues();
        values.put("name", "流氓润");
        values.put("phone", 138992);
        values.put("money", 14000);
        //arg0:指定内容提供者的主机名
        resolver.insert(Uri.parse("content://com.itheima.people/person"), values);
        
        values.clear();
        values.put("name", "侃哥");
        values.put("phone", 15999);
        //arg0:指定内容提供者的主机名
        resolver.insert(Uri.parse("content://com.itheima.people/handsome"), values);
    }
    
    public void delete(View v){
        ContentResolver resolver = getContentResolver();
        int i = resolver.delete(Uri.parse("content://com.itheima.people"), "name = ?", new String[]{"凤姐"});
        System.out.println(i);
    }
    
    public void update(View v){
        ContentResolver resolver = getContentResolver();
        ContentValues values = new ContentValues();
        values.put("money", 16001);
        int i = resolver.update(Uri.parse("content://com.itheima.people"), values, "name = ?", new String[]{"春晓"});
        System.out.println(i);
    }
    
    public void query(View v){
        ContentResolver resolver = getContentResolver();
        Cursor cursor = resolver.query(Uri.parse("content://com.itheima.people/person"), null, null, null, null);
        while(cursor.moveToNext()){
            String name = cursor.getString(1);
            String phone = cursor.getString(2);
            String money = cursor.getString(3);
            System.out.println(name + ";" + phone + ";" + money);
        }
    }
    public void queryOne(View v){
        ContentResolver resolver = getContentResolver();
        Cursor cursor = resolver.query(Uri.parse("content://com.itheima.people/person/4"), null, null, null, null);
        if(cursor.moveToNext()){
            String name = cursor.getString(1);
            String phone = cursor.getString(2);
            String money = cursor.getString(3);
            System.out.println(name + ";" + phone + ";" + money);
        }
    }
}

View Code

 

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