Android中的ContentProvider和ContentResolver

最新推荐文章于 2025-09-13 09:50:31 发布

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最新推荐文章于 2025-09-13 09:50:31 发布

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文章标签：移动开发 python 数据库

原文链接：https://my.oschina.net/sjh1995/blog/646909

本文详细介绍了Android中的ContentProvider组件，包括如何自定义ContentProvider类来实现数据的增删改查操作，并展示了如何在其他应用程序中通过ContentResolver访问这些数据。

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顾名思义ContentProvider就是将自己的数据提供给别人，ContentResolver则是接受别人的数据

自定义一个类继承ContentProvider类

public class MyContentProvider extends ContentProvider {

private static final String AUTHORITY = "com.example.contentprovider.MyContentProvider";//记得在清单文件中注册provide并命名，name必须为该类的完整名称（加包名），添加authority（域名）【为了让别人访问】，一般以包名命名
private static final int INSERT = 1;
private static final int DELETE = 2;
private static final int UPDATE = 3;
private static final int QUERY = 4;
MyHelp myhelp;//数据库的创建在这里就不说了
private static Context context;
private ContentResolver mContent;
static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
匹配URI类
static{//在类加载的时候添加这些URI
  matcher.addURI(AUTHORITY, "insert", INSERT);
  matcher.addURI(AUTHORITY, "delete", DELETE);
  matcher.addURI(AUTHORITY, "update", UPDATE);
  matcher.addURI(AUTHORITY, "query", QUERY);

}

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
  // TODO Auto-generated method stub

  if(matcher.match(uri)==DELETE)
  {
   SQLiteDatabase db=myhelp.getWritableDatabase();

   db.delete("person", selection, selectionArgs);

   mContent.notifyChange(uri, null);



  }else
  {
   throw new IllegalArgumentException("uri not matched!");
  }
  return 0;
}

@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
return null;
}

@Override
public Uri insert(Uri uri, ContentValues values) {
  // TODO Auto-generated method stub



  if(matcher.match(uri)==INSERT)
  {
   SQLiteDatabase db=myhelp.getWritableDatabase();
   db.insert("person", null, values);

   mContent.notifyChange(uri, null);



  }else
  {
   throw new IllegalArgumentException("uri not matched!");
  }

  return null;
}

@Override
public boolean onCreate() {
  // TODO Auto-generated method stub
  context = this.getContext();
  myhelp = new MyHelp(context);
  mContent = context.getContentResolver();
  return false;
}

@Override
public Cursor query(Uri uri, String[] projection, String selection,
   String[] selectionArgs, String sortOrder) {
  // TODO Auto-generated method stub

  if(matcher.match(uri)==QUERY)
  {
   SQLiteDatabase db=myhelp.getWritableDatabase();
   db.query("person", projection, selection, selectionArgs, null, null, null);

   mContent.notifyChange(uri, null);



  }else
  {
   throw new IllegalArgumentException("uri not matched!");
  }
  return null;
}

@Override
public int update(Uri uri, ContentValues values, String selection,
   String[] selectionArgs) {
  // TODO Auto-generated method stub
  if(matcher.match(uri)==UPDATE)
  {
   SQLiteDatabase db=myhelp.getWritableDatabase();

   db.update("person", values, selection, selectionArgs);

   mContent.notifyChange(uri, null);



  }else
  {
   throw new IllegalArgumentException("uri not matched!");
  }
  return 0;
}

}

在另一个测试应用中，这两个不是一个应用，用于访问上面的应用，要用到ContentResolver

public class MainActivity extends Activity {
private static final String AUTHORITY = "com.example.contentprovider.MyContentProvider";
ContentResolver mContent;

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

        mContent = getContentResolver();

        mContent.registerContentObserver(Uri.parse("content://"+AUTHORITY), true,new MyObserver(new Handler()));//注册监视，观察数据是否发生改变（可以不加该方法）

    }

    class MyObserver extends ContentObserver
    {

  public MyObserver(Handler handler) {
   super(handler);
   // TODO Auto-generated constructor stub

  }

  @Override
  public void onChange(boolean selfChange) {
   // TODO Auto-generated method stub
   super.onChange(selfChange);
   Toast.makeText(MainActivity.this, "is changed...", 0).show();
  }


    }

    public void insert(View v)//按钮的点击事件，在布局文件中已经定义
    {
    Uri uri = Uri.parse("content://" + AUTHORITY + "/insert");

ContentValues cv = new ContentValues();

  cv.put("id", 4);
  cv.put("name", "tom");
  mContent.insert(uri, cv);
    }

    public void delete(View v)
    {
    Uri uri = Uri.parse("content://" + AUTHORITY + "/delete");
    mContent.delete(uri, "id=?", new String[]{String.valueOf(4)});
    }

    public void update(View v)
    {
    Uri uri = Uri.parse("content://" + AUTHORITY + "/update");
    ContentValues cv = new ContentValues();

cv.put("name", "lily");

  mContent.update(uri, cv, "id=?",
    new String[] { String.valueOf(2) });
    }

    public void query(View v)
    {
    Uri uri = Uri.parse("content://" + AUTHORITY + "/query");
    mContent.query(uri, null, null, null, null);
    }

转载于:https://my.oschina.net/sjh1995/blog/646909