安卓初級教程（3）：ContentProvider的運用原理

 package com.example.android.provider;

 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Map;
 import android.app.Activity;
 import android.content.ContentValues;
 import android.database.Cursor;
 import android.net.Uri;
 import android.os.Bundle;
 import android.widget.ListView;
 import android.widget.SimpleAdapter;

 //這是第一個先看的java檔，testprovider.java是繼承這個java檔的。

 public class ProviderTest extends Activity {
 //ProvideTest
     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         //Content Provider和Uri。我們要學習的重中之重就在以下這兩行。
         //在這裡getIntent()是意圖從另外一個java檔中獲取數據。如何從另一個java檔中抓取數據，就是借助Uri.parse。
         //Uri uri_test是定義項，為了之後在Cusor cur之中抓取數據。
         getIntent().setData(Uri.parse("content://com.example.android.provider.testprovider"));
         Uri uri_test = getIntent().getData();

         //精妙之處就在於這個values和另一個java檔之中的values是處於何種關係?手
         ContentValues values = new ContentValues();
         values.put("name", "陳翹鈞");
         values.put("description", "68206021");
         getContentResolver().insert(uri_test, values);
         values.put("name", "馮幹傑");
         values.put("description", "60746017");
         getContentResolver().insert(uri_test, values);
         //Content Provider
         Cursor cur = managedQuery(uri_test, null, null, null, null);
         cur.moveToFirst();
         //ArrayList
         ArrayList<Map<String, Object>> data = new ArrayList<Map<String, Object>>();
         Map<String, Object> item;
         //ArrayList data
             for (int i = 0; i < cur.getCount(); i++) {
                 item = new HashMap<String, Object>();
                 item.put("column00", cur.getString(0));
                 item.put("column01", cur.getString(1));
                 item.put("column02", cur.getString(2));
                 data.add(item);
                 cur.moveToNext();
             }
             cur.close();
             //ArrayList data，mListView01
             ListView mListView01 = new ListView(this);
             SimpleAdapter adapter = new SimpleAdapter(this, data,
                 R.layout.main, new String[] {"column00", "column01", "column02" }, new int[] {
                     R.id.TextView01, R.id.TextView02, R.id.TextView03 });
             mListView01.setAdapter(adapter);
             setContentView(mListView01);
     }
 }

 package com.example.android.provider;

 import android.content.ContentProvider;
 import android.content.ContentValues;
 import android.content.Context;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteOpenHelper;
 import android.database.sqlite.SQLiteQueryBuilder;
 import android.net.Uri;
 import android.provider.BaseColumns;

 public class TestProvider extends ContentProvider {

     private static class DatabaseHelper extends SQLiteOpenHelper {

         DatabaseHelper(Context context) {
             super(context, "test.db", null, 1);
         }

         @Override
         public void onCreate(SQLiteDatabase db) {
             db.execSQL("CREATE TABLE test (" + BaseColumns._ID
                     + " INTEGER PRIMARY KEY," + "name TEXT,"
                     + "description TEXT" + ");");
         }

         @Override
         public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
             // TODO Auto-generated method stub
             db.execSQL("DROP TABLE IF EXISTS test");
             onCreate(db);
         }
     }
     //DatabaseHelper，databaseHelper
     DatabaseHelper databaseHelper;
     //Content Providers，onCreate()
     @Override
     public boolean onCreate() {
         databaseHelper = new DatabaseHelper(getContext());
         return true;
     }
     //Content Providers，insert()
     @Override
     public Uri insert(Uri uri, ContentValues values) {
         SQLiteDatabase db = databaseHelper.getWritableDatabase();
         db.insert("test", null, values);
         return null;
     }
     //Content Providers，query()
     @Override
     public Cursor query(Uri uri, String[] projection, String selection,
             String[] selectionArgs, String sortOrder) {
         SQLiteDatabase db = databaseHelper.getReadableDatabase();
         SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
         qb.setTables("test");
         Cursor c = qb.query(db, projection, selection, selectionArgs, null,
                 null, null);
         return c;
     }
     //Content Providers，delete()
     @Override
     public int delete(Uri uri, String selection, String[] selectionArgs) {
         // TODO Auto-generated method stub
         return 0;
     }
     //Content Providers，getType()
     @Override
     public String getType(Uri uri) {
         // TODO Auto-generated method stub
         return null;
     }
     //Content Providers，update()
     @Override
     public int update(Uri uri, ContentValues values, String selection,
             String[] selectionArgs) {
         // TODO Auto-generated method stub
         return 0;
     }
 }