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
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
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
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
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; } } }