Content Provider

• 需要一个Authority
• Uri 
• 跨进程通信
• 每次insert update..，都需要notifyChange
• 专门用于应用间数据共享，也就是跨进程通信
• 底层也是基于Binder，但使用起来方便
• 通过contentResolver的query、update、insert和delete方法即可
• 系统预置了许多contentProvider，比如通讯录、日程表信息等
• 自定义一个ContentProvider  ，contentProvider需要在清单文件里面进行注册

  package com.lzw.cha01.myapplication.chapter2;
  
  import android.content.ContentProvider;
  import android.content.ContentValues;
  import android.content.Context;
  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;
  import android.util.Log;
  
  
  /**
   * MyApplication
   * Created by lzw on 2019/3/11. 10:41:46
   * 邮箱：632393724@qq.com
   * All Rights Saved! Chongqing AnYun Tech co. LTD
   */
  public class BookProvider extends ContentProvider {
      private static final String TAG = "BookProvider";
      public static final String AUTHORITY = "com.lzw.cha01.myapplication.chapter2.book.provider";
      public static final Uri BOOK_CONTENT_URI = Uri.parse("content://"+AUTHORITY+"/book");
      public static final Uri USER_CONTENT_URI = Uri.parse("content://"+AUTHORITY+"/user");
      public static final int BOOK_URI_CODE = 0;
      public static final int USER_URI_CODE =1;
      private static final UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
  
      private SQLiteDatabase mDb;
      private Context context;
      static {
          uriMatcher.addURI(AUTHORITY,"book",BOOK_URI_CODE);
          uriMatcher.addURI(AUTHORITY,"user",USER_URI_CODE);
      }
  
      private void initProviderData(){
          mDb = new DbOpenHelper(context).getWritableDatabase();
          mDb.execSQL("delete from  "+ DbOpenHelper.BOOK_TABLE_NAME);
          mDb.execSQL("delete from  "+ DbOpenHelper.USER_TABLE_NAME);
          mDb.execSQL("insert into " + DbOpenHelper.BOOK_TABLE_NAME +" values(3,'android');");
          mDb.execSQL("insert into " + DbOpenHelper.BOOK_TABLE_NAME +" values(4,'IOS');");
          mDb.execSQL("insert into " + DbOpenHelper.BOOK_TABLE_NAME +" values(5,'HTML5');");
          mDb.execSQL("insert into " + DbOpenHelper.USER_TABLE_NAME +" values(1,'jake',1);");
          mDb.execSQL("insert into " + DbOpenHelper.USER_TABLE_NAME +" values(2,'jasmine',0)");
  
      }
  
      @Override
      public boolean onCreate() {
          context = getContext();
          initProviderData();
          return false;
      }
  
      @Nullable
      @Override
      public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
          Log.i(TAG, "query: current thread:"+Thread.currentThread().getName());
          String tbName = getTableName(uri);
          if (tbName == null){
              throw new IllegalArgumentException("Unsupported URI:"+uri);
          }
          return mDb.query(tbName,projection,selection,selectionArgs,null,null,sortOrder,null);
  
      }
  
      @Nullable
      @Override
      public String getType(@NonNull Uri uri) {
          Log.i(TAG, "getType,");
          return null;
      }
  
      @Nullable
      @Override
      public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
          Log.i(TAG, "insert: ");
          String tbName = getTableName(uri);
          if (tbName == null){
              throw new IllegalArgumentException("Unsupported URI:"+uri);
          }
          mDb.insert(tbName,null,values);
          context.getContentResolver().notifyChange(uri,null);
          return uri;
      }
  
      @Override
      public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
          Log.i(TAG, "delete: ");
          String tbName = getTableName(uri);
          if (tbName == null){
              throw new IllegalArgumentException("Unsupported URI:"+uri);
          }
          int count = mDb.delete(tbName,selection,selectionArgs);
          if (count > 0){
              context.getContentResolver().notifyChange(uri,null);
          }
          return count;
      }
  
      @Override
      public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
          Log.i(TAG, "update: ");
          String tbName = getTableName(uri);
          if (tbName == null){
              throw new IllegalArgumentException("Unsupported URI:"+uri);
          }
          int row = mDb.update(tbName,values,selection,selectionArgs);
          if (row > 0){
              context.getContentResolver().notifyChange(uri,null);
          }
          return row;
      }
  
      private String getTableName(Uri uri){
          String tableName  = null;
          switch (uriMatcher.match(uri)){
              case BOOK_URI_CODE:
                  tableName = DbOpenHelper.BOOK_TABLE_NAME;
                  break;
              case USER_URI_CODE:
                  tableName = DbOpenHelper.USER_TABLE_NAME;
                  break;
                  default:break;
          }
          return tableName;
      }
  }
  

  　　

• 建一个数据库

  public class DbOpenHelper extends SQLiteOpenHelper {
      private static final String TAG = "DbOpenHelper";
      private static final String DB_NAME = "BOOK";
      private static final int DB_VERSION = 1;
      public static final String BOOK_TABLE_NAME = "book";
      public static final String USER_TABLE_NAME = "user";
  
      private String CREATE_TABLE_USER = "CREATE TABLE IF NOT EXISTS "
              +BOOK_TABLE_NAME+"(_id INTEGER PRIMARY KEY,name TEXT)";
  
      private String CREATE_TABLE_BOOK = "CREATE TABLE IF  NOT EXISTS  "+
              USER_TABLE_NAME+"(_id  INTEGER PRIMARY KEY, name TEXT,"+
              "sex INT)";
  
      public DbOpenHelper(Context context) {
          super(context,DB_NAME,null,DB_VERSION);
      }
  
      @Override
      public void onCreate(SQLiteDatabase db) {
          db.execSQL(CREATE_TABLE_BOOK);
          db.execSQL(CREATE_TABLE_USER);
      }
  
      @Override
      public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
  
      }
  }
  

  　　

• 用法

          Uri bookUri = Uri.parse("content://com.lzw.cha01.myapplication.chapter2.book.provider/book");
          ContentValues values = new ContentValues();
          values.put("_id",6);
          values.put("name","程序设计的艺术");
          getContentResolver().insert(bookUri,values);
          Cursor bookCursor = getContentResolver().query(bookUri,new String[]{"_id","name"},null,null,null);
          while (bookCursor.moveToNext()){
              Book book = new Book();
              book.setBookId(bookCursor.getInt(0));
              book.setBookName(bookCursor.getString(1));
              Log.d(TAG, "onCreate: query book;"+book.toString());
          }
          bookCursor.close();
  
          Uri userUri = Uri.parse("content://com.lzw.cha01.myapplication.chapter2.book.provider/user");
          Cursor userCursor = getContentResolver().query(userUri,new String[]{"_id","name","sex"},null,null,null);
          while (userCursor.moveToNext()){
              User user = new User();
              user.setName(userCursor.getString(1));
              user.setSex(userCursor.getInt(2));
              user.setUserId(userCursor.getInt(0));
              Log.d(TAG, "onCreate: query user:"+user.toString());
          }
          userCursor.close();