安卓学习-Loaders-加载器
实时加载数据
数据使用SQLite数据库保存，而使用ContentProvider进行数据的请求与访问
Person.java
package com.example.administrator.loaders;
/**
* Created by Administrator on 2016/4/4.
*/
public class Person {
private int id;
private String name;
private int age;
public Person()
{
}
public Person(int id, String name, int age) {
this.id = id;
this.name = name;
this.age = age;
}
public Person(String name, int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return "Person{" +
"age=" + age +
", id=" + id +
", name='" + name + '\'' +
'}';
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
PersonMetadata.java
package com.example.administrator.loaders;
import android.provider.BaseColumns;
/**
* Created by Administrator on 2016/4/4.
*/
//finale 不让继承
public final class PersonMetadata {
public static abstract class Person implements BaseColumns {
public static final String TABLE_NAME="person";
public static final String NAME="name";
public static final String AGE="age";
}
}
DatabaseAdapter.java
package com.example.administrator.loaders;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.ArrayList;
/**
* Created by Administrator on 2016/4/4.
*/
public class DatabaseAdapter {
private DatabaseHelper dbHelper;
public DatabaseAdapter(Context context) {
dbHelper = new DatabaseHelper(context);
}
public void save(Person person) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(PersonMetadata.Person.NAME, person.getName());
values.put(PersonMetadata.Person.AGE, person.getAge());
db.insert(PersonMetadata.Person.TABLE_NAME, null, values);
db.close();
}
public Cursor list()
{
SQLiteDatabase db= dbHelper.getReadableDatabase();
Cursor c=db.query(PersonMetadata.Person.TABLE_NAME, null, null, null, null, null, null);
return c;
}
public void delete(int id) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String whereClause = PersonMetadata.Person._ID + "=?";
String[] whereArgs = {String.valueOf(id)};
db.delete(PersonMetadata.Person.TABLE_NAME, whereClause, whereArgs);
db.close();
}
public void update(Person person) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(PersonMetadata.Person.NAME, person.getName());
values.put(PersonMetadata.Person.AGE, person.getAge());
String whereClause = PersonMetadata.Person._ID + "=?";
String[] whereArgs = {String.valueOf(person.getId())};
db.update(PersonMetadata.Person.TABLE_NAME, values, whereClause, whereArgs);
db.close();
}
public ArrayList<Person> findAll()
{
SQLiteDatabase db= dbHelper.getReadableDatabase();
Cursor c=db.query(PersonMetadata.Person.TABLE_NAME, null, null, null, null, null, null);
ArrayList<Person> list=new ArrayList<Person>();
Person person=null;
while (c.moveToNext())
{
person=new Person();
person.setId(c.getInt(c.getColumnIndexOrThrow(PersonMetadata.Person._ID)));
person.setName(c.getString(c.getColumnIndexOrThrow(PersonMetadata.Person.NAME)));
person.setAge(c.getInt(c.getColumnIndexOrThrow(PersonMetadata.Person.AGE)));
list.add(person);
}
c.close();
db.close();
return list;
}
public Person findById(int id)
{
SQLiteDatabase db= dbHelper.getReadableDatabase();
Cursor c=db.query(PersonMetadata.Person.TABLE_NAME, null, PersonMetadata.Person._ID+"=?", new String[]{String.valueOf(id)}, null, null, null);
Person person=null;
if (c.moveToNext())
{
person=new Person();
person.setId(c.getInt(c.getColumnIndexOrThrow(PersonMetadata.Person._ID)));
person.setName(c.getString(c.getColumnIndexOrThrow(PersonMetadata.Person.NAME)));
person.setAge(c.getInt(c.getColumnIndexOrThrow(PersonMetadata.Person.AGE)));
}
c.close();
db.close();
return person;
}
public static class DatabaseHelper extends SQLiteOpenHelper {
private static final String DB_NAME = "cp.db";
private static final int VERSION = 1;
private static final String CREATE_TABLE = "CREATE TABLE person(_id INTEGER PRIMARY KEY AUTOINCREMENT," +
"name TEXT,age INT)";
private static final String DROP_TABLE = "DROP TABLE IF EXISTS person";
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL(DROP_TABLE);
db.execSQL(CREATE_TABLE);
}
}
}
PersonContentProvider.java
<provider android:authorities="com.example.administrator.personcontentprovider" android:name=".PersonContentProvider"></provider>
-------------------------------------------------------------------
package com.example.administrator.loaders;
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;
/**
* 自定义内容提供者
* Created by Administrator on 2016/4/4.
*/
public class PersonContentProvider extends ContentProvider {
private static final String AUTHORITY = "com.example.administrator.personcontentprovider";
//创建一个URI的匹配器
private static UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
private static final int SINGLE_CODE = 2;//返回单个记录的匹配码
private static final int MUTIPLE_CODE = 1;//标识返回多个记录的匹配码
//text/plain image/jpg
private static final String SINGLE_TYPE = "vnd.android.cursor.item/person";
private static final String MUTIPLE_TYPE = "vnd.android.cursor.dir/person";
static {
uriMatcher.addURI(AUTHORITY, "person", MUTIPLE_CODE);
uriMatcher.addURI(AUTHORITY, "person/#", SINGLE_CODE);
}
private DatabaseAdapter.DatabaseHelper dbHelper;
@Override
public boolean onCreate() {
dbHelper = new DatabaseAdapter.DatabaseHelper(getContext());
return true;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
switch (uriMatcher.match(uri)) {
case SINGLE_CODE:
SQLiteDatabase db = dbHelper.getReadableDatabase();
long id = ContentUris.parseId(uri);
selection = PersonMetadata.Person._ID + "=?";
selectionArgs = new String[]{String.valueOf(id)};
return db.query(PersonMetadata.Person.TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
case MUTIPLE_CODE:
db = dbHelper.getReadableDatabase();
return db.query(PersonMetadata.Person.TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
}
return null;
}
@Override
public String getType(Uri uri) {
switch (uriMatcher.match(uri)) {
case SINGLE_CODE:
return SINGLE_TYPE;
case MUTIPLE_CODE:
return MUTIPLE_TYPE;
}
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
switch (uriMatcher.match(uri)) {
case MUTIPLE_CODE:
SQLiteDatabase db = dbHelper.getWritableDatabase();
long id = db.insert(PersonMetadata.Person.TABLE_NAME, null, values);
uri = ContentUris.withAppendedId(uri, id);
db.close();
break;
}
return uri;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
switch (uriMatcher.match(uri))
{
case SINGLE_CODE:
SQLiteDatabase db = dbHelper.getWritableDatabase();
long id = ContentUris.parseId(uri);
selection = PersonMetadata.Person._ID + "=?";
selectionArgs = new String[]{String.valueOf(id)};
int row = db.delete(PersonMetadata.Person.TABLE_NAME, selection, selectionArgs);
db.close();
return row;
case MUTIPLE_CODE:
db = dbHelper.getWritableDatabase();
row = db.delete(PersonMetadata.Person.TABLE_NAME, selection, selectionArgs);
db.close();
return row;
}
return 0;
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
switch (uriMatcher.match(uri))
{
case SINGLE_CODE:
SQLiteDatabase db = dbHelper.getWritableDatabase();
long id = ContentUris.parseId(uri);
selection = PersonMetadata.Person._ID + "=?";
selectionArgs = new String[]{String.valueOf(id)};
int row = db.update(PersonMetadata.Person.TABLE_NAME, values, selection, selectionArgs);
db.close();
return row;
case MUTIPLE_CODE:
db = dbHelper.getWritableDatabase();
row = db.update(PersonMetadata.Person.TABLE_NAME, values, selection, selectionArgs);
db.close();
return row;
}
return 0;
}
}
MainActivity.java
package com.example.administrator.loaders;
import android.app.LoaderManager;
import android.content.CursorLoader;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class MainActivity extends ActionBarActivity implements LoaderManager.LoaderCallbacks<Cursor> {
private DatabaseAdapter dbAdapter;
SimpleCursorAdapter dataAdapter;
CursorLoader loader;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbAdapter = new DatabaseAdapter(this);
ListView lv = (ListView) findViewById(R.id.listView);
dataAdapter =
new SimpleCursorAdapter(this, R.layout.list_item, dbAdapter.list(),
new String[]{PersonMetadata.Person._ID, PersonMetadata.Person.NAME,
PersonMetadata.Person.AGE},
new int[]{R.id.textView_id, R.id.textView_name,
R.id.textView_age}, SimpleCursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);
lv.setAdapter(dataAdapter);
//初始化一个loader（id，bundler参数,回调接口）
getLoaderManager().initLoader(0, null, this);
}
public void addClick(View view) {
dbAdapter.save(new Person("xiaofei",18));
//重启加载器
// getLoaderManager().restartLoader(0,null,this);
//loader.commitContentChanged();API 18可用
loader.onContentChanged();//内容发生了变化，通知加载器
}
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
System.out.println("onCreateLoader");
Uri uri=Uri.parse("content://com.example.administrator.personcontentprovider/person");
//创建一个游标加载器（上下文，CP的URI，要查询的列数组，查询条件，查询条件的值，排序条件）
loader=new CursorLoader(this,uri,null,null,null,null);
return loader;
}
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
System.out.println("onLoadFinished");
dataAdapter.swapCursor(data);
}
@Override
public void onLoaderReset(Loader<Cursor> loader) {
System.out.println("onLoaderReset");
dataAdapter.swapCursor(null);
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?> <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="com.example.administrator.loaders.MainActivity"> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text=" 添加" android:onClick="addClick" android:id="@+id/button" android:layout_alignParentTop="true" android:layout_alignParentLeft="true" android:layout_alignParentStart="true" android:layout_alignParentRight="true" android:layout_alignParentEnd="true" /> <ListView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/listView" android:layout_below="@+id/button" android:layout_alignParentLeft="true" android:layout_alignParentStart="true" /> </RelativeLayout>
list_item.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_margin="@dimen/activity_vertical_margin" android:orientation="vertical"> <TextView android:id="@+id/textView_id" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="New Text" /> <TextView android:id="@+id/textView_name" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="New Text" /> <TextView android:id="@+id/textView_age" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="New Text" /> </LinearLayout>
activity_main2.xml
<?xml version="1.0" encoding="utf-8"?> <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="com.example.administrator.loaders.MainActivity2"> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="add" android:onClick="addClick" android:id="@+id/button2" android:layout_alignParentTop="true" android:layout_alignParentLeft="true" android:layout_alignParentStart="true" android:layout_alignParentRight="true" android:layout_alignParentEnd="true" /> <ListView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/listView2" android:layout_below="@+id/button2" android:layout_alignParentLeft="true" android:layout_alignParentStart="true" /> </RelativeLayout>
MainActivity2.java
package com.example.administrator.loaders;
import android.app.LoaderManager;
import android.content.AsyncTaskLoader;
import android.content.Context;
import android.content.Loader;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import java.util.ArrayList;
public class MainActivity2 extends ActionBarActivity implements LoaderManager.LoaderCallbacks<ArrayList<Person>> {
private MyAdapter myAdapter;
private DatabaseAdapter dbAdapter;
private DataAsyncTaskLoader loader;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
ListView lv = (ListView) findViewById(R.id.listView2);
dbAdapter = new DatabaseAdapter(this);
myAdapter = new MyAdapter(this, dbAdapter.findAll());
lv.setAdapter(myAdapter);
getLoaderManager().initLoader(0, null, this);
}
public void addClick(View view) {
dbAdapter.save(new Person("小龙",18));
loader.onContentChanged();
}
@Override
public Loader<ArrayList<Person>> onCreateLoader(int id, Bundle args) {
loader = new DataAsyncTaskLoader(this, dbAdapter);
return loader;
}
@Override
public void onLoadFinished(Loader<ArrayList<Person>> loader, ArrayList<Person> data) {
myAdapter.setPersons(data);
myAdapter.notifyDataSetChanged();
}
@Override
public void onLoaderReset(Loader<ArrayList<Person>> loader) {
myAdapter.setPersons(null);
}
//自定义的loader 泛型
private static class DataAsyncTaskLoader extends AsyncTaskLoader<ArrayList<Person>> {
private DatabaseAdapter dbAdapter;
private ArrayList<Person> data;
public DataAsyncTaskLoader(Context context, DatabaseAdapter dbAdapter) {
super(context);
this.dbAdapter = dbAdapter;
}
//该方法在后台线程中执行，用来加载数据
@Override
public ArrayList<Person> loadInBackground() {
System.out.println("loadInBackground");
data = dbAdapter.findAll();
return data;
}
//用于发送结果
@Override
public void deliverResult(ArrayList<Person> data) {
if (isReset()) {
return;
}
if (isStarted()) {
super.deliverResult(data);
}
}
//正在加载中
@Override
protected void onStartLoading() {
if (data != null) {
deliverResult(data);
}
if (takeContentChanged()) {
forceLoad();//强制加载数据
}
super.onStartLoading();
}
}
private static class MyAdapter extends BaseAdapter {
private ArrayList<Person> persons;
private Context context;
public void setPersons(ArrayList<Person> persons) {
this.persons = persons;
}
public MyAdapter(Context context, ArrayList<Person> persons) {
this.context = context;
this.persons = persons;
}
@Override
public int getCount() {
return persons.size();
}
@Override
public Object getItem(int position) {
return persons.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder vh = null;
if (convertView == null) {
convertView = LayoutInflater.from(context).inflate(R.layout.list_item, null);
vh = new ViewHolder();
vh.tv_id = (TextView) convertView.findViewById(R.id.textView_id);
vh.tv_name = (TextView) convertView.findViewById(R.id.textView_name);
vh.tv_age = (TextView) convertView.findViewById(R.id.textView_age);
convertView.setTag(vh);
} else {
vh = (ViewHolder) convertView.getTag();
}
Person p = persons.get(position);
vh.tv_id.setText(String.valueOf(p.getId()));
vh.tv_name.setText(p.getName());
vh.tv_age.setText(String.valueOf(p.getAge()));
return convertView;
}
private static class ViewHolder {
TextView tv_id;
TextView tv_name;
TextView tv_age;
}
}
}