android中contentProvider及ContentResolver

野性酷女 2023-01-05 05:28 245阅读 0赞

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这个技术是解决应用之间的一个调用，如常见的应用间数据库查询，内容提供者暴露接口，内容解析器ContentResolver通过调用相应CRUD接口，内容提供者需要在清单文件进行定义。
案例：
我们新建一个PersonProvider继承ContentProvider，并在CRUD实现上借助Sqlite工具类进行操作。
这个同时需要理解一些理论性的知识，如URI的格式content://com.hbk.hbk_provider.personprovider/person/3
调用的URI是否合法，用到的相关API，有
UriMatcher.addURI(String authority, String path, int code) // 添加合法URI
int android.content.UriMatcher.match(Uri uri)// 判断Uri是否合法
long android.content.ContentUris.parseId(Uri contentUri)// 提取uri的id
Uri ContentUris.withAppendedId(Uri contentUri, long id)// 这个一般用在插入，使得插入后的Uri有id值

PersonProvider.java

  1. package com.hbk.hbk_provider;
  3. import org.apache.http.client.utils.URIUtils;
  5. import android.content.ContentProvider;
  6. import android.content.ContentUris;
  7. import android.content.ContentValues;
  8. import android.content.UriMatcher;
  9. import android.database.Cursor;
  10. import android.database.sqlite.SQLiteDatabase;
  11. import android.net.Uri;
  12. import android.util.Log;
  14. public class PersonProvider extends ContentProvider { 
  16.     private DbHelper dbHelper;
  17.     private static UriMatcher matchers = new UriMatcher(UriMatcher.NO_MATCH);
  19.     static{ 
  20.         matchers.addURI("com.hbk.hbk_provider.personprovider", "/person", 1);
  21.         matchers.addURI("com.hbk.hbk_provider.personprovider", "/person/#", 2);//#匹配任意数字
  22.     }
  24.     public PersonProvider() { 
  25.         Log.e("TAG", "PersonProvider()");
  26.     }
  27.     @Override
  28.     public boolean onCreate() { 
  29.         Log.e("TAG", "PersonProvider onCreate()");
  30.         dbHelper = new DbHelper(getContext());
  31.         return false;
  32.     }
  34.     /** * content://com.hbk.hbk_provider.personprovider/person 不根据id查询 * content://com.hbk.hbk_provider.personprovider/person/3 根据id查询 */
  35.     @Override
  36.     public Cursor query(Uri uri, String[] projection, String selection,
  37.             String[] selectionArgs, String sortOrder) { 
  38.         SQLiteDatabase database = dbHelper.getReadableDatabase();
  39.         // 根据
  40.         int code = matchers.match(uri);
  41.         if(code == 1){ //不根据id查询
  42.             // 
  43.             Cursor cursor = database.query("person", projection, selection, selectionArgs, null, null, null);
  44.             return cursor;
  45.         }else if(code == 2){ 
  46.             // 根据id查询
  47.             long id = ContentUris.parseId(uri);
  48.             Cursor cursor = database.query("person", projection, "_id=?", new String[]{ id+""}, null, null, null);
  49.             return cursor;
  50.         }else{ 
  51.             throw new RuntimeException("查询的uri不合法");
  52.         }
  53.     }
  55.     @Override
  56.     public String getType(Uri uri) { 
  57.         // TODO Auto-generated method stub
  58.         return null;
  59.     }
  61.     /** * content://com.hbk.hbk_provider.personprovider/person 插入 * content://com.hbk.hbk_provider.personprovider/person/3 根据id插入(没有) */
  62.     @Override
  63.     public Uri insert(Uri uri, ContentValues values) { 
  64.         SQLiteDatabase database = dbHelper.getReadableDatabase();
  65.         int code = matchers.match(uri);
  66.         if(code == 1){ //不根据id查询
  67.             // 
  68.             long id = database.insert("person", null, values);
  69.             uri = ContentUris.withAppendedId(uri, id);
  70.             database.close();
  71.             return uri;    
  72.         }else { 
  73.             database.close();
  74.             throw new RuntimeException("插入的uri不合法");
  75.         }
  76.     }
  78.     /** * content://com.hbk.hbk_provider.personprovider/person 不根据id删除 * content://com.hbk.hbk_provider.personprovider/person/3 根据id删除 */
  79.     @Override
  80.     public int delete(Uri uri, String selection, String[] selectionArgs) { 
  81.         SQLiteDatabase database = dbHelper.getReadableDatabase();
  82.         int code = matchers.match(uri);
  83.         int deleteCount = -1;
  84.         if(code == 1){ //不根据id删除
  85.             deleteCount = database.delete("person", selection, selectionArgs);
  86.         }else if(code == 2){ 
  87.             long id = ContentUris.parseId(uri);
  88.             deleteCount = database.delete("person", "_id="+id, null);
  89.         }else{ 
  90.             database.close();
  91.             throw new RuntimeException("删除的uri不合法");
  92.         }
  93.         database.close();
  94.         return deleteCount;
  95.     }
  98.     /** * content://com.hbk.hbk_provider.personprovider/person 不根据id更新 * content://com.hbk.hbk_provider.personprovider/person/3 根据id更新 */
  99.     @Override
  100.     public int update(Uri uri, ContentValues values, String selection,
  101.             String[] selectionArgs) { 
  102.         SQLiteDatabase database = dbHelper.getReadableDatabase();
  103.         int code = matchers.match(uri);
  104.         int updateCount = -1;
  105.         if(code == 1){ //不根据id更新
  106.             updateCount = database.update("person", values, selection, selectionArgs);
  107.         }else if(code == 2){ 
  108.             long id = ContentUris.parseId(uri);
  109.             updateCount = database.update("person", values, "_id="+id, null);
  110.         }else{ 
  111.             database.close();
  112.             throw new RuntimeException("更新的uri不合法");
  113.         }
  114.         database.close();
  115.         return updateCount;
  116.     }
  118. }

在清单文件中进行定义，exported为true表示允许其他营业进行调用，一般authorities的值为全类名小写，这个提供给内容解析器进行标识的字符串。

  1. <provider android:name="com.hbk.hbk_provider.PersonProvider" android:authorities="com.hbk.hbk_provider.personprovider" android:exported="true"/>

DbHelper.java常用的工具类

  1. package com.hbk.hbk_provider;
  3. import android.content.Context;
  4. import android.database.sqlite.SQLiteDatabase;
  5. import android.database.sqlite.SQLiteOpenHelper;
  6. import android.util.Log;
  8. public class DbHelper extends SQLiteOpenHelper { 
  10.     public DbHelper(Context context) { 
  11.         super(context, "huangbaokang.db", null,1);
  12.     }
  14.     @Override
  15.     public void onCreate(SQLiteDatabase db) { 
  16.         Log.i("TAG","建表。。。");
  17.         db.execSQL("create table person(_id integer primary key autoincrement,name varchar)");
  18.         db.execSQL("insert into person(name) values('huangbaokang')");
  19.     }
  21.     @Override
  22.     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
  24.     }
  26. }

内容解析调用方android工程
布局
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  1. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" >
  3.     <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:onClick="insert" android:text="INSERT" />
  5.     <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:onClick="delete" android:text="DELETE" />
  7.     <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:onClick="update" android:text="UPDATE" />
  9.     <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:onClick="query" android:text="QUERY" />
  11. </LinearLayout>

处理Activity

  1. package com.hbk.hbk_resolver;
  3. import android.app.Activity;
  4. import android.content.ContentResolver;
  5. import android.content.ContentValues;
  6. import android.database.Cursor;
  7. import android.net.Uri;
  8. import android.os.Bundle;
  9. import android.view.View;
  10. import android.widget.Toast;
  12. public class MainActivity extends Activity { 
  14.     @Override
  15.     protected void onCreate(Bundle savedInstanceState) { 
  16.         super.onCreate(savedInstanceState);
  17.         setContentView(R.layout.activity_main);
  18.     }
  20.     /* * 通过ContentResolver调用ContentProvider插入一条记录 */
  21.     public void insert(View v) { 
  22.         //1. 得到ContentResolver对象
  23.         ContentResolver resolver = getContentResolver();
  24.         //2. 调用其insert
  25.         Uri uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person");
  26.         //uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person/3");//将抛异常
  27.         ContentValues values = new ContentValues();
  28.         values.put("name", "JACK");
  29.         uri = resolver.insert(uri, values);
  31.         Toast.makeText(this, uri.toString(), 1).show();
  32.     }
  34.     /* * 通过ContentResolver调用ContentProvider更新一条记录 */
  35.     public void update(View v) { 
  36.         //1. 得到ContentResolver对象
  37.         ContentResolver resolver = getContentResolver();
  38.         //2. 执行update
  39.         Uri uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person/2");
  40.         ContentValues values = new ContentValues();
  41.         values.put("name", "JACK2");
  42.         int updateCount = resolver.update(uri, values, null, null);
  44.         Toast.makeText(this, "updateCount="+updateCount, 1).show();
  45.     }
  47.     /* * 通过ContentResolver调用ContentProvider删除一条记录 */
  48.     public void delete(View v) { 
  49.         //1. 得到ContentResolver对象
  50.         ContentResolver resolver = getContentResolver();
  51.         //2. 执行delete
  52.         Uri uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person/2");
  53.         int deleteCount = resolver.delete(uri, null, null);
  54.         Toast.makeText(this, "deleteCount="+deleteCount, 1).show();
  55.     }
  56.     public void query(View v){ 
  57.         ContentResolver contentResolver = getContentResolver();
  58.         //2. 调用其query, 得到cursor
  59.         Uri uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person");
  60.         Cursor cursor = contentResolver.query(uri, null, null, null, null);
  61.         while(cursor.moveToNext()){ 
  62.             int id = cursor.getInt(0);
  63.             String name = cursor.getString(1);
  64.             Toast.makeText(this, "id="+id+" name="+name, 0).show();
  65.         }
  66.         cursor.close();
  67.     }
  68. }

工程架构
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