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android contentProvider用法

編輯：初級開發

存儲數據的方式很多，在android平時有sharedpreference file sqlite等．這裡主要分析下數據庫存儲．為了共享數據庫．可以讓數據庫披上contentprovider 外衣．具體看例子
[size=12]package com.misoo.SQ02;
import Java.util.ArrayList;
import Java.util.HashMap;
import Java.util.Map;
import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.Net.Uri;
import android.os.Bundle;
import android.view.VIEw;
import android.widget.ListVIEw;
import android.widget.SimpleAdapter;
public class ac01 extends ListActivity {
public static int g_variable;
public static final String AUTHORITY = "com.misoo.provider.SQ02";
public static final Uri CONTENT_URI =
Uri.parse("content://" + AUTHORITY + "/StudentTable");
private static final String[] PROJECTION = new String[] {
"stud_no", "stud_name" };
@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = getIntent();
if (intent.getData() == null) intent.setData(CONTENT_URI);
Cursor cur = getContentResolver().query(getIntent().getData(),
PROJECTION, null, null, null);
ArrayList<Map<String, Object>> coll
= new ArrayList<Map<String, Object>>();
Map<String, Object> item;
cur.moveToFirst();
while(!cur.isAfterLast()) {
item = new HashMap<String, Object>();
item.put("c1", cur.getString(0) + ", " + cur.getString(1));
coll.add(item);
cur.moveToNext(); }
this.setListAdapter(new SimpleAdapter(this, coll,
android.R.layout.simple_list_item_1, new String[] { "c1" },
new int[] {android.R.id.text1})); }
@Override
protected void onListItemClick(ListView l, VIEw v, int position, long id){
finish(); }
package com.misoo.SQ02;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.Net.Uri;
import android.util.Log;
public class DataProvider extends ContentProvider {
private static final String DATABASE_NAME = "StudDB_2.db";
private static final int DATABASE_VERSION = 2;
private static final String TABLE_NAME = "StudentTable";
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION); @Override public void onCreate(SQLiteDatabase db) {
db.execSQL("Create TABLE " + TABLE_NAME + " ("
+ "stud_no" + " TEXT," + "stud_name" + " TEXT" + ");");
String sql_1 = "insert into "+ TABLE_NAME +
" (stud_no, stud_name) values('S108', 'Lily Chen');";
String sql_2 = "insert into " + TABLE_NAME +
" (stud_no, stud_name) values('S201', 'Tom Kao');";
String sql_3 = "insert into " + TABLE_NAME +
" (stud_no, stud_name) values('S333', 'Peter Rabbit');";
try {
db.execSQL(sql_1); db.execSQL(sql_2); db.execSQL(sql_3);
} catch (SQLException e) { Log.e("ERROR", e.toString()); } @Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {} private DatabaseHelper mOpenHelper;
@Override public boolean onCreate() {
mOpenHelper = new DatabaseHelper(getContext());
return true; @Override public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteDatabase db = mOpenHelper.getReadableDatabase();
Cursor c = db.query(TABLE_NAME, projection, null, null, null, null, null);
return c; @Override public String getType(Uri uri)
{ return null; }
@Override public Uri insert(Uri uri, ContentValues initialValues)
{ return uri; }
@Override public int delete(Uri uri, String where, String[] whereArgs)
{ return 0; }
@Override public int update(Uri uri, ContentValues values,
String where, String[] whereArgs)
{ return 0; }
}[/size] 從例子可以看出。不管怎麼表達，最後要得到SQLiteDatabase引用．然後用這個引用去操作數據庫．在這裡通過contentprovide 包了SQLlitOpenhelper ，通過這個來創建數據庫．創建表．然後通過getContentResolver 來操作數據庫．這個代碼應該不難，關鍵我想，系統如何知道我要操作哪個數據庫裡的哪個表呢？這需要用戶指定
public static final String AUTHORITY = "com.misoo.provider.SQ02";
public static final Uri CONTENT_URI =
Uri.parse("content://" + AUTHORITY + "/StudentTable"); 這兩句就是指定了哪個數據庫，指定了哪個表．　這說明在manifest.XML 裡一定要加上這麼幾句 <provider android:name="DataProvider"
android:authoritIEs="com.misoo.provider.SQ02">
</provider> 有了這個東西就知道是哪個數據了．就可以開始操作了．

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