ContentProvider的用法有2种，一种是使用现有的内容提供器来读取和操作相应程序中的数据，另一种是创建自己的内容提供器给我们程序的数据提供外部访问接口。
今天学习自定义ContentProvider使用
1、新建DatabaseProvider继承ContentProvider，实现其6个方法
public boolean onCreate()
在创建ContentProvider时使用，通常用来完成数据库的创建和升级，返回true表示初始化创建成功public Cursor query()
用于查询指定uri的数据返回一个Cursorpublic Uri insert()
用于向指定uri的ContentProvider中添加数据public int delete()
用于删除指定uri的数据public int update()
用户更新指定uri的数据public String getType()
用于返回指定的Uri中的数据MIME类型
package com.example.databasetest;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
public class DatabaseProvider extends ContentProvider {
public static final int BOOK_DIR = 0;
public static final int BOOK_ITEM = 1;
public static final int CATEGORY_DIR = 2;
public static final int CATEGORY_ITEM = 3;
public static final String AUTHORITY = "com.example.databasetest.provider";
private static UriMatcher uriMatcher;
private MyDatabaseHelper dbHelper;
static {
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI(AUTHORITY, "book", BOOK_DIR);
uriMatcher.addURI(AUTHORITY, "book/#", BOOK_DIR);
uriMatcher.addURI(AUTHORITY, "category", CATEGORY_DIR);
uriMatcher.addURI(AUTHORITY, "category/#", CATEGORY_ITEM);
}
public DatabaseProvider() {
}
@Override
public boolean onCreate() {
dbHelper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 2);
return true;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
Cursor cursor = null;
switch (uriMatcher.match(uri)){
case BOOK_DIR:
cursor = db.query("Book", projection, selection, selectionArgs,
null, null, sortOrder);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
cursor = db.query("Book", projection, "id = ?", new String[]{bookId},
null, null, sortOrder);
break;
case CATEGORY_DIR:
cursor = db.query("Category", projection, selection, selectionArgs,
null, null, sortOrder);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
cursor = db.query("Category", projection, "id = ?", new String[]{categoryId},
null, null, sortOrder);
break;
default:
break;
}
return cursor;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
Uri uriReturn = null;
switch (uriMatcher.match(uri)){
case BOOK_DIR:
case BOOK_ITEM:
long newBookId = db.insert("Book", null, values);
uriReturn = Uri.parse("content://" + AUTHORITY + "/book/" + newBookId);
break;
case CATEGORY_DIR:
case CATEGORY_ITEM:
long newCategoryId = db.insert("Category", null, values);
uriReturn = Uri.parse("content://" + AUTHORITY + "/category/" + newCategoryId);
break;
default:
break;
}
return uriReturn;
}
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
int updateRow = 0;
switch (uriMatcher.match(uri)){
case BOOK_DIR:
updateRow = db.update("Book", values, selection, selectionArgs);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
updateRow = db.update("Book", values, "id = ?", new String[]{bookId});
break;
case CATEGORY_DIR:
updateRow = db.update("Category", values, selection, selectionArgs);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
updateRow = db.update("Category", values, "id = ?", new String[]{categoryId});
break;
}
return updateRow;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
int deleteRow = 0;
switch (uriMatcher.match(uri)){
case BOOK_DIR:
deleteRow = db.delete("Book", selection, selectionArgs);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
deleteRow = db.delete("Book", "id = ?", new String[]{bookId});
break;
case CATEGORY_DIR:
deleteRow = db.delete("Category", selection, selectionArgs);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
deleteRow = db.delete("Category", "id = ?", new String []{categoryId});
break;
default:
break;
}
return deleteRow;
}
@Override
public String getType(Uri uri) {
switch (uriMatcher.match(uri)){
case BOOK_DIR:
return "vnd.android.cursor.dir/vnd.com.example.databasetest.provider.book";
case BOOK_ITEM:
return "vnd.android.cursor.item/vnd.com.example.databasetest.provider.book";
case CATEGORY_DIR:
return "vnd.android.cursor.dir/vnd.com.example.databasetest.provider.category";
case CATEGORY_ITEM:
return "vnd.android.cursor.item/vnd.com.example.databasetest.provider.category";
}
return null;
}
}
MyDatabaseHelper类
package com.example.databasetest;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;
public class MyDatabaseHelper extends SQLiteOpenHelper {
public static final String CREATE_BOOK = "create table Book ("
+"id integer primary key autoincrement,"
+"author text,"
+"price real,"
+"pages integer,"
+"name text)";
public static final String CREATE_CATEGORY= "create table Category ("
+"id integer primary key autoincrement,"
+"category_name text,"
+"category_code integer)";
private Context mContext;
public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
this.mContext = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK);
db.execSQL(CREATE_CATEGORY);
// Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table if exists Book");
db.execSQL("drop table if exists Category");
onCreate(db);
}
}
主MainActivity
package com.example.databasetest;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = (Button) findViewById(R.id.create_database);
dbHelper = new MyDatabaseHelper(MainActivity.this, "BookStore.db",null, 2);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dbHelper.getWritableDatabase();
}
});
Button saveData = (Button) findViewById(R.id.add_data);
saveData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", "The Da Vinci Code");
values.put("author", "Dan Brown");
values.put("pages", 454);
values.put("price", 16.96);
db.insert("Book", null, values);
values.clear();
values.put("name", "The Lost Symbol");
values.put("author", "Dan Brown");
values.put("pages", 510);
values.put("price", 19.95);
db.insert("Book", null, values);
}
});
Button updateData = (Button) findViewById(R.id.update_data);
updateData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("price", 10.99);
db.update("Book", values, "name=?", new String[]{"The Da Vinci Code"});
}
});
Button deleteData = (Button) findViewById(R.id.delete_data);
deleteData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.delete("Book","name=?", new String[]{"The Da Vinci Code"});
}
});
Button queryData = (Button) findViewById(R.id.query_data);
queryData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
Cursor cursor = db.query("Book",null, null, null,null,null,null);
if(cursor.moveToFirst()){
do{
String name = cursor.getString(cursor.getColumnIndex("name"));
String author = cursor.getString(cursor.getColumnIndex("author"));
int pages = cursor.getInt(cursor.getColumnIndex("pages"));
double price = cursor.getDouble(cursor.getColumnIndex("price"));
Log.d("MainActivity", "Book name is "+name);
Log.d("MainActivity", "Book author is "+author);
Log.d("MainActivity", "Book pages is "+pages);
Log.d("MainActivity", "Book price is "+price);
}while (cursor.moveToNext());
}
}
});
}
}
布局文件activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/create_database"
android:text="Create Database"/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/add_data"
android:text="Add Data"/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/update_data"
android:text="Update Data"/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/delete_data"
android:text="Delete Data"/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/query_data"
android:text="Query Data"/>
</LinearLayout>
AndroidManifest.xml添加(Android Studio自动添加)
<provider
android:name=".DatabaseProvider"
android:authorities="com.example.databasetest.provider"
android:enabled="true"
android:exported="true">
</provider>
另外新建项目ProviderTest调用
布局文件activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">
<Button
android:id="@+id/add_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Add Data to Book"/>
<Button
android:id="@+id/query_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Query Data from Book"/>
<Button
android:id="@+id/update_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Update Data to Book"/>
<Button
android:id="@+id/delete_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Delete Data from Book"/>
</LinearLayout>
主MainActivity
package com.example.providertest;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
private String newId;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button addData = (Button) findViewById(R.id.add_data);
addData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Uri uri = Uri.parse("content://com.example.databasetest.provider/book");
ContentValues values = new ContentValues();
values.put("name", "A Clash of King");
values.put("author", "George Martin");
values.put("pages", 1040);
values.put("price", 22.85);
Uri newUri = getContentResolver().insert(uri,values);
newId = newUri.getPathSegments().get(1);
}
});
Button queryData = (Button) findViewById(R.id.query_data);
queryData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Uri uri = Uri.parse("content://com.example.databasetest.provider/book");
Cursor cursor = getContentResolver().query(uri, null, null,
null, null);
if (null != cursor){
while (cursor.moveToNext()){
String name = cursor.getString(cursor.getColumnIndex("name"));
String author = cursor.getString(cursor.getColumnIndex("author"));
int pages = cursor.getInt(cursor.getColumnIndex("pages"));
double price = cursor.getDouble(cursor.getColumnIndex("price"));
Log.d("MainActivity", "The book name is "+name);
Log.d("MainActivity", "The book author is "+author);
Log.d("MainActivity", "The book pages is "+pages);
Log.d("MainActivity", "The book price is "+price);
}
cursor.close();
}
}
});
Button updateData = (Button) findViewById(R.id.update_data);
updateData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Uri uri = Uri.parse("content://com.example.databasetest.provider/book"+newId);
ContentValues values = new ContentValues();
values.put("name", "A Storm of Sword");
values.put("pages", 1216);
values.put("price", 24.05);
getContentResolver().update(uri, values, null, null);
}
});
Button deleteData = (Button) findViewById(R.id.delete_data);
deleteData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Uri uri = Uri.parse("content://com.example.databasetest.provider/book"+newId);
getContentResolver().delete(uri, null, null);
}
});
}
}
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