在 Android中，对于数据的存贮，有几种方式，有文件方式，有文件式数据库方式,网络数据,Android自带了一个SQLite数据库，做嵌入开发的人对这个跨平台的本地文件数据库一定不会陌生，在Android对于数据的访问，提出了新的方式，ContentProvider方式，我们首先来看看SQLite在 Android中的使用，在Android中有最简单的使用方式，就是利Context对象的openorCreateDatabase
我们来看看一段代码：

Java代码

1. importandroid.app.Activity;
2. importandroid.content.Intent;
3. importandroid.database.Cursor;
4. importandroid.database.sqlite.SQLiteDatabase;
5. importandroid.os.Bundle;
6. importandroid.view.Menu;
7. importandroid.view.MenuItem;
8. importandroid.widget.TextView;
10. publicclassDBActivityextendsActivity{
11. privateSQLiteDatabasemdb=null;
12. /**Calledwhentheactivityisfirstcreated.*/
13. @Override
14. publicvoidonCreate(BundlesavedInstanceState){
15. super.onCreate(savedInstanceState);
16. initDatabase();
17. setContentView(R.layout.main);
18. }
19. @Override
20. publicbooleanonCreateOptionsMenu(Menumenu){
21. //TODOAuto-generatedmethodstub
22. super.onCreateOptionsMenu(menu);
23. menu.add(1,Menu.FIRST+1,1,"GetName");
24. menu.add(1,Menu.FIRST+2,2,"Test");
25. returntrue;
26. }
28. publicbooleanonOptionsItemSelected(MenuItemitem){
29. //TODOAuto-generatedmethodstub
30. super.onOptionsItemSelected(item);
31. switch(item.getItemId())
32. {
33. caseMenu.FIRST+1:
34. {
35. TextViewtv=(TextView)this.findViewById(R.id.view_main);
36. tv.setText(this.getName());
37. break;
38. }
39. caseMenu.FIRST+2:
40. {
41. this.setTitle("DelItem...");
42. break;
43. }
44. }
45. returntrue;
46. }
48. privatevoidinitDatabase()
49. {
50. mdb=this.openOrCreateDatabase("dbfile",0,null);
51. Stringsql_create="createtabletest(idint,nameTEXT)";
52. mdb.execSQL(sql_create);
53. Stringsql_insert="insertintotest(id,name)values(3,'name3')";
54. mdb.execSQL(sql_insert);
55. }
56. privateStringgetName()
57. {
58. Stringname=null;
60. Cursorcur=mdb.rawQuery("select*fromtest",null);
61. cur.moveToFirst();
62. while(!cur.isLast())
63. {
64. name=name+cur.getString(1)+"\r\n";
65. cur.moveToNext();
66. }
67. returnname;
68. }
69. }

import android.app.Activity;import android.content.Intent;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.widget.TextView;public class DBActivity extends Activity { private SQLiteDatabase mdb = null;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        initDatabase();        setContentView(R.layout.main);            }    @Override public boolean onCreateOptionsMenu(Menu menu) {  // TODO Auto-generated method stub  super.onCreateOptionsMenu(menu);     menu.add(1, Menu.FIRST +1, 1, "GetName");    menu.add(1, Menu.FIRST +2, 2, "Test");     return true;   }        public boolean onOptionsItemSelected(MenuItem item) {  // TODO Auto-generated method stub  super.onOptionsItemSelected(item);  switch (item.getItemId())  {   case Menu.FIRST+ 1:   {    TextView tv = (TextView)this.findViewById(R.id.view_main);    tv.setText(this.getName());    break;   }   case Menu.FIRST + 2:   {    this.setTitle("Del Item...");    break;   }     }  return true; }        private void initDatabase()    {     mdb = this.openOrCreateDatabase("dbfile", 0, null);     String sql_create = "create table test (id int, name TEXT)";     mdb.execSQL(sql_create);     String sql_insert = "insert into test(id, name) values(3, 'name3')";     mdb.execSQL(sql_insert);    }    private String getName()    {     String name = null;          Cursor cur = mdb.rawQuery("select * from test", null);     cur.moveToFirst();     while (!cur.isLast())     {      name = name  + cur.getString(1)+ "\r\n";      cur.moveToNext();     }     return name;    }}

我们再来看看单独使用SQLiteOpenHelper方式：
先由SQLiteOpenHelper继承一个数据库操作类，其中onCreate, onUpgrade必须重载并实现，

Java代码

1. importandroid.content.Context;
2. importandroid.database.Cursor;
3. importandroid.database.sqlite.SQLiteDatabase;
4. importandroid.database.sqlite.SQLiteOpenHelper;
6. publicclassDatabaseHelperextendsSQLiteOpenHelper{
7. @Override
8. publicvoidonCreate(SQLiteDatabasedb){
9. //TODOAuto-generatedmethodstub
10. }
11. @Override
12. publicvoidonUpgrade(SQLiteDatabasedb,intoldVersion,intnewVersion){
13. //TODOAuto-generatedmethodstub
14. }
15. publicDatabaseHelper(Contextct,StringdbName)
16. {
17. super(ct,dbName,null,1);
18. }
19. publicbooleaninsert(Stringinsert)
20. {
21. this.getWritableDatabase().execSQL(insert);
22. returntrue;
23. }
24. publicbooleanupdate(Stringupdate)
25. {
26. this.getWritableDatabase().execSQL(update);
27. returntrue;
28. }
29. publicbooleandelete(Stringdel)
30. {
31. this.getWritableDatabase().execSQL(del);
32. returntrue;
33. }
34. publicCursorquery(Stringquery)
35. {
36. Cursorcur=this.getReadableDatabase().rawQuery(query,null);
37. returncur;
38. }
39. }

import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DatabaseHelper extends SQLiteOpenHelper { @Override public void onCreate(SQLiteDatabase db) {  // TODO Auto-generated method stub   } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {  // TODO Auto-generated method stub   } public DatabaseHelper(Context ct,String dbName) {   super(ct,dbName,null,1);   }  public boolean insert(String insert) {  this.getWritableDatabase().execSQL(insert);  return true; } public boolean update(String update) {  this.getWritableDatabase().execSQL(update);  return true; } public boolean delete(String del) {  this.getWritableDatabase().execSQL(del);  return true; } public Cursor query(String query) {  Cursor cur = this.getReadableDatabase().rawQuery(query, null);  return cur; }}

再创建一个使用者（消费者）

Java代码

1. importandroid.app.Activity;
2. importandroid.content.Intent;
3. importandroid.database.Cursor;
4. importandroid.database.sqlite.SQLiteDatabase;
5. importandroid.os.Bundle;
6. importandroid.view.Menu;
7. importandroid.view.MenuItem;
8. importandroid.widget.TextView;
10. publicclassDBActivityextendsActivity{
11. privateSQLiteDatabasemdb=null;
12. privateDatabaseHelperhelper=null;
13. /**Calledwhentheactivityisfirstcreated.*/
14. @Override
15. publicvoidonCreate(BundlesavedInstanceState){
16. super.onCreate(savedInstanceState);
17. initDatabase();
18. setContentView(R.layout.main);
19. }
20. @Override
21. publicbooleanonCreateOptionsMenu(Menumenu){
22. //TODOAuto-generatedmethodstub
23. super.onCreateOptionsMenu(menu);
24. menu.add(1,Menu.FIRST+1,1,"GetName");
25. menu.add(1,Menu.FIRST+2,2,"Test");
26. returntrue;
27. }
29. publicbooleanonOptionsItemSelected(MenuItemitem){
30. //TODOAuto-generatedmethodstub
31. super.onOptionsItemSelected(item);
32. switch(item.getItemId())
33. {
34. caseMenu.FIRST+1:
35. {
36. TextViewtv=(TextView)this.findViewById(R.id.view_main);
37. tv.setText(this.getName());
38. break;
39. }
40. caseMenu.FIRST+2:
41. {
42. this.setTitle("DelItem...");
43. break;
44. }
45. }
46. returntrue;
47. }
49. privatevoidinitDatabase()
50. {
51. helper=newDatabaseHelper(this,"dbfile");
52. //mdb=this.openOrCreateDatabase("dbfile",0,null);
53. //Stringsql_create="createtabletest(idint,nameTEXT)";
54. //mdb.execSQL(sql_create);
55. Stringsql_insert="insertintotest(id,name)values(55,'namexx')";
56. //mdb.execSQL(sql_insert);
57. helper.insert(sql_insert);
58. }
59. privateStringgetName()
60. {
61. Stringname=null;
62. //mdb=helper.getReadableDatabase();
63. Cursorcur=helper.query("select*fromtest");
64. cur.moveToFirst();
65. do
66. {
67. name=name+cur.getString(1)+"\n";
69. }while(cur.moveToNext());
71. returnname;
72. }
73. }

import android.app.Activity;import android.content.Intent;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.widget.TextView;public class DBActivity extends Activity { private SQLiteDatabase mdb = null; private DatabaseHelper helper = null;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        initDatabase();        setContentView(R.layout.main);            }    @Override public boolean onCreateOptionsMenu(Menu menu) {  // TODO Auto-generated method stub  super.onCreateOptionsMenu(menu);     menu.add(1, Menu.FIRST +1, 1, "GetName");    menu.add(1, Menu.FIRST +2, 2, "Test");     return true;   }        public boolean onOptionsItemSelected(MenuItem item) {  // TODO Auto-generated method stub  super.onOptionsItemSelected(item);  switch (item.getItemId())  {   case Menu.FIRST+ 1:   {    TextView tv = (TextView)this.findViewById(R.id.view_main);    tv.setText(this.getName());    break;   }   case Menu.FIRST + 2:   {    this.setTitle("Del Item...");    break;   }     }  return true; }        private void initDatabase()    {     helper = new DatabaseHelper(this,"dbfile");     //mdb = this.openOrCreateDatabase("dbfile", 0, null);     //String sql_create = "create table test (id int, name TEXT)";     //mdb.execSQL(sql_create);     String sql_insert = "insert into test(id, name) values(55, 'namexx')";     //mdb.execSQL(sql_insert);     helper.insert(sql_insert);    }    private String getName()    {     String name = null;       //mdb = helper.getReadableDatabase();     Cursor cur = helper.query("select * from test");     cur.moveToFirst();     do     {      name = name  + cur.getString(1)+ "\n";                 } while(cur.moveToNext());                return name;    }}

在来看看使用ContentProvider

Java代码

1. importandroid.content.ContentProvider;
2. importandroid.content.ContentValues;
3. importandroid.database.Cursor;
4. importandroid.net.Uri;
5. importandroid.widget.Toast;
7. publicclassTestProviderextendsContentProvider{
8. privateDatabaseHelpermdbHelper=null;
9. finalstaticStringTABLE_NAME="test";
10. @Override
11. publicintdelete(Uriarg0,Stringarg1,String[]arg2){
12. mdbHelper.getWritableDatabase().delete(TABLE_NAME,arg1,arg2);
13. return0;
14. }
16. @Override
17. publicStringgetType(Uriuri){
18. //TODOAuto-generatedmethodstub
19. returnnull;
20. }
22. @Override
23. publicUriinsert(Uriuri,ContentValuesvalues){
24. //TODOAuto-generatedmethodstub
25. mdbHelper.getWritableDatabase().insert(TABLE_NAME,"",values);
26. returnnull;
27. }
29. @Override
30. publicbooleanonCreate(){
31. //TODOAuto-generatedmethodstub
32. mdbHelper=newDatabaseHelper(this.getContext(),"dbfile");
33. returntrue;
34. }
36. @Override
37. publicCursorquery(Uriuri,String[]projection,Stringselection,
38. String[]selectionArgs,StringsortOrder){
39. Cursorcur=mdbHelper.getReadableDatabase().query(TABLE_NAME,projection,selection,null,null,null,null);
40. Toast.makeText(this.getContext(),"testCur!",Toast.LENGTH_SHORT);
41. returncur;
42. }
44. @Override
45. publicintupdate(Uriuri,ContentValuesvalues,Stringselection,
46. String[]selectionArgs){
47. mdbHelper.getWritableDatabase().update(TABLE_NAME,values,selection,null);
48. return0;
49. }
51. }

import android.content.ContentProvider;import android.content.ContentValues;import android.database.Cursor;import android.net.Uri;import android.widget.Toast;public class TestProvider extends ContentProvider {    private DatabaseHelper mdbHelper = null;    final static String TABLE_NAME = "test"; @Override public int delete(Uri arg0, String arg1, String[] arg2) {  mdbHelper.getWritableDatabase().delete(TABLE_NAME, arg1, arg2);  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  mdbHelper.getWritableDatabase().insert(TABLE_NAME, "", values);  return null; } @Override public boolean onCreate() {  // TODO Auto-generated method stub  mdbHelper = new DatabaseHelper(this.getContext(), "dbfile");  return true; } @Override public Cursor query(Uri uri, String[] projection, String selection,   String[] selectionArgs, String sortOrder) {  Cursor cur = mdbHelper.getReadableDatabase().query(TABLE_NAME,projection,selection,null,null,null, null);  Toast.makeText(this.getContext(), "test Cur!", Toast.LENGTH_SHORT);  return cur; } @Override public int update(Uri uri, ContentValues values, String selection,   String[] selectionArgs) {  mdbHelper.getWritableDatabase().update(TABLE_NAME, values, selection, null);  return 0; }}

老规矩,AndroidManifest.xml来定义这个Provider
<provider android:label="test_provider" android:authorities="com.my.provider" android:name="TestProvider">
</provider>
这里的android:authorities = "com.my.provider"是标识这个ContentProvider，调用者可以根据这个标识来找到它，
我们组合一个能找到它的Uri,
public class ProviderConst {
public static final Uri MY_TEST_URI = Uri.parse("content://com.my.provider/test");

}

content 指的是内容提供者ContentProvider。
//com.my.provider映射到我们已定义的那个ContentProvider标识
/test这个作为一个参数，传给ContentProvider，可以根据这个参数来决定操作目标，比如数据库中的哪张表，文件中的那一部分数据等。

我们来操作这个内容提供者：

Java代码

1. privateStringgetName()
2. {
3. Stringname=null;
4. Cursorcur=this.getContentResolver().query(ProviderConst.MY_TEST_URI,newString[]{"id","name"},null,null,null);
5. if(cur==null)
6. returnnull;
7. cur.moveToFirst();
8. do
9. {
10. name=name+cur.getString(1)+"\n";
12. }while(cur.moveToNext());
14. returnname;
15. }

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