自定义一个自己的ContentProvider程序

首先，新建一个数据库类：MyHelper.java

package com.china.anonymous.contentproviderdemoone;
    

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

/**
 * Created by Anonymous on 2016/1/31.
 */
public class MyHelper extends SQLiteOpenHelper {

      private static final String fileName = "demo.db";
      private static final int version = 1;


      public MyHelper(Context context) {
            super(context, fileName,null, version);
      }

      @Override
      public void onCreate(SQLiteDatabase sqLiteDatabase) {

            String sql = "create table student(_ID integer primary key autoincrement,name text not null)";
            sqLiteDatabase.execSQL(sql);
      }

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

      }
}

To create a new class which extends ContentProvider

package com.china.anonymous.contentproviderdemoone;

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.Nullable;

public class MyContentProvider extends ContentProvider {

      private static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
      private static final int multiple_Items = 1;
      private static final int single_item = 2;
      private MyHelper helper = null;

      static {

            matcher.addURI("com.china.anonymous.contentproviderdemoone.MyContentProvider", "student", multiple_Items);
            matcher.addURI("com.china.anonymous.contentproviderdemoone.MyContentProvider", "student/#", single_item);

      }

      @Override
      public boolean onCreate() {
            helper = new MyHelper(getContext());
            return false;
      }

      @Nullable
      @Override
      public Cursor query(Uri uri, String[] strings, String s, String[] strings1, String s1) {

            //返回一个游标

            Cursor cursor = null;
            SQLiteDatabase db = helper.getReadableDatabase();
            int flag = matcher.match(uri);
            switch (flag) {
                  case single_item:
                        long id = ContentUris.parseId(uri);
                        String where_id = "_ID=" + id;
                        cursor = db.query("student", strings, where_id, strings1, null, null, null);


                  case multiple_Items:
                        cursor = db.query("student", strings, s, strings1, null, null, null);
            }
            return cursor;
      }

      @Nullable
      @Override
      public String getType(Uri uri) {

            int flag = matcher.match(uri);
            switch (flag) {

                  //查询单条记录，前面那一句固定写法
                  case single_item:
                        return "vnd.android.cursor.item/item";

                  //查询整个表
                  case multiple_Items:
                        return "vnd.android.cursor.dir/items";
                  default:
                        throw new UnsupportedOperationException("not supported operation:" + uri);
            }
      }

      @Nullable
      @Override
      public Uri insert(Uri uri, ContentValues contentValues) {

            //返回一个标志，判断是多条记录（从表中操作）还是单挑记录（操作指定记录）
            int flag = matcher.match(uri);
            SQLiteDatabase db = helper.getWritableDatabase();
            Uri newUri = null;

            //因为创建的表是自动添加的，所以就不用写单条记录的
            switch (flag) {
                  case multiple_Items:
                        long id = db.insert("student", null, contentValues);
                        //把新添加的id加入表中
                        newUri = ContentUris.withAppendedId(uri, id);
            }

            //返回一个新的uri
            return newUri;
      }

      @Override
      public int delete(Uri uri, String s, String[] strings) {

            //获取指定要删除的从uri中获取id，

            int flag = matcher.match(uri);
            SQLiteDatabase db = helper.getWritableDatabase();
            int deleteItem = 0;

            switch (flag) {

                  case single_item:
                        //获取单挑的uri中的id
                        long id = ContentUris.parseId(uri);
                        String where_id = "_ID=" + id;
                        deleteItem = db.delete("student", where_id, strings);

                  case multiple_Items:
                        deleteItem = db.delete("student", s, strings);
            }
            return deleteItem;
      }

      @Override
      public int update(Uri uri, ContentValues contentValues, String s, String[] strings) {

            //update主要是获取指定要修改的的uri的id，返回修改后的id

            int flag = matcher.match(uri);
            SQLiteDatabase db = helper.getWritableDatabase();
            int upDataItem = 0;
            switch (flag) {

                  case single_item:
                        long id = ContentUris.parseId(uri);
                        String where_id = "_ID=" + id;
                        upDataItem = db.update("student", contentValues, where_id, strings);


                  case multiple_Items:
                        upDataItem = db.update("student", contentValues, s, strings);
            }

            return upDataItem;
      }

}

在AndroidManifest.xml中添加provider

<provider
        android:authorities="com.china.anonymous.contentproviderdemoone.MyContentProvider"
        android:name=".MyContentProvider"/>

在主程序中应用，用contentResolver
package com.china.anonymous.contentproviderdemoone;

import android.content.ContentResolver;
import android.content.ContentValues;
import android.net.Uri;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

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

            ContentResolver resolver = getContentResolver();
            Uri uri = Uri.parse("content://com.china.anonymous.contentproviderdemoone.MyContentProvider/student");

            ContentValues value = new ContentValues();
            value.put("name", "change");
            resolver.update(uri, value, "_ID=6", null);

            resolver.delete(uri, "_ID=9", null);
      }
}

来自为知笔记(Wiz)