Sqlite ContentProvider Loader 上下文对话框

2023-01-04 20:41:29

一、整体工程图

二、activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >

    <ListView

        android:id="@+id/listView1"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_alignParentTop="true" >

    </ListView>

</RelativeLayout>

三、add_name.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="240dp"

    android:layout_height="wrap_content"

    android:orientation="vertical" >

    <TextView

        android:id="@+id/textView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="姓名：" />

    <EditText

        android:id="@+id/username"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_marginBottom="4dp"

        android:layout_marginLeft="4dp"

        android:layout_marginRight="4dp"

        android:layout_marginTop="16dp"

        android:hint="username"

        android:inputType="textEmailAddress" />

    <Button

        android:id="@+id/btnAdd"

        android:layout_width="match_parent"

        android:layout_height="wrap_content" android:text="确定">

    </Button>

</LinearLayout>

四、contentmenu.xml

<?xml version="1.0" encoding="utf-8"?>

<menu xmlns:android="http://schemas.android.com/apk/res/android" >

    <item

        android:id="@+id/menu_add"

        android:orderInCategory="100"

        android:showAsAction="never"

        android:title="添加">

    </item>

	<item

        android:id="@+id/menu_delete"

        android:orderInCategory="100"

        android:showAsAction="never"

        android:title="删除">

    </item>

</menu>

五、MainActivity.java

package com.example.loadermanagerdemo;

import android.net.Uri;

import android.os.Bundle;

import android.app.Activity;

import android.app.AlertDialog;

import android.app.LoaderManager;

import android.app.LoaderManager.LoaderCallbacks;

import android.content.ContentResolver;

import android.content.ContentValues;

import android.content.CursorLoader;

import android.content.Loader;

import android.database.Cursor;

import android.util.Log;

import android.view.ContextMenu;

import android.view.LayoutInflater;

import android.view.Menu;

import android.view.MenuInflater;

import android.view.MenuItem;

import android.view.View;

import android.view.ContextMenu.ContextMenuInfo;

import android.widget.AdapterView.AdapterContextMenuInfo;

import android.widget.Button;

import android.widget.EditText;

import android.widget.ListView;

import android.widget.SimpleCursorAdapter;

import android.widget.TextView;

public class MainActivity extends Activity {

	private LoaderManager manager;

	private ListView listview;

	private AlertDialog alertDialog;

	private SimpleCursorAdapter mAdapter;

	private final String TAG="main";

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.activity_main);

		listview = (ListView) findViewById(R.id.listView1);

		mAdapter = new SimpleCursorAdapter(MainActivity.this,

				android.R.layout.simple_list_item_1, null,

				new String[] { "name" }, new int[] { android.R.id.text1 },0);

		listview.setAdapter(mAdapter);

		manager = getLoaderManager();

		manager.initLoader(1000, null, callbacks);

		registerForContextMenu(listview);

	}

	@Override

	public void onCreateContextMenu(ContextMenu menu, View v,

			ContextMenuInfo menuInfo) {

		super.onCreateContextMenu(menu, v, menuInfo);

		MenuInflater inflater = getMenuInflater();

		inflater.inflate(R.menu.contentmenu, menu);

	}

	@Override

	public boolean onContextItemSelected(MenuItem item) {

		AdapterContextMenuInfo info = (AdapterContextMenuInfo) item

				.getMenuInfo();

		switch (item.getItemId()) {

		case R.id.menu_add:

			AlertDialog.Builder builder = new AlertDialog.Builder(

					MainActivity.this);

			final View view = LayoutInflater.from(MainActivity.this).inflate(

					R.layout.add_name, null);

			Button btnAdd = (Button) view.findViewById(R.id.btnAdd);

			btnAdd.setOnClickListener(new View.OnClickListener() {

				@Override

				public void onClick(View v) {

					EditText etAdd = (EditText) view

							.findViewById(R.id.username);

					String name = etAdd.getText().toString();

					ContentResolver contentResolver = getContentResolver();

					ContentValues contentValues = new ContentValues();

					contentValues.put("name", name);

					Uri uri = Uri

							.parse("content://com.example.loadermanagerdemo.StudentContentProvider/student");

					Uri result = contentResolver.insert(uri, contentValues);

					/*if (result != null) {

						manager.restartLoader(1000, null, callbacks);

					}*/

					alertDialog.dismiss();

					//Log.i(TAG, "添加数据成功，name="+name);

				}

			});

			builder.setView(view);

			alertDialog = builder.show();

			return true;

		case R.id.menu_delete:

			TextView tv = (TextView) info.targetView;

			String name = tv.getText().toString();

			Uri url = Uri

					.parse("content://com.example.loadermanagerdemo.StudentContentProvider/student");

			ContentResolver contentResolver = getContentResolver();

			String where = "name=?";

			String[] selectionArgs = { name };

			int count = contentResolver.delete(url, where, selectionArgs);

			/*if (count == 1) {

				manager.restartLoader(1000, null, callbacks);

			}*/

			//Log.i(TAG, "删除数据成功，name="+name);

			return true;

		default:

			return super.onContextItemSelected(item);

		}

	}

	private LoaderManager.LoaderCallbacks<Cursor> callbacks = new LoaderCallbacks<Cursor>() {

		@Override

		public Loader<Cursor> onCreateLoader(int id, Bundle bundle) {

			Uri uri = Uri

					.parse("content://com.example.loadermanagerdemo.StudentContentProvider/student");

			CursorLoader loader = new CursorLoader(MainActivity.this, uri,

					null, null, null, null);

			Log.i("jltxgcy", "onCreateLoader被执行。");

			return loader;

		}

		@Override

		public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {

			mAdapter.swapCursor(cursor);

			//listview.setAdapter(mAdapter);

			Log.i("jltxgcy", "onLoadFinished被执行。");

		}

		@Override

		public void onLoaderReset(Loader<Cursor> loader) {

			mAdapter.swapCursor(null);

			Log.i("jltxgcy", "onLoaderReset被执行。");

		}

	};

	@Override

	public boolean onCreateOptionsMenu(Menu menu) {

		getMenuInflater().inflate(R.menu.main, menu);

		return true;

	}

}

六、StudentContentProvider.java

package com.example.loadermanagerdemo;

import com.example.loadermanagerdemo.dbhelper.DbHelper;

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 android.util.Log;

public class StudentContentProvider extends ContentProvider {

	private DbHelper helper;

	private final String TAG = "main";

	private final static UriMatcher URI_MATCHAR = new UriMatcher(

			UriMatcher.NO_MATCH);

	private final static int STUDENT = 1;

	private final static int STUDENTS = 2;

	static {

		URI_MATCHAR.addURI(

				"com.example.loadermanagerdemo.StudentContentProvider",

				"student", STUDENTS);

		URI_MATCHAR.addURI(

				"com.example.loadermanagerdemo.StudentContentProvider",

				"student/#", STUDENT);

	}

	public StudentContentProvider() {

	}

	@Override

	public int delete(Uri uri, String selection, String[] selectionArgs) {

		int count = -1;

		int flag = URI_MATCHAR.match(uri);

		SQLiteDatabase database = helper.getWritableDatabase();

		switch (flag) {

		case STUDENT:

			long stuid = ContentUris.parseId(uri);

			String where_value = "_id=?";

			String[] where_args = { String.valueOf(stuid) };

			count = database.delete("student", where_value, where_args);

			break;

		case STUDENTS:

			count = database.delete("student", selection, selectionArgs);

			break;

		}

		Log.i(TAG, "---->>" + count);

		getContext().getContentResolver().notifyChange(uri, null);

		return count;

	}

	@Override

	public String getType(Uri uri) {

		int flag = URI_MATCHAR.match(uri);

		switch (flag) {

		case STUDENT:

			return "vnd.android.cursor.item/student";

		case STUDENTS:

			return "vnd.android.cursor.dir/students";

		}

		return null;

	}

	@Override

	public Uri insert(Uri uri, ContentValues values) {

		int flag = URI_MATCHAR.match(uri);

		SQLiteDatabase database = helper.getWritableDatabase();

		Uri returnUri = null;

		if (STUDENTS == flag) {

			long id = database.insert("student", null, values);

			returnUri = ContentUris.withAppendedId(uri, id);

		}

		Log.i(TAG, "---->>" + returnUri.toString());

		getContext().getContentResolver().notifyChange(uri, null);

		return returnUri;

	}

	@Override

	public boolean onCreate() {

		helper = new DbHelper(getContext());

		return false;

	}

	@Override

	public Cursor query(Uri uri, String[] projection, String selection,

			String[] selectionArgs, String sortOrder) {

		Cursor cursor = null;

		SQLiteDatabase database=helper.getReadableDatabase();

		int flag = URI_MATCHAR.match(uri);

		switch (flag) {

		case STUDENTS:

			cursor=database.query(true, "student", null, selection, selectionArgs, null, null, null, null);

			break;

		case STUDENT:

			long stuid=ContentUris.parseId(uri);

			String where_value="_id=?";

			String[] where_args={String.valueOf(stuid)};

			cursor=database.query(true, "student", null, where_value, where_args, null, null, null, null);

			break;

		}

		cursor.setNotificationUri(getContext().getContentResolver(), uri);

		return cursor;

	}

	@Override

	public int update(Uri uri, ContentValues values, String selection,

			String[] selectionArgs) {

		int count = -1;

		int flag = URI_MATCHAR.match(uri);

		SQLiteDatabase database = helper.getWritableDatabase();

		switch (flag) {

		case STUDENTS:

			count = database

					.update("student", values, selection, selectionArgs);

			break;

		case STUDENT:

			long stuid = ContentUris.parseId(uri);

			String where_value = "_id=?";

			String[] where_args = { String.valueOf(stuid) };

			count = database.update("student", values, where_value, where_args);

			break;

		}

		getContext().getContentResolver().notifyChange(uri, null);

		return count;

	}

}

七、DbHelper.java

package com.example.loadermanagerdemo.dbhelper;

import android.content.ContentValues;

import android.content.Context;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

public class DbHelper extends SQLiteOpenHelper {

	private static String name="mydb.db";

	private static int version=1;

	public DbHelper(Context context) {

		super(context, name, null, version);

	}

	@Override

	public void onCreate(SQLiteDatabase database) {

		String sql="Create table student(_id integer primary key autoincrement,name varchar(64))";

		database.execSQL(sql);

		ContentValues values=new ContentValues();

		values.put("name", "Jack");

		database.insert("student", null, values);

	}

	@Override

	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

		// TODO Auto-generated method stub

	}

}

八、详解

只要开启程序，就会调用StudentContentProvider中的onCreate方法，然后MainActivity中ContentResolver操作StudentContentProvider类，StudentContentProvider操作DbHelper类。

数据库部分内容请看http://www.w3school.com.cn/sql/sql_create_table.asp。

insert into Persons VALUES (1,'Gates', 'Bill', 'Xuanwumen 10', 'Beijing')。

主键为NULL，代表自增长。对应到Android的SQL语句就变成字符串了。

manager.initLoader(1000, null, callbacks)调用了onCreateLoader。

Loader实现了异步加载，只要想StudentContentProvider插入数据，就会调用onLoadFinished更新了Cursor，通过mAdapter.swapCursor(cursor)更新了Listview。如果不是Listview，那么此处也是进行更新UI操作，只不过不能向刚才用一句程序mAdapter.swapCursor(cursor)就搞定。

查询Cursor变化是异步的，在有数据插入，更新，删除的地方要加上getContext().getContentResolver().notifyChange(uri, null);

如果退出Activity，那么会调用onLoaderReset，清空cursor。

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