ContentProvider--------详解内容提供器

ContentProvider简介

     内容提供者( ContentProvider ) 主要用于不同应用程序之间的数据共享,并且提供CRUD,内容提供者一般提供两种用法:

1     第一种使用现有的内容提供器来读取和操作数据比如: 查询 音乐 , 视频 , 联系人等等一些信息;

2     第二种就是实现自己的内容提供器给我们的程序提供外界的接口

      下面我会用一个我写好的一个类来给大家介绍基本的方法 :

package com.example.liangshaoteng.contentprovider;import android.content.ContentProvider;import android.content.ContentValues;import android.content.UriMatcher;import android.database.Cursor;import android.net.Uri;import android.support.annotation.Nullable;import android.widget.Toast;/** * Created by liangshaoteng on 17-6-21. */public class MyContentProvider extends ContentProvider {    public static final int TABLE1_DIR = 0;    public static final int TABLE1_ITEM = 1;    public static final int TABLE2_DIR = 2;    public static final int TABLE2_ITEM = 3;    //一般都是用我们的包名    public static final String uriPath = "com.example.liangshaoteng.contentprovider";    private static UriMatcher uriMatcher;    static {        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);        uriMatcher.addURI(uriPath, "table1", TABLE1_DIR);        uriMatcher.addURI(uriPath, "table1/#", TABLE1_ITEM);        uriMatcher.addURI(uriPath, "table2", TABLE2_DIR);        uriMatcher.addURI(uriPath, "table2/#", TABLE2_ITEM);    }    @Override    public boolean onCreate() {        return false;    }    /**     * @param uri           //用来查询那张表     * @param projection    //用来查询那些列     * @param selection     * @param selectionArgs //用于查询那些行     * @param sortOrder     //用于对结果进行排序     * @return     */    @Nullable    @Override    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {        switch (uriMatcher.match(uri)) {            case TABLE1_DIR:                Toast.makeText(getContext(), "查询table1表中所有的数据", Toast.LENGTH_LONG).show();                break;            case TABLE1_ITEM:                Toast.makeText(getContext(), "查询table1表中单条的数据", Toast.LENGTH_LONG).show();                break;            case TABLE2_DIR:                Toast.makeText(getContext(), "查询table2表中所有的数据", Toast.LENGTH_LONG).show();                break;            case TABLE2_ITEM:                Toast.makeText(getContext(), "查询table2表中单条的数据", Toast.LENGTH_LONG).show();                break;            default:                break;        }        return null;    }    /**     * @param uri //根据传来的uri返回相应的MIME     * @return     */    @Nullable    @Override    public String getType(Uri uri) {        switch (uriMatcher.match(uri)) {            case TABLE1_DIR:                return "vnd.android.cursor.dir/vnd.com.example.liangshaoteng.contentprovider.table1";            case TABLE1_ITEM:                return "vnd.android.cursor.item/vnd.com.example.liangshaoteng.contentprovider.table1";            case TABLE2_DIR:                return "vnd.android.cursor.dir/vnd.com.example.liangshaoteng.contentprovider.table2";            case TABLE2_ITEM:                return "vnd.android.cursor.item/vnd.com.example.liangshaoteng.contentprovider.table2";            default:                break;        }        return null;    }    /**     * @param uri    //确定添加到那张表     * @param values //待添加的数据保存在values     * @return //返回一条表示新添加数据的uri     */    @Nullable    @Override    public Uri insert(Uri uri, ContentValues values) {        return null;    }    /**     * @param uri           //用来删除那张表     * @param selection     //用来约束删除那些行     * @param selectionArgs     * @return //并返回删除的行数     */    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        return 0;    }    /**     * @param uri           //用于更新那张表     * @param values        //新数据保存在values     * @param selection     * @param selectionArgs //约束更新哪一行     * @return     */    @Override    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {        return 0;    }}

对于访问现有的内容提供器我就不多说了,就给大家看一下我写的一个CRUD的代码看着挺多其实挺简单的,有什么不懂得或者有不同意见或建议的请给出指示谢谢!

首先给大家看一下效果图:

下面我们需要创建一张表:

 

package com.example.liangshaoteng.contentprovider;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.widget.Toast;/** * Created by liangshaoteng on 17-6-21. */public class MyDatabaseHelper extends SQLiteOpenHelper {    private Context context;    public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);        this.context = context;    }    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL("create table Book(_id integer primary key autoincrement,author,price,pages,name)");        Toast.makeText(context, "创建成功!", Toast.LENGTH_LONG).show();    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {    }}

其次就是创建我们的内容提供器:

   记得要在manifest里面注册!

   下面我就简单的写的具体还需要你根据项目需求来写

package com.example.liangshaoteng.contentprovider;import android.content.ContentProvider;import android.content.ContentValues;import android.content.UriMatcher;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.net.Uri;public class DataContentProvider extends ContentProvider {    public static final int TABLE1_DIR = 0;    public static final int TABLE1_ITEM = 1;    public static final int TABLE2_DIR = 2;    public static final int TABLE2_ITEM = 3;    public static final String AUTHORITY = "com.example.liangshaoteng.contentprovider";    private static UriMatcher uriMatcher;    static {        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);        uriMatcher.addURI(AUTHORITY, "book", TABLE1_DIR);        uriMatcher.addURI(AUTHORITY, "book/#", TABLE1_ITEM);        uriMatcher.addURI(AUTHORITY, "category", TABLE2_DIR);        uriMatcher.addURI(AUTHORITY, "category/#", TABLE2_ITEM);    }    private MyDatabaseHelper myDatabaseHelper;    public DataContentProvider() {    }    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        // Implement this to handle requests to delete one or more rows.        SQLiteDatabase writableDatabase = myDatabaseHelper.getWritableDatabase();        int deleteRows = 0;        switch (uriMatcher.match(uri)) {            case TABLE1_DIR:                deleteRows = writableDatabase.delete("Book", selection, selectionArgs);                break;            case TABLE1_ITEM:                String sBook = uri.getPathSegments().get(1);                deleteRows = writableDatabase.delete("Book", "id=?", new String[]{sBook});                break;            case TABLE2_DIR:                deleteRows = writableDatabase.delete("Category", selection, selectionArgs);                break;            case TABLE2_ITEM:                String sCategory = uri.getPathSegments().get(1);                deleteRows = writableDatabase.delete("Category", "id=?", new String[]{sCategory});                break;            default:                break;        }        return deleteRows;    }    @Override    public String getType(Uri uri) {        // TODO: Implement this to handle requests for the MIME type of the data        switch (uriMatcher.match(uri)) {            case TABLE1_DIR:                return "vnd.android.cursor.dir/vnd.com.example.liangshaoteng.contentprovider.book";            case TABLE1_ITEM:                return "vnd.android.cursor.item/vnd.com.example.liangshaoteng.contentprovider.book";            case TABLE2_DIR:                return "vnd.android.cursor.dir/vnd.com.example.liangshaoteng.contentprovider.category";            case TABLE2_ITEM:                return "vnd.android.cursor.item/vnd.com.example.liangshaoteng.contentprovider.category";            default:                break;        }        return null;    }    @Override    public Uri insert(Uri uri, ContentValues values) {        // TODO: Implement this to handle requests to insert a new row.        SQLiteDatabase writableDatabase = myDatabaseHelper.getWritableDatabase();        Uri uriReturn = null;        switch (uriMatcher.match(uri)) {            case TABLE1_DIR:            case TABLE1_ITEM:                long bookBook = writableDatabase.insert("Book", null, values);                uriReturn = Uri.parse("content://" + AUTHORITY + "/book/" + bookBook);                break;            case TABLE2_DIR:            case TABLE2_ITEM:                long bookCategory = writableDatabase.insert("Category", null, values);                uriReturn = Uri.parse("content://" + AUTHORITY + "/category/" + bookCategory);                break;            default:                break;        }        return uriReturn;    }    @Override    public boolean onCreate() {        // TODO: Implement this to initialize your content provider on startup.        myDatabaseHelper = new MyDatabaseHelper(getContext(), "BookStores.db", null, 1);        return true;    }    @Override    public Cursor query(Uri uri, String[] projection, String selection,                        String[] selectionArgs, String sortOrder) {        // TODO: Implement this to handle query requests from clients.        SQLiteDatabase readableDatabase = myDatabaseHelper.getReadableDatabase();        Cursor cursor = null;        switch (uriMatcher.match(uri)) {            case TABLE1_DIR:                cursor = readableDatabase.query("Book", projection, selection, selectionArgs, null, null, sortOrder);                break;            case TABLE1_ITEM:                String s = uri.getPathSegments().get(1);                cursor = readableDatabase.query("Book", projection, "id=?", new String[]{s}, null, null, sortOrder);                break;            case TABLE2_DIR:                cursor = readableDatabase.query("Category", projection, selection, selectionArgs, null, null, sortOrder);                break;            case TABLE2_ITEM:                String s1 = uri.getPathSegments().get(1);                cursor = readableDatabase.query("Category", projection, "id=?", new String[]{s1}, null, null, sortOrder);                break;            default:                break;        }        return cursor;    }    @Override    public int update(Uri uri, ContentValues values, String selection,                      String[] selectionArgs) {        // TODO: Implement this to handle requests to update one or more rows.        SQLiteDatabase writableDatabase = myDatabaseHelper.getWritableDatabase();        int updatedRows = 0;        switch (uriMatcher.match(uri)) {            case TABLE1_DIR:                updatedRows = writableDatabase.update("Book", values, selection, selectionArgs);                break;            case TABLE1_ITEM:                String sBook = uri.getPathSegments().get(1);                updatedRows = writableDatabase.update("Book", values, "id=?", new String[]{sBook});                break;            case TABLE2_DIR:                updatedRows = writableDatabase.update("Category", values, selection, selectionArgs);                break;            case TABLE2_ITEM:                String sCategory = uri.getPathSegments().get(1);                updatedRows = writableDatabase.update("Category", values, "id=?", new String[]{sCategory});                break;            default:                break;        }        return updatedRows;    }}

好了基本上就是这样了! 不足之处还望指出 !