Android学习笔记十九.使用ContentProvider实现数据共享(一)

package com.example.android_contentprovider_1;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
public class FirstProvider extends ContentProvider {
 //1.第一次创建该ContentProvider时调用该方法
 @Override
 public boolean onCreate() {
  System.out.println("====onCreate方法被调用=====");
  return false;
 }
 //2.实现查询方法，该方法应该返回查询得到的Cursor
 @Override
 public Cursor query(Uri uri, String[] projection, String where,
   String[] selectionArgs, String sortOrder) {
  System.out.println("====query方法被调用=====");
  System.out.println("where参数为："+where);
  return null;
 }
 //3.该方法的返回值代表了该ContentProvider所提供数据的MIME类型
 @Override
 public String getType(Uri uri) {
  return null;
 }
 //4.实现插入的方法，该方法应该返回新插入的记录的Uri
 @Override
 public Uri insert(Uri uri, ContentValues values) {
  System.out.println(uri+"====insert被调用=====");
  System.out.println("values参数为:"+values);
  return null;
 }
 //5.实现删除方法，该方法应该返回被删除的记录条数
 @Override
 public int delete(Uri uri, String where, String[] selectionArgs) {
  System.out.println(uri+"====delete方法被调用=====");
  System.out.println("where参数为："+where);
  return 0;
 }
 //6.实现更新方法，该方法应该返回被更新的记录条数
 @Override
 public int update(Uri uri, ContentValues values, String selection,
   String[] selectionArgs) {
  System.out.println(uri+"====update方法被调用=====");
  System.out.println("values参数为:"+values);
  return 0;
 }
}

package com.example.android_contentresolver_2;

import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
public class FirstResolver extends Activity {
 ContentResolver contentResolver;
 Uri uri=Uri.parse("content://com.example.android_contentprovider_1");	//解析一个uri用以获取对应的ContentProvider
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
 //1.获取系统的ContentResolver对象
  contentResolver=getContentResolver();
 }
 //2.调用ContentResolver的query()方法
 public void query(View source)
 {
  Cursor c=contentResolver.query(uri, null, "query_where", null, null);//实际返回的是该Uri对应的ContentProvider的query()的返回值
  Toast.makeText(this, "远程ContentProvider返回的Cursor为"+c, Toast.LENGTH_SHORT).show();
 }
 //3.调用ContentResolver的insert()方法
 public void insert(View source)
 {
  ContentValues values=new ContentValues();
  values.put("name", "jiangdongguo");
  Uri newUri=contentResolver.insert(uri, values);	//将键值对插入到uri对应的ContentProvider共享数据中
  Toast.makeText(this, "远程ContentProvider新插入记录的Uri为:"+newUri, Toast.LENGTH_SHORT).show();
 }
 //4.调用ContentResolver()的update()方法
 public void update(View source)
 {
  ContentValues values=new ContentValues();
  values.put("name", "zhongxian");
  int count=contentResolver.update(uri, values, "update_where", null);
  Toast.makeText(this, "远程ContentProvider更新记录数为:"+count, Toast.LENGTH_SHORT).show();
 }
 //5.调用ContentResoler的delete()方法
 public void delete(View source)
 {
  int count=contentResolver.delete(uri, "delete_where", null);//实际返回的是该ContentProvider的delete()的返回值
  Toast.makeText(this, "远程ContentProvider删除记录数为:"+count, Toast.LENGTH_SHORT).show();
 }
 
}