Android之LoaderManager的使用

新建一個DbHelper類

package com.example.contentprovider;

import android.content.Context;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase.CursorFactory;

public class DbHelper extends SQLiteOpenHelper {
	private static String name="student.db";
	private static int version=1;

	public DbHelper(Context context) {
		super(context, name, null, version);
		// TODO Auto-generated constructor stub
	}


	@Override
	public void onCreate(SQLiteDatabase db) {
		// TODO Auto-generated method stub
		String sql="create table student(id integer primary key autoincrement,name varchar(64),address varchar(64),sex varchar(8) )";
		db.execSQL(sql);
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub

	}

}

一個StudentProvider內容提供者類

package com.example.contentprovider;

import java.util.Currency;

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 StudentProvider extends ContentProvider {
	private DbHelper dbHelper=null;
	private final String TAG="StudentProvider";
	private final static int STUDENT=1;//操作單條記錄
	private final static int STUDENTS=2;//操作多條記錄
	private final static UriMatcher uriMatcher=new UriMatcher(UriMatcher.NO_MATCH);

	static{
		uriMatcher.addURI("com.example.contentprovider.StudentProvider", "student/#", STUDENT);
		uriMatcher.addURI("com.example.contentprovider.StudentProvider", "student", STUDENTS);
	}

	@Override
	public boolean onCreate() {
		// TODO Auto-generated method stub
		dbHelper=new DbHelper(getContext());
		return true;
	}

	@Override
	public Cursor query(Uri uri, String[] projection, String selection,
			String[] selectionArgs, String sortOrder) {


		Log.i(TAG, "query：1");
		// TODO Auto-generated method stub
		int flg=uriMatcher.match(uri);
		int count=-1;
		SQLiteDatabase db=null;
		Cursor cursor=null;
		switch (flg) {
		case STUDENT:
			Log.i(TAG, "query：2");
			long id=ContentUris.parseId(uri);
			try {
				db=dbHelper.getWritableDatabase();
				String whereClause="id = "+id;
				if (selection!=null && !selection.equals("")) {
					whereClause+="and "+selection;
				}
				cursor=db.query("student", null, whereClause, selectionArgs, null, null, null);
				String name="";
				while (cursor.moveToNext()) {
					name=cursor.getString(cursor.getColumnIndex("name"));
				}
				Log.i(TAG, "name---->"+name);
			} catch (Exception e) {
				Log.i(TAG, "excepton-->"+e.getMessage());
				// TODO: handle exception
			}finally{
				if (db!=null) {
					db.close();
				}
			}
			break;

		case STUDENTS:
			Log.i(TAG, "query：3");
			db=dbHelper.getWritableDatabase();
			try {
				cursor=db.query("student", projection, selection, selectionArgs, null, null, null);
				String name="";
				while (cursor.moveToNext()) {
					name=cursor.getString(cursor.getColumnIndex("name"));
					Log.i(TAG, "name---->"+name);
				}
			} catch (Exception e) {
				Log.i(TAG, "message-->"+e.getMessage());
				// TODO: handle exception
			}finally{
				if (db!=null) {
					db.close();
				}
			}
			break;
		}
		Log.i(TAG, "query：end");
		return cursor;
	
	}

	@Override
	public String getType(Uri uri) {
		// TODO Auto-generated method stub
		int code=uriMatcher.match(uri);
		switch (code) {
		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) {
		// TODO Auto-generated method stub
		Uri requestUri=null;
		SQLiteDatabase db=dbHelper.getWritableDatabase();
		long id=db.insert("student", null, values);
		requestUri=ContentUris.withAppendedId(uri, id);
		Log.i(TAG, "--->"+requestUri);
		return requestUri;
	}

	@Override
	public int delete(Uri uri, String selection, String[] selectionArgs) {
		Log.i(TAG, "1");
		// TODO Auto-generated method stub
		int flg=uriMatcher.match(uri);
		int count=-1;
		SQLiteDatabase db=null;
		switch (flg) {
		case STUDENT:
			Log.i(TAG, "2");
			long id=ContentUris.parseId(uri);
			try {
				db=dbHelper.getWritableDatabase();
				String whereClause="id = "+id;
				if (selection!=null && !selection.equals("")) {
					whereClause+="and "+selection;
				}
				count=db.delete("student", whereClause, selectionArgs);
				Log.i(TAG, "count---->"+count);
			} catch (Exception e) {
				Log.i(TAG, "excepton-->"+e.getMessage());
				// TODO: handle exception
			}finally{
				if (db!=null) {
					db.close();
				}
			}
			break;

		case STUDENTS:
			Log.i(TAG, "3");
			db=dbHelper.getWritableDatabase();
			try {
				count=db.delete("student", selection, selectionArgs);
				Log.i(TAG, "count---->"+count);
			} catch (Exception e) {
				// TODO: handle exception
			}finally{
				if (db!=null) {
					db.close();
				}
			}
			break;
		}
		return count;
	}

	@Override
	public int update(Uri uri, ContentValues values, String selection,
			String[] selectionArgs) {

		Log.i(TAG, "1");
		// TODO Auto-generated method stub
		int flg=uriMatcher.match(uri);
		int count=-1;
		SQLiteDatabase db=null;
		switch (flg) {
		case STUDENT:
			Log.i(TAG, "2");
			long id=ContentUris.parseId(uri);
			try {
				db=dbHelper.getWritableDatabase();
				String whereClause="id = "+id;
				if (selection!=null && !selection.equals("")) {
					whereClause+="and "+selection;
				}
				count=db.update("student", values, whereClause, selectionArgs);
				Log.i(TAG, "count---->"+count);
			} catch (Exception e) {
				Log.i(TAG, "excepton-->"+e.getMessage());
				// TODO: handle exception
			}finally{
				if (db!=null) {
					db.close();
				}
			}
			break;

		case STUDENTS:
			Log.i(TAG, "3");
			db=dbHelper.getWritableDatabase();
			try {
				count=db.update("student", values, selection, selectionArgs);
				Log.i(TAG, "count---->"+count);
			} catch (Exception e) {
				// TODO: handle exception
			}finally{
				if (db!=null) {
					db.close();
				}
			}
			break;
		}
		return count;
	
	}

}

MainActivity類：

package com.example.contentprovider;

import java.util.ArrayList;
import java.util.List;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.app.Dialog;
import android.app.LoaderManager;
import android.app.LoaderManager.LoaderCallbacks;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.content.CursorLoader;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.ContextMenu;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.view.ContextMenu.ContextMenuInfo;
import android.widget.AdapterView;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.AdapterView.OnItemLongClickListener;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import android.os.Build;

public class MainActivity extends ActionBarActivity {
	private String TAG="MainActivity";
	private LoaderManager manager=null;
	private ListView listView;
	private String tempName;
	private MyAdapter adapter;

	public String getTempName() {
		return tempName;
	}
	public void setTempName(String tempName) {
		this.tempName = tempName;
	}
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.fragment_main);
		listView=(ListView) findViewById(R.id.listView);
		manager=getLoaderManager();//加載LoaderManager，完成異步加載數據的操作
		manager.initLoader(1001, null, callbacks);
		registerForContextMenu(listView);
		adapter=new MyAdapter(MainActivity.this);
		
	}
	@Override
	public void onCreateContextMenu(ContextMenu menu, View v,
			ContextMenuInfo menuInfo) {
		// TODO Auto-generated method stub
		super.onCreateContextMenu(menu, v, menuInfo);
		getMenuInflater().inflate(R.menu.main, menu);

	}


	@Override
	public boolean onContextItemSelected(MenuItem item) {
		// TODO Auto-generated method stub
		switch (item.getItemId()) {
		case R.id.add:
			//			Toast.makeText(MainActivity.this, "add", 1).show();
			final Dialog dialog=getAddDialog();
			Button button=(Button) dialog.findViewById(R.id.add);
			button.setOnClickListener(new OnClickListener() {
				@Override
				public void onClick(View v) {
					// TODO Auto-generated method stub
					ContentResolver resolver=getContentResolver();
					Uri url=Uri.parse("content://com.example.contentprovider.StudentProvider/student");
					ContentValues values=new ContentValues();
					EditText text=(EditText) dialog.findViewById(R.id.stuName);
					String name=text.getText().toString();
					values.put("name", name);
					Uri returUri=resolver.insert(url, values);
					if (returUri!=null) {
						manager.restartLoader(1001, null, callbacks);
						dialog.dismiss();
						Toast.makeText(MainActivity.this, "添加成功", Toast.LENGTH_SHORT).show();
					}

				}
			});
			dialog.show();
			break;

		case R.id.delete:
			AdapterContextMenuInfo info=(AdapterContextMenuInfo) item.getMenuInfo();
//			Toast.makeText(MainActivity.this, "position-->"+info.position+"   id--->"+
//			info.id, Toast.LENGTH_SHORT).show();
			String name=(String) adapter.getItem(info.position);
//			String name=MainActivity.this.getTempName();
			//			Toast.makeText(MainActivity.this, "name--->"+MainActivity.this.getTempName(), 1).show();
			ContentResolver resolver=getContentResolver();
			Uri url=Uri.parse("content://com.example.contentprovider.StudentProvider/student");
			int count=resolver.delete(url, "name=?", new String[]{name});
			if (count>=1) {
				manager.restartLoader(1001, null, callbacks);
				Toast.makeText(MainActivity.this, "刪除成功", Toast.LENGTH_SHORT).show();
			}
			break;
		}
		return super.onContextItemSelected(item);
	}

	public Dialog getAddDialog(){
		Dialog dialog=new Dialog(MainActivity.this);
		dialog.setContentView(R.layout.add);
		return dialog;
	}

	private LoaderCallbacks<Cursor> callbacks=new LoaderCallbacks<Cursor>() {
		@Override
		public Loader<Cursor> onCreateLoader(int id, Bundle arg1) {
			// TODO Auto-generated method stub
			CursorLoader loader=new CursorLoader(MainActivity.this);
			Uri uri=Uri.parse("content://com.example.contentprovider.StudentProvider/student");
			loader.setUri(uri);
			return loader;
		}

		//完成對UI的數據提取，更新UI的操作
		@Override
		public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
			// TODO Auto-generated method stub
			//把數據提取出來，放到適配器中完成對UI的更新操作
			List<String> list=null;
			String name="";
			if (cursor.moveToFirst()) {
				list=new ArrayList<String>();
				name=cursor.getString(cursor.getColumnIndex("name"));
				list.add(name);
				while(cursor.moveToNext()){
					name=cursor.getString(cursor.getColumnIndex("name"));
					list.add(name);
				}
			}
			Log.i(TAG, "list.size----->"+list.size());
			//使用BaseAdater
			adapter.setList(list);
			listView.setAdapter(adapter);
			adapter.notifyDataSetChanged();

			//使用ArrayAdapter
			//			ArrayAdapter< String> arrayAdapter=new ArrayAdapter<String>(MainActivity.this,
			//					R.layout.fragment_main,R.id.textView1, list);
			//			listView.setAdapter(arrayAdapter);

		}

		@Override
		public void onLoaderReset(Loader<Cursor> arg0) {
			// TODO Auto-generated method stub

		}
	};

	public class MyAdapter extends BaseAdapter{
		private List<String> list=null;
		private Context context;
		public MyAdapter(Context context){
			this.context=context;
		}
		public void setList(List<String> list){
			this.list=list;
		}
		@Override
		public int getCount() {
			// TODO Auto-generated method stub
			return list.size();
		}

		@Override
		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return list.get(position);
		}

		@Override
		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			// TODO Auto-generated method stub
			TextView textView=null;
			if (convertView==null) {
				textView=new TextView(context);
			}else{
				textView=(TextView) convertView;
			}
			textView.setText(list.get(position).toString());
			return textView;
		}

	}


	@Override
	public boolean onCreateOptionsMenu(Menu menu) {

		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}




}

xml佈局文件：fragment_main.xml

<LinearLayout 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:orientation="vertical"
    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="com.example.contentprovider.MainActivity$PlaceholderFragment" >

    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </ListView>

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/listView"
        android:layout_alignParentTop="true"
        android:text="TextView" />

</LinearLayout>

彈出的對話框的佈局文件：add.xml

<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <EditText
        android:id="@+id/stuName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_x="113dp"
        android:layout_y="65dp"
        android:text="添加" />

</AbsoluteLayout>

menu文件：main.xml

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