Android--简单开发和使用ContentProvider数据共享

今天学习的时候学到了ContentProvider数据共享这个东东，所以自己写了个小例子:

我们要开发ContentProvider的话，需要创建一个类去继承ContentProvider,里面会让你重写四个方法，这四个方法就是数据共享用到的方法

包括SQLite的插入、查询、删除。。

所以，如何共享我们的数据，就看你如何重写这几个方法。

下面是操作步骤，我是用Android studio写的

1、先看工程结构

2、我们建立一个继承ContentProvider的类，创建步骤（右键→new→othet→Provider）

3、ContentProvider共享的数据是SQLite里面的数据，为了方便我把创建SQLite的数据库和创建表的操作也写在了ContentProvider的onCreate()方法里面了

  代码

package provider;

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 toolclass.MySQLiteOpenHelper;

public class MyContentProvider extends ContentProvider {

    private static final String AUTHORITY = "com.example.fanlei.mycontentprovider";//地址
    private static final String DB_FILE   = "friends.db";//数据库名称
    private static final String DB_TABLE  = "friends";   //表名
    private static final int URI_ROOT     = -1;
    private static final int DB_TABLE_FRIENDS = 1;
    public  static final Uri CONTENT_URI  = Uri.parse("content://" + AUTHORITY + "/" + DB_TABLE);//Uri所对应的资源
    private static final UriMatcher uriMatcher = new UriMatcher(URI_ROOT);//检查传过来的Uri
    static {
        uriMatcher.addURI(AUTHORITY,DB_TABLE,DB_TABLE_FRIENDS);
    }
    private MySQLiteOpenHelper helper;
    private SQLiteDatabase db;

    public MyContentProvider() {

    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // Implement this to handle requests to delete one or more rows.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public String getType(Uri uri) {
        // TODO: Implement this to handle requests for the MIME type of the data
        // at the given URI.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        //检查传过来的Uri是否是正确的，若不正确，则抛出异常
        if (uriMatcher.match(uri) != DB_TABLE_FRIENDS){
            throw new IllegalArgumentException("Unknown URI:" + uri);
        }
        Long rawId = db.insert(DB_TABLE,null,values);
        Uri returnUri = ContentUris.withAppendedId(CONTENT_URI,rawId);
        getContext().getContentResolver().notifyChange(returnUri,null);
        return returnUri;
    }

    @Override
    public boolean onCreate() {
        helper = new MySQLiteOpenHelper(getContext(),DB_FILE,null,1);
        db     = helper.getWritableDatabase();
        String sql = "CREATE TABLE IF NOT EXISTS " + DB_TABLE +"(" +
                "_id primary key," +
                "name text," +
                "sexId text," +
                "address text);";
        db.execSQL(sql);
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        //检查传过来的Uri是否是正确的，若不正确，则抛出异常
        if (uriMatcher.match(uri) != DB_TABLE_FRIENDS){
            throw new IllegalArgumentException("Unknown URI:" + uri);
        }
        Cursor cursor = db.query(true,DB_TABLE,projection,selection,selectionArgs,null,null,sortOrder,null);
        cursor.setNotificationUri(getContext().getContentResolver(),uri);
        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.
        throw new UnsupportedOperationException("Not yet implemented");
    }
}

其实，ContentProvider里面重写的方法也是封装了SQLiteDataBase的方法的操作，只不过他需要一个具体的Uri去指向我们具体的资源。

ContentProvider开发完成后，我在主函数里面调用了我们写的这个ContentProvider里面的方法，布局什么的都很简单。

我只是插入了数据，查询数据

下面是主函数:

package com.example.fanlei.mycontentproviderdemo;

import android.annotation.TargetApi;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import provider.MyContentProvider;


public class MainActivity2 extends ActionBarActivity {

    private ContentResolver contentResolver;
    private Uri uri;

    private EditText et_1,et_2,et_3;
    private Button btn_1,btn_2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_activity2);
        contentResolver = getContentResolver();
        uri = MyContentProvider.CONTENT_URI;

        et_1 = (EditText) findViewById(R.id.et_1);
        et_2 = (EditText) findViewById(R.id.et_2);
        et_3 = (EditText) findViewById(R.id.et_3);

        btn_1 = (Button) findViewById(R.id.btn_1);
        btn_2 = (Button) findViewById(R.id.btn_2);
        //加入
        btn_1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ContentValues cv = new ContentValues();//键值  就是 列名
                cv.put("name",et_1.getText().toString());
                cv.put("sexId",et_2.getText().toString());
                cv.put("address",et_3.getText().toString());

                contentResolver.insert(uri,cv);
                Toast.makeText(MainActivity2.this,"加入成功",Toast.LENGTH_SHORT).show();
            }
        });
        //查询
        btn_2.setOnClickListener(new View.OnClickListener() {
            @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
            @Override
            public void onClick(View v) {
                Cursor cursor = contentResolver.query(uri,null,"name like ?",new String[]{"%23%"},null,null);
                while (cursor.moveToNext()){
                    String name    = cursor.getString(cursor.getColumnIndex("name"));
                    String sexId   = cursor.getString(cursor.getColumnIndex("sexId"));
                    String address = cursor.getString(cursor.getColumnIndex("address"));

                    Log.d("asdasd",name+"^^"+sexId+"^^"+address);

                }
            }
        });
    }
}

====================================以上是简单的开发=======================================

下面是使用我们上面的工程创建的ContentProvider

先看工程结构：

我这里建立了一个工具类去存放上一个工程Uri。

布局什么的都很简单，就一个TextView和Button，就不放了。

下面是主函数的代码

package com.example.fanlei.textmycontentproviderdemo;

import android.content.ContentResolver;
import android.database.ContentObserver;
import android.database.Cursor;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import provider.PeopleInfoProvider;


public class MainActivity extends ActionBarActivity {

    private TextView tv_show;
    private Button button;

    private ContentResolver contentResolver;

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

        tv_show = (TextView) findViewById(R.id.tv_show);
        button = (Button) findViewById(R.id.btn);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Cursor cursor = contentResolver.query(PeopleInfoProvider.CONTENT_URI,null,null,null,null);
                StringBuilder sb = new StringBuilder();
                while (cursor.moveToNext()){
                    String name    = cursor.getString(cursor.getColumnIndex("name"));
                    String sexId   = cursor.getString(cursor.getColumnIndex("sexId"));
                    String address = cursor.getString(cursor.getColumnIndex("address"));
                    sb.append(name).append(sexId).append(address);
                }
                tv_show.setText(sb.toString());
            }
        });

        contentResolver.registerContentObserver(PeopleInfoProvider.CONTENT_URI,true,new MyObserver(new Handler()));
    }

    private class MyObserver extends ContentObserver{
        /**
         * Creates a content observer.
         * @param handler The handler to run {@link #onChange} on, or null if none.
         */
        public MyObserver(Handler handler) {
            super(handler);
        }

        @Override
        public void onChange(boolean selfChange) {
            super.onChange(selfChange);

            Cursor cursor = contentResolver.query(PeopleInfoProvider.CONTENT_URI,null,null,null,null);
            StringBuilder sb = new StringBuilder();
            while (cursor.moveToNext()){
                String name    = cursor.getString(cursor.getColumnIndex("name"));
                String sexId   = cursor.getString(cursor.getColumnIndex("sexId"));
                String address = cursor.getString(cursor.getColumnIndex("address"));
                sb.append(name).append(sexId).append(address);
                Log.d("-----update----",sb.toString());
            }
            tv_show.setText(sb.toString());
        }
    }
}

对了，这里我写了一个内部类去继承了ContentObserver这个类，它的作用就是当共享的数据发生改变时，就会触发这个方法。