ContentProvider&ContentResolver
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2024-02-09 16:50:16
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一.ContentProvider是什么
1.ContentProvider是Android四大组件之一
2.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
3.ContentProvider主要用于不同的应用程序间，不同进程间的数据共享
二.ContentResolver是什么
1.vContentResolver是数据调用者，ContentResolver数据发布出来后，通过ContentResolver对象结合Uri进行调用
2.通过ContentResolver可以调用ContentProvider的增删改查操作
三.URI是什么，标准格式是什么
URI是什么
1.通用资源标识符简称Uri
2.Uri代表操作数据的地址，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
content://:此部分是固定写法,用来表明这是一个Uri
com.android.contacts:此部分指定了要访问的资源的存放地址
contacts：此部分指定了要访问资源的路径
四.UriMatcher是什么
1.用于匹配Uri的Uri规则工具类
2.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
五.如何使用ContentProvider
我写的是一个学生表，有id,name,age,下面通过这个例子来体现如何使用ContentProvider
1.使用SQLite技术，创建好数据库和数据表
package com.example.practiceapplication.sqlite;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
/**
* Created by lyj on 2018/6/21.
*/
public class StuSQLiteHelper extends SQLiteOpenHelper{
private String sql="create table stu(" +
"id integer primary key autoincrement not null,"+
"name text," +
"age integer" +
")";
public StuSQLiteHelper(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) {
}
}2.新建类继承ContentProvider
会报错，第四步是解决方法
package com.example.practiceapplication.sqlite;
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;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
/**
* Created by lyj on 2018/6/21.
*/
public class StudentProvider extends ContentProvider {
}3.创建UriMatcher,定义Uri规则
private UriMatcher uriMatcher; {
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI("content://com.example.practiceapplication.sqlite.StudentProvider", "stu", 1);
uriMatcher.addURI("content://com.example.practiceapplication.sqlite.StudentProvider", "tea", 1);
}4.重写6个抽象方法
package com.example.practiceapplication.sqlite;
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;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
/**
* Created by lyj on 2018/6/21.
*/
public class StudentProvider extends ContentProvider {
private SQLiteDatabase sqLiteDatabase;
private StuSQLiteHelper stuSQLiteHelper;
private UriMatcher uriMatcher;
private Cursor cursor;
@Override
public boolean onCreate() {
stuSQLiteHelper = new StuSQLiteHelper(getContext(), "stu_db", null, 1);
return false;
}
{
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI("content://com.example.practiceapplication.sqlite.StudentProvider", "stu", 1);
uriMatcher.addURI("content://com.example.practiceapplication.sqlite.StudentProvider", "tea", 1);
}
@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] strings, @Nullable String s, @Nullable String[] strings1, @Nullable String s1) {
// switch (uriMatcher.match(uri)) {
// case 1:
cursor = sqLiteDatabase.query("stu", null, null, null, null, null, null);
//
// break;
// case 2:
// break;
// default:
// break;
//
// }
return cursor;
}
@Nullable
@Override
public String getType(@NonNull Uri uri) {
return null;
}
@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues contentValues) {
sqLiteDatabase = stuSQLiteHelper.getWritableDatabase();
long id = sqLiteDatabase.insert("stu", null, contentValues);
return ContentUris.withAppendedId(uri, id);
}
@Override
public int delete(@NonNull Uri uri, @Nullable String s, @Nullable String[] strings) {
sqLiteDatabase = stuSQLiteHelper.getWritableDatabase();
return sqLiteDatabase.delete("stu", s, strings);
}
@Override
public int update(@NonNull Uri uri, @Nullable ContentValues contentValues, @Nullable String s, @Nullable String[] strings) {
sqLiteDatabase = stuSQLiteHelper.getWritableDatabase();
return sqLiteDatabase.update("stu", contentValues, s, strings);
}
}
5.在AndroidManifest中注册provider
<provider
android:name=".sqlite.StudentProvider"
android:authorities="com.example.practiceapplication.sqlite.StudentProvider"
android:exported="true" />6.ContentResolver对ContentProvider共享的数据进行增删改查
package com.example.lyj.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","鹏鹏");
contentValues.put("age","20");
contentResolver.update(uri,contentValues,"name=? and age=?",new String[]{name3,age3});
break;
default:
break;
}
}
}