ContentProvider

• ContentProvider是什么
• ContentResolver是什么
• URI是什么，标准格式是什么
• UriMatcher是什么
• 如何使用ContentProvider

ContentProvider是什么

• ContentProvider是Android四大组件之一
• ContentProvider是一种数据包装器，它提供统一的接口对数据进行操作，调用者不用关心数据到底是如何存储的
• ContentProvider主要用于不同应用程序间，不同进程间的数据共享

ContentResolver是什么

• ContentResolver是数据调用者，ContentProvider将数据发布出来后，通过ContentResolve对象结合URI进行调用
• 通过ContentResolver可以调用ContentProvider的增、删、改、查操作

URI是什么，标准格式是什么

• 通用资源标识符（Universal Resource Identifier）简称Uri

• URI代表要操作数据的地址，每个ContentProvider发布数据时都有一个唯一的地址
  标准格式：content://com.android.contacts/contacts

  UriMatcher是什么

• 用于匹配URI的URI规则工具类

• 当调用者传递过来URI时，我们需要对URI进行解析，确定调用者需要执行哪个操作

  如何使用ContentProvider

package com.example.a17708.pratice;

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

public class SQLiteHelper extends SQLiteOpenHelper{
    private String sql="create table student("+
            "id integer primary key autoincrement not null,"+
            "name text,"+
            "age integer"+
            ")";
    public SQLiteHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL(sql);

    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }
}

package com.example.17708.myapplication;

import android.content.ContentResolver;
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.Button;
import android.widget.EditText;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.List;

public class ProviderActivity extends AppCompatActivity implements View.OnClickListener{
    private Uri uri;
    private ContentResolver contentResolver;

    private EditText stuage_et, stuname_et;
    private ListView stu_lv;
    private SQLiteAdapter adapter;
    private Button add_button, search_button, update_button, delete_button;

    private List<SQLiteStu> sqLiteStuList=new ArrayList<>();

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

        stuAge_et = findViewById(R.id.stuAge_et);
        stuName_et = findViewById(R.id.stuName_et);

        add_button = findViewById(R.id.add_button);
        add_button.setOnClickListener(this);

        search_button = findViewById(R.id.search_button);
        search_button.setOnClickListener(this);

        update_button = findViewById(R.id.update_button);
        update_button.setOnClickListener(this);

        delete_button = findViewById(R.id.delete_button);
        delete_button.setOnClickListener(this);

        stu_lv=findViewById(R.id.stu_lv);

        uri=Uri.parse("content://com.example.practiceapplication.sqlite.StudentProvider");
        contentResolver=getContentResolver();

    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.search_button:
                sqLiteStuList.clear();

                Cursor cursor=contentResolver.query(uri,new String[]{"id","name","age"},null,null,null);

                cursor.moveToFirst();

                    do {
                        int id = cursor.getInt(cursor.getColumnIndex("id"));
                        String name = cursor.getString(cursor.getColumnIndex("name"));
                        String age = cursor.getString(cursor.getColumnIndex("age"));

                        SQLiteStu sqLiteStu = new SQLiteStu(id, name, age);
                        sqLiteStuList.add(sqLiteStu);
                        adapter = new SQLiteAdapter(this, sqLiteStuList);

                        stu_lv.setAdapter(adapter);

                    } while (cursor.moveToNext());


                break;
            case R.id.add_button:
                String age1= stuAge_et.getText().toString();
                String name1=stuName_et.getText().toString();

                ContentValues values=new ContentValues();
                values.put("name",name1);
                values.put("age",age1);

                contentResolver.insert(uri,values);
                break;
            case R.id.delete_button:
                String name2=stuName_et.getText().toString();
                String age2= stuAge_et.getText().toString();

                contentResolver.delete(uri,"name=? and age=?",new String[]{name2,age2});
                break;
            case R.id.update_button:
                String age3= stuAge_et.getText().toString();
                String name3=stuName_et.getText().toString();

                ContentValues contentValues=new ContentValues();
                contentValues.put("name","ycc");
                contentValues.put("age","20");

                contentResolver.update(uri,contentValues,"name=? and age=?",new String[]{name3,age3});
                break;
            default:
                break;
        }
    }
}