Android 自定义ContentProvider简单实例
Android允许我们定义自己的的ContentProvider对象来共享数据，练练手，简单来实现一下。
要使用ContentProvider来操作数据，必须要有保存数据的场所。可以使用文件或SQLite数据库的方式来保存数据，通常使用SQLite数据库。
1，创建一个数据库帮助类，归根结底都是它在操作数据库。代码如下：
package com.njue;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class DBManager extends SQLiteOpenHelper {
public static final String myProvider_table_name="myProvider_table_name";
String sql="create table myProvider_table_name(id integer,name text)";
public DBManager(Context context) {
super(context, "myPrivoder.db", null, 1);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase arg0) {
// TODO Auto-generated method stub
arg0.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
2，创建一个myProvider类，该类继承ContentProvider，实现其抽象方法来操作数据库，该类引用DBManager类来获得数据库实例。
package com.njue;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
public class myProvider extends ContentProvider {
DBManager dbHelper;
@Override
public int delete(Uri arg0, String arg1, String[] arg2) {
// TODO Auto-generated method stub
SQLiteDatabase db=dbHelper.getWritableDatabase();
int id=db.delete(DBManager.myProvider_table_name, arg1, arg2);
if(id!=0)return id;
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
SQLiteDatabase db=dbHelper.getWritableDatabase();
db.insert(DBManager.myProvider_table_name, "id", values);
return null;
}
@Override
public boolean onCreate() {
// TODO Auto-generated method stub
dbHelper=new DBManager(getContext());
return true;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
// TODO Auto-generated method stub
SQLiteDatabase db=dbHelper.getWritableDatabase();
Cursor c=db.query(DBManager.myProvider_table_name,projection, selection, selectionArgs, null, null, sortOrder);
return c;
}
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// TODO Auto-generated method stub
SQLiteDatabase db=dbHelper.getWritableDatabase();
int id=db.update(DBManager.myProvider_table_name, values, selection, selectionArgs);
if(id!=0)return id;
return 0;
}
}
3，ContextProvider必须声明才能使用，因此，需要在AndroidManifest.xml配置文件中声明。声明很简单，需要类名称和授权名称两个属性。
<provider android:name="myProvider"
android:authorities="com.njue.myProvider" />
到这里，我们自定义的ContentProvider就完成了。我们可以在Eclipse中的File Explorer 窗口中看到自定义的ContentProvider
4，简单测试
package com.njue;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class Content_providerActivity extends Activity {
/** Called when the activity is first created. */
Uri uri;
String AUTHORITY="content://com.njue.myProvider/myProvider_table_name";
ContentResolver cr;
EditText input;
Button insert;
TextView show;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
input=(EditText)findViewById(R.id.input);
insert=(Button)findViewById(R.id.insert);
show=(TextView)findViewById(R.id.show);
uri=uri.parse(AUTHORITY);
cr=this.getContentResolver();
insert.setOnClickListener(new Button.OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
ContentValues values=new ContentValues();
values.put("name", input.getText().toString());
cr.insert(uri, values);
Cursor c=cr.query(uri, null, null, null, null);
show.setText("");
c.moveToFirst();
while(c.moveToNext()){
show.append(c.getString(1)+"\r\n");
}
input.setText("");
}});
}
}
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