安卓初級教程（3）：ContentProvider的運用原理

 1 package com.example.android.provider;
 2 
 3 import java.util.ArrayList;
 4 import java.util.HashMap;
 5 import java.util.Map;
 6 import android.app.Activity;
 7 import android.content.ContentValues;
 8 import android.database.Cursor;
 9 import android.net.Uri;
10 import android.os.Bundle;
11 import android.widget.ListView;
12 import android.widget.SimpleAdapter;
13 
14 //這是第一個先看的java檔，testprovider.java是繼承這個java檔的。
15 
16 public class ProviderTest extends Activity {
17 //ProvideTest
18     /** Called when the activity is first created. */
19     @Override
20     public void onCreate(Bundle savedInstanceState) {
21         super.onCreate(savedInstanceState);
22         //Content Provider和Uri。我們要學習的重中之重就在以下這兩行。
23         //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。
24         //Uri uri_test是定義項，為了之後在Cusor cur之中抓取數據。
25         getIntent().setData(Uri.parse("content://com.example.android.provider.testprovider"));
26         Uri uri_test = getIntent().getData();
27         
28         //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
29         ContentValues values = new ContentValues();
30         values.put("name", "陳翹鈞");
31         values.put("description", "68206021");
32         getContentResolver().insert(uri_test, values);
33         values.put("name", "馮幹傑");
34         values.put("description", "60746017");
35         getContentResolver().insert(uri_test, values);
36         //Content Provider
37         Cursor cur = managedQuery(uri_test, null, null, null, null);
38         cur.moveToFirst();
39         //ArrayList
40         ArrayList<Map<String, Object>> data = new ArrayList<Map<String, Object>>();
41         Map<String, Object> item;
42         //ArrayList data
43             for (int i = 0; i < cur.getCount(); i++) {
44                 item = new HashMap<String, Object>();
45                 item.put("column00", cur.getString(0));
46                 item.put("column01", cur.getString(1));
47                 item.put("column02", cur.getString(2));
48                 data.add(item);
49                 cur.moveToNext();
50             }
51             cur.close();
52             //ArrayList data，mListView01
53             ListView mListView01 = new ListView(this);
54             SimpleAdapter adapter = new SimpleAdapter(this, data,
55                 R.layout.main, new String[] {"column00", "column01", "column02" }, new int[] {
56                     R.id.TextView01, R.id.TextView02, R.id.TextView03 });
57             mListView01.setAdapter(adapter);
58             setContentView(mListView01);      
59     }
60 }

 1 package com.example.android.provider;
 2 
 3 import android.content.ContentProvider;
 4 import android.content.ContentValues;
 5 import android.content.Context;
 6 import android.database.Cursor;
 7 import android.database.sqlite.SQLiteDatabase;
 8 import android.database.sqlite.SQLiteOpenHelper;
 9 import android.database.sqlite.SQLiteQueryBuilder;
10 import android.net.Uri;
11 import android.provider.BaseColumns;
12 
13 public class TestProvider extends ContentProvider {
14     
15     private static class DatabaseHelper extends SQLiteOpenHelper {
16         
17         DatabaseHelper(Context context) {
18             super(context, "test.db", null, 1);
19         }
20         
21         @Override
22         public void onCreate(SQLiteDatabase db) {
23             db.execSQL("CREATE TABLE test (" + BaseColumns._ID
24                     + " INTEGER PRIMARY KEY," + "name TEXT,"
25                     + "description TEXT" + ");");
26         }
27         
28         @Override
29         public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
30             // TODO Auto-generated method stub
31             db.execSQL("DROP TABLE IF EXISTS test");
32             onCreate(db);
33         }
34     }
35     //DatabaseHelper，databaseHelper
36     DatabaseHelper databaseHelper;
37     //Content Providers，onCreate()
38     @Override
39     public boolean onCreate() {
40         databaseHelper = new DatabaseHelper(getContext());
41         return true;
42     }
43     //Content Providers，insert()
44     @Override
45     public Uri insert(Uri uri, ContentValues values) {
46         SQLiteDatabase db = databaseHelper.getWritableDatabase();
47         db.insert("test", null, values);
48         return null;
49     }
50     //Content Providers，query()
51     @Override
52     public Cursor query(Uri uri, String[] projection, String selection,
53             String[] selectionArgs, String sortOrder) {
54         SQLiteDatabase db = databaseHelper.getReadableDatabase();
55         SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
56         qb.setTables("test");
57         Cursor c = qb.query(db, projection, selection, selectionArgs, null,
58                 null, null);
59         return c;
60     }
61     //Content Providers，delete()
62     @Override
63     public int delete(Uri uri, String selection, String[] selectionArgs) {
64         // TODO Auto-generated method stub
65         return 0;
66     }
67     //Content Providers，getType()
68     @Override
69     public String getType(Uri uri) {
70         // TODO Auto-generated method stub
71         return null;
72     }
73     //Content Providers，update()
74     @Override
75     public int update(Uri uri, ContentValues values, String selection,
76             String[] selectionArgs) {
77         // TODO Auto-generated method stub
78         return 0;
79     }
80 }