安卓开发之内容提供者案例

创建私有数据库

package com.lidaochen.test001;

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

public class MyOpenHelper extends SQLiteOpenHelper {
    public MyOpenHelper(Context context)
    {
        super(context, "lidaochen.db", null, 1);
    }

    // 表结构的初始化
    @Override
    public void onCreate(SQLiteDatabase db)
    {
        db.execSQL("create table info(_id integer primary key autoincrement,name varchar(20),money varchar(20))");
        db.execSQL("insert into info(name,money) values(?,?)", new String[]{"张三", "5000"});
        db.execSQL("insert into info(name,money) values(?,?)", new String[]{"李四", "3000"});
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
    {

    }
}

package com.lidaochen.test001;

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

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MyOpenHelper myOpenHelper = new MyOpenHelper(getApplicationContext());
        // 获取数据库对象
        SQLiteDatabase db = myOpenHelper.getReadableDatabase();
        Cursor cursor = db.query("info", null, null, null, null, null, null);
        if (cursor != null && cursor.getCount() > 0)
        {
            while (cursor.moveToNext())
            {
                String name = cursor.getString(1);
                String phone = cursor.getString(2);
                System.out.println("name：" + name + "--------" + phone);
            }
        }
    }
}

package com.lidaochen.test001;

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

public class AccountProvider extends ContentProvider {
    private MyOpenHelper myOpenHelper;
    private static final int QUERYSUCCESS = 0;
    private static final int INSERTSUCCESS = 1;
    private static final int UPDATESUCCESS = 2;
    private static final int DELETESUCCESS = 3;
    // 定义路径匹配器
    private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    // 定义静态代码块 添加匹配原则
    static
    {
        sURIMatcher.addURI("com.lidaochen.provider", "query", QUERYSUCCESS);
        sURIMatcher.addURI("com.lidaochen.provider", "insert", INSERTSUCCESS);
        sURIMatcher.addURI("com.lidaochen.provider", "update", UPDATESUCCESS);
        sURIMatcher.addURI("com.lidaochen.provider", "delete", DELETESUCCESS);
    }

    public AccountProvider() {
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs)
    {
        int code = sURIMatcher.match(uri);
        if (code == DELETESUCCESS)
        {
            SQLiteDatabase db =myOpenHelper.getReadableDatabase();
            // 代表影响的行数
            int delete = db.delete("info", selection, selectionArgs);
            // 关闭数据库
            db.close();
            if (delete > 0)
            {
                getContext().getContentResolver().notifyChange(uri, null);
            }
            return delete;
        }
        else
        {
            throw new IllegalArgumentException("您的路径不匹配，请检查路径！");
        }
    }

    @Override
    public String getType(Uri uri) {
        // TODO: Implement this to handle requests for the MIME type of the data
        // at the given URI.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public Uri insert(Uri uri, ContentValues values)
    {
        int code = sURIMatcher.match(uri);
        if (code == INSERTSUCCESS)
        {
            // 获取数据库对象
            SQLiteDatabase db = myOpenHelper.getReadableDatabase();
            // 返回值代表新插入行数的ID
            long insert = db.insert("info", null, values);
            // 关闭数据库
            db.close();
            if (insert > 0)
            {
                // 发送一条消息 说明数据库发生了改变
                getContext().getContentResolver().notifyChange(uri, null);
            }
            Uri uri2 = Uri.parse("com.lidaochen.insert/" + insert);
            return uri2;
        }
        else
        {
            throw new IllegalArgumentException("您的路径不匹配，请检查路径！");
        }
    }

    @Override
    public boolean onCreate() {
        myOpenHelper = new MyOpenHelper(getContext());
        return false;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)
    {
        int code = sURIMatcher.match(uri);
        if (code == QUERYSUCCESS)
        {
            // 说明路径匹配成功  把query方法给实现   数据库的查询方法  对数据库进行查询的操作
            // 获取数据库对象
            SQLiteDatabase db = myOpenHelper.getReadableDatabase();
            // 这里需要注意 cursor 不能关闭
            Cursor cursor = db.query("info", projection, selection ,selectionArgs, null, null, sortOrder);
            // 数据库被人操作了 自己发送一条信息
            getContext().getContentResolver().notifyChange(uri, null);
            return cursor;
        }
        else
        {
            throw new IllegalArgumentException("您的路径不匹配，请检查路径！");
        }
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs)
    {
        int code = sURIMatcher.match(uri);
        if (code == UPDATESUCCESS)
        {
            SQLiteDatabase db = myOpenHelper.getReadableDatabase();
            int update = db.update("info", values, selection, selectionArgs);
            // 关闭数据库
            db.close();
            if (update > 0)
            {
                getContext().getContentResolver().notifyChange(uri, null);
            }
            return update;
        }
        else
        {
            throw new IllegalArgumentException("您的路径不匹配，请检查路径！");
        }
    }
}

读取上面应用创建的数据库

package com.lidaochen.test002;

import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

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

    // 对数据库进行增加一条记录
    public void click1(View v)
    {
        Uri uri = Uri.parse("content://com.lidaochen.provider/insert");
        ContentValues values = new ContentValues();
        values.put("name", "王五");
        values.put("money", 1000);
        Uri insert = getContentResolver().insert(uri, values);
        System.out.println("insert：" + insert);
    }

    // 对数据库进行删除一条记录
    public void click2(View v)
    {
        Uri uri = Uri.parse("content://com.lidaochen.provider/delete");
        int delete = getContentResolver().delete(uri, "name=?", new String[]{"王五"});
        Toast.makeText(getApplicationContext(), "删除了第" + delete + "行", Toast.LENGTH_SHORT).show();
    }

    // 对数据库进行修改一条记录
    public void click3(View v)
    {
        Uri uri = Uri.parse("content://com.lidaochen.provider/update");
        ContentValues values = new ContentValues();
        values.put("money", 999);
        int update = getContentResolver().update(uri, values, "name=?", new String[]{"李四"});
        Toast.makeText(getApplicationContext(), "更新了第" + update + "行", Toast.LENGTH_SHORT).show();
    }

    // 对数据库进行查找一条记录
    public void click4(View v)
    {
        // 由于 第一个应用里面的私有数据库已经通过内容提供者给暴露出来了 所以可以直接通过内容的解析者进行访问
        // 通过上下文获取内容的解析者
        // 路径和你定义的路径是一样的
        Uri uri = Uri.parse("content://com.lidaochen.provider/query");
        Cursor cursor = getContentResolver().query(uri, null, null, null, null);
        if (cursor != null && cursor.getCount() > 0)
        {
            while (cursor.moveToNext())
            {
                String name = cursor.getString(1);
                String phone = cursor.getString(2);
                System.out.println("第二个应用name: " + name + "------" + phone);
            }
        }
    }
}