第四大组件ContentProvider
功能：数据共享
按照文件路径和格式
无论哪种数据持久化方法，数据共享的接口统一为ContentProvider
系统自带应用的数据
通讯：拨号 短信 联系人
多媒体：音乐 视频 图片 拍照
其他：Home Launcher
一、新建ex0814_contentprovider项目
ContentProvider负责组织应用程序的数据，向其他应用程序提供数据。
清单配置如下：（增加属性authorities）
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<provider
android:name="com.example.ex0814_contentprovider.MyContentProvider"
android:authorities="com.example.provider.student"
android:enabled="true"
android:exported="true" >
</provider>
</application>代码如下：
//ex0814_contentresolver项目和ex0814_contentprovider项目。
public class MyContentProvider extends ContentProvider
{//创建一个数据共享接口ContentProvider，让其他的应用可以对他进行增删改查
private SQLiteDatabase mDb;
private static final String TABLE_NAME = "student";
private static final String CULUMN_NAME_NAME = "name";
private static final String CULUMN_NAME_PHONE = "phone";
// 步骤：
// 1.新建一个项目，删除Activity和清单中的 Activity的配置
// 2.新建android object，选择contentprovider，并设置 authorities属性
// 3.字符串建议：packagename + provider + 数据功能名
// 4.在provider类中，创建MySqliteOpenhelper的内部类
// 5.在onCreate（）里面获取SQLiteDatabase对象
// 6.实现增删改查的方法
public MyContentProvider()
{
}
//重写增删改查的方法
@Override
public int delete(Uri uri, String selection, String[] selectionArgs)
{
int delete = mDb.delete(TABLE_NAME, selection, selectionArgs);
return delete;
}
@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)
{//values由ex0814_contentresolver项目传来
long insert = mDb.insert(TABLE_NAME, null, values);
Uri withAppendedId = ContentUris.withAppendedId(uri, insert);
return withAppendedId;
}
@Override
public boolean onCreate()
{
MySqliteOpenhelper openhelper = new MySqliteOpenhelper(getContext(), 1);
mDb = openhelper.getWritableDatabase();
return false;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder)
{
Cursor query = mDb.query(TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
return query;
}
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs)
{
int update = mDb.update(TABLE_NAME, values, selection, selectionArgs);
return update;
}
public class MySqliteOpenhelper extends SQLiteOpenHelper
{
public MySqliteOpenhelper(Context context, int version)
{
super(context, "cuijing.db", null, version);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db)
{//创建表，一运行，会去检查是否有表，如果已经有了，或者版本号更新，都不会再执行onCreate（）;
Log.e("MySqliteOpenhelper", "onCreate");
db.execSQL("CREATE TABLE student(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),phone VARCHAR(20))");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{//如果已经有表存在，并且版本号有更新，就会执行onUpgrade（）；
Log.e("MySqliteOpenhelper", "onUpgrade");
db.execSQL("ALTER TABLE student ADD COLUMN weight INTEGER");
}
}
}二、新建ex0814_contentresolver项目
使用其他应用的Provider的方法：
1. getContentResolver()
2. resolver.query(uri, )
ContentResolver则负责获取ContentProvider提供的数据，修改/添加/删除更新数据等。
代码如下：
public class MainActivity extends Activity implements OnClickListener
{//ex0814_contentresolver查询ex0814_contentprovider项目的数据库，通过ex0814_contentprovider提供的provider共享接口。
private EditText mEt_name;
private EditText mEt_phone;
private ContentResolver contentResolver;
private TextView textView;
private ListView listView;
private static final String TABLE_NAME = "student";
private static final String CULUMN_NAME_NAME = "name";
private static final String CULUMN_NAME_PHONE = "phone";
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
contentResolver = getContentResolver();
findViewById(R.id.btn_baocun).setOnClickListener(this);
findViewById(R.id.btn_delete).setOnClickListener(this);
findViewById(R.id.btn_selector).setOnClickListener(this);
findViewById(R.id.btn_update).setOnClickListener(this);
listView = (ListView) findViewById(R.id.listView1);
mEt_name = (EditText) findViewById(R.id.et_name);
mEt_phone = (EditText) findViewById(R.id.et_phone);
}
@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;
}
@Override
public void onClick(View v)
{
switch (v.getId())
{
case R.id.btn_baocun:
insert();
break;
case R.id.btn_delete:
delete();
break;
case R.id.btn_selector:
selector();
break;
case R.id.btn_update:
update();
break;
default:
break;
}
}
private void update()
{//修改
Editable et_name = mEt_name.getText();
Editable et_phone = mEt_phone.getText();
ContentValues values = new ContentValues();
values.put(CULUMN_NAME_PHONE, et_phone.toString());//修改号码
contentResolver.update(Uri.parse("content://com.example.provider.student"), values, "name=?", new String[]{et_name.toString()});//根据名字修改号码
}
private void selector()
{//查询
Cursor cursor = contentResolver.query(Uri.parse("content://com.example.provider.student"), null, null, null, null);
String[] from = {CULUMN_NAME_NAME,CULUMN_NAME_PHONE};
int[] to = {android.R.id.text1,android.R.id.text2};
// 使用 SimpleCursorAdapter，要把创建表中的自增ID修改成_id
SimpleCursorAdapter adapter = new SimpleCursorAdapter(MainActivity.this, android.R.layout.simple_list_item_2, cursor, from, to);
listView.setAdapter(adapter);
}
private void delete()
{//删除
Editable et_name = mEt_name.getText();
contentResolver.delete(Uri.parse("content://com.example.provider.student"), "name=?", new String[]{et_name.toString()});//删除的是数据库里editext显示为name的数据
}
private void insert()
{//把ex0814_contentresolver项目里editext的内容插入到ex0814_contentprovider项目的数据库（database）里
ContentValues values = new ContentValues();
Editable et_name = mEt_name.getText();
Editable et_phone = mEt_phone.getText();
values.put("name", et_name.toString());
values.put("phone", et_phone.toString());
contentResolver.insert(Uri.parse("content://com.example.provider.student"), values);//uri格式必须以content：//开头，uri内容为ex0814_contentprovider的anthoritise（属性）
}
}
